Audio devices

Abstract

An embodiment of the present specification provides an acoustic device, the acoustic device including: a diaphragm; and a housing that accommodates the diaphragm and has a first acoustic cavity and a second acoustic cavity formed on the front and rear sides of the diaphragm, respectively, wherein the diaphragm radiates sound to the first acoustic cavity and the second acoustic cavity, respectively, and emits sound from a first acoustic hole coupled to the first acoustic cavity and a second acoustic hole coupled to the second acoustic cavity, respectively; a sound-absorbing structure that is coupled to the second acoustic cavity and absorbs sound within a target frequency range that passes through the second acoustic cavity and is transmitted to the second acoustic hole, the sound-absorbing structure including a fine-perforated plate and a cavity, the fine-perforated plate including through-holes, and the second acoustic cavity communicating with the cavity through the through-holes; and a hanging structure that wears the housing near a user's ear canal in a position that does not block the ear canal opening.

Description

[Technical Field]

[0001] The present specification relates to the field of acoustics, and in particular to acoustic devices.

[0002] [Incorporated by reference] This application claims priority to International Application No. PCT / CN2023 / 100403, filed June 15, 2023, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] To solve the sound leakage problem of a sound generating unit, two or more sound sources are typically used to generate two sound signals with opposite phases. Under far-field conditions, the difference in acoustic distance between the two sound sources with opposite phases and a specific point in the far-field is essentially negligible, so the two sound signals cancel each other out, reducing sound leakage in the far-field. While this method can achieve a certain level of sound leakage reduction, it still has certain limitations. For example, the wavelength of high-frequency sound leakage is shorter, and under far-field conditions, the distance between the two sound sources is not negligible relative to the wavelength, so the sound signals generated by the two sound sources cannot be canceled out. Furthermore, for example, when the acoustic transmission structure of the sound generating unit resonates, there is a certain phase difference between the phase of the sound signal actually radiated from the sound output port of the sound generating unit and the original phase of the sound wave generation position. This increases an additional resonance peak in the transmitted sound wave, causing a disturbance in the sound field distribution, making it difficult to ensure the effect of reducing sound leakage in the far-field at high frequencies and potentially increasing sound leakage.

[0004] Therefore, it is desirable to provide an acoustic device that has excellent sound field directionality. Summary of the Invention

[0005] An acoustic device according to one embodiment of the present specification includes: a diaphragm; and a housing that accommodates the diaphragm and has a first acoustic cavity and a second acoustic cavity formed corresponding to the front and rear sides of the diaphragm, wherein the diaphragm radiates sound to the first acoustic cavity and the second acoustic cavity, respectively, and emits sound from a first acoustic hole coupled to the first acoustic cavity and a second acoustic hole coupled to the second acoustic cavity, respectively; a sound-absorbing structure that is coupled to the second acoustic cavity and absorbs sound within a target frequency range that passes through the second acoustic cavity and is transmitted to the second acoustic hole, the sound-absorbing structure including a fine-perforated plate and a cavity, the fine-perforated plate including through-holes, and the second acoustic cavity communicating with the cavity via the through-holes; and a hanging structure that wears the housing near a user's ear canal in a position that does not block the ear canal opening.

[0006] In some embodiments, the ratio of the open area of ​​the first acoustic hole to the open area of ​​the second acoustic hole is in the range of 0.5 to 2.

[0007] In some embodiments, the difference in acoustic loading between the first acoustic hole and the second acoustic hole is less than 0.15.

[0008] In some embodiments, an angle between a normal to a side surface of the finely perforated plate facing the second acoustic cavity and a vibration direction of the vibrating membrane is in the range of 0° to 90°.

[0009] In some embodiments, the sound-absorbing structure is installed in the vibration direction of the vibration membrane, and the angle between the normal to the side of the micro-perforated plate facing the second acoustic cavity and the vibration direction of the vibration membrane is in the range of 0° to 10°.

[0010] In some embodiments, the acoustic device further includes a magnetic circuit assembly and a coil, the coil connected to the diaphragm and at least a portion of which is located in a magnetic gap formed by the magnetic circuit assembly, the coil vibrating the diaphragm to generate sound when energized, and the micro-perforated plate includes an annular structure disposed around the magnetic circuit assembly.

[0011] In some embodiments, the diameter of the through holes is in the range of 0.2 mm to 0.4 mm, the aperture ratio of the micro-perforated plate is in the range of 1% to 5%, the thickness of the micro-perforated plate is in the range of 0.2 mm to 0.7 mm, and the height of the cavity is in the range of 4 mm to 9 mm.

[0012] In some embodiments, the target frequency range includes 4 kHz.

[0013] In some embodiments, the diameter of the through holes is in the range of 0.1 mm to 0.3 mm, the aperture ratio of the micro-perforated plate is in the range of 0.5% to 5%, the thickness of the micro-perforated plate is in the range of 0.2 mm to 0.6 mm, and the height of the cavity is in the range of 4 mm to 10 mm.

[0014] In some embodiments, the target frequency range includes 2 kHz to 3 kHz.

[0015] In some embodiments, the acoustic device further includes a magnetic circuit assembly and a coil, the coil is connected to the diaphragm and at least a portion of the coil is located in a magnetic gap formed by the magnetic circuit assembly, the coil vibrates the diaphragm to generate sound when energized, and the micro-perforated plate and the magnetic circuit assembly are spaced apart in the vibration direction of the diaphragm.

[0016] In some embodiments, the diameter of the through holes is in the range of 0.1 mm to 0.2 mm, the aperture ratio of the micro-perforated plate is in the range of 2% to 5%, the thickness of the micro-perforated plate is in the range of 0.2 mm to 0.7 mm, and the height of the cavity is in the range of 7 mm to 10 mm.

[0017] In some embodiments, the target frequency range includes 4 kHz.

[0018] In some embodiments, the diameter of the through holes is in the range of 0.1 mm to 0.3 mm, the aperture ratio of the micro-perforated plate is in the range of 0.5% to 5%, the thickness of the micro-perforated plate is in the range of 0.2 mm to 0.6 mm, and the height of the cavity is in the range of 4 mm to 10 mm.

[0019] In some embodiments, the target frequency range includes 2 kHz to 3 kHz.

[0020] In some embodiments, the housing has long and short axis directions that are perpendicular to the vibration direction of the vibration membrane and perpendicular to each other, the sound-absorbing structure is installed in the long axis direction, and the angle between the side of the fine-perforated plate facing the second acoustic cavity and the long axis direction is in the range of 0° to 90°.

[0021] In some embodiments, the side of the micro-perforated plate facing the second acoustic cavity is perpendicular to the longitudinal axis.

[0022] In some embodiments, the housing has a long axis direction and a short axis direction that are perpendicular to the vibration direction of the vibration membrane and are perpendicular to each other, the sound-absorbing structure is installed in the short axis direction, and the angle between the side of the fine-perforated plate facing the second acoustic cavity and the short axis direction is in the range of 0° to 90°.

[0023] In some embodiments, the side of the micro-perforated plate facing the second acoustic cavity is perpendicular to the minor axis direction.

[0024] In some embodiments, the sound absorbing structure includes a plurality of independently installed sub-sound absorbing structures, each of which includes a sub-micro-perforated plate and a sub-cavity.

[0025] The present application will be further illustrated by exemplary embodiments, which are not limiting and will be described in detail with reference to the drawings, in which like numbers refer to like structures. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram of an exemplary ear according to some embodiments herein. [Figure 2] 1 is an exemplary structural diagram of an acoustic device according to some embodiments of the present disclosure. [Figure 3A] 1 is a schematic diagram of an exemplary wearing of an acoustic device according to some embodiments herein. [Figure 3B] 1 is a schematic diagram of an acoustic device in an unworn state according to some embodiments of the present disclosure. [Figure 4] 3B is a schematic diagram of an acoustic cavity formed by the acoustic device shown in FIG. 3A. [Figure 5] 10 is a schematic diagram illustrating an exemplary mounting of an acoustic device according to some other embodiments of the present disclosure. [Figure 6] FIG. 6 is a schematic diagram of an acoustic cavity formed by the acoustic device shown in FIG. 5. [Figure 7] 1 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. [Figure 8A] FIG. 8 is a schematic diagram of a sound field distribution of sound pressure levels of low and medium frequencies of the acoustic device shown in FIG. 7. [Figure 8B] FIG. 8 is a schematic diagram of a sound field distribution of high-frequency sound pressure levels of the acoustic device shown in FIG. 7. [Figure 9] 1 is a schematic diagram of an acoustic device having a sound absorbing structure installed therein, according to some embodiments of the present disclosure. [Figure 10]10A and 10B are diagrams illustrating the sound absorption effect when an acoustic device according to some embodiments of the present specification uses a metal micro-perforated plate and a non-metal micro-perforated plate, respectively. [Figure 11] 10A and 10B are frequency response curve diagrams for acoustic devices according to some embodiments of the present disclosure when using a metallic micro-perforated plate and a non-metallic micro-perforated plate, respectively. [Figure 12] FIG. 10 is a frequency response curve diagram of the second acoustic hole measured when a 025HY type gauze is placed on the side of the micro-perforated plate facing the vibrating membrane and when no gauze is placed, according to some examples of the present specification. [Figure 13] FIG. 10 is a curve diagram of sound absorption coefficient for micro-perforated plate sound absorbing structures with different cavity heights, according to some embodiments of the present disclosure. [Figure 14] FIG. 10 is a comparison diagram of the change trend of the maximum sound absorption coefficient and the change trend of the 0.5 sound absorption octave for different cavity heights according to some examples herein. [Figure 15] 10A and 10B are diagrams illustrating the sound absorption effect of micro-perforated plates with through-hole diameters of 0.15 mm and 0.3 mm, respectively, according to some embodiments of the present disclosure. [Figure 16] 3A and 3B are frequency response curves for a micro-perforated plate 351 with a hole diameter of 0.15 mm and a micro-perforated plate 351 with a hole diameter of 0.3 mm, according to some embodiments herein. [Figure 17] 1 is a schematic diagram of an acoustic device having a sound absorbing structure installed therein, according to some embodiments of the present disclosure. [Figure 18] 10A-10C are frequency response curve diagrams of the second acoustic cavity of the acoustic device corresponding to different filling rates of the filler material, according to some embodiments herein. [Figure 19] 1 is a schematic diagram of an acoustic device having a sound absorbing structure installed therein, according to some embodiments of the present disclosure. [Figure 20] FIG. 1 is a schematic diagram of another acoustic device having a sound absorbing structure installed therein, according to some embodiments of the present disclosure. [Figure 21] 1 is a diagram illustrating the internal structure of an acoustic device according to some embodiments of the present disclosure. [Figure 22]1 is a diagram illustrating the internal structure of an acoustic device according to some embodiments of the present disclosure. [Figure 23A] FIG. 4 is a frequency response curve diagram of the second acoustic hole of the acoustic device. [Figure 23B] FIG. 10 is a frequency response curve diagram of another second acoustic hole of the acoustic device. [Figure 24] 1 is a diagram illustrating the internal structure of an acoustic device according to some embodiments of the present disclosure. [Figure 25A] 1 is a diagram illustrating the internal structure of an acoustic device according to some embodiments of the present disclosure. [Figure 25B] FIG. 2 is a diagram illustrating the internal structure of another acoustic device according to some embodiments of the present disclosure. [Figure 26] FIG. 25C is a frequency response curve diagram of the second acoustic hole of the acoustic device shown in FIGS. 25A and 25B. [Figure 27] 1 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. [Figure 28A] 1 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. [Figure 28B] 1 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. [Figure 28C] 1 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. [Figure 29A] 1 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. [Figure 29B] 1 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. [Figure 29C] 1 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. [Figure 30] FIG. 10 is a schematic diagram of an acoustic device according to some other embodiments of the present specification. DETAILED DESCRIPTION OF THE INVENTION

[0027] In order to more clearly describe the technical means of the embodiments of the present application, the drawings necessary for describing the embodiments will be briefly described below. Obviously, the drawings described below are only examples or parts of the embodiments of the present application, and those skilled in the art can apply the present application to other similar scenarios based on these drawings without any creative effort. Unless otherwise clear from the context or described otherwise, the same symbols in the drawings represent the same structures or operations.

[0028] It should be understood that the terms "system," "device," "unit," and / or "module" used herein are ways of distinguishing between various levels of assemblies, elements, components, parts, or structures. However, other terms may be used in place of the above terms if they achieve the same purpose.

[0029] As used herein and in the claims, unless the context clearly dictates otherwise, terms such as "a," "one," "one kind," and / or "the" do not specifically refer to the singular but may include the plural. In general, the terms "comprise" and "containing" merely indicate the inclusion of explicitly identified steps and elements, and these steps and elements are not an exclusive listing, and a method or apparatus may include other steps or elements.

[0030] This application uses flowcharts to describe the operations performed by the system according to the embodiments of this application. It should be understood that the preceding and subsequent operations are not necessarily performed in exact order. Instead, the steps may be performed in reverse order or simultaneously. Also, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0031] FIG. 1 is a schematic diagram of an exemplary ear unit according to some embodiments of the present application. As shown in FIG. 1 , the ear unit 100 (also referred to as the pinna) may include an external auditory canal 101, a concha cavity 102, a concha navicularis 103, a triangular fossa 104, an antihelix 105, a scapha 106, a helix 107, an earlobe 108, a tragus 109, and a crus helix 1071. In some embodiments, an acoustic device can be stably worn by being supported by one or more parts of the ear unit 100. In some embodiments, parts such as the external auditory canal 101, the concha cavity 102, the concha navicularis 103, and the triangular fossa 104 have a certain depth and volume in three-dimensional space, which can meet the wearing needs of the acoustic device. For example, an acoustic device (e.g., an in-ear earphone) may be worn in the external auditory canal 101. In some embodiments, the acoustic device can be worn in parts of the ear unit 100 other than the external auditory canal 101. For example, the acoustic device can be attached to the concha 103, the triangular fossa 104, the antihelix 105, the scaphoid fossa 106, the helix 107, or a combination thereof. In some embodiments, the acoustic device may be attached to the user's earlobe 108 or other locations to improve comfort and reliability when worn. By attaching the acoustic device and transmitting sound through a location other than the ear canal 101 of the ear unit 100, the user's ear canal 101 can be "opened." When a user wears the acoustic device, the acoustic device does not block the user's ear canal 101 (or ear canal or ear canal opening), allowing the user to receive not only sound from the acoustic device but also sound from the environment (e.g., horns, bicycle bells, voices of people around, traffic control, etc.), thereby reducing the likelihood of traffic accidents. In this specification, an acoustic device that does not block the user's ear canal 101 (or ear canal or ear canal opening) when worn by a user may be referred to as an open-type earphone. In some embodiments, based on the structure of the ear portion 100, the acoustic device can be designed to have a structure that fits the ear portion 100, allowing the sound-generating portion of the acoustic device to be worn at different positions on the ear portion.For example, if the acoustic device is an earphone, the earphone may include a suspension structure (e.g., an ear hook) and an audio generating unit, the audio generating unit and the suspension structure may be physically connected, and the suspension structure may conform to the shape of the pinna so that the entire or a portion of the audio generating unit is located in front of the tragus 109 (e.g., the area M3 surrounded by the dotted line in FIG. 1). Also, for example, when a user wears the earphone, the entire or a portion of the audio generating unit may contact the upper part of the ear canal 101 (e.g., the location of one or more parts such as the concha navicularis 103, the triangular fossa 104, the antihelix 105, the scapha 106, the helix 107, and the crus helix 1071). Also, for example, when a user is wearing earphones, the entire or partial structure of the sound generating unit may be located within a cavity formed by one or more parts of the ear unit 100 (e.g., the concha scapula 102, the concha navicularis 103, the triangular fossa 104, etc.) (e.g., the area M1 surrounded by dotted lines in Figure 1, which includes at least the concha navicularis 103 and the triangular fossa 104, and the area M2 including at least the concha navicularis 102).

[0032] Because there may be individual differences among different users, ears may have different shapes, sizes, and other dimensions. For ease of explanation and understanding, unless otherwise specified, this specification primarily uses an ear model having a "standard" shape and dimensions as a reference to further describe the wearing method of an acoustic device on the ear model in different embodiments. For example, a simulator including a head and its (left and right) ears manufactured in accordance with ANSI:S3.36, S3.25, and IEC:60318-7 standards, such as the GRAS 45BC KEMAR, can be used as a reference for wearing an acoustic device, representing a scenario in which most users normally wear an acoustic device. By way of example only, the reference ear may have the relevant characteristics that the vertical axis dimension of the projection of the auricle onto the sagittal plane is within the range of 49.5 mm to 74.3 mm, and the sagittal axis dimension of the projection of the auricle onto the sagittal plane is within the range of 36.6 mm to 55 mm. Therefore, in this application, the terms "worn by a user," "in a worn state," and "in a worn state" may refer to the acoustic device described herein being worn in the ear section of the simulator. Naturally, in consideration of individual differences among different users, the structure, shape, size, thickness, etc. of one or more parts of the ear section 100 may have certain differences, and the acoustic device may be designed differently to meet the needs of different users. These differentiated designs may be adapted to different ear sections by having different ranges of value for characteristic parameters of one or more parts of the acoustic device (e.g., the sound generating section, ear hook, etc.)

[0033] In fields such as medicine and anatomy, three basic cutting planes of the human body—the sagittal plane, the coronal plane, and the horizontal plane—and three basic axes—the sagittal axis, the coronal axis, and the vertical axis—can be defined. The sagittal plane refers to a cutting plane perpendicular to the ground along the front-to-back direction of the body, dividing the body into two parts, the left and the right. The coronal plane refers to a cutting plane perpendicular to the ground along the left-to-right direction of the body, dividing the body into two parts, the front and the back. The horizontal plane refers to a cutting plane parallel to the ground along the up-down direction of the body, dividing the body into two parts, the top and the bottom. Accordingly, the sagittal axis refers to an axis perpendicular to the coronal plane along the front-to-back direction of the body, the coronal axis refers to an axis perpendicular to the sagittal plane along the left-to-right direction of the body, and the vertical axis refers to an axis perpendicular to the horizontal plane along the up-down direction of the body. Furthermore, the "front side of the ear" described in this application is a concept opposite to the "rear side of the ear," the former referring to the side of the ear opposite the head, and the latter referring to the side of the ear facing the head. Looking at the ear of the simulator along the coronal axis of the human body, a schematic diagram of the front profile of the ear is obtained as shown in Figure 1.

[0034] FIG. 2 is an exemplary structural diagram of an acoustic device according to some embodiments of the present disclosure.

[0035] As shown in FIG. 2, the acoustic device 10 may include a sound generating unit 11 and a suspension structure 12.

[0036] In some embodiments, the acoustic device 10 may include, but is not limited to, an air-conduction acoustic device and a bone-conduction acoustic device. In some embodiments, the acoustic device 10 may be combined with products such as glasses, a head-mounted acoustic device, a head-mounted display, or an AR / VR helmet. In some embodiments, the acoustic device 10 may include a low-frequency (e.g., 30 Hz to 150 Hz) speaker, a mid-low-frequency (e.g., 150 Hz to 500 Hz) speaker, a mid-high-frequency (e.g., 500 Hz to 5 kHz) speaker, a high-frequency (e.g., 5 kHz to 16 kHz) speaker, or a full-frequency (e.g., 30 Hz to 16 kHz) speaker, or any combination thereof. The terms "low frequency," "high frequency," etc., used herein, generally refer to a range of frequencies, and different application scenarios may have different distinctions. For example, a crossover frequency may be determined, with the low frequency representing the frequency range below the crossover frequency and the high frequency representing the frequency range above the crossover frequency. The crossover frequency may be any value within the audible range of the human ear, such as 500 Hz, 600 Hz, 700 Hz, 800 Hz, 1000 Hz, etc.

[0037] As shown in FIG. 2, the acoustic device 10 may include a sound generating unit 11 and a suspension structure 12.

[0038] In some embodiments, the acoustic device 10 may have the sound-generating unit 11 attached to the user's body (e.g., the head, neck, or upper torso of a human body) by a suspension structure 12. In some embodiments, the acoustic device 10 may have the sound-generating unit 11 fixed by the suspension structure 12 in a position near the ear but not blocking the ear canal.

[0039] In some embodiments, the suspension structure 12 may have one end connected to the sound-generating unit 11 and the other end extending along the boundary between the user's ear 100 and the head. In some embodiments, the suspension structure 12 may have an arc-shaped structure that fits around the user's auricle 100 so as to be suspended from the user's auricle 100. For example, the suspension structure 12 may have an arc-shaped structure that fits around the boundary between the user's head and auricle 100 so as to be hung between the user's auricle 100 and the head. In some embodiments, the suspension structure 12 may have a clamping structure that fits around the user's auricle 100 so as to be clamped to the user's auricle 100. In some embodiments, the suspension structure 12 may include, but is not limited to, a suspension structure, an elastic band, or the like, to better secure the audio device 10 to the user and prevent it from falling off during use. In some embodiments, the acoustic device 10 may not include a suspension structure 12, and the sound-generating unit 11 may be fixed near the user's pinna 100 in a suspended or clamped manner.

[0040] For example, when the acoustic device 10 is worn, the suspension structure 12 may be hung between the back of the user's auricle 100 and the head, and the sound-generating unit 11 may be in contact with the front of the user's auricle 100 (e.g., region M3 in FIG. 1 ) or the auricle 100 (e.g., regions M1 and M2 in FIG. 1 ), and the suspension structure 12 or a combination of the suspension structure 12 and the sound-generating unit 11 may apply a pressing force to the front of the auricle 100 or the auricle 100. The sound-generating unit 11 may be pressed against the front of the auricle 100 or regions where the cavity of the concha 102, the navicularis concha 103, the triangular fossa 104, the antihelix 105, etc. are located under the action of the pressing force so as not to block the auditory canal opening 101 of the auricle 100 when the acoustic device 10 is worn.

[0041] The sound generating unit 11 can generate sound and input it into the user's ear canal. In some embodiments, the sound generating unit 11 may have a regular or irregular shape, such as a ring shape, an ellipse shape, a racetrack shape, a polygonal shape, a U-shape, a V-shape, or a semicircular shape, so that it can be directly hung on the user's auricle 100. In some embodiments, the sound generating unit 11 may have a major axis direction Y, a minor axis direction Z, and a thickness direction X, which are perpendicular to each other. The major axis direction Y may be defined as the direction in which the extension dimension is large in the shape of a two-dimensional projection plane of the sound generating unit 11 (e.g., a projection of the sound generating unit 11 onto a plane on which the inner surface is located or a projection onto a sagittal plane) (e.g., when the projection shape is rectangular or approximately rectangular, the major axis direction is the longitudinal direction of the rectangle or approximately rectangular). For convenience of explanation, the projection of the sound generating unit onto the sagittal plane will be described in this specification. The minor axis direction Z may be defined as the direction perpendicular to the major axis direction Y in the shape of the projection of the sound generating unit 11 onto the sagittal plane (for example, if the projection shape is rectangular or approximately rectangular, the minor axis direction is the width direction of the rectangle or approximately rectangular). The thickness direction X may be defined as the direction perpendicular to the sagittal plane, and for example, coincides with the coronal axis direction, both of which face the left-right direction of the body.

[0042] In some embodiments, the sound-generating unit 11 may include a diaphragm (not shown) and a housing 111 that accommodates the diaphragm. The housing 111 (or the sound-generating unit 11) may be connected to the suspension structure 12. In some embodiments, the diaphragm is an element that can receive an excitation signal, convert it into sound waves, and output the sound. The diaphragm generates sound by generating corresponding mechanical vibrations in response to the excitation signal (e.g., an electrical signal). In some embodiments, the sound-generating unit 11 may further include a voice coil and a magnetic circuit assembly. One end of the voice coil is fixedly connected to the diaphragm, and the other end is inserted into a magnetic gap formed by the magnetic circuit assembly. By supplying a current to the voice coil, the voice coil vibrates within the magnetic gap, causing the diaphragm to vibrate and generate sound waves.

[0043] In some embodiments, the diaphragm may divide the housing 111 into a first acoustic cavity and a second acoustic cavity of the acoustic device, a first acoustic hole 112 formed in the housing 111 being acoustically coupled to the first acoustic cavity and allowing sound generated in the first acoustic cavity to escape from the housing 111, and a second acoustic hole 113 formed in the housing 111 being acoustically coupled to the second acoustic cavity and allowing sound generated in the second acoustic cavity to escape from the housing 111. In some embodiments, the first acoustic hole 112 may be located on a side of the housing 111 that is close to or facing the pinna 100, such that the first acoustic hole is directed toward or close to the ear canal opening, and the first acoustic hole 112 allows sound generated by the diaphragm to escape from the housing 111 and then transmit to the ear canal so that the sound can be heard by the user. The sound emitted through the first acoustic hole 112 can also propagate outside the acoustic device 10 and the pinna 100, thereby forming a first sound leakage in the far field. In some embodiments, a second acoustic hole 113 is formed on another side of the housing 111 (e.g., the side away from the user's ear canal or the side opposite the user's ear canal). The second acoustic hole 113 is farther from the ear canal opening than the first acoustic hole 112, and the sound propagated through the second acoustic hole 113 forms a second sound leakage in the far field. The intensity of the first sound leakage and the intensity of the second sound leakage are similar, and the phases of the first sound leakage and the second sound leakage are (substantially) opposite each other, thereby canceling out each other in the far field and helping to reduce sound leakage in the far field of the acoustic device 10. For more details about the sound generating unit 11, please refer to the contents of other parts of this specification, such as Figures 3A and 3B and the corresponding specifications.

[0044] In some embodiments, when the user wears the acoustic device 10, the sound generating unit 11 may be worn near the user's ear canal 101 at a position that does not block the ear canal opening 101. In some embodiments, the projection of the sound generating unit 11 onto the sagittal plane may not cover the user's ear canal opening 101 when the acoustic device 10 is worn. For example, the projection of the sound generating unit 11 onto the sagittal plane may be on both the left and right sides of the head, in front of the tragus on the sagittal axis of the human body (e.g., the position indicated by the solid-line box A in FIG. 2). In this case, the sound generating unit 11 is located in front of the user's tragus, the long axis of the sound generating unit 11 is vertical or nearly vertical, the projection of the short axis direction Z onto the sagittal plane coincides with the sagittal axis direction, the projection of the long axis direction X onto the sagittal plane coincides with the vertical axis direction, and the thickness direction Z is perpendicular to the sagittal plane. Furthermore, for example, the projection of the sound generating unit 11 onto the sagittal plane may be at the antihelix 105 (e.g., the position indicated by the dotted-line box C in FIG. 2). In this case, at least a portion of the sound generating unit 11 is located in the antihelix 105, the long axis of the sound generating unit 11 is horizontal or approximately horizontal, the projection of the long axis direction Y of the sound generating unit 11 onto the sagittal plane coincides with the sagittal axis direction, the projection of the short axis direction Z onto the sagittal plane coincides with the vertical axis direction, and the thickness direction X is perpendicular to the sagittal plane. In this way, the sound generating unit 11 is prevented from blocking the auditory canal, freeing both ears of the user, and also increasing the contact area between the sound generating unit 11 and the ear unit 100, thereby improving the wearing comfort of the acoustic device 10. In some embodiments, when worn, the projection of the sound generating unit 11 onto the sagittal plane may cover or at least partially cover the user's auditory canal opening 101. For example, the projection of the sound generating unit 11 onto the sagittal plane may be within the cavity of the concha 102 (e.g., the position indicated by the dotted line frame B in FIG. 2 ) and may contact the crus helix 1071 and / or the helix 107. At this time, at least a portion of the sound generating unit 11 is located within the cavity of the concha 102, the sound generating unit 11 is in an inclined state, the projection of the short axis direction Z of the sound generating unit 11 onto the sagittal plane may have a certain angle with the sagittal axis direction, i.e., the short axis direction Z is also installed at an inclination, the projection of the long axis direction Y onto the sagittal plane may have a certain angle with the sagittal axis direction, i.e., the long axis direction Y is also installed at an inclination, and the thickness direction X is perpendicular to the sagittal plane.

[0045] 3A, in the worn state, the end FE of the sound generating unit 11 may be inserted into the cavity of the concha. Preferably, the sound generating unit 11 and the suspension structure 12 may be arranged to jointly hold the pinna 100 from both the front and rear of the region of the pinna 100 corresponding to the cavity of the concha 102, in order to increase the resistance of the acoustic device 10 to falling off the ear and further improve the stability of the acoustic device 10 when worn. For example, the end FE of the sound generating unit is pressed into the cavity of the concha in the thickness direction X. Furthermore, for example, the end FE abuts against the cavity of the concha in the major axis direction Y and / or the minor axis direction Z (e.g., abuts against the inner wall of the cavity of the concha facing the end FE). The end FE of the sound generating unit 11 refers to the end of the sound generating unit 11 that is arranged opposite the fixed end connected to the suspension structure 12, and is also referred to as the free end. The sound generating unit 11 may have a regular structure or an irregular structure, but will be described here as an example to further explain the end FE of the sound generating unit 11. For example, if the sound generating unit 11 has a rectangular parallelepiped structure, the end wall surface of the sound generating unit 11 is a plane, and in this case, the end FE of the sound generating unit 11 is an end side wall installed opposite the fixed end of the sound generating unit 11 connected to the hanging structure 12. Furthermore, for example, if the sound generating unit 11 is a sphere, an ellipsoid, or an irregular structure, the end FE of the sound generating unit 11 may refer to a specific region away from the fixed end obtained by cutting the sound generating unit 11 along the XZ plane (a plane formed by the minor axis direction Z and the thickness direction X), and the ratio of the dimension of the specific region along the major axis direction Y to the dimension of the sound generating unit along the major axis direction Y may be 0.05 to 0.2.

[0046] 3A and 3B, the ear hook 12 is described as a suspension structure 12 by way of example. In some embodiments, the ear hook 12 may include a first portion 121 and a second portion 122 connected in order, where the first portion 121 may be hung between the rear-medial surface of the user's auricle 100 and the head, and the second portion 122 extends toward the anterior-lateral surface of the ear (the side opposite the human head along the coronal axis of the ear) and is connected to the sound-generating unit 11, thereby fixing the sound-generating unit 11 in a position near the user's ear canal without blocking the ear canal opening. In some embodiments, a first acoustic hole may be formed on the side of the sound-generating unit 11 facing the auricle 100, so that sound generated by the diaphragm is emitted from the sound-generating unit 11 and then transmitted to the user's ear canal opening 101.

[0047] 3B , in some embodiments, the inner surface IS of the housing is formed with a first acoustic hole 112 communicating with the first acoustic cavity, thereby allowing sound generated in the first acoustic cavity to escape from the housing and then travel to the ear canal so that the sound can be heard by the user. Another side of the housing (e.g., the upper wall US or the lower wall LS) may be formed with one or more second acoustic holes 113 communicating with the second acoustic cavity, thereby allowing sound generated in the second acoustic cavity to escape from the housing and then interfere with and cancel out the sound emitted from the first acoustic hole 112 in the far field. In some embodiments, the second acoustic hole 113 is located farther from the ear canal than the first acoustic hole 112, thereby reducing anti-phase cancellation at the listening position between the sound output from the second acoustic hole 113 and the sound output from the first acoustic hole 112.

[0048] By inserting at least a portion of the sound-generating unit 11 into the cavity of the concha, it is possible to increase the listening volume at the listening position (e.g., the opening of the ear canal), particularly the listening volume for mid- and low-frequency sounds, while still maintaining an excellent effect of canceling sound leakage in the far field. Simply by way of illustrative example, when the entire or partial structure of the sound-generating unit 11 is inserted into the cavity of the concha 102, the sound-generating unit 11 and the cavity of the concha 102 form a structure similar to a cavity (hereinafter abbreviated as a "similar cavity structure"). In the embodiments of the specification, the "similar cavity structure" may be understood as a semi-enclosed structure surrounded by the side walls of the sound-generating unit 11 and the structure of the cavity of the concha 102, and this semi-enclosed structure does not completely seal and isolate the listening position (e.g., the opening of the ear canal) from the external environment, but has a leaking structure (e.g., an opening, a gap, a tube, etc.) that acoustically communicates with the external environment. When a user wears the acoustic device 10, one or more first acoustic holes 112 are provided on the side of the housing of the sound-generating unit 11 that is close to or facing the user's ear canal, and one or more second acoustic holes 113 may be provided on another side wall of the housing of the sound-generating unit 11 (e.g., a side wall that is away from or opposite the user's ear canal), and the first acoustic holes 112 are acoustically coupled to the first acoustic cavity of the acoustic device 10, and the second acoustic holes 113 are acoustically coupled to the second acoustic cavity of the acoustic device 10. For example, if the sound generating unit 11 includes one first acoustic hole 112 and one second acoustic hole 113, the sound output from the first acoustic hole 112 and the sound output from the second acoustic hole 113 can be regarded as approximately two sound sources, and the sounds from these two sound sources have opposite phases. The sound generating unit 11 and the inner wall corresponding to the cavity of the concha 102 form a similar cavity structure, and the sound source corresponding to the first acoustic hole 112 is located within the similar cavity structure, and the sound source corresponding to the second acoustic hole 113 is located outside the similar cavity structure, forming the acoustic model shown in Figure 4.

[0049] As shown in FIG. 4 , the similar cavity structure 402 may include a listening position and at least one sound source 401A. Here, "including" may indicate that at least one of the listening position and the sound source 401A is located inside the similar cavity structure 402, or that at least one of the listening position and the sound source 401A is located at the edge of the similar cavity structure 402. The listening position may correspond to the entrance of the ear canal or inside the ear canal, or may be an acoustic reference point of the ear, such as an ear reference point (ERP) or an eardrum reference point (DRP), or may be an entrance structure leading to the listener. The sound source 401B is located outside the similar cavity structure 402, and the sound sources 401A and 401B, which are out of phase with each other, radiate sounds into the surrounding space, generating sound wave interference cancellation and achieving a sound leakage cancellation effect. Specifically, because sound source 401A is surrounded by similar cavity structure 402, most of the radiated sound reaches the listening position either directly or by reflection. In contrast, without similar cavity structure 402, most of the sound radiated from sound source 401A would not reach the listening position. Therefore, by installing the cavity structure, the volume of the sound reaching the listening position is significantly increased. Also, only a small portion of the anti-phase sound radiated from anti-phase sound source 401B outside similar cavity structure 402 enters similar cavity structure 402 through leakage structure 403 of similar cavity structure 402. This corresponds to the generation of secondary sound source 401B' in leakage structure 403, and the intensity of secondary sound source 401B' is significantly lower than that of sound source 401B and sound source 401A. The sound generated by the secondary sound source 401B' experiences less anti-phase cancellation in the cavity relative to the sound source 401A, which significantly increases the listening volume at the listening position.Regarding sound leakage, when sound source 401A radiates sound to the outside from cavity leaking structure 403, this is equivalent to secondary sound source 401A' being generated in leaking structure 403, and since almost all of the sound radiated from sound source 401A is output from leaking structure 403 and the scale of similar cavity structure 402 is much smaller (at least one order of magnitude smaller) than the spatial scale for evaluating sound leakage, it is considered that the strength of secondary sound source 401A' is about the same as the strength of sound source 401A and still maintains the same sound leakage reduction effect.

[0050] In some embodiments of the present specification, a portion or the entire structure of the sound generating unit 11 is inserted into the cavity of the concha, thereby forming a similar cavity structure communicating with the outside between the sound generating unit 11 and the contours of the cavity of the concha. Furthermore, the first acoustic hole 112 can be positioned on the housing of the sound generating unit toward the opening of the user's ear canal and close to the edge of the cavity of the concha to form the acoustic model shown in FIG. 4, thereby enabling a user to hear a higher listening volume when wearing the audio device. In other words, by specially designing the structure and wearing method of the sound generating unit, the sound generating unit 11 can have excellent sound output efficiency. Here, excellent sound output efficiency may be understood as meaning that even when a small input signal is provided to the sound generating unit 11 (e.g., a small input voltage or input power is provided to the diaphragm of the sound generating unit 11), the sound generating unit can still provide a sufficiently high volume to the user, i.e., generate a sound pressure exceeding a certain threshold, within the user's ear canal.

[0051] In some embodiments, the sound generating unit may have a different mounting method than the one inserted into the cavity of the concha in Fig. 3A, and excellent sound output efficiency may be achieved. Hereinafter, a detailed description will be given taking the acoustic device 10 shown in Fig. 5 as an example.

[0052] FIG. 5 is a schematic diagram of an exemplary wearing of an acoustic device according to some other embodiments of the present disclosure.

[0053] In some embodiments, when the acoustic device 10 is in a worn state, the sound generating unit 11 may at least partially cover the antihelix region of the user. In this case, the sound generating unit 11 is located above the cavity of the concha 102 and the ear canal, leaving the ear canal open. In some embodiments, the housing of the sound generating unit 11 may include at least one first acoustic hole 112 and a second acoustic hole 113. The first acoustic hole 112 is acoustically coupled to a first acoustic cavity of the acoustic device 10, and the second acoustic hole 113 is acoustically coupled to a second acoustic cavity of the acoustic device 10. The sound output from the first acoustic hole 112 and the sound output from the second acoustic hole 113 can be considered to be substantially two sound sources, and the sounds from these two sound sources are out of phase with each other. When a user wears the acoustic device, the first acoustic hole 112 is located on a side wall of the sound generating unit 11 facing or close to the user's ear canal, and the second acoustic hole 113 is located on a side wall of the sound generating unit 11 facing away from or opposite the user's ear canal. In this case, the sound generating unit 11 and the user's auricle 100 can be regarded as a baffle structure. The sound source corresponding to the first acoustic hole 112 is located on one side of the baffle, and the sound source corresponding to the second acoustic hole 113 is located on the other side of the baffle, bypassing the sound generating unit 11 and the user's auricle 100, thereby forming the acoustic model shown in FIG. 6.

[0054] As shown in Figure 6, when a baffle is installed between sound source A1 and sound source A2, in the near field, the sound field of sound source A2 can only interfere with the sound waves of sound source A1 at the listening position by bypassing the baffle, which corresponds to an increase in the acoustic distance from sound source A2 to the listening position. Therefore, assuming that sound sources A1 and A2 have the same amplitude, the amplitude difference between the sound waves of sound source A1 and sound source A2 at the listening position is greater than when a baffle is not installed. This reduces the degree to which the sounds of the two paths cancel each other out at the listening position, resulting in a higher volume at the listening position. In the far field, the sound waves generated by sound source A1 and sound source A2 can interfere over a wide spatial range without bypassing the baffle (similar to when there is no baffle), so there is no significant increase in sound leakage in the far field compared to when there is no baffle. Therefore, by placing a baffle structure around one of sound sources A1 and A2, the volume at the near-field listening position can be significantly increased without significantly increasing the sound leakage volume in the far field.

[0055] In some embodiments of the present specification, at least a portion of the sound generating unit 11 is covered by the antihelix region of the user, so that the user can hear a higher listening volume when wearing the sound device. In this manner, the sound generating unit 11 can have excellent sound output efficiency.

[0056] FIG. 7 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. As shown in FIG. 7, the acoustic device 200 may include a housing 210 and a diaphragm 220. The diaphragm 220 may be disposed within a cavity defined by the housing 210, and a first acoustic cavity 230 and a second acoustic cavity 240 for emitting sound are disposed on the front and rear sides of the diaphragm 220, respectively. The housing 210 may be provided with a first acoustic hole 211 and a second acoustic hole 212, and the first acoustic cavity 230 may be acoustically coupled to the first acoustic hole 211, and the second acoustic cavity 240 may be acoustically coupled to the second acoustic hole 212. When a user wears the acoustic device 200, the acoustic device 200 may be positioned near the user's auricle, and the first acoustic hole 211 may face the user's ear canal. The second acoustic hole 212 may be farther from the ear canal opening than the first acoustic hole 211, and the distance between the first acoustic hole 211 and the ear canal opening may be smaller than the distance between the second acoustic hole 212 and the ear canal opening.

[0057] In some embodiments, the front and rear sides of the vibrating membrane 220 can serve as sound wave generating structures, respectively, and generate a pair of sound waves (or sounds) with equal amplitudes and (approximately) opposite phases. In some embodiments, the pair of sound waves with equal amplitudes and opposite phases can be radiated to the outside from the first acoustic hole 211 and the second acoustic hole 212, respectively. When the vibrating membrane 220 outputs sound waves, the sound wave (also referred to as the first sound wave) on the front side of the vibrating membrane 220 can pass through the first acoustic cavity 230 and radiate from the first acoustic hole 211, and the sound wave (also referred to as the second sound wave) on the rear side of the vibrating membrane 220 can pass through the second acoustic cavity 240 and radiate from the second acoustic hole 212, thereby forming a dual sound source including the first acoustic hole 211 and the second acoustic hole 212. The dual sound sources can interfere and cancel each other out at a spatial point (e.g., in the far field), thereby effectively improving the sound leakage problem in the far field of the acoustic device 200.

[0058] 8A is a schematic diagram of the sound field distribution of mid-low frequency sound pressure levels of the acoustic device shown in FIG. 7. As shown in FIG. 8A, within the mid-low frequency range (e.g., 50 Hz to 1 kHz), the sound field distribution in the pinna 100 area of ​​the acoustic device 200 exhibits excellent directionality. The high sound pressure sound field area is distributed close to the ear canal opening 101, and the low sound pressure sound field area is distributed away from the ear canal opening 101, resulting in a significant sound leakage reduction effect. That is, within the mid-low frequency range, the dual sound sources formed by the first acoustic hole 211 and the second acoustic hole 212 of the acoustic device 200 output sound waves that are opposite or nearly opposite in phase, and based on the principle of antiphase cancellation of sound waves, the two sound waves cancel each other out in the far field, thereby achieving the effect of reducing sound leakage in the far field.

[0059] 8B is a schematic diagram of the sound field distribution of high-frequency sound pressure levels of the acoustic device shown in FIG. 7. As shown in FIG. 8B, the sound field distribution of the acoustic device 200 is disturbed within the high frequency range. In some embodiments, within the high frequency range (e.g., 1500 Hz to 20 kHz), the wavelengths of the first and second sound waves are shorter than those within the mid-low frequency range. In this case, the distance between the dual sound sources formed by the first acoustic hole 211 and the second acoustic hole 212 is not negligible relative to the wavelength, so the sound waves emitted from the two sound sources cannot be canceled out. This makes it difficult to ensure the effect of reducing sound leakage in the far field of the sound generating unit within the high frequency range, and may even increase sound leakage and cause a disturbance in the sound field distribution of the sound generating unit. As a mere illustrative example, due to the distance between the first acoustic hole 211 and the second acoustic hole 212, the acoustic distance of the first sound wave to a particular spatial point (e.g., the far field) is different from the acoustic distance of the second sound wave to the particular spatial point, so that the phase difference between the first sound wave and the second sound wave at the spatial point is small (e.g., the phases are the same or close), and the first sound wave and the second sound wave cannot interfere and cancel each other out at the spatial point, but overlap at the spatial point, which may increase the amplitude of the sound waves at the spatial point and increase sound leakage.

[0060] In some embodiments, sound waves emanating from both the front and rear sides of the vibrating membrane 220 may pass through the acoustic transmission structure before being radiated to the outside through the first acoustic hole 211 and / or the second acoustic hole 212. The acoustic transmission structure may refer to an acoustic path through which sound waves pass when radiating from the vibrating membrane 220 to the external environment. In some embodiments, the acoustic transmission structure may include the housing 210 between the vibrating membrane 220 and the first acoustic hole 211 and / or the second acoustic hole 212. In some embodiments, the acoustic transmission structure may include an acoustic cavity (including the first acoustic cavity 230 and the second acoustic cavity 240). In some embodiments, the acoustic transmission structure may be acoustically connected to the first acoustic hole 211 and / or the second acoustic hole 212, and the first acoustic hole 211 and / or the second acoustic hole 212 may be part of the acoustic transmission structure. In some embodiments, if the sound waves generated by the vibrating membrane 220 are not emitted in the desired direction or are away from the ear canal opening, the sound waves may be guided in the desired direction by a sound conduit and then emitted to the external environment using the first sound hole 211 and / or the second sound hole 212. Thus, the sound transmission structure may further include a sound conduit.

[0061] In some embodiments, the acoustic transmission structure may have a resonant frequency, and when the frequency of the sound waves generated by the vibrating membrane 220 is near the resonant frequency, the acoustic transmission structure may resonate. Under the action of the acoustic transmission structure, the sound waves in the acoustic transmission structure also resonate, which may change the frequency components of the transmitted sound waves (e.g., add an additional resonant peak to the transmitted sound waves) or change the phase of the sound waves transmitted in the acoustic transmission structure. Compared to when there is no resonance, the phase and / or amplitude of the sound waves radiated from the first acoustic hole 211 and / or the second acoustic hole 212 change, and the change in phase and / or amplitude may cause a disturbance in the sound field near the resonant frequency of the dual sound source structure and affect the interference cancellation effect at the spatial point of the sound waves radiated from the first acoustic hole 211 and the second acoustic hole 212. For example, when resonance occurs, the phase difference between the sound waves emitted from the first acoustic hole 211 and the second acoustic hole 212 changes. For example, if the phase difference between the sound waves emitted from the first acoustic hole 211 and the second acoustic hole 212 is small (for example, less than 120°, less than 90°, or 0), the interference cancellation effect of the sound waves at the spatial point decreases, making it difficult to achieve a sound leakage reduction effect. Alternatively, sound waves with small phase differences may overlap at the spatial point, increasing the amplitude of sound waves near the resonance frequency at the spatial point (for example, in the far field), which may increase far-field sound leakage from the acoustic device 200. Furthermore, for example, the resonance may increase the amplitude of the transmitted sound waves near the resonance frequency of the acoustic transmission structure (e.g., expressed as a resonance peak near the resonance frequency), causing a disturbance in the sound field near the resonance frequency of the dual sound source structure. In this case, the difference in amplitude between the sound waves emitted from the first acoustic hole 211 and the second acoustic hole 212 is large, reducing the effect of interference cancellation at the spatial point of the sound waves, making it difficult to achieve a sound leakage reduction effect. In some embodiments, if parameters such as the volumes of the first acoustic cavity 230 and the second acoustic cavity 240 of the sound generating unit, and the sizes and heights of the first acoustic hole 211 and the second acoustic hole 212 are different, the first acoustic cavity 230 and the second acoustic cavity 240 (which may also be referred to as acoustic cavities for short) may have different resonance frequencies, i.e., the resonance frequencies of the acoustic transmission structures on the front and rear sides of the acoustic device 200 may be different.In some embodiments, the blocking of high frequency sound waves by structures such as the pinna 100 and / or the effect on the reflection of sound waves can cause disruptions in the sound field distribution of the acoustic device 200 .

[0062] 7 to 8B, the dual sound source may cause a disturbed sound field in the high frequency range, resulting in a poor sound leakage reduction effect and possibly even increasing sound leakage. To improve the sound leakage reduction effect of the acoustic device in the high frequency range, a sound absorbing structure may be installed in the second acoustic cavity of the acoustic device. The sound absorbing structure absorbs sound waves within a target frequency range of the second acoustic cavity to reduce or avoid the overlap of the first and second sound waves at a specific spatial point (e.g., the far field) outside the acoustic device, thereby reducing the amplitude of the sound waves within the target frequency range at the spatial point, adjusting the directionality of the acoustic device and achieving the effect of reducing sound leakage in the far field.

[0063] The sound-absorbing structure refers to a structure that has an absorbing effect on sound waves within a specific frequency band (e.g., within a target frequency range). The sound-absorbing structure is coupled to the second acoustic cavity and can absorb sound that passes through the second acoustic cavity within the target frequency range and is radiated to the second acoustic hole. Accordingly, within the target frequency range, the sound pressure level at the second acoustic hole when the sound-absorbing structure is not installed may be greater than the sound pressure level at the second acoustic hole when the sound-absorbing structure is installed.

[0064] In some embodiments, the target frequency range may include a frequency range near the resonant frequency of the second acoustic cavity. The sound-absorbing structure absorbs sound waves near the resonant frequency of the second acoustic cavity to prevent changes in the phase and / or amplitude of the second sound waves due to resonance near the resonant frequency of the second acoustic cavity and further reduces the amplitude of the sound waves near the resonant frequency, thereby ensuring the sound leakage reduction effect of the acoustic device 200. In some embodiments, the resonant frequency may be in a mid-to-high frequency band, for example, 2 kHz to 8 kHz. Accordingly, the target frequency range may include frequencies in the mid-to-high frequency band. For example, the target frequency range may be in a range from 1 kHz to 10 kHz. In some embodiments, in the high frequency range, the distance between the dual sound sources formed by the first and second acoustic holes is not negligible relative to the wavelength. Therefore, the first and second sound waves may not interfere and cancel each other out at a spatial point, but may overlap at a spatial point, increasing the amplitude of the sound waves at that spatial point. In some embodiments, the target frequency range may further include frequencies higher than the resonant frequency to reduce the overlap of the first and second sound waves in the high frequency range, thereby increasing the amplitude of the sound waves. This allows the sound-absorbing structure to absorb sound waves in the high frequency range, reducing or avoiding the overlap of the first and second sound waves at a spatial point, thereby reducing the amplitude of the sound waves in the target frequency range at that spatial point. For example, the target frequency range may be in the range of 1 kHz to 20 kHz. The resonant frequency of the second acoustic cavity may be obtained using various measurement methods. For example, when measuring a frequency response curve of a second acoustic cavity without or without a sound-absorbing structure, the first acoustic hole is left open, and a microphone device is used to measure the frequency response curve at the position of the second acoustic hole (e.g., the microphone device is placed 2 mm to 5 mm in front of the second acoustic hole), and the resonant frequency corresponding to the resonant peak of the frequency response curve is obtained.

[0065] In some embodiments, the acoustic device may have different sound effects at different spatial points by installing a sound-absorbing structure (e.g., the position of the sound-absorbing structure, the sound-absorbing frequency, etc.). In some embodiments, the resonance of the first acoustic cavity also affects the sound radiation of the second acoustic cavity, causing an extra resonance peak in the frequency response curve measured at the position of the second acoustic hole. Therefore, the target frequency range may include the resonance frequency of the first acoustic cavity to avoid the resonance of the first acoustic cavity from increasing an additional resonance peak in the sound waves transmitted within the second acoustic cavity. In some embodiments, a separate sound-absorbing structure is installed in the first acoustic cavity to absorb sound waves near the resonance frequency of the first acoustic cavity, preventing the sound waves near the resonance frequency of the first acoustic cavity and the sound waves in the same frequency range output from the second acoustic hole from interfering and being reinforced at spatial points (e.g., spatial points), thereby reducing the amplitude of the sound waves near the resonance frequency of the first acoustic cavity received at the spatial points. In some embodiments, the sound absorbing structure may be installed in both the first acoustic cavity and the second acoustic cavity, thereby absorbing sound waves near the resonant frequency of the first and second sound waves and better reducing the amplitude of the sound waves at any spatial point. In some embodiments, the sound absorbing structure may absorb low-frequency sounds in a specific frequency range. For example, a sound absorbing structure may be installed in the second acoustic cavity to reduce low-frequency sounds in a specific frequency range output from the second acoustic hole, preventing the low-frequency sounds in the specific frequency range and the low-frequency sounds in the same frequency range output from the first acoustic hole from interfering and canceling each other at a spatial point (e.g., in the near field), thereby increasing the volume of the sound in the specific frequency range in the near field (i.e., transmitted to the user's ear) of the acoustic device. In some embodiments, the sound absorbing structure may further include sub-sound absorbing structures that absorb sounds in different frequency ranges, for example, mid- to high-frequency sounds and low-frequency sounds, respectively, to absorb sounds in different frequency ranges.

[0066] In some embodiments, in the high-frequency range higher than the resonant frequency of the second acoustic cavity, the wavelength of the high-frequency sound wave is short, so the distance between the two acoustic holes (e.g., the distance between the geometric centers of the two acoustic holes) may affect the phase difference at the spatial point of the sound waves emitted from the two acoustic holes, thereby reducing the sound leakage reduction effect in the high-frequency range of the dual sound source formed by the two acoustic holes. Therefore, in order to reduce the high-frequency output of the second acoustic cavity, the target frequency range may include a high-frequency range higher than the resonant frequency of the second acoustic cavity, so that the sound-absorbing structure can absorb the high-frequency sound waves and improve the problem that the sound leakage reduction effect in the high-frequency range of the dual sound source is not ideal.

[0067] Because the human ear is sensitive to sounds between 3 kHz and 6 kHz within the high frequency range around the resonant frequency, in some embodiments, the target frequency range may include a frequency range between 3 kHz and 6 kHz to achieve more directional and effective sound leakage reduction. In some embodiments, the target frequency range may include a frequency range between 4 kHz and 6 kHz. In some embodiments, the target frequency range may include a range lower than the resonant frequency. For example, because the human ear is most sensitive to sounds around 1 kHz to 3 kHz, the target frequency range may include a frequency range between 1 kHz and 3 kHz. Note that the resonant frequency here mainly refers to the resonant frequency of the second acoustic cavity, and in some embodiments, it may be the resonant frequency of either the second acoustic cavity or the first acoustic cavity, and will hereinafter be abbreviated as resonant frequency.

[0068] Based on the above embodiment, the sound absorbing structure can absorb the first and / or second sound waves in the target frequency range, thereby reducing the amplitude of the sound waves in the target frequency range at the spatial point. For the first and second sound waves outside the target frequency range (e.g., sound waves below the resonant frequency), the first and second sound waves can pass through the acoustic transmission structure and be transmitted to the spatial point, where they can interfere with each other, thereby reducing the amplitude of the sound waves outside the target frequency range at the spatial point. That is, the first and second sound waves outside the target frequency range (or called the first frequency range) can interfere and cancel each other out at a spatial point to achieve the effect of reducing sound leakage from dual sound sources, and the first and / or second sound waves within the target frequency range (or called the second frequency range) can be absorbed by the sound-absorbing structure, thereby reducing or avoiding the first and / or second sound waves from interfering and being reinforced at the spatial point, or lowering or absorbing additional resonance peaks generated by the first or second sound waves under the action of the acoustic transmission structure to reduce the amplitude of the sound waves within the target frequency range at the spatial point. As a result, in the embodiments of the present specification, by installing a sound-absorbing structure, the acoustic device can output first and second sound waves in a first frequency range, and the output of sound waves near the resonant frequency of the acoustic transmission structure of the acoustic device (e.g., the second acoustic hole) or sound waves with frequencies higher than the resonant frequency can be reduced, ensuring interference cancellation in the first frequency range of the acoustic device, and reducing or avoiding the increase in the amplitude of sound waves in the second frequency range at a spatial point (e.g., the far field), thereby adjusting the directionality of the acoustic device and ensuring the sound leakage reduction effect across the entire frequency band.

[0069] The sound absorption effect of a sound-absorbing structure is the amount of sound that the sound-absorbing structure can absorb in a target frequency range and can be expressed as the sound pressure level of the sound. For example, the sound absorption effect of a sound-absorbing structure can be expressed as the difference between sound pressure levels measured at the same frequency and at the same position corresponding to the second acoustic cavity when the sound-absorbing structure is present and when the sound-absorbing structure is absent in the target frequency range. By way of example only, the difference between the sound pressure levels of the second acoustic hole when the sound-absorbing structure is present and when the sound-absorbing structure is absent can be expressed as the difference between the sound pressure levels of the second acoustic cavity when the sound-absorbing structure is present and when the sound-absorbing structure is absent. For example only, the sound pressure levels of the second acoustic hole when the sound-absorbing structure is present and when the sound-absorbing structure is absent can be measured by placing a measuring microphone directly facing the second acoustic hole at a distance of approximately 2 mm to 5 mm from the second acoustic hole and measuring the sound pressure levels of the second acoustic hole when the sound-absorbing structure is present and when the sound-absorbing structure is absent. The measurement frequency is near the resonant frequency of the second acoustic cavity or near 1 kHz. In some embodiments, the difference between the sound pressure levels measured at the same frequency at the same position in the second acoustic cavity with and without the sound absorbing structure may be 3 dB or more. For example, the difference between the sound pressure levels of the second acoustic hole measured at the same frequency with and without the sound absorbing structure may be 3 dB or more. In some embodiments, the target frequency range may be referred to as the sound absorption bandwidth of the sound absorbing structure. When the sound absorption bandwidth is in the range of 3 kHz to 6 kHz, the sound absorbing structure can effectively absorb sound waves in the range of 3 kHz to 6 kHz, and the sound absorption effect is 3 dB or more, thereby improving sound leakage of the acoustic device in the range of 3 kHz to 6 kHz. In some embodiments, the sound absorption effect of the sound absorbing structure may be 5 dB or more within the target frequency range to further reduce sound leakage of the acoustic device. In some embodiments, the sound absorption effect of the sound absorbing structure may be 6 dB or more within the target frequency range to further reduce sound leakage of the acoustic device. In some embodiments, in order to further reduce sound leakage from the acoustic device, the sound absorbing effect of the sound absorbing structure may be 8 dB or more within the target frequency range.In some embodiments, the sound absorbing effect of the sound absorbing structure may be 10 dB or more within the target frequency range to further reduce sound leakage from the acoustic device. In some embodiments, the sound absorbing effect of the sound absorbing structure may be different within different frequency ranges. For example, within the range of 3 kHz to 6 kHz, the sound absorbing effect of the sound absorbing structure may be 3 dB or more. Also, within the range of 4 kHz to 6 kHz, the sound absorbing effect of the sound absorbing structure may be 6 dB or more. Furthermore, within the range of 5 kHz to 6 kHz, the sound absorbing effect of the sound absorbing structure may be 8 dB or more, thereby more effectively reducing sound leakage within higher frequency ranges.

[0070] The frequency response curve of the second acoustic cavity has a resonant peak at a specific frequency (e.g., a resonant frequency), and the vibration amplitude at the resonant frequency is large. Therefore, in order to achieve a high sound leakage reduction effect at the resonant frequency of the second acoustic cavity, the sound absorbing structure needs to absorb more sound at the resonant frequency. Therefore, in some embodiments, the sound absorbing effect of the sound absorbing structure for sound at the resonant frequency or sound whose vibration frequency is near the resonant frequency is 14 dB or more. In this way, sound waves at or near the resonant frequency of the second acoustic cavity are effectively absorbed by the sound absorbing structure, reducing or preventing the sound waves from resonating near the resonant frequency under the action of the acoustic cavity. This reduces the sound leakage reduction effect at a spatial point due to changes in the amplitude difference and phase difference between the first sound wave and the second sound wave near the resonant frequency, thereby reducing or avoiding the situation where the two sets of sounds no longer cancel each other out but instead interfere and reinforce each other, thereby reducing sound leakage at a spatial point in the far field of the acoustic device. In some embodiments, to further reduce sound leakage from an acoustic device, the sound absorbing structure has a sound absorption effect of 16 dB or more for sounds at a resonant frequency or sounds with vibration frequencies near the resonant frequency. In some embodiments, to further reduce sound leakage from an acoustic device, the sound absorbing structure has a sound absorption effect of 18 dB or more for sounds at a resonant frequency or sounds with vibration frequencies near the resonant frequency. In some embodiments, to further reduce sound leakage from an acoustic device, the sound absorbing effect of the sound absorbing structure has a sound absorption effect of 20 dB or more for sounds at a resonant frequency or sounds with vibration frequencies near the resonant frequency. In some embodiments, to further reduce sound leakage from an acoustic device, the sound absorbing effect of the sound absorbing structure has a sound absorption effect of 22 dB or more for sounds at a resonant frequency or sounds with vibration frequencies near the resonant frequency. In some embodiments, to further reduce sound leakage from an acoustic device, the sound absorbing effect of the sound absorbing structure has a sound absorption effect of 25 dB or more for sounds at a resonant frequency or sounds with vibration frequencies near the resonant frequency.

[0071] In some embodiments, the sound absorbing structure may include at least one of an absorptive sound absorbing structure and a reactive sound absorbing structure. For example, the function of the sound absorbing structure can be realized by an absorptive sound absorbing structure. Also, for example, the function of the sound absorbing structure can be realized by a reactive sound absorbing structure. Furthermore, for example, the function of the sound absorbing structure can be realized by a sound absorbing structure that is a combination of an absorptive sound absorbing structure and a reactive sound absorbing structure.

[0072] An absorptive sound-absorbing structure may refer to a structure that can provide acoustic resistance when sound waves pass through it. In some embodiments, the absorptive sound-absorbing structure may include at least one of a porous sound-absorbing material or an acoustic gauze. In some embodiments, the absorptive sound-absorbing structure may be installed at any position in the first sound wave transmission path and / or the second sound wave transmission path. For example, the porous sound-absorbing material or the acoustic gauze may be attached to an inner wall of the sound transmission structure. Also, for example, the porous sound-absorbing material or the acoustic gauze may constitute at least a portion of the inner wall of the sound transmission structure. Furthermore, for example, the porous sound-absorbing material or the acoustic gauze may fill at least a portion of the interior of the sound transmission structure. A reactive sound-absorbing structure may refer to a structure that absorbs sound using resonance. In some embodiments, the reactive sound-absorbing structure may include, but is not limited to, a Helmholtz sound-absorbing cavity, a perforated plate sound-absorbing structure, a micro-perforated plate sound-absorbing structure, a thin plate, a thin film, a quarter-wave resonator tube, etc., or any combination thereof. In some embodiments, the absorptive-reactive composite sound-absorbing structure may incorporate both an absorptive and a reactive sound-absorbing structure to achieve the sound-absorbing function. For example, the absorptive-reactive composite sound-absorbing structure may include a micro-perforated board sound-absorbing structure and a porous sound-absorbing material or acoustic gauze, with the porous sound-absorbing material or acoustic gauze located within the cavity of the micro-perforated board sound-absorbing structure or within the sound-transmitting structure. For example, the absorptive-reactive composite sound-absorbing structure may include a quarter-wave resonator tube structure and a porous sound-absorbing material or acoustic gauze, with the quarter-wave resonator tube structure located inside or outside the sound-transmitting structure, and the porous sound-absorbing material or acoustic gauze located within the sound-transmitting structure. For example, the absorptive-reactive composite sound-absorbing structure may include a micro-perforated board sound-absorbing structure, a quarter-wave resonator tube structure, and a porous sound-absorbing material or acoustic gauze.

[0073] The sound absorbing structure may be coupled to a second acoustic cavity. In some embodiments, the sound absorbing structure may include a micro-perforated board sound absorbing structure. The micro-perforated board sound absorbing structure includes a micro-perforated board and a cavity, the micro-perforated board including through holes, and the acoustic cavity coupled to the micro-perforated board structure communicates with the cavity through the through holes in the micro-perforated board. For more details on the micro-perforated board sound absorbing structure, please refer to the contents elsewhere in this specification, for example, Figure 9 and the corresponding specification contents.

[0074] In some embodiments of the present specification, by installing a sound absorbing structure so as to be coupled to the second acoustic cavity, sound waves within a target frequency range are absorbed by the sound absorbing structure, and the sound waves can be reduced or prevented from resonating around a specific frequency (e.g., a resonant frequency) under the action of the acoustic cavity, thereby reducing or avoiding a situation in which the amplitude difference and phase difference between the first sound wave and the second sound wave around the specific frequency of the cavity reduces the sound leakage reduction effect at the spatial point, and thus the two sets of sounds not only do not cancel each other out but also interfere and reinforce each other, thereby reducing sound leakage in the target frequency range. The first sound wave and the second sound wave outside the target frequency range can cancel each other out, reducing sound leakage at the spatial point.

[0075] In some embodiments, to reduce sound leakage in the far field of the acoustic device 10, the intensities of the first and second sound leakage should be close to each other, in addition to being opposite or nearly opposite in phase. Therefore, the first acoustic hole 112 and the second acoustic hole 113 may have similar acoustic loads (acoustic resistances). In some embodiments, to ensure that the acoustic loads of the first and second acoustic holes 112 and 113 are similar, the first and second acoustic holes 112 and 113 should have similar open area. In some embodiments, the ratio of the open area of ​​the first acoustic hole 112 to the open area of ​​the second acoustic hole 113 is 0.5 to 2. In some embodiments, the ratio of the opening areas of the first acoustic hole 112 and the second acoustic hole 113 is 1.0 to 1.8 so that the acoustic loads of the first acoustic hole 112 and the second acoustic hole 113 are similar and the opening area of ​​the first acoustic hole 112 is sufficiently large to ensure a good listening experience for the user. In some embodiments, the ratio of the opening areas of the first acoustic hole 112 and the second acoustic hole 113 is 0.5 to 0.9 so that the acoustic loads of the first acoustic hole 112 and the second acoustic hole 113 are similar and the opening area of ​​the second acoustic hole 113 is sufficiently large to ensure a good far-field sound leakage reduction effect. When two or more second acoustic holes 113 are provided, the opening area of ​​the second acoustic holes 113 refers to the total opening area of ​​the multiple second acoustic holes 113. In some embodiments, other parameters of the first acoustic hole 112 and the second acoustic hole 113 may be set so that the acoustic load of the first acoustic hole 112 is similar to the acoustic load of the second acoustic hole 113. For example, the first acoustic hole 112 and the second acoustic hole 113 may be provided with acoustic resistance meshes having the same or similar acoustic resistance.

[0076] In some embodiments, the difference in acoustic load between the first acoustic hole 112 and the second acoustic hole 113 is less than 0.15 to make the intensities of the first sound leakage and the second sound leakage similar. In some embodiments, the difference in acoustic load between the first acoustic hole 112 and the second acoustic hole 113 is less than 0.1 to make the intensities of the first sound leakage and the second sound leakage similar. In some embodiments, the difference in acoustic load between the first acoustic hole 112 and the second acoustic hole 113 is less than 0.05 to make the intensities of the first sound leakage and the second sound leakage similar. In some embodiments, there may be one or more second acoustic holes 113. When there are two or more second acoustic holes 113, the acoustic load of the second acoustic holes 113 refers to the sum of the acoustic loads of the second acoustic holes 113.

[0077] In some embodiments, the acoustic load of the first acoustic hole 112 and the acoustic load of the second acoustic hole 113 are close to each other, and sound generated by the second acoustic cavity and radiated to the outside (e.g., far field) through the second acoustic hole 112 cannot be ignored. In some embodiments, when the sound waves radiated to the outside from the second acoustic cavity pass through the acoustic transmission structure between the diaphragm and the second acoustic hole 113, the sound waves inside the structure also resonate due to the resonance of the acoustic transmission structure. Compared to when there is no resonance, the phase and / or amplitude of the sound waves radiated from the second acoustic hole 113 change, and the change in phase and / or amplitude may cause disturbance in the sound field near the resonance frequency of the sound generating unit 11, which may affect the interference cancellation effect in the far field of the sound waves radiated from the first acoustic hole 112 and the second acoustic hole 113. Therefore, by adjusting the sound waves of the second acoustic cavity, the output within the target frequency range of the second acoustic cavity (e.g., including the resonant frequency of the acoustic transmission structure) can be reduced without affecting the low-frequency output of the second acoustic cavity, thereby achieving a sound leakage reduction effect in the far field. For example, by installing a sound-absorbing structure to absorb sound waves within the target frequency range of the second acoustic cavity and adjusting the sound waves of the second acoustic cavity, sound leakage in the far field can be effectively reduced. Furthermore, by making the intensities of the first sound leakage and the second sound leakage closer in frequency bands outside the target frequency range (e.g., low frequency bands), sound leakage in the far field can be effectively reduced.

[0078] FIG. 9 is a schematic diagram of an acoustic device equipped with a sound absorbing structure according to some embodiments of the present disclosure.

[0079] 9 , in some embodiments, an acoustic device 300 may include a housing 310 and a vibrating membrane 320. The vibrating membrane 320 is disposed within an accommodating cavity defined by the housing 310, and a first acoustic cavity 330 and a second acoustic cavity 340 are disposed on the front and rear sides of the vibrating membrane 320, respectively. A first acoustic hole 311 and a second acoustic hole 312 are disposed in the housing 310, and the first acoustic cavity 330 may be acoustically coupled to the first acoustic hole 311, and the second acoustic cavity 340 may be acoustically coupled to the second acoustic hole 312.

[0080] 9, acoustic device 300 may further include a micro-perforated board sound absorbing structure 350, which may be coupled to second acoustic cavity 340. In some embodiments, micro-perforated board sound absorbing structure 350 may include a micro-perforated board 351 and a cavity 352, where micro-perforated board 351 includes through-holes, and second acoustic cavity 340 coupled to the micro-perforated board structure communicates with cavity 352 through the through-holes of the micro-perforated board. Note that acoustic device 300 shown in FIG. 9 is merely an illustrative example, and various changes or modifications may be made to the specific installation manner of micro-perforated board sound absorbing structure 350.

[0081] The sound waves from the second acoustic cavity 340 enter the cavity 352 of the micro-perforated sound absorbing structure 350 through one or more through-holes and can cause the micro-perforated sound absorbing structure 350 to resonate under certain conditions. For example, if the vibration frequency of the sound waves entering the cavity 352 is close to the resonant frequency of the micro-perforated sound absorbing structure 350, the sound waves entering the cavity 352 will cause the micro-perforated sound absorbing structure 350 to resonate. The air in the cavity 352 resonates with the micro-perforated sound absorbing structure 350, dissipating energy and achieving a sound absorption effect. The frequency of the sound waves absorbed by the micro-perforated sound absorbing structure 350 is the same as or close to its resonant frequency.

[0082] In some embodiments, the material of the micro-perforated plate 351 may be metal (e.g., aluminum) or non-metal (e.g., acrylic, polycarbonate (PC), etc.). If the micro-perforated plate 351 is a non-metal plate, the thermal conductivity of the non-metal plate is low, and the process of the sound waves passing through the through holes can be considered an adiabatic process. If the micro-perforated plate 351 is a metal plate, the thermal conductivity of the metal plate is high, and the diameter of the through holes is small, and the process of the sound waves passing through the through holes can be considered an isothermal process. Because heat conduction means increased energy consumption, metal plates have a higher equivalent attenuation than non-metal plates.

[0083] 10 is a diagram showing the sound absorption effects of acoustic devices according to some embodiments of the present specification when using a metallic micro-perforated plate and a non-metallic micro-perforated plate. In FIG. 10, the horizontal axis represents the sound absorption frequency, the vertical axis represents the sound absorption coefficient, and curve L1 represents the sound absorption effect of the non-metallic micro-perforated plate, while curve L2 represents the sound absorption effect of the metallic micro-perforated plate. As shown in FIG. 10, the maximum sound absorption coefficient of the metallic micro-perforated plate is slightly lower than that of the non-metallic micro-perforated plate, but the sound absorption bandwidth of the metallic micro-perforated plate is wider than that of the non-metallic micro-perforated plate. This is because the metallic micro-perforated plate has better thermal conductivity and therefore a greater equivalent attenuation for sound waves passing through it.

[0084] FIG. 11 shows frequency response curves for acoustic devices according to some embodiments of the present disclosure, each using a metal micro-perforated plate and a non-metal micro-perforated plate. In FIG. 11, the horizontal axis represents frequency, the vertical axis represents sound pressure level, and curve L3 represents the frequency response when a metal micro-perforated plate is used. Curve L4 represents the frequency response when a non-metal micro-perforated plate is used. The frequency response here refers to the frequency response of the second acoustic hole (e.g., a point 10 mm away from the second acoustic hole). As shown in FIG. 11, the metal micro-perforated plate has a higher sound absorption effect than the non-metal micro-perforated plate in the mid-low frequency range (e.g., below 4 kHz), reducing sound leakage from the acoustic device by approximately 2 to 3 dB. In this case, the metal micro-perforated plate is an aluminum plate, which slightly reduces the sound absorption effect of the non-metal micro-perforated plate. However, using a non-metal micro-perforated plate reduces the weight of the acoustic device, thereby improving the lightness of the acoustic device and reducing the cost of the acoustic device. In some embodiments, metal plates and non-metal plates have their own advantages, so that the metal micro-perforated plate or the non-metal micro-perforated plate can be flexibly selected depending on weight, cost, corrosion resistance, etc.

[0085] If the natural frequency of the micro-perforated plate 351 attached to the acoustic device (or referred to as the fixed state) is within the target frequency range, the micro-perforated plate 351 may resonate within the target frequency range, which may affect the sound absorption effect. Therefore, the natural frequency of the micro-perforated plate 351 in the fixed state should be much greater than the target frequency. In some embodiments, since it is difficult to measure the natural frequency of the micro-perforated plate 351 in the fixed state, the natural frequency of the micro-perforated plate 351 in the free state can represent the natural frequency of the micro-perforated plate 351 in the fixed state. The free state may be the state when the micro-perforated plate 351 is not attached to the acoustic device, and the natural frequency of the micro-perforated plate 351 in the fixed state is much greater than the natural frequency of the free state. The method for measuring the natural frequency in the free state may be as follows. While maintaining the micro-perforated plate 351 in a free state, a vibrator applies a vibration force to the micro-perforated plate 351, the vibration amplitude of which is constant and the frequency of which varies from low to high. A laser vibrometer is used to measure and record the velocity amplitude of the micro-perforated plate 351. The frequency at which the velocity range of the micro-perforated plate 351 first reaches a maximum is defined as the natural frequency of the free state of the micro-perforated plate 351. In some embodiments, the sound absorption bandwidth is in the range of 3 kHz to 6 kHz. To avoid the natural frequency of the fixed state of the micro-perforated plate being within the sound absorption bandwidth, the theoretical value of the natural frequency of the free state of the micro-perforated plate 351 may be greater than 500 Hz (e.g., 500 Hz to 3.6 kHz), so that the natural frequency of the fixed state is much greater than the upper sound absorption limit frequency (i.e., the maximum frequency of the sound absorption bandwidth, e.g., 6 kHz). The natural frequency is also related to the stiffness and mass of the micro-perforated plate 351, so that the natural frequency can be determined by setting the stiffness and / or mass of the micro-perforated plate 351, thereby absorbing sound waves within a target frequency range. In some embodiments, micro-perforated plates 351 with different shapes, materials, etc., have different stiffness and / or mass, and therefore different natural frequencies. In some embodiments, the micro-perforated plate 351 may have a regular or irregular shape, such as a circle, a sector, a rectangle, or a diamond. In some embodiments, the material of the micro-perforated plate 351 may be a non-metallic material or a metallic material.

[0086] In some embodiments, micro-perforated plate 351 may be a racetrack-type micro-perforated plate. In some embodiments, when micro-perforated plate 351 is a racetrack-type micro-perforated plate, the Young's modulus of the material is in the range of 5 GPa to 200 GPa so that the natural frequency of micro-perforated plate 351 in the free state is in the range of 500 Hz to 3.6 kHz. For example, the Young's modulus of the material is in the range of 10 GPa to 180 GPa. For example, the Young's modulus of the material is in the range of 20 GPa to 150 GPa. For example, the Young's modulus of the material is in the range of 50 GPa to 100 GPa. In some embodiments, the thickness of micro-perforated plate 351 can affect its natural frequency. When micro-perforated plate 351 is a racetrack-type micro-perforated plate, the thickness of the racetrack-type micro-perforated plate may be in the range of 0.1 mm to 0.8 mm so that the natural frequency of micro-perforated plate 351 in the free state is in the range of 500 Hz to 3.6 kHz. For example, the thickness of the racetrack-type micro-perforated plate may be in the range of 0.2 mm to 0.7 mm, or in the range of 0.3 mm to 0.6 mm.

[0087] In some embodiments, the micro-perforated plate 351 may be a circular micro-perforated plate. Given the same parameters (e.g., hole diameter, thickness, open area ratio, and cavity (e.g., cavity 352) height), the circular micro-perforated plate 351 has a lower natural frequency than the racetrack-type micro-perforated plate 351. Therefore, the circular micro-perforated plate must be made of a material with greater stiffness and / or a greater thickness than the racetrack-type micro-perforated plate to ensure that its natural frequency is much greater than the upper sound absorption frequency limit. In some embodiments, when the micro-perforated plate 351 is a circular micro-perforated plate, the Young's modulus of the material of the micro-perforated plate 351 is in the range of 50 GPa to 200 GPa to ensure that the free-state natural frequency of the micro-perforated plate 351 is in the range of 500 Hz to 3.6 kHz. For example, the Young's modulus of the material of the circular micro-perforated plate is in the range of 60 GPa to 180 GPa. For example, the Young's modulus of the material of the circular micro-perforated plate is in the range of 80 GPa to 150 GPa. For example, the Young's modulus of the material of the circular micro-perforated plate is in the range of 100 GPa to 150 GPa. In some embodiments, when the micro-perforated plate 351 is a circular micro-perforated plate, the thickness of the circular micro-perforated plate should be in the range of 0.3 mm to 1 mm so that the free-state natural frequency of the micro-perforated plate 351 is in the range of 500 Hz to 3.6 kHz. For example, the thickness of the circular micro-perforated plate should be in the range of 0.4 mm to 0.9 mm. For example, the thickness of the circular micro-perforated plate should be in the range of 0.5 mm to 0.8 mm. For example, the thickness of the circular micro-perforated plate should be in the range of 0.6 mm to 0.7 mm.

[0088] By setting the Young's modulus and / or thickness of the micro-perforated plate 351 and adjusting its natural frequency, it is possible to prevent the natural frequency of the micro-perforated plate 351 in a fixed state from being within the sound absorption bandwidth and affecting its sound absorption effect.

[0089] In some embodiments, a waterproof ventilation structure may be installed on the side of the micro-perforated plate 351 facing the diaphragm 320, and the waterproof ventilation structure can provide waterproofing and dustproofing. Specifically, the through-holes in the micro-perforated plate 351 have a relatively small diameter, which makes capillary action more likely to occur. If water gets in, it is difficult for it to be expelled, which affects the sound leakage reduction effect of the sound absorbing structure. Therefore, a waterproof ventilation structure must be installed at the interface between the micro-perforated plate 351 and the second acoustic cavity 340. In some embodiments, the waterproof ventilation structure may cover the entire side where the micro-perforated plate 351 and the second acoustic cavity 340 come into contact. In some embodiments, the waterproof ventilation structure may cover all of the through-holes in the micro-perforated plate 351 so that the through-holes communicate with the second acoustic cavity 340 via the waterproof ventilation structure.

[0090] In some embodiments, the waterproof breathable structure may be gauze. FIG. 12 illustrates frequency response curves of the second acoustic hole measured when 025HY-type gauze is installed on the side of the micro-perforated plate facing the vibration membrane and when no gauze is installed, according to some embodiments of the present disclosure. In FIG. 12, the horizontal axis represents frequency, and the vertical axis represents sound pressure level. Curve L5 represents the frequency response curve measured at the second acoustic hole 312 (e.g., 10 mm away from and directly in front of the second acoustic hole 312) when 025HY-type gauze is installed, and curve L6 represents the frequency response curve measured at the second acoustic hole 312 (e.g., 10 mm away from and directly in front of the second acoustic hole 312) when no gauze is installed. As shown in FIG. 12, curve L5 is slightly higher than curve L6, and the difference in sound pressure level between the two is not significant. As a result, the sound absorption effect of the micro-perforated plate 351 with the 025HY gauze installed is slightly reduced compared to the micro-perforated plate 351 without the gauze, but the impact is not significant and the plate can still fulfill its waterproof and dustproofing role to a certain extent (for example, an acoustic device using the 025HY gauze can pass the IPX7 waterproof test). Therefore, in some embodiments, to achieve the waterproof and dustproof purpose through the micro-perforated plate sound absorbing structure, the 025HY gauze may be installed on the side of the micro-perforated plate 351 facing the diaphragm. In some embodiments, the acoustic resistance of the 025HY gauze is less than 50 MKS Rayls. As a result, the gauze may be installed on the side of the micro-perforated plate 351 facing the diaphragm, and the acoustic resistance of the gauze may be less than 50 MKS Rayls, thereby providing waterproof and dustproofing and having little impact on the output effect of the acoustic device (e.g., the second acoustic hole).

[0091] The cavity 352 is located on the opposite side of the micro-perforated plate 351 from the second acoustic cavity 340 and communicates with the outside only through the through-holes in the micro-perforated plate 351. In some embodiments, the shape of the cavity 352 includes, but is not limited to, a rectangular parallelepiped as shown in FIG. 9 , and may include regular shapes such as a sphere or a cylinder, or irregular shapes such as a racetrack. In some embodiments, the cavity 352 has a constant height D (see FIG. 9 ), and the larger the cavity height D, the wider its sound absorption bandwidth. Therefore, in some embodiments, increasing the cavity height D can improve the sound absorption effect of the micro-perforated plate sound absorbing structure. Note that if the cavity 352 has a regular shape, its height dimension is equal to the cavity height D. If cavity 352 has an irregular shape, it is difficult to determine its height dimension, and the equivalent height D of the cavity can be expressed as the ratio of the volume of cavity 352 to the area of ​​micro-perforated plate 351 (i.e., the area of ​​the side of the micro-perforated plate facing cavity 352). The volume of irregular cavity 352 can be measured by an adhesive injection method, in which a special adhesive is injected into cavity 352 through the acoustic hole of the acoustic output device, and after molding, the housing is peeled off. The volume of the special adhesive after molding is measured using a drainage method to obtain the volume of irregular cavity 352.

[0092] 13 is a curve diagram of the sound absorption coefficient of the micro-perforated plate sound absorbing structure according to some embodiments of the present disclosure when the cavity height is different. As shown in FIG. 13, with the increase in the cavity height D, the abscissa of the peak of the corresponding curve gradually shifts to the left, the peak of the corresponding curve gradually decreases, but the coverage width of the corresponding curve gradually increases. Therefore, the larger the cavity height D, the lower the corresponding sound absorption frequency, the smaller the maximum sound absorption coefficient, but the wider the sound absorption bandwidth.

[0093] FIG. 14 is a comparison diagram of the change trend of the maximum sound absorption coefficient and the change trend of the 0.5 sound absorption octave for different cavity heights according to some embodiments of the present specification. The 0.5 sound absorption octave refers to the octave range traversed by the sound absorption curve when the sound absorption coefficient is 0.5. The larger the octave, the wider the sound absorption bandwidth. As shown in FIG. 14, with an increase in cavity height D, the corresponding maximum sound absorption coefficient gradually decreases, but the 0.5 sound absorption octave gradually increases, that is, the sound absorption bandwidth gradually widens.

[0094] As described above, the greater the height D of the cavity 352, the wider the sound absorption bandwidth can be obtained near the desired resonant sound absorption frequency. However, the greater the cavity height, the smaller the maximum sound absorption coefficient corresponding to the resonant sound absorption frequency. Therefore, in some embodiments, to achieve both the sound absorption bandwidth and the maximum sound absorption coefficient of the micro-perforated panel sound absorbing structure, the cavity height D may be in the range of 0.5 mm to 10 mm. For example, the cavity height D may be in the range of 2 mm to 9 mm. Furthermore, for example, the cavity height D may be in the range of 4 mm to 9 mm. Furthermore, for example, the cavity height D may be in the range of 7 mm to 10 mm.

[0095] In some embodiments, a plurality of through-holes may be provided in the micro-perforated plate 351, and the plurality of through-holes may be distributed at intervals. In some embodiments, the plurality of through-holes may be distributed arbitrarily as a whole. For example, the plurality of through-holes may be distributed in an array. Also, for example, the plurality of through-holes may be distributed in a circular pattern around a central point. In some embodiments, the spacing between the through-holes (abbreviated as hole spacing) may be the same or different. The spacing between through-holes described in the specification is the minimum distance between the edge of a through-hole and the edge of an adjacent through-hole.

[0096] In some embodiments, the hole spacing between the through holes may be much larger than the hole diameter of the through holes (here, hole diameter is the diameter of the through holes), and the ratio of the hole spacing to the hole diameter of the through holes may be greater than 3. In some embodiments, the hole spacing may be much larger than the hole diameter of the through holes, and the ratio of the hole spacing to the hole diameter of the through holes may be greater than 5. In some embodiments, the hole spacing may be much larger than the hole diameter of the through holes, and the ratio of the hole spacing to the hole diameter of the through holes may be greater than 7. In some embodiments, the hole spacing may be much larger than the hole diameter of the through holes, and the ratio of the hole spacing to the hole diameter of the through holes may be greater than 10. When the hole spacing is larger than the hole diameter, the characteristics of the sound waves transmitted between each hole do not affect each other.

[0097] In some embodiments, the spacing between the through-holes in the micro-perforated plate may be much smaller than the wavelength of sound in the target frequency range. In some embodiments, the ratio of the wavelength of sound in the target frequency range to the hole spacing may be greater than 5. In some embodiments, the ratio of the wavelength of sound in the target frequency range to the hole spacing may be greater than 7. In some embodiments, the ratio of the wavelength of sound in the target frequency range to the hole spacing may be greater than 10. By way of example only, the target frequency range may be 3 kHz to 6 kHz, and the wavelength of sound in the target frequency range may be in the range of 53 mm to 110 mm. The ratio of the wavelength of sound in the target frequency range to the hole spacing may be greater than 5, for example, the hole spacing may be in the range of 10 mm to 22 mm. When the hole spacing is much smaller than the wavelength, the reflection of sound waves by the hole spacing plate (the region of the micro-perforated plate 351 between the edge of a through-hole and the edge of an adjacent through-hole) can be ignored, thereby avoiding the influence of the reflection of the hole spacing on the sound wave propagation process.

[0098] In some embodiments, within the effective hole size range, the smaller the hole size of the through holes, the greater the acoustic resistance when sound waves pass through the through holes, the greater the energy consumption, and the wider the sound absorption bandwidth. Therefore, by setting the hole size of the through holes to a smaller size, the sound absorption effect of the fine-perforated sound absorbing structure can be improved. The effective hole size range is the range within which the sound absorption bandwidth of a fine-perforated sound absorbing structure having hole sizes within that range can meet the sound leakage reduction requirements. When the hole size is within the effective hole size range, the smaller the hole size, the higher the sound absorption effect. When the hole size is smaller than the effective hole size range, the sound absorption bandwidth is significantly narrowed. In some embodiments, the effective hole size range may be 0.1 mm to 1 mm. Taking into consideration the requirements for the manufacturing process, in some embodiments, the effective hole size range may be 0.2 mm to 0.4 mm. For example, the effective hole size range may be 0.2 mm to 0.3 mm. In some embodiments, the effective hole size range may be 0.1 mm to 0.4 mm. For example, the effective pore size range may be 0.1 mm to 0.2 mm.

[0099] FIG. 15 illustrates the sound absorption effect of micro-perforated panels having through-hole diameters of 0.15 mm and 0.3 mm, respectively, according to some embodiments of the present disclosure. In FIG. 15, the horizontal axis represents sound absorption frequency, and the vertical axis represents sound absorption coefficient. Curve 151 represents the sound absorption effect of micro-perforated panel 351 having a hole diameter of 0.15 mm, and curve 152 represents the sound absorption effect of micro-perforated panel 351 having a hole diameter of 0.3 mm. As shown in FIG. 15, curve 151 is wider than curve 152, but the heights of the two are similar. From the above, it can be seen that the sound absorption bandwidth and sound absorption effect of micro-perforated panel 351 having a hole diameter of 0.15 mm are significantly better than those of micro-perforated panel 351 having a hole diameter of 0.3 mm.

[0100] FIG. 16 is a frequency response curve diagram for a micro-perforated plate 351 having a hole diameter of 0.15 mm and a micro-perforated plate 351 having a hole diameter of 0.3 mm according to some embodiments of the present disclosure. In FIG. 16, the horizontal axis represents frequency, and the vertical axis represents sound pressure level. Curve 161 represents the frequency response for a micro-perforated plate 351 having a hole diameter of 0.15 mm, and curve 162 represents the frequency response for a micro-perforated plate 351 having a hole diameter of 0.3 mm, where the frequency response is the frequency response of the sound emitted from the second acoustic hole. As shown in FIG. 16, the sound leakage of curve 161 in the frequency range of 2 kHz to 4 kHz is approximately 6 dB lower than that of curve 162. From the above, the sound absorption effect of the micro-perforated plate 351 having a hole diameter of 0.15 mm in the mid-to-high frequency range is clearly superior to that of the micro-perforated plate 351 having a hole diameter of 0.3 mm. Therefore, in some embodiments, to achieve a higher sound absorption effect, a finely perforated plate 351 with a hole diameter of 0.15 mm or close to 0.15 mm may be used. For example, a finely perforated plate 351 with a hole diameter in the range of 0.1 mm to 0.2 mm may be used. In some embodiments, taking into account the needs for dust prevention and drainage, a finely perforated plate 351 with a hole diameter of 0.3 mm or close to 0.3 mm (for example, 0.28 mm to 0.35 mm) may be used.

[0101] In some embodiments, the aperture ratio of the micro-perforated plate 351 may be less than 5% to avoid too many through-holes and too small hole spacing that would affect the characteristics of the sound waves transmitted between the through-holes. The aperture ratio is proportional to the total area of ​​the through-holes and the area of ​​the side of the micro-perforated plate 351 that is closest to the second acoustic cavity 340.

[0102] In some embodiments, if the size of the micro-perforated board sound absorbing structure is too small, the process may be difficult, and if the cavity height D is too large, the size of the acoustic device may be large. Therefore, an absorptive sound absorbing structure can be used to improve the sound absorbing effect of the micro-perforated board sound absorbing structure. FIG. 17 is a schematic diagram of an acoustic device equipped with a sound absorbing structure, according to some embodiments of the present disclosure. As shown in FIG. 17, the absorptive sound absorbing structure may be installed in a cavity 352 of the micro-perforated board sound absorbing structure. In some embodiments, the absorptive sound absorbing structure may further include a filler material 354 (e.g., N'Bass particles or a porous sound absorbing material). The filler material 354 increases the equivalent height of the cavity 352 of the micro-perforated board sound absorbing structure, thereby improving the sound absorbing effect of the micro-perforated board sound absorbing structure and reducing the design size of the acoustic device 400. Specifically, the filler material 354 has a "sponge" effect, and when sound waves propagate, air molecules are adsorbed into and desorbed from the voids in the filler material 354, which can be considered to reduce the sound speed in the filler material 354, which is equivalent to increasing the volume of the cavity 352, thereby achieving the purpose of widening the sound absorption bandwidth of the micro-perforated plate 351 and increasing the sound absorption coefficient (without affecting the center frequency of sound absorption), further improving the sound absorption effect of the micro-perforated plate sound absorption structure, and reducing the design size of the acoustic device.

[0103] In some embodiments, N'Bass (aluminosilicate) sound-absorbing particles may be filled into cavity 352. In some embodiments, N'Bass sound-absorbing particles may be filled into cavity 352 in a number of ways. By way of example only, N'Bass sound-absorbing particles may be filled directly into cavity 352, or N'Bass sound-absorbing particles may be filled into a powder pack and the powder pack placed into cavity 352, or N'Bass sound-absorbing particles may be potted into a gauze of a particular shape and the powder pack placed into cavity 352, or N'Bass sound-absorbing particles may be filled into cavity 352 using at least two of the above filling methods.

[0104] In some embodiments, the smaller the N'Bass sound-absorbing particles, the smaller the spacing between each sound-absorbing particle, i.e., the stronger the adsorption effect on air molecules. Accordingly, the smaller the particles, the more N'Bass sound-absorbing particles must be packed, which increases costs. Therefore, to ensure sound absorption while also considering costs, the diameter of the N'Bass sound-absorbing particles may be in the range of 0.15 mm to 0.7 mm. For example, the diameter of the N'Bass sound-absorbing particles may be in the range of 0.15 mm to 0.6 mm. For example, the diameter of the N'Bass sound-absorbing particles may be in the range of 0.2 mm to 0.6 mm. For example, the diameter of the N'Bass sound-absorbing particles may be in the range of 0.3 mm to 0.5 mm.

[0105] In some embodiments, the filling rate of the N'Bass sound-absorbing particles in cavity 352 gradually increases, so that the more N'Bass sound-absorbing particles there are in cavity 352, the higher the sound-absorbing effect. The filling rate refers to the ratio of the volume of the filled N'Bass sound-absorbing particles to the volume of cavity 352. However, if the N'Bass sound-absorbing particles completely fill cavity 352, the pressure from the plate surface of the micro-perforated plate sound-absorbing structure on the N'Bass sound-absorbing particles may cause the N'Bass sound-absorbing particles to crack, blocking the gaps between the N'Bass sound-absorbing particles and reducing the sound-absorbing effect.

[0106] FIG. 18 illustrates frequency response curves of the second acoustic cavity of an acoustic device corresponding to different filler material filler ratios, according to some embodiments of the present disclosure. As shown in FIG. 18, when the filler material (e.g., N'Bass sound-absorbing particles) filler ratio is 0%, i.e., when no filler material is filled in the cavity of the micro-perforated sound-absorbing structure, the frequency response curve corresponding to the second acoustic cavity of the acoustic device exhibits a single peak near 2 kHz (as indicated by the dashed circle in FIG. 18), indicating a louder sound output from the second acoustic cavity at 2 kHz. When the filler material filler ratio is 25%, i.e., when 25% of the cavity of the micro-perforated sound-absorbing structure is filled with filler material, the peak near 2 kHz is more absorbed, but a small peak still exists. When the filler material filler ratio is 50%, i.e., when 50% of the cavity of the micro-perforated sound-absorbing structure is filled with filler material, the peak near 2 kHz is further absorbed, and the corresponding frequency response curve is flat. When the filler material fills 75%, i.e., when 75% of the space in the cavity of the micro-perforated plate sound absorbing structure is filled with filler material, the peak around 2 kHz is further absorbed, but another peak is formed around 3 kHz, resulting in a slight increase in the output volume of the second acoustic cavity around 3 kHz. When the filler material fills 100%, i.e., when the entire space in the cavity of the micro-perforated plate sound absorbing structure is filled with filler material, the peak around 2 kHz is further absorbed, but the peak around 3 kHz is further increased and the peak is obvious, resulting in a further increase in the output volume of the second acoustic cavity around 3 kHz. In some embodiments, the filler material fill rate may range from 30% to 100% to flatten the frequency response curve of the second acoustic cavity and minimize the appearance of peaks in the curve within a predetermined range (e.g., the range from 2 kHz to 3 kHz). In some embodiments, the filler material fill rate may be within the range of 70% to 95%. For example, the fill rate may be in the range of 75% to 90%. Also, for example, the fill rate may be in the range of 80% to 90%. In some embodiments, taking into account the cost of packing the N'Bass sound-absorbing particles, the fill rate may be in the range of 75% to 85%. For example, the fill rate may be 80%.

[0107] By setting the filling rate of the N'Bass sound-absorbing particles within the range of 70% to 95%, the sound absorption effect can be guaranteed while avoiding the pressure from the fine-perforated plate sound-absorbing structure to the N'Bass sound-absorbing particles that would block gaps and reduce the sound absorption effect.

[0108] In some embodiments, because the diameter of the N'Bass sound-absorbing particles is close to or smaller than the diameter of the through-holes, gauze 353 may be placed between the N'Bass sound-absorbing particles and the micro-perforated plate 351 to prevent the N'Bass sound-absorbing particles from blocking the through-holes, as shown in FIG. 17 . In some embodiments, gauze 353 may be placed on the side of the micro-perforated plate 351 that faces away from the second acoustic cavity 340 (or the diaphragm 320), and the gauze 353 covers all of the through-holes in the micro-perforated plate 351. In some embodiments, gauze 353 may be placed in the cavity 352 between the N'Bass sound-absorbing particles and the micro-perforated plate 351. Specifically, the gauze 353 may be connected to the inner wall of the cavity 352 between the N'Bass sound-absorbing particles and the micro-perforated plate 351.

[0109] In some embodiments, the micro-perforated plate sound absorbing structure may be positioned facing the second acoustic cavity, and the angle between the normal to the side of the micro-perforated plate facing the second acoustic cavity and the vibration direction of the diaphragm (e.g., angle α shown in FIG. 20) is between 0° and 90°, thereby effectively absorbing sound waves of the target frequency in the second acoustic cavity. Note that the angle here is the absolute value of the angle between the normal and the vibration direction of the diaphragm. For example, for the micro-perforated plate sound absorbing structures 350 and 350′ shown in FIG. 28C, the angles between the normal to the side of the micro-perforated plate facing the second acoustic cavity 340 and the vibration direction of the diaphragm are both 90°.

[0110] In some embodiments, the micro-perforated plate may be disposed parallel or nearly parallel to the diaphragm. For example, the angle between the normal of the micro-perforated plate facing the second acoustic cavity and the vibration direction of the diaphragm may be in the range of 0° to 10°, thereby improving the assembly tolerance of the sound absorbing structure and the housing and avoiding the need to increase the thickness dimension of the sound-generating unit along the vibration direction due to an excessively large inclination angle of the micro-perforated plate sound absorbing structure, thereby helping to reduce the volume and / or weight of the sound-generating unit.

[0111] In some embodiments, to accommodate different structural or functional requirements, the micro-perforated plate may be tilted relative to the diaphragm. For example, the angle between the normal to the side of the micro-perforated plate facing the second acoustic cavity and the vibration direction of the diaphragm may be between 0° and 90°. In some embodiments, the angle between the normal to the side of the micro-perforated plate facing the second acoustic cavity and the vibration direction of the diaphragm may be between 10° and 45°. In this case, the micro-perforated plate may be tilted to a certain degree relative to the diaphragm to achieve a specific structure or meet specific sound absorption needs. For example, the micro-perforated plate may be tilted to a certain degree relative to the diaphragm, thereby adjusting the distance between the two second acoustic holes and further adjusting the sound absorption effect. In some embodiments, the angle between the normal to the side of the micro-perforated plate facing the second acoustic cavity and the vibration direction of the diaphragm may be in the range of 45° to 90°. For example, the angle between the normal to the side of the micro-perforated plate facing the second acoustic cavity and the vibration direction of the diaphragm may be 90°. That is, the micro-perforated plate may be installed perpendicular to the diaphragm. In this case, the micro-perforated plate sound absorbing structure may be installed at a corner of the second acoustic cavity to avoid an excessively large inclination angle of the micro-perforated plate sound absorbing structure, which would increase the thickness of the sound generating unit. As an example, as shown in FIG. 28B , the micro-perforated plate may be installed in the long axis direction of the sound generating unit and inclined relative to the vibration direction of the diaphragm and the long axis direction Y of the sound generating unit. Furthermore, for example, as shown in FIG. 29B , the micro-perforated plate may be installed in the short axis direction of the sound generating unit and inclined relative to the vibration direction of the diaphragm and the short axis direction Z of the sound generating unit. Hereinafter, with reference to FIGS. 19 to 29C, an embodiment in which the finely perforated plate is installed parallel to or inclined with respect to the diaphragm will be described as an example.

[0112] In some embodiments, the micro-perforated board sound absorbing structure 350 may be disposed inside the housing of the acoustic device, extending along the vibration direction of the diaphragm 320. For example, the micro-perforated board sound absorbing structure 350 may be disposed in the vibration direction of the diaphragm 320, and the angle between the normal to the side of the micro-perforated board of the micro-perforated board sound absorbing structure 350 facing the second acoustic cavity (or the plane on which the micro-perforated board is located) and the vibration direction may be in the range of 0° to 10°.

[0113] 19 is a schematic diagram of an acoustic device having a sound-absorbing structure according to some embodiments of the present disclosure. As shown in FIG. 19, the finely perforated plate 351 included in the acoustic device 500 may be disposed in the vibration direction of the diaphragm 320, and the normal to the side of the finely perforated plate 351 facing the second acoustic cavity 340 is essentially parallel to the vibration direction of the diaphragm 320. In this case, the second acoustic holes 312 are located on the side of the second acoustic cavity 340 adjacent to the finely perforated plate 351.

[0114] 20 is a schematic diagram of another acoustic device having a sound-absorbing structure according to some embodiments of the present disclosure. As shown in FIG. 20, the micro-perforated plate 351 included in the acoustic device 500 may be disposed in the vibration direction of the diaphragm, and the normal to the side of the micro-perforated plate 351 facing the second acoustic cavity 340 and the vibration direction of the diaphragm 320 form a certain angle α, the angle α being greater than 0° and less than 10°. In this case, the second acoustic holes 312 are located on the side of the second acoustic cavity 340 adjacent to the micro-perforated plate 351.

[0115] In some embodiments of the present specification, by arranging the micro-perforated board sound absorbing structure in the vibration direction of the diaphragm, the space of the rear cavity can be fully utilized, and the second acoustic hole located on the side of the sound generating unit (e.g., the upper wall US or the lower wall LS) can be arranged adjacent to the micro-perforated board sound absorbing structure. For example, when the second acoustic hole is arranged on the upper wall US or the lower wall LS shown in FIG. 3B , which is away from the ear canal opening of the sound generating unit, the micro-perforated board sound absorbing structure is arranged in the vibration direction of the diaphragm and is connected to the upper wall US and the lower wall LS, so that the micro-perforated board sound absorbing structure is arranged adjacent to the second acoustic hole, thereby improving the sound absorption effect of the micro-perforated board sound absorbing structure at the second acoustic hole. When multiple second acoustic holes are installed in the upper wall US or lower wall LS of the sound-generating unit, by arranging the micro-perforated sound-absorbing structure in the vibration direction of the diaphragm, the distance from each second acoustic hole to the micro-perforated sound-absorbing structure is short, thereby ensuring the overall sound-absorbing effect of the micro-perforated sound-absorbing structure for all second acoustic holes. Furthermore, the angle between the normal to the side of the micro-perforated sound-absorbing structure facing the second acoustic cavity and the vibration direction of the diaphragm may be set to be within the range of 0° to 10°, thereby avoiding the need to increase the thickness dimension of the sound-generating unit in the vibration direction due to an excessively large inclination angle of the micro-perforated sound-absorbing structure, which helps reduce the volume and / or weight of the sound-generating unit.

[0116] In some embodiments, when a micro-perforated sound absorbing structure is disposed in the vibration direction of the diaphragm for an acoustic device using the mounting method shown in FIG. 3A (i.e., a portion of the sound generating unit is inserted into the cavity of the concha), the micro-perforated sound absorbing structure may be disposed at one end of the sound generating unit away from the end FE along the longitudinal axis. This arrangement avoids an increase in the thickness of the end FE of the sound generating unit along the vibration direction, thereby preventing the sound generating unit from being too thick to be inserted into the cavity of the concha. In some embodiments, when a micro-perforated sound absorbing structure is disposed in the vibration direction of the diaphragm for an acoustic device using the mounting method shown in FIG. 5 (i.e., a portion of the sound generating unit covers the antihelical region), the micro-perforated sound absorbing structure may be disposed at any position along the length or width of the sound generating unit without affecting the mounting of the acoustic device.

[0117] In some embodiments, the angle between the normal to the side surface of the micro-perforated plate facing the second acoustic cavity and the vibration direction may be in the range of 0° to 10°, and the micro-perforated plate sound absorbing structure may not be arranged in the vibration direction of the diaphragm. For example, as shown in FIG. 28A, the angle between the normal to the side surface of the micro-perforated plate facing the second acoustic cavity and the vibration direction may be approximately 0°, and the micro-perforated plate sound absorbing structure may be arranged in the major axis direction Y of the sound generating unit. Also, for example, as shown in FIG. 29A, the angle between the normal to the side surface of the micro-perforated plate facing the second acoustic cavity and the vibration direction may be approximately 0°, and the micro-perforated plate sound absorbing structure may be arranged in the minor axis direction Z of the sound generating unit. For details on the arrangement of the micro-perforated plate sound absorbing structure in the major axis and / or minor axis directions, please refer to FIGS. 28A to 29C and their related descriptions.

[0118] 21 and 22 are diagrams illustrating the internal structure of an acoustic device according to some embodiments of the present disclosure.

[0119] 21 and 22 , a vibrating membrane 720 of an acoustic device 700 divides the receiving cavity of a housing 710 into a first acoustic cavity 730 and a second acoustic cavity 740, and the acoustic device further includes a coil 722, a frame 723, and a magnetic circuit assembly 721. The frame 723 is installed around the vibrating membrane 720, the coil 722, and the magnetic circuit assembly 721 to provide a mounting and fixing platform. The vibrating membrane 720 may be connected to the housing 710 by the frame 723. The vibrating membrane 720 covers the coil 722 and the magnetic circuit assembly 721 in the vibration direction. At least a portion of the coil 722 enters the magnetic gap formed by the magnetic circuit assembly 721 and is connected to the vibrating membrane 720. When the coil 722 is energized, the magnetic field generated interacts with the magnetic field formed by the magnetic circuit assembly 721 to drive the vibrating membrane 720 to generate mechanical vibrations, which then propagate through a medium such as air to generate sound. The sound is output from a hole in the housing 710. A micro-perforated plate sound absorbing structure may be disposed within the second acoustic cavity 740. For example, the micro-perforated plate sound absorbing structure may be disposed around the magnetic circuit assembly 721. The micro-perforated plate sound absorbing structure includes a micro-perforated plate 751 and a packing layer 753, and the side of the micro-perforated plate 751 away from the vibrating membrane 720 along the vibration direction is connected to the packing layer 753. The micro-perforated plate 751 has an annular structure and is disposed around the magnetic circuit assembly 721. The packing layer 753 is filled with N'Bass sound absorbing particles or a porous sound absorbing material. In some embodiments, the housing 710 (e.g., backplate 752) and the magnetic circuit assembly 721 may form a sealed cavity, i.e., the cavity of the micro-perforated plate sound absorbing structure, and the packing layer 753 may be filled within the cavity.

[0120] In some embodiments, the magnetic circuit assembly 721 includes a magnetically permeable plate 7211, a magnet 7212, and a magnetically permeable cover 7213, where the magnetically permeable plate 7211 and the magnet 7212 are connected to each other, the side of the magnet 7212 away from the magnetically permeable plate 7211 is attached to the bottom wall of the magnetically permeable cover 7213, and a magnetic gap is formed between the peripheral side of the magnet 7212 and the peripheral inner wall of the magnetically permeable cover 7213. In some embodiments, the peripheral outer wall of the magnetically permeable cover 7213 is connected and fixed to the frame 723. In some embodiments, both the magnetically permeable cover 7213 and the magnetically permeable plate 7211 can be made of a magnetically permeable material (e.g., iron, etc.).

[0121] In some embodiments, the micro-perforated plate 751 may have multiple through-holes, which are arranged around the magnet assembly to ensure appropriate hole spacing and aperture ratio. In some embodiments, a sealed cavity of a certain height must be formed on the side of the micro-perforated plate 751 away from the vibrating membrane. If the entire micro-perforated plate 751 were placed on the opposite side of the magnetic circuit assembly from the vibrating membrane, the micro-perforated plate 751 and the filling layer 753 would occupy too much space in the housing 710, making it difficult to meet the design requirements for a compact acoustic device. In the acoustic device 700 of this embodiment, the micro-perforated plate 751 has an annular structure around the magnetic circuit assembly, which not only effectively utilizes the circumferential space of the magnetic circuit assembly but also avoids increasing the thickness (i.e., the dimension along the vibration direction) of the acoustic device, thereby contributing to a compact acoustic device design.

[0122] As can be seen from the above, the cavity height D, the thickness of the micro-perforated plate 751, the hole diameter of the through holes, and the aperture ratio all affect the sound absorption bandwidth and sound absorption coefficient of the micro-perforated plate 751, and the comprehensive value of the above parameters can be seen from the following explanation.

[0123] In general, the acoustic impedance of a single through-hole in the micro-perforated plate 751 is:

[0124]

number

[0125] In equation (1), ρ is the air density, μ is the air kinetic viscosity coefficient, t is the thickness, and d is the hole diameter. If the thickness of the through-hole is the same as the hole diameter, it is necessary to consider modifying the end of the through-hole, i.e., increasing the effective thickness by 0.85d. When multiple through-holes are installed in the micro-perforated plate 751, the acoustic resistance is equivalent to the acoustic resistance of the multiple through-holes connected in parallel, i.e., the acoustic impedance of the micro-perforated plate 751 is obtained by dividing the acoustic impedance of a single through-hole by the aperture ratio.

[0126]

number

[0127] In equation (2), σ is the aperture ratio, k is the wave number, and the equation is

[0128]

number

[0129] where ω is the angular frequency and c is the speed of sound. The cavity 652 of the micro-perforated plate sound absorbing structure is equivalent to an acoustic capacitance, and its acoustic impedance is:

[0130]

number

[0131] In equation (3), D is the height of the cavity. The acoustic impedance of the micro-perforated plate sound absorbing structure may be expressed as:

[0132]

number

[0133] After normalization:

number

[0134] In equation (5), r is the relative acoustic impedance, and m is the relative acoustic mass, and specifically, it is as follows:

[0135]

number

[0136]

number

[0137] When sound waves are incident perpendicularly, the sound absorption coefficient α of the finely perforated plate sound absorbing structure can be calculated as follows:

[0138]

number

[0139] The resonance frequency of the sound absorbing structure 350 is as follows:

[0140]

number

[0141] As can be seen from equations (1) to (9), the sound absorption bandwidth and sound absorption coefficient of the sound absorbing structure 350 can be controlled by adjusting the hole diameter, aperture ratio, thickness, and cavity height of the finely perforated plate 751.

[0142] In addition, the values ​​of parameters such as hole diameter, open area ratio, thickness, and cavity height can be combined with the sound absorption coefficient, sound absorption frequency range, and structural dimensions to comprehensively determine the combination of parameters. For example, the sound absorption bandwidth and maximum sound absorption coefficient of a sound-absorbing structure are mutually constrained and can be balanced according to actual needs. For example, the smaller the hole diameter of a micro-perforated panel, the wider the sound absorption bandwidth. A wide sound absorption bandwidth corresponds to the effective hole diameter range. When the hole diameter is within the effective hole diameter range, the smaller the hole diameter, the higher the sound absorption effect. When the hole diameter is smaller than the effective hole diameter range, the sound absorption bandwidth is significantly narrowed. In addition, for example, a small hole diameter, a large open area ratio, a small thickness, and a small cavity height are suitable for a high-frequency sound absorption range, and conversely, for a low-frequency sound absorption range.

[0143] In some embodiments, the parameter combination of the micro-perforated plate 751 is determined based on the resonant frequency of the second acoustic cavity 740, so that the sound absorbing structure absorbs sound waves near the resonant frequency of the second acoustic cavity 740, avoiding changes in the phase and / or amplitude of the second sound waves due to resonance of the second acoustic cavity 740 near the resonant frequency, and further reducing the amplitude of the sound waves near the resonant frequency, thereby ensuring a sound leakage reduction effect. In some embodiments, the parameter combination of the micro-perforated plate 751 may be set so that the target frequency range of the sound absorption includes the resonant frequency, thereby absorbing sounds near the resonant frequency. In some embodiments, the second acoustic cavity 740 may resonate around 4 kHz, and because the human ear is sensitive to sounds near this frequency, the parameter range of the sound absorbing structure may be set to include 4 kHz to achieve more directional and effective sound leakage reduction.

[0144] In some embodiments, the micro-perforated plate 751 may have a hole diameter in the range of 0.2 mm to 0.4 mm, an open area ratio in the range of 1% to 5%, a thickness in the range of 0.2 mm to 0.7 mm, and a cavity height in the range of 4 mm to 9 mm. In some embodiments, the micro-perforated plate 751 may have a hole diameter in the range of 0.25 mm to 0.35 mm, an open area ratio in the range of 1.2% to 4.5%, a thickness in the range of 0.3 mm to 0.6 mm, and a cavity height in the range of 5 mm to 8 mm. By way of example only, the micro-perforated plate 751 may have a hole diameter of 0.25 mm, an open area ratio of 2.8%, a thickness in the range of 0.4 mm, and a cavity height in the range of 6 mm. For example, the micro-perforated plate 751 may have a hole diameter of 0.3 mm, a hole ratio of 3.2%, a thickness of 0.5 mm, and a cavity height of 6.5 mm. For example, the micro-perforated plate 751 may have a hole diameter of 0.35 mm, a hole ratio of 3.6%, a thickness of 0.55 mm, and a cavity height of 7 mm.

[0145] Figure 23A is a frequency response curve diagram of a second acoustic hole of an acoustic device. Figure 23B is a frequency response curve diagram of another second acoustic hole of an acoustic device. In Figures 23A and 23B, the horizontal axis represents frequency, and the vertical axis represents sound pressure level. Curve a1 represents the frequency response of the second acoustic hole of acoustic device 200 (without a micro-perforated plate sound absorbing structure), curve a2 represents the frequency response of another second acoustic hole of acoustic device 200, curve b1 represents the frequency response of the second acoustic hole of acoustic device 300 (with a micro-perforated plate sound absorbing structure), curve b2 represents the frequency response of another second acoustic hole of acoustic device 300, curve c1 represents the frequency response of the second acoustic hole of acoustic device 400 (with a micro-perforated plate sound absorbing structure and N'Bass sound absorbing particles), and curve c2 represents the frequency response of another second acoustic hole of acoustic device 400. The second acoustic hole and the other second acoustic hole are acoustic holes at different positions on the housing corresponding to the second acoustic cavity. Curves b1, b2, c1, and c2 are all measured under conditions where the micro-perforated plate has the above parameter combination, which is a hole diameter of 0.2 mm to 0.4 mm, an open area ratio of 1% to 5%, a thickness of 0.2 mm to 0.7 mm, and a cavity height of 4 mm to 9 mm. Specifically, the micro-perforated plate has a hole diameter of 0.3 mm, an open area ratio of 2.8%, a thickness of 0.6 mm, and a cavity height of 6 mm.

[0146] As shown in Figures 23A and 23B, curves a1 and a2 show a high resonant peak near 4 kHz, with 3.8 kHz corresponding to the resonant frequency of the second acoustic cavity. After the installation of the micro-perforated panel sound absorbing structure (curves b1 and b2), the sound pressure level is effectively reduced by 4 dB to 20 dB in the frequency range from 3 kHz to 6 kHz, reaching a minimum near 4 kHz. This allows the micro-perforated panel sound absorbing structure to effectively absorb sound waves in the 3 kHz to 6 kHz range, and the sound absorption of the micro-perforated panel sound absorbing structure near 4 kHz is approximately 20 dB. This reduces or prevents sound waves from resonating near the resonant frequency under the action of the second acoustic cavity, thereby reducing sound leakage at the resonant frequency. After the cavity of the micro-perforated panel sound absorbing structure is filled with N'Bass sound absorbing particles (curves c1 and c2), the sound absorption frequency range is expanded, and both of these combined sound absorption methods have excellent sound absorption effects. By setting the finely perforated plate 751 so that the hole diameter is in the range of 0.2 mm to 0.4 mm, the aperture ratio is in the range of 1% to 5%, the thickness is in the range of 0.2 mm to 0.7 mm, and the cavity height is in the range of 4 mm to 9 mm, sound waves of approximately 4 kHz can be effectively absorbed, thereby reducing sound leakage from acoustic devices at approximately 4 kHz.

[0147] FIG. 24 is a diagram illustrating the internal structure of an acoustic device according to some embodiments of the present disclosure.

[0148] 24 , acoustic device 800 includes a diaphragm 820, a magnetic circuit assembly 821, a coil (not shown), and a frame (not shown). The diaphragm 820 divides the receiving cavity of housing 810 into a first acoustic cavity 830 and a second acoustic cavity 840. The engagement between diaphragm 820, magnetic circuit assembly 821, coil, and frame is similar to that of acoustic device 700. A micro-perforated plate sound-absorbing structure is coupled to second acoustic cavity 840. Micro-perforated plate 851 is disposed on the opposite side of magnetic circuit assembly 821 from diaphragm 820, and micro-perforated plate 851 and magnetic circuit assembly 821 are disposed with a gap between them in the vibration direction. In some embodiments, the micro-perforated plate may be a panel that conforms to the shape of second acoustic cavity 840 or housing 810 (e.g., oval, circular, etc.). In some embodiments, the micro-perforated plate 851 may have parameters such as hole diameter, aperture ratio, and hole spacing that are consistent with the relevant parameters of the micro-perforated plate (e.g., an annular micro-perforated plate installed around the magnetic circuit assembly). In this way, the panel-structured micro-perforated plate has a larger area and a larger number of through holes, resulting in a higher sound absorption effect, a simpler structure, and easier assembly. In some embodiments, the micro-perforated plate 851 may have parameters that are different from those of the annular micro-perforated plate. For example, under the premise that the sound absorption frequency bands are maintained similar, the aperture ratio of the micro-perforated plate 851 installed at a distance from the magnetic circuit assembly may be smaller than the aperture ratio of the annular micro-perforated plate. In this case, the relatively large area of ​​the micro-perforated plate 851 still ensures a high sound absorption effect. Also, for example, under the premise that the sound absorption frequency band is maintained similar, the hole diameter of the finely perforated plate 851 installed at a distance from the magnetic circuit assembly may be larger than the hole diameter of the finely perforated plate with the above-mentioned annular structure, and in this case, since the area of ​​the finely perforated plate 851 is relatively large, a high sound absorption effect can still be ensured.

[0149] In some embodiments of the present specification, the micro-perforated plate and the magnetic circuit assembly are spaced apart in the vibration direction of the diaphragm, thereby improving the sound absorption effect of the micro-perforated plate sound absorbing structure, simplifying the structure and making it easy to assemble. In addition, the micro-perforated plate and the magnetic circuit assembly are spaced apart in the vibration direction of the diaphragm, allowing for more flexible design of parameters such as hole diameter and aperture ratio, ensuring sound absorption effect, and simplifying the manufacturing process.

[0150] In some embodiments, for an acoustic device using the mounting method shown in Figure 5 (i.e., the sound generating unit partially covers the antihelix region), the perforated plate and magnetic circuit assembly are installed at intervals in the vibration direction of the diaphragm, thereby improving the sound absorption effect of the fine perforated plate sound absorbing structure without affecting the mounting of the acoustic device, and allowing for more flexible design of parameters such as hole diameter and opening rate.

[0151] In some embodiments, by determining the parameter combination of the micro-perforated plate 851 based on the resonant frequency of the second acoustic cavity 840, the sound absorbing structure absorbs sound waves near the resonant frequency of the second acoustic cavity 840, avoiding changes in the phase and / or amplitude of the second sound waves due to resonance of the second acoustic cavity 840 near the resonant frequency, and further reducing the amplitude of the sound waves near the resonant frequency, thereby reducing sound leakage. In some embodiments, the parameter combination of the micro-perforated plate 851 may be set so that the target frequency range of the sound absorption includes the resonant frequency, thereby absorbing sound near the resonant frequency. In some embodiments, the second acoustic cavity 840 may resonate around 4 kHz, and because the human ear is sensitive to sound near this frequency, the parameter range of the sound absorbing structure may be set to include 4 kHz in order to achieve more directional and effective sound leakage reduction.

[0152] In some embodiments, the micro-perforated plate 851 may have a hole diameter in the range of 0.1 mm to 0.2 mm, an open area ratio in the range of 2% to 5%, a thickness in the range of 0.2 mm to 0.7 mm, and a cavity height in the range of 7 mm to 10 mm. By way of example only, the micro-perforated plate 851 may have a hole diameter in the range of 0.1 mm to 0.2 mm, an open area ratio in the range of 2.18% to 4.91%, a thickness in the range of 0.3 mm to 0.6 mm, and a cavity height in the range of 7.5 mm to 9.5 mm. For example, the micro-perforated plate 851 may have a hole diameter of 0.15 mm, an open area ratio of 2.18%, a thickness in the range of 0.3 mm, and a cavity height in the range of 8 mm. For example, the micro-perforated plate 851 may have a hole diameter of 0.15 mm, a hole ratio of 2.76%, a thickness of 0.4 mm, and a cavity height of 8.5 mm. For example, the micro-perforated plate 851 may have a hole diameter of 0.15 mm, a hole ratio of 3.61%, a thickness of 0.5 mm, and a cavity height of 9 mm.

[0153] In some embodiments of the present specification, by setting the parameter combination of the fine-perforated plate so that the hole diameter is in the range of 0.1 mm to 0.2 mm, the aperture ratio is in the range of 2% to 5%, the thickness is in the range of 0.2 mm to 0.7 mm, and the cavity height is in the range of 7 mm to 10 mm, the target frequency range of the sound-absorbing structure including the fine-perforated plate includes 4 kHz, and an optimal sound absorption effect is achieved around 4 kHz, thereby reducing or avoiding sound waves from resonating around the resonant frequency under the action of the second acoustic cavity, and reducing sound leakage at the resonant frequency.

[0154] In some embodiments, the second acoustic cavity (e.g., second acoustic cavity 740 shown in FIG. 21, second acoustic cavity 840 shown in FIG. 24, etc.) may resonate around 2 kHz to 3 kHz, and since the human ear is sensitive to sounds around this frequency, the parameter range may be set so that the target frequency range of the sound absorbing structure includes 2 kHz to 3 kHz in order to achieve more directional and effective sound leakage reduction.

[0155] In some embodiments, a micro-perforated plate (e.g., micro-perforated plate 751, micro-perforated plate 851, etc.) may have a hole diameter in the range of 0.1 mm to 0.3 mm, an open area ratio in the range of 0.5% to 5%, a thickness in the range of 0.2 mm to 0.6 mm, and a cavity height in the range of 4 mm to 10 mm. By way of example only, a micro-perforated plate may have a hole diameter in the range of 0.2 mm to 0.3 mm, an open area ratio in the range of 0.7% to 2.3%, a thickness in the range of 0.25 mm to 0.55 mm, and a cavity height in the range of 4 mm to 7.5 mm. For example, to achieve a sound absorption center frequency of approximately 3 kHz for a micro-perforated plate sound absorbing structure, the micro-perforated plate may have a hole diameter of 0.2 mm, an open area ratio of 0.87%, a thickness of 0.3 mm, and a cavity height of 4.5 mm. For example, to set the central sound absorption frequency of the micro-perforated panel sound absorbing structure to around 3 kHz, the micro-perforated panel may have a hole diameter of 0.25 mm, a hole ratio of 1%, a thickness of 0.4 mm, and a cavity height of 4.5 mm.Furthermore, for example, to set the central sound absorption frequency of the micro-perforated panel sound absorbing structure to around 3 kHz, the micro-perforated panel may have a hole diameter of 0.3 mm, a hole ratio of 0.97%, a thickness of 0.4 mm, and a cavity height of 4.5 mm.

[0156] In some embodiments of the present specification, by setting the parameter combination of the fine-perforated plate so that the hole diameter is in the range of 0.1 mm to 0.3 mm, the aperture ratio is in the range of 0.5% to 5%, the thickness is in the range of 0.2 mm to 0.6 mm, and the cavity height is in the range of 4 mm to 10 mm, the target frequency range of the sound-absorbing structure including the fine-perforated plate includes 2 kHz to 3 kHz, and an optimal sound absorption effect is achieved around 2 kHz to 3 kHz, thereby achieving more directional and effective sound leakage reduction.

[0157] In some embodiments, the cavity of the micro-perforated plate sound absorbing structure may include a regular or irregular shape, such as a sphere, a cylinder, or a racetrack. For example, the cavity may be a ring-shaped cavity disposed around the magnetic circuit assembly, as shown in FIG. 25A. For example, the cavity may be a flat plate-shaped cavity, as shown in FIG. 25B. In some embodiments, as shown in FIGS. 25A and 25B, the cavity height and the cross-sectional area perpendicular to the cavity height are different, but the cavity volume is the same. Based on this, we will combine FIG. 26 to determine the effect of the cavity volume and cavity height on the sound absorbing effect of the sound absorbing structure.

[0158] FIG. 26 is a frequency response curve diagram of the second acoustic hole of the acoustic device shown in FIGS. 25A and 25B. In FIG. 26, the horizontal axis represents frequency, and the vertical axis represents sound pressure level. Curve 261 represents the frequency response of the second acoustic hole of the acoustic device shown in FIG. 25A, and curve 262 represents the frequency response of the same second acoustic hole of the acoustic device shown in FIG. 25B. Curve 261 was measured when the micro-perforated plate had a parameter combination of 0.3 mm hole diameter, 2.1% open area ratio, 0.6 mm thickness, and 4 mm cavity height. Curve 262 was measured when the micro-perforated plate had a parameter combination of 0.3 mm hole diameter, 2.1% open area ratio, 0.6 mm thickness, and 2 mm cavity height. The cavities of the acoustic devices shown in FIGS. 25A and 25B were filled with the same volume of N'Bass sound-absorbing particles, and the cavity volumes corresponding to the two curves were the same. As shown in Figure 26, curve 261 essentially overlaps with curve 262. This means that, while the volume of the cavity in the sound-absorbing structure remains unchanged, adjusting the cavity height and shape has a negligible effect on the sound-absorbing effect of the sound-absorbing structure. Therefore, in some embodiments, the cavity height and shape may be adjusted without changing the volume of the cavity in the sound-absorbing structure to meet the functional and structural needs of the acoustic device. For example, by reducing the cavity height without changing the volume of the cavity in the sound-absorbing structure, the dimensions of the acoustic device can be reduced, allowing for a more compact design.

[0159] FIG. 27 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure.

[0160] As shown in FIG. 27 , in some embodiments, the orientation A of the micro-perforated plate 351 may be inclined relative to the vibration direction, i.e., the normal of the side of the micro-perforated plate 351 facing the second acoustic cavity forms a certain angle α with the vibration direction. For example, 10°<α<90°. In some embodiments, as shown in FIG. 27 , the acoustic device 900 has two second acoustic holes (i.e., second acoustic holes 3121 and 3122), which may be located on opposite sides of the housing 310, for example, facing back to back in a direction perpendicular to the vibration direction, to maximize the destruction of the high-pressure region of the sound field in the second acoustic cavity. Taking the acoustic device 10 shown in FIG. 3A above, in which a portion of the sound-generating unit is inserted into the cavity of the concha when worn, as an example, and combining FIG. 27 , the first acoustic hole 311 is located on the inner surface IS facing the ear canal, the second acoustic hole 3122 is located on the upper wall US, and the second acoustic hole 3121 is located on the lower wall LS. In some embodiments, the distance to the inner surface IS of the second acoustic hole 3121 and the distance to the inner surface IS of the second acoustic hole 3122 in the vibration direction (i.e., the thickness direction X shown in FIG. 3A ) may be different. In this case, the micro-perforated plate 351 may be inclined so that the distances to the two second acoustic holes of the micro-perforated plate 351 (e.g., the connection point between the micro-perforated plate 351 and the housing 310) are the same or close to each other, thereby ensuring that the sound absorption effects of the two second acoustic holes by the micro-perforated plate 351 are essentially the same. Specifically, the direction B of the line connecting the centers of the two second acoustic holes is approximately parallel to the arrangement direction A of the micro-perforated plate, or the difference between the shortest distance from the centroid of the second acoustic hole 3121 to the micro-perforated plate 351 and the shortest distance from the centroid of the second acoustic hole 3122 to the micro-perforated plate 351 is within a predetermined range, for example, not exceeding 1 / 10 of the dimension in the vibration direction of the sound generating unit.

[0161] In some embodiments, the distance to the inner surface IS of the second acoustic hole 3121 may be the same as the distance to the inner surface IS of the second acoustic hole 3122. When a part of the sound generating part of the acoustic device is inserted into the cavity of the concha or covers the antihelical region in the worn state (for example, as shown in FIG. 3A or FIG. 5), the distance from the second acoustic hole 3122 located on the lower wall LS to the opening of the ear canal is shorter, and the sound absorbing structure 350 can be adjusted to absorb more of the sound emitted from the second acoustic hole 3122 to avoid cancellation in the near field between the sound emitted from the second acoustic hole 3122 and the sound emitted from the first acoustic hole 311. At this time, the finely perforated plate 351 is more inclined with respect to the second acoustic hole 3122, so that the distance from the finely perforated plate 351 to the second acoustic hole 3122 is shorter than the distance from the finely perforated plate 351 to the second acoustic hole 3121, and therefore the sound absorption effect at the second acoustic hole 3122 of the finely perforated plate 351 is higher than the sound absorption effect at the second acoustic hole 3121 of the finely perforated plate 351. By installing it in this manner, the amount of sound emitted from the second acoustic hole 3122 located on the lower wall LS is relatively small, which reduces the interference and cancellation in the near field between the sound emitted from the second acoustic hole 3122 and the sound emitted from the first acoustic hole 311, thereby ensuring a good listening effect at the ear canal opening.

[0162] 28A to 28C are schematic configuration diagrams of acoustic devices according to some embodiments of the present specification.

[0163] In some embodiments, as shown in FIGS. 28A to 28C , the housing 310 included in the acoustic device 1000 has a major axis direction Y and a minor axis direction Z that are perpendicular to the vibration direction of the diaphragm 320 (i.e., the thickness direction X) and perpendicular to each other, and the micro-perforated plate structure may be disposed in the major axis direction. For example, a certain angle is formed between the side surface of the micro-perforated plate 351 facing the second acoustic cavity 340 and the major axis direction Y, and the angle may be in the range of 0° to 90°. For a specific description of the thickness direction X, the major axis direction Y, and the minor axis direction Z, please refer to FIG. 3A . Note that the angle here is the absolute value of the angle between the side surface of the micro-perforated plate 351 and the major axis direction Y. For example, for the micro-perforated plate sound absorbing structures 350 and 350′ shown in FIG. 28C , the angle between the side surface of the micro-perforated plate facing the second acoustic cavity 340 and the major axis direction Y is both 90°.

[0164] In some embodiments, a certain angle β is formed between the orientation of the micro-perforated plate 351 and the longitudinal axis direction Y, where 0°≦β≦90°. In some embodiments, as shown in FIG. 28A , the side of the micro-perforated plate 351 facing the second acoustic cavity 340 may be approximately parallel to the longitudinal axis direction Y. In some embodiments, as shown in FIG. 28B , the angle β between the side of the micro-perforated plate 351 facing the second acoustic cavity 340 and the longitudinal axis direction Y is greater than 0° and less than 90°. In some embodiments, as shown in FIG. 28C , the side of the micro-perforated plate 351 facing the second acoustic cavity 340 is approximately perpendicular to the longitudinal axis direction Y. In some embodiments, in order to ensure the sound absorption effect of the micro-perforated plate sound absorbing structure, when the side of the micro-perforated plate 351 facing the second acoustic cavity 340 is approximately perpendicular to the longitudinal axis direction Y, the micro-perforated plate 351 is installed toward or close to the second acoustic hole, thereby reducing the distance between the micro-perforated plate 351 and the second acoustic hole as much as possible and improving the sound absorption effect.

[0165] In some embodiments, to accommodate the wearing style of the acoustic device in which the sound-generating unit is inserted into the cavity of the concha, as shown in FIG. 3A , the dimension of the sound-generating unit along the longitudinal axis direction Y is appropriately increased so that the end FE of the sound-generating unit can be positioned within the cavity of the concha of the user. In some embodiments, when the dimension of the acoustic device 1000 along the longitudinal axis direction Y is large, the fine-perforated plate 351 is positioned close to the second acoustic hole to better absorb sound waves from the second acoustic hole. In some embodiments, the fine-perforated plate 351 is positioned approximately along the longitudinal axis direction Y to prevent assemblies inside the housing 310 (e.g., a diaphragm, a magnetic circuit assembly, etc.) from affecting the absorption of sound waves from the second acoustic hole by the fine-perforated plate 351. In some embodiments, if the vibrating membrane 320 cannot completely cover the second acoustic cavity 340 along the longitudinal axis direction Y, a partition plate 313 arranged along the longitudinal axis direction Y may be installed, and the partition plate 313 and the vibrating membrane 320 together divide the interior of the housing 310 to form the first acoustic cavity 330 and the second acoustic cavity 340.

[0166] In some embodiments of the present invention, the micro-perforated sound absorbing structure can be positioned approximately along the longitudinal axis Y to appropriately increase the dimension of the sound generating unit along the longitudinal axis Y. For example, in the mounting method shown in FIG. 3A , the end FE of the sound generating unit can be more easily inserted into the cavity of the concha. Furthermore, when the micro-perforated sound absorbing structure is positioned along the longitudinal axis Y, the cavity extending along the longitudinal axis Y of the sound generating unit has a sufficiently large space. For example, in the thickness direction, the extending cavity does not include a magnetic circuit assembly, so parameters such as the position and height of the cavity in the micro-perforated sound absorbing structure are not limited by the magnetic circuit assembly. This allows the cavity height in the micro-perforated sound absorbing structure to be increased and the sound absorption effect to be improved. Alternatively, if the cavity height in the sound absorbing structure does not change, the micro-perforated sound absorbing structure can be positioned upward (e.g., in the positive X direction shown in FIG. 28A ), thereby reducing the thickness dimension of the sound generating unit.

[0167] 28A to 28C are merely examples, and when the micro-perforated plate sound absorbing structure is installed along the longitudinal axis direction Y, parameters such as the position and orientation of the micro-perforated plate sound absorbing structure may not be limited to the examples shown in Figures 28A to 28C. In some embodiments, when the micro-perforated plate sound absorbing structure is installed along the longitudinal axis direction Y, the side of the micro-perforated plate facing the second acoustic cavity 340 may be approximately facing another side wall of the housing 310, for example, approximately facing the upper wall and / or lower wall where the second acoustic holes are located, as long as the micro-perforated plate mainly faces the second acoustic cavity (i.e., does not face away from the rear side of the diaphragm), and this specification is not limited thereto.

[0168] 29A to 29C are schematic configuration diagrams of acoustic devices according to some embodiments of the present specification.

[0169] In some embodiments, as shown in FIGS. 29A to 29C , the housing 310 included in the acoustic device 1100 has a major axis direction Y and a minor axis direction Z that are perpendicular to the vibration direction of the diaphragm 320 (i.e., the thickness direction X) and are orthogonal to each other. The fine-perforated plate structure may be disposed in the minor axis direction. For example, a certain angle is formed between the side surface of the fine-perforated plate 351 facing the second acoustic cavity 340 and the minor axis direction Z. The angle may be within a range of 0° to 90°. For a specific description of the thickness direction X, the major axis direction Y, and the minor axis direction Z, please refer to FIG. 3A . Note that the angle here is the absolute value of the angle between the side surface of the fine-perforated plate 351 and the minor axis direction Z, as described above.

[0170] In some embodiments, a certain angle γ is formed between the arrangement direction of the micro-perforated plate 351 and the short axis direction Z, and 0°≦γ≦90°. In some embodiments, as shown in FIG. 29A , the side of the micro-perforated plate 351 facing the second acoustic cavity 340 may be approximately parallel to the short axis direction Z. In some embodiments, as shown in FIG. 29B , the angle γ between the side of the micro-perforated plate 351 facing the second acoustic cavity 340 and the short axis direction Z is greater than 0° and less than 90°. In some embodiments, as shown in FIG. 29C , the side of the micro-perforated plate 351 facing the second acoustic cavity 340 may be approximately perpendicular to the short axis direction Z.

[0171] In some embodiments, to accommodate the wearing method of the acoustic device in which the sound generating unit can be located in the antihelix region as shown in FIG. 5 , the dimension of the sound generating unit along the short axis direction Z can be appropriately increased so that the sound generating unit (e.g., the first acoustic hole) is closer to the ear canal. In some embodiments, when the dimension of the acoustic device 1100 along the short axis direction Z is large, the fine-perforated plate 351 is positioned closer to the second acoustic hole to better absorb sound waves from the second acoustic hole. In some embodiments, the fine-perforated plate 351 and the diaphragm 320 are positioned approximately along the short axis direction Z to prevent assemblies inside the housing 310 (e.g., a diaphragm, a magnetic circuit assembly, etc.) from affecting the absorption of sound waves from the second acoustic hole by the fine-perforated plate 351. In some embodiments, if the vibrating membrane 320 cannot completely cover the second acoustic cavity 340 along the short axis direction Z, a partition plate 313 arranged along the short axis direction Z may be installed, and the partition plate 313 and the vibrating membrane 320 together divide the interior of the housing 310 to form the first acoustic cavity 330 and the second acoustic cavity 340.

[0172] In some embodiments of the present invention, by arranging the micro-perforated plate approximately along the short-axis direction Z, the dimension of the sound-generating unit along the short-axis direction Z can be appropriately increased. For example, in the wearing method shown in FIG. 5, the first acoustic hole of the sound-generating unit is closer to the ear canal, improving the user's listening experience. Furthermore, when the micro-perforated plate sound-absorbing structure is arranged along the short-axis direction Z, the cavity extending along the short-axis direction Z of the sound-generating unit has a sufficiently large space. For example, in the thickness direction, the extending cavity does not include a magnetic circuit assembly, so parameters such as the position and height of the cavity in the micro-perforated plate sound-absorbing structure are not limited by the magnetic circuit assembly. This allows the cavity height in the micro-perforated plate sound-absorbing structure to be increased and the sound absorption effect to be improved. Alternatively, if the cavity height in the sound-absorbing structure does not change, the micro-perforated plate sound-absorbing structure may be arranged upward (e.g., in the positive X direction shown in FIG. 29A), thereby reducing the thickness dimension of the sound-generating unit.

[0173] Note that the fine-perforated sound-absorbing structures shown in Figures 29A to 29C are merely examples, and when the fine-perforated sound-absorbing structure is installed along the short-axis direction Z, parameters such as the position and orientation of the fine-perforated sound-absorbing structure do not have to be limited to the examples shown in Figures 29A to 29C. For example, the side of the micro-perforated plate 351 shown in Figures 29A to 29C facing the second acoustic cavity 340 may be approximately facing the upper wall where the first acoustic hole 311 is located or the side wall (e.g., the upper wall or lower wall) where the second acoustic hole is located, and in some embodiments, when the micro-perforated plate sound absorbing structure is installed along the short axis direction Z, the side of the micro-perforated plate facing the second acoustic cavity 340 may be approximately facing the other side wall of the housing 310, for example, facing both ends along the long axis direction Y of the housing 310 (e.g., toward the end FE or on the opposite side from the end FE), as long as the micro-perforated plate is mainly facing the second acoustic cavity (i.e., not facing away from the rear side of the vibration membrane), and this specification is not limited thereto.

[0174] FIG. 30 is a schematic diagram of an acoustic device according to some other embodiments of the present specification.

[0175] 30 , in some embodiments, the sound absorbing structure of acoustic device 1200 may include a plurality of independently installed sub-sound absorbing structures, such as sub-sound absorbing structure 350a, sub-sound absorbing structure 350b, etc. In some embodiments, each sub-sound absorbing structure includes a sub-micro-perforated plate and a sub-cavity, for example, sub-sound absorbing structure 350a includes sub-micro-perforated plate 351a and sub-cavity 352a, and sub-sound absorbing structure 350b includes sub-micro-perforated plate 351b and sub-cavity 352b.

[0176] In some embodiments, instead of a relatively large sound absorbing structure, multiple independently installed sub-sound absorbing structures with smaller volumes may be installed within second acoustic cavity 340. In some embodiments, multiple sub-sound absorbing structures may be installed at different positions within second acoustic cavity 340. Flexible design of the installation positions of the sub-sound absorbing structures allows for full utilization of the space within second acoustic cavity 340, contributing to the miniaturization of acoustic device 1200. In some embodiments, when acoustic device 1200 has multiple second acoustic holes, one or more sub-sound absorbing structures may be installed corresponding to each second acoustic hole so that sound waves from each second acoustic hole are all absorbed by the sound absorbing structure, ensuring a sound absorbing effect. In some embodiments, the positions and number of sub-sound absorbing structures corresponding to each second acoustic hole may be adjusted so that the sound absorbing effect of the sound absorbing structure for each second acoustic hole is different. For example, to reduce cancellation in the near field between the second acoustic hole and the first acoustic hole, the distance between the sub-sound absorbing structure and the second acoustic hole may be made smaller, or more sub-sound absorbing structures may be placed around the second acoustic hole. In some embodiments, the parameter combinations of the multiple sub-sound absorbing structures may be different so that the target frequency ranges in which the multiple sub-sound absorbing structures absorb sound are different and sound absorption in different frequency bands is achieved.

[0177] Although the basic concepts have been described above, it will be apparent to those skilled in the art that the detailed disclosure above is merely provided by way of example and is not intended to limit the present specification. Although not expressly described herein, those skilled in the art may make various changes, improvements, and modifications to the present specification. These changes, improvements, and modifications are intended to be suggested by the present specification and are therefore within the spirit and scope of the exemplary embodiments of the present specification.

[0178] Additionally, certain terms are used herein to describe embodiments of the present specification. For example, "one embodiment," "one embodiment," and / or "some embodiments" refer to particular features, structures, or characteristics associated with at least one embodiment of the present specification. Therefore, it is emphasized and understood that two or more references to "one embodiment" or "one embodiment" or "one alternative embodiment" in various parts of the present specification do not necessarily all refer to the same embodiment. Furthermore, particular features, structures, or characteristics of one or more embodiments of the present specification may be combined as appropriate.

[0179] Additionally, unless expressly stated in the claims, the enumerated order of processing elements or sequences described herein, the use of alphanumeric characters, or the use of other designations does not limit the order of the procedures and methods herein. While the above disclosure has set forth through various examples what are presently believed to be various useful embodiments of the invention, it should be understood that such details are merely illustrative, and that the appended claims are not limited to the disclosed embodiments, but rather are intended to cover all modifications and equivalent combinations within the spirit and scope of the embodiments herein. For example, the system assembly described above may be implemented by a hardware device, or may be implemented as a software-only solution, e.g., by installing the described system on an existing server or mobile device.

[0180] Similarly, in the foregoing description of embodiments herein, it should be understood that various features may be grouped together in a single embodiment, drawing, or description for the purpose of simplifying the description and facilitating an understanding of one or more embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed subject matter requires more features than are recited in each claim. In fact, an embodiment may include fewer than all features of a single embodiment disclosed above.

[0181] In some embodiments, numbers describing the number of components and attributes are used; it should be understood that the numbers describing such embodiments are, in some instances, modified by the modifiers "about," "approximately," or "generally." Unless otherwise specified, "about," "approximately," or "generally" indicates that the number may vary by ±20%. Thus, in some embodiments, all numerical parameters used in the specification and claims are approximations that may vary depending on the specific characteristics of a particular embodiment. In some embodiments, numerical parameters should be used with the stated number of significant digits and with ordinary rounding techniques. While the numerical ranges and parameters used to determine ranges in some embodiments herein are approximations, in specific embodiments, such numerical values ​​are set as precisely as possible.

[0182] All patents, patent applications, published patent applications, and other materials, such as papers, books, specifications, publications, and documents, referenced herein are incorporated herein by reference in their entirety, except for prosecution history documents that are inconsistent with or inconsistent with the content of this specification and documents that may have a limiting effect on the broadest scope of the claims herein (now or later related to this specification). Furthermore, to the extent that explanations, definitions, and / or term usage in the accompanying materials herein are inconsistent with or inconsistent with the content set forth herein, the explanations, definitions, and / or term usage in this specification shall control.

[0183] Finally, it should be understood that the embodiments described herein are merely illustrative of the principles of the embodiments herein. Other variations may be within the scope of the present disclosure. Thus, by way of example, and not of limitation, alternative configurations of the embodiments herein may be considered consistent with the teachings herein. Thus, the embodiments herein are not limited to the embodiments expressly introduced and described herein. [Explanation of symbols]

[0184] 10 Sound equipment 11. Sound generation section 112 1st acoustic hole 113 2nd acoustic hole 310 Housing 313 Partition 320 Vibrating membrane 340 Second Acoustic Cavity 350 Fine perforated plate sound absorption structure 350a sub-sound absorbing structure 351a Sub-fine perforated plate 352a Subcavity 351 Fine perforated plate 352 Cavity 353 Gauze 354 Filling material 721 Magnetic Circuit Assembly 722 Coil 723 frames 7211 Magnetically permeable plate 7212 Magnet 7213 Magnetically Permeable Cover

Claims

1. A diaphragm; a housing that accommodates the diaphragm and has a first acoustic cavity and a second acoustic cavity formed on a front side and a rear side of the diaphragm, respectively, wherein the diaphragm radiates sound into the first acoustic cavity and the second acoustic cavity, respectively, and emits sound from a first acoustic hole coupled to the first acoustic cavity and a second acoustic hole coupled to the second acoustic cavity, respectively; a sound absorbing structure coupled to the second acoustic cavity, absorbing sound within a target frequency range that passes through the second acoustic cavity and is transmitted to the second acoustic hole, the sound absorbing structure including a micro-perforated plate and a cavity, the micro-perforated plate including through holes, and the second acoustic cavity communicating with the cavity through the through holes; a suspension structure for mounting the housing near the user's ear canal in a position that does not block the ear canal opening.

2. 2. The acoustic device according to claim 1, wherein a ratio of the open area of ​​the first acoustic hole to the open area of ​​the second acoustic hole is in a range of 0.5 to 2.

3. The acoustic device of claim 1 , wherein a difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.

15.

4. The acoustic device according to any one of claims 1 to 3, wherein the angle between the normal to the side of the finely perforated plate facing the second acoustic cavity and the vibration direction of the vibrating membrane is in the range of 0° to 90°.

5. 5. The acoustic device of claim 4, wherein the sound-absorbing structure is installed in the vibration direction of the diaphragm, and the angle between the normal to the side of the fine-perforated plate facing the second acoustic cavity and the vibration direction of the diaphragm is in the range of 0° to 10°.

6. a magnetic circuit assembly; 6. The acoustic device of claim 5, further comprising: a coil connected to the diaphragm and at least a portion of which is located in a magnetic gap formed by the magnetic circuit assembly, the coil vibrating the diaphragm to generate sound when energized; and the micro-perforated plate including an annular structure disposed around the magnetic circuit assembly.

7. 7. The acoustic device of claim 6, wherein the through-hole diameter is in the range of 0.2 mm to 0.4 mm, the aperture ratio of the micro-perforated plate is in the range of 1% to 5%, the thickness of the micro-perforated plate is in the range of 0.2 mm to 0.7 mm, and the height of the cavity is in the range of 4 mm to 9 mm.

8. 8. The acoustic device of claim 7, wherein the target frequency range includes 4 kHz.

9. 7. The acoustic device of claim 6, wherein the through-hole diameter is in the range of 0.1 mm to 0.3 mm, the aperture ratio of the micro-perforated plate is in the range of 0.5% to 5%, the thickness of the micro-perforated plate is in the range of 0.2 mm to 0.6 mm, and the height of the cavity is in the range of 4 mm to 10 mm.

10. 10. The acoustic device of claim 9, wherein the target frequency range comprises 2 kHz to 3 kHz.

11. a magnetic circuit assembly; 6. The acoustic device of claim 5, further comprising a coil connected to the diaphragm and at least a portion of which is located in a magnetic gap formed by the magnetic circuit assembly, the coil vibrating the diaphragm to generate sound when energized, and the micro-perforated plate and the magnetic circuit assembly being spaced apart in the vibration direction of the diaphragm.

12. 12. The acoustic device of claim 11, wherein the through-hole diameter is in the range of 0.1 mm to 0.2 mm, the aperture ratio of the micro-perforated plate is in the range of 2% to 5%, the thickness of the micro-perforated plate is in the range of 0.2 mm to 0.7 mm, and the height of the cavity is in the range of 7 mm to 10 mm.

13. 13. The acoustic device of claim 12, wherein the target frequency range includes 4 kHz.

14. 12. The acoustic device of claim 11, wherein the through-hole diameter is in the range of 0.1 mm to 0.3 mm, the aperture ratio of the micro-perforated plate is in the range of 0.5% to 5%, the thickness of the micro-perforated plate is in the range of 0.2 mm to 0.6 mm, and the height of the cavity is in the range of 4 mm to 10 mm.

15. 15. The acoustic device of claim 14, wherein the target frequency range comprises 2 kHz to 3 kHz.

16. 5. The acoustic device of claim 4, wherein the housing has long and short axis directions that are perpendicular to the vibration direction of the diaphragm and perpendicular to each other, the sound absorbing structure is installed in the long axis direction, and the angle between the side of the finely perforated plate facing the second acoustic cavity and the long axis direction is in the range of 0° to 90°.

17. 17. The acoustic device of claim 16, wherein the side of the micro-perforated plate facing the second acoustic cavity is perpendicular to the longitudinal axis.

18. 5. The acoustic device of claim 4, wherein the housing has a major axis direction and a minor axis direction that are perpendicular to the vibration direction of the diaphragm and are orthogonal to each other, the sound absorbing structure is installed in the minor axis direction, and the angle between the side of the finely perforated plate facing the second acoustic cavity and the minor axis direction is in the range of 0° to 90°.

19. 19. The acoustic device of claim 18, wherein the side of the micro-perforated plate facing the second acoustic cavity is perpendicular to the minor axis direction.

20. 2. The acoustic device according to claim 1, wherein the sound absorbing structure comprises a plurality of independently installed sub-sound absorbing structures, each of which comprises a sub-micro-perforated plate and a sub-cavity.

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