Audio devices

Abstract

An embodiment of the present specification provides an acoustic device, the acoustic device including: a diaphragm; a housing that accommodates the diaphragm and has a first acoustic cavity and a second acoustic cavity formed corresponding to a front side and a rear side of the diaphragm, respectively; 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; and a sound absorbing structure coupled to the second acoustic cavity that absorbs sound that passes through the second acoustic cavity and is transmitted to the second acoustic hole within a target frequency range including a resonant frequency of the second acoustic cavity.

Description

[Technical Field]

[0001] The present disclosure relates to the field of acoustic devices, and more particularly to acoustic devices.

[0002] [Incorporated by reference] This application claims priority from an international application with application number PCT / CN2022 / 101273, filed on June 24, 2022, and from a Chinese application with application number 202211455122.0, filed on November 21, 2022, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] To solve the problem of sound leakage from an acoustic device, two or more sound sources are typically used to generate two out-of-phase acoustic signals. Under far-field conditions, the difference in acoustic distance between the two out-of-phase sound sources and a specific point in the far-field is essentially negligible, so the two acoustic signals cancel each other out, reducing far-field sound leakage. 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 than 1 / 2 Hz, and under far-field conditions, the distance between the two sound sources is not negligible relative to the wavelength, so the sound signals from the two sound sources cannot be canceled out. Furthermore, for example, when the acoustic transmission structure of an acoustic device resonates, there is a certain phase difference between the phase of the acoustic signal actually emitted from the sound outlet of the acoustic device and the original phase at the sound wave generation position, which adds an additional resonance peak to the transmitted sound wave, causing a disturbance in the sound field distribution, making it difficult to ensure the effect of reducing far-field sound leakage at high frequencies and potentially increasing sound leakage. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, it is desirable to provide an acoustic device that has excellent sound field directionality. [Means for solving the problem]

[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, 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; and a sound-absorbing structure that is coupled to the second acoustic cavity and absorbs sound that passes through the second acoustic cavity and is transmitted to the second acoustic hole, within a target frequency range that includes the resonant frequency of the second acoustic cavity.

[0006] In some embodiments, the target frequency range further includes a resonant frequency of the first acoustic cavity.

[0007] In some embodiments, the target frequency range includes 3 kHz to 6 kHz.

[0008] In some embodiments, the sound absorbing effect of the sound absorbing structure for sounds in the target frequency range is 3 dB or greater.

[0009] In some embodiments, the sound absorbing effect of the sound absorbing structure on sound at the resonant frequency is 14 dB or greater.

[0010] In some embodiments, the sound absorbing structure comprises a micro-perforated plate and a cavity, the micro-perforated plate comprising a through hole, and the second acoustic cavity coupled to the sound absorbing structure communicates with the cavity via the through hole.

[0011] In some embodiments, the cavity is filled with N'Bass sound absorbing particles.

[0012] In some embodiments, the N'Bass sound absorbing particles have a diameter in the range of 0.15 mm to 0.7 mm.

[0013] In some embodiments, the filling rate of the N'Bass sound absorbing particles in the cavity is in the range of 70% to 95%.

[0014] In some embodiments, gauze is placed between the N'Bass sound absorbing particles and the micro-perforated plate.

[0015] In some embodiments, the cavity is filled with a porous sound absorbing material, the porous sound absorbing material having a porosity greater than 70%.

[0016] In some embodiments, the ratio of the spacing between the through-holes to the diameter of the through-holes is greater than 5.

[0017] In some embodiments, the ratio of the wavelength of sound in the target frequency range to the hole spacing between the through-holes in the micro-perforated plate is greater than five.

[0018] 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.

[0019] 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.

[0020] In some embodiments, the micro-perforated plate comprises a racetrack micro-perforated plate or a circular micro-perforated plate.

[0021] In some embodiments, the thickness of the circular micro-perforated plate is in the range of 0.3 mm to 1 mm.

[0022] In some embodiments, the micro-perforated plate has a Young's modulus in the range of 5 GPa to 200 GPa.

[0023] In some embodiments, the natural frequency of the micro-perforated plate is greater than 500 Hz.

[0024] In some embodiments, the natural frequency of the micro-perforated plate is in the range of 500 Hz to 3.6 kHz.

[0025] In some embodiments, the height of the cavity is in the range of 0.5 mm to 10 mm.

[0026] In some embodiments, the micro-perforated plate comprises a metal micro-perforated plate.

[0027] In some embodiments, a waterproof ventilation structure is provided on the side of the micro-perforated plate facing the vibration membrane.

[0028] 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 centered around the magnetic circuit assembly.

[0029] 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 and the magnetic circuit assembly are spaced apart in the vibration direction of the diaphragm.

[0030] 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 causing the diaphragm to vibrate and generate sound when energized, and the micro-perforated plate including a magnetically permeable element of the magnetic circuit assembly.

[0031] 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, 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; and a sound absorbing structure that is coupled to the second acoustic cavity and absorbs sound that passes through the second acoustic cavity within a target frequency range and is transmitted to the second acoustic hole, wherein within the target frequency range, the sound pressure level of the second acoustic hole when the sound absorbing structure is not installed is greater than the sound pressure level of the second acoustic hole when the sound absorbing structure is installed.

[0032] In some embodiments, the target frequency range includes 3 kHz to 6 kHz.

[0033] In some embodiments, within the target frequency range, the difference between the sound pressure level of the second acoustic hole when the sound absorbing structure is not installed and the sound pressure level of the second acoustic hole when the sound absorbing structure is installed is 3 dB or more.

[0034] In some embodiments, the target frequency range includes a resonant frequency of the second acoustic cavity.

[0035] In some embodiments, at the resonant frequency, the difference between the sound pressure level of the second acoustic hole when the sound absorbing structure is not installed and the sound pressure level of the second acoustic hole when the sound absorbing structure is installed is 14 dB or more.

[0036] In some embodiments, the sound absorbing structure comprises a micro-perforated plate and a cavity, the micro-perforated plate comprising a through hole, and the second acoustic cavity coupled to the sound absorbing structure communicates with the cavity via the through hole.

[0037] In some embodiments, the cavity is filled with N'Bass sound absorbing particles.

[0038] In some embodiments, the N'Bass sound absorbing particles have a diameter in the range of 0.15 mm to 0.7 mm.

[0039] In some embodiments, the filling rate of the N'Bass sound absorbing particles in the cavity is in the range of 70% to 95%.

[0040] In some embodiments, gauze is placed between the N'Bass sound absorbing particles and the micro-perforated plate.

[0041] In some embodiments, the cavity is filled with a porous sound absorbing material, the porous sound absorbing material having a porosity greater than 70%.

[0042] In some embodiments, the ratio of the spacing between the through-holes to the diameter of the through-holes is greater than 5.

[0043] In some embodiments, the ratio of the wavelength of sound in the target frequency range to the hole spacing between the through-holes in the micro-perforated plate is greater than five.

[0044] 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.

[0045] 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.

[0046] In some embodiments, the micro-perforated plate comprises a racetrack micro-perforated plate or a circular micro-perforated plate.

[0047] In some embodiments, the thickness of the circular micro-perforated plate is in the range of 0.3 mm to 1 mm.

[0048] In some embodiments, the micro-perforated plate has a Young's modulus in the range of 5 GPa to 200 GPa.

[0049] In some embodiments, the natural frequency of the micro-perforated plate is greater than 500 Hz.

[0050] In some embodiments, the natural frequency of the micro-perforated plate is in the range of 500 Hz to 3.6 kHz.

[0051] In some embodiments, the height of the cavity is in the range of 0.5 mm to 10 mm.

[0052] In some embodiments, the micro-perforated plate comprises a metal micro-perforated plate.

[0053] In some embodiments, a waterproof ventilation structure is provided on the side of the micro-perforated plate facing the vibration membrane.

[0054] 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 centered around the magnetic circuit assembly.

[0055] 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 and the magnetic circuit assembly are spaced apart in the vibration direction of the diaphragm.

[0056] 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 causing the diaphragm to vibrate and generate sound when energized, and the micro-perforated plate including a magnetically permeable element of the magnetic circuit assembly.

[0057] The present application will be further illustrated by exemplary embodiments, which are not limiting and are illustrated in detail in the drawings, in which like numerals refer to like structures. [Brief explanation of the drawings]

[0058] [Figure 1] 1 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. [Figure 2A] 2 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. 1. [Figure 2B] 2 is a schematic diagram of a sound field distribution of high-frequency sound pressure levels of the acoustic device shown in FIG. 1. [Figure 3] FIG. 1 is a block diagram of an audio device according to some embodiments of the present disclosure. [Figure 4] 10A-10C are frequency response curve diagrams of an acoustic device with different sound absorbing structures installed thereon, in accordance with some embodiments of the present disclosure. [Figure 5] 10A-10C are frequency response curve diagrams of an acoustic device with different sound absorbing structures installed thereon, in accordance with some embodiments of the present disclosure. [Figure 6]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 7] 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 8] 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 9] 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 speaker (or vibrating membrane) and when no gauze is placed, according to some examples of the present specification. [Figure 10] 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 11] 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 12] 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 13] 10A-10C illustrate frequency response curves for a micro-perforated plate with 0.15 mm hole diameter and a micro-perforated plate with 0.3 mm hole diameter, according to certain embodiments herein. [Figure 14] FIG. 10 illustrates the sound absorption effect of micro-perforated panels with different cavity heights, when the hole diameter is 0.15 mm, the aperture ratio is 2.18%, and the thickness is 0.3 mm, according to some examples herein. [Figure 15] FIG. 10 illustrates the sound absorption effect of micro-perforated panels of different thicknesses when the hole diameter is 0.3 mm, the aperture ratio is 2.18%, and the cavity height is 5 mm, according to some examples herein. [Figure 16] 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 17] 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 18] 1A-1C are frequency response curves for several examples herein without a micro-perforated plate, with a micro-perforated plate alone, with a micro-perforated plate in combination with N'Bass sound-absorbing particles, and with a micro-perforated plate in combination with a porous sound-absorbing material. [Figure 19] 1 is a diagram illustrating the internal structure of an acoustic device according to some embodiments of the present disclosure. [Figure 20] 1 is a diagram illustrating the internal structure of an acoustic device 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] 22 is a frequency response curve diagram of the acoustic device shown in FIGS. 19 and 20 and the acoustic device shown in FIG. 21. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0059] In order to more clearly describe the technical means of the embodiments of the present application, the following will briefly describe the drawings necessary for describing the embodiments. Obviously, the drawings described below are only some examples or 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 language environment or otherwise described, the same numbers in the drawings indicate the same structures or operations.

[0060] 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, parts, portions, or assemblies, however, other terms may be used in place of the above terms if they achieve the same purpose.

[0061] As used in this application and 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 also include the plural. In general, the terms "comprise" and "containing" are intended to indicate only the inclusion of explicitly identified steps and elements, and these steps and elements are not an exclusive listing; a method or apparatus may also include other steps or elements.

[0062] Flowcharts are used herein to describe operations performed by systems according to embodiments of the present invention. It should be understood that the preceding and following operations are not necessarily performed in exact order. Instead, steps may be performed in reverse order or simultaneously. Other operations may also be added to these processes, or one or more operations may be removed from these processes.

[0063] FIG. 1 is a schematic diagram of an acoustic device according to some embodiments of the present disclosure. As shown in FIG. 1, the acoustic device 100 may include a housing 110 and a speaker 120. The speaker 120 may be installed within a cavity defined by the housing 110, and a first acoustic cavity 130 and a second acoustic cavity 140 for emitting sound may be installed on both the front and rear sides of the speaker 120, respectively. The housing 110 may have a first acoustic hole 111 and a second acoustic hole 112, and the first acoustic cavity 130 may be acoustically coupled to the first acoustic hole 111, and the second acoustic cavity 140 may be acoustically coupled to the second acoustic hole 112. When a user uses the acoustic device 100, the acoustic device 100 may be positioned near the user's auricle, and the first acoustic hole 111 may face the opening of the user's ear canal, so that sound emitted from the first acoustic hole 111 can be transmitted to the user's ear canal. The second acoustic hole 112 may be farther from the ear canal opening than the first acoustic hole 111, and the distance between the first acoustic hole 111 and the ear canal opening may be smaller than the distance between the second acoustic hole 112 and the ear canal opening.

[0064] In some embodiments, the front and rear sides of the speaker 120 can each serve as a sound wave generating structure, generating a pair of sound waves (or sounds) with equal amplitudes and 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 111 and the second acoustic hole 112, respectively. When the speaker 120 outputs sound waves, the sound wave on the front side of the speaker 120 (also referred to as the first sound wave) can pass through the first acoustic cavity 130 and radiate from the first acoustic hole 111, and the sound wave on the rear side of the speaker 120 (also referred to as the second sound wave) can pass through the second acoustic cavity 140 and radiate from the second acoustic hole 112, thereby forming a dipole sound source including the first acoustic hole 111 and the second acoustic hole 112. The dipole 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 audio device 100.

[0065] Fig. 2A is a schematic diagram of the sound field distribution of mid-low frequency sound pressure levels of the acoustic device 100 shown in Fig. 1. As shown in Fig. 2A, the sound field distribution of the acoustic device 100 exhibits good dipole directivity within the mid-low frequency range (e.g., 50 Hz to 1 kHz), and the sound leakage reduction effect of the dipole sound source is remarkable. That is, within the mid-low frequency range, the dipole sound source formed by the first acoustic hole 111 and the second acoustic hole 112 of the acoustic device 100 outputs sound waves that are opposite or nearly opposite in phase, and according to 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 far-field sound leakage.

[0066] Figure 2B is a schematic diagram of the sound field distribution of high frequency sound pressure levels of the acoustic device 100 shown in Figure 1. As shown in Figure 2B, the sound field distribution of the acoustic device 100 is disturbed within the high frequency range.

[0067] In some embodiments, in the high frequency range (e.g., 1500 Hz to 20 kHz), the wavelengths of the first and second sound waves are shorter than those in the mid-low frequency range. In this case, the distance between the dipole sound source formed by the first acoustic hole 111 and the second acoustic hole 112 cannot be ignored relative to the wavelength, so the sound waves emitted from the two sound sources cannot be canceled out, which makes it difficult to ensure the effect of reducing far-field sound leakage of the acoustic device in the high frequency range, and may even increase sound leakage and cause disturbances in the sound field distribution of the acoustic device. As a mere illustrative example, due to the distance between the first acoustic hole 111 and the second acoustic hole 112, 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.

[0068] In some embodiments, sound waves emanating from both the front and rear sides of the speaker 120 may pass through an acoustic transmission structure before being radiated to the outside through the first acoustic hole 111 and / or the second acoustic hole 112. The acoustic transmission structure may refer to an acoustic path through which sound waves pass when radiating from the speaker 120 to the external environment. In some embodiments, the acoustic transmission structure may include the housing 110 between the speaker 120 and the first acoustic hole 111 and / or the second acoustic hole 112. In some embodiments, the acoustic transmission structure may include an acoustic cavity. The acoustic cavity may be an amplitude space reserved for a diaphragm (not shown) of the speaker 120. For example, the acoustic cavity may include a cavity formed between the diaphragm of the speaker 120 and the housing 110. For example, the acoustic cavity may further include a cavity formed between the diaphragm of the speaker 120 and a driving system (e.g., a magnetic circuit assembly) of the speaker 120. In some embodiments, the acoustic transmission structure may be in acoustic communication with the first acoustic hole 111 and / or the second acoustic hole 112, and the first acoustic hole 111 and / or the second acoustic hole 112 may be part of the acoustic transmission structure. In some embodiments, when the speaker 120 is far from the ear canal opening, or when the radiation direction of sound waves generated by the speaker 120 is not in a desired direction or is away from the ear canal opening, the sound waves may be guided to a desired location by a sound conduit and then radiated to the external environment using the first acoustic hole 111 and / or the second acoustic hole 112. Thus, the acoustic transmission structure may further include a sound conduit.

[0069] In some embodiments, the acoustic transmission structure may have a resonant frequency, and when the frequency of the sound waves generated by the speaker 120 is near the resonant frequency, the acoustic transmission structure may resonate. Under the effect of the acoustic transmission structure, the sound waves in the acoustic transmission structure may 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 111 and / or the second acoustic hole 112 may change, and the change in phase and / or amplitude may cause a disturbance in the sound field near the resonant frequency of the dipole structure and affect the interference cancellation effect at the spatial point of the sound waves radiated from the first acoustic hole 111 and the second acoustic hole 112. For example, when resonance occurs, the phase difference between the sound waves emitted from the first acoustic hole 111 and the second acoustic hole 112 changes. For example, if the phase difference between the sound waves emitted from the first acoustic hole 111 and the second acoustic hole 112 is small (for example, less than 120°, less than 90°, or 0), the interference cancellation effect at the spatial point of the sound waves will be reduced, making it difficult to achieve a sound leakage reduction effect. Alternatively, sound waves with small phase differences will 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 the far-field sound leakage of the acoustic device 100. Furthermore, for example, the above-mentioned 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 dipole structure. At this time, the difference in amplitude between the sound waves emitted from the first acoustic hole 111 and the second acoustic hole 112 is large, the interference cancellation effect at the spatial point of the sound waves is reduced, and it is difficult to achieve a sound leakage reduction effect. In some embodiments, if parameters such as the volumes of the first acoustic cavity 130 and the second acoustic cavity 140 of the acoustic device, and the sizes and heights of the first acoustic hole 111 and the second acoustic hole 112 are different, the resonance frequencies of the first acoustic cavity and the second acoustic cavity (which may also be abbreviated as acoustic cavities) may differ, that is, the resonance frequencies of the acoustic transmission structures on the front and rear sides of the acoustic device may differ.In some embodiments, the blocking of high frequency sound waves by structures such as the pinna 210 and / or their effect on the reflection of sound waves can cause disruptions to the sound field distribution of the acoustic device 100 .

[0070] Because the first acoustic hole 111 faces the opening of the user's ear canal and the second acoustic hole 112 is farther from the opening of the ear canal than the first acoustic hole 111, the sound waves radiated from the second acoustic hole 112 account for the majority of the sound waves radiated from the acoustic device to the outside, that is, the sound waves radiated from the second acoustic hole 112 of the acoustic device 100 play a dominant role in the turbulent sound field distribution. Therefore, by adjusting the structure of the acoustic device 100, it is possible to reduce the output of the second acoustic cavity within a target frequency range (e.g., including the resonant frequency of the acoustic transmission structure and the high frequency range) without affecting the low-frequency output of the second acoustic cavity, thereby achieving the effect of reducing sound leakage in the far-field.

[0071] 3 is a block diagram of an acoustic device according to some embodiments of the present disclosure. In some embodiments, as shown in FIG. 3, an acoustic device 300 may include a housing 310, a diaphragm 321, and a sound-absorbing structure 330.

[0072] The housing 310 may be a regular or irregular three-dimensional structure having an internal storage cavity. For example, the housing 310 may be a hollow frame structure, including, but not limited to, regular shapes such as a rectangular frame, a circular frame, a regular polygonal frame, and any irregular shape such as a racetrack shape. The housing 310 can house the speaker and sound-absorbing structure 330. In some embodiments, the housing 310 can be made of metal (e.g., stainless steel, copper, etc.), plastic (e.g., polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), and acrylonitrile-butadiene-styrene copolymer (ABS)), composite material (e.g., metal composite material or non-metal composite material), epoxy resin, phenolic, ceramic, polyimide, fiberglass (e.g., FR4-fiberglass), etc., or any combination thereof. The housing 310 may be provided with a first acoustic hole 111 and a second acoustic hole 112 for outputting sound waves, and the speaker 120 outputs sound waves with a phase difference from the first acoustic hole 111 and the second acoustic hole 112.

[0073] A speaker is a device that can receive an electrical signal, convert it into an audio signal, and output it. In some embodiments, speaker types may be classified according to frequency, including low-frequency (e.g., 30 Hz to 150 Hz) speakers, mid-low-frequency (e.g., 150 Hz to 500 Hz) speakers, mid-high-frequency (e.g., 500 Hz to 5 kHz) speakers, high-frequency (e.g., 5 kHz to 16 kHz) speakers, and wideband (e.g., 30 Hz to 16 kHz) speakers, or any combination thereof. Here, low frequency, high frequency, etc., refer only to approximate frequency ranges, and different application scenarios may have different classification methods. For example, a crossover frequency is determined, and low frequency refers to the frequency range below the crossover frequency, and high frequency refers to 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, or 1000 Hz.

[0074] In some embodiments, the speaker may include a vibrating membrane 321, which divides the receiving cavity of the housing 310 to form a first acoustic cavity and a second acoustic cavity. The vibrating membrane 321 may have an elastic thin film structure. In some embodiments, the material of the vibrating membrane 321 may include, but is not limited to, one or more of polyimide (PI), polyethylene terephthalate (PET), polyethyleneimine (PEI), polyetheretherketone (PEEK), silica gel, polycarbonate (PC), vinyl polymer (PVC), acrylonitrile-butadiene-styrene copolymer (ABS), polyethylene (PE), and parylene (PPX), and may be a multi-layer composite material formed by combining the above materials. In some embodiments, the first acoustic cavity may be acoustically coupled to the first acoustic hole, and the second acoustic cavity may be acoustically coupled to the second acoustic hole. When the vibrating membrane 321 vibrates, sound waves may be emitted to the front and rear sides of the vibrating membrane 321, and the front side of the vibrating membrane 321 may be the side away from the drive system (e.g., magnetic circuit assembly) of the vibrating membrane 321, and the rear side of the vibrating membrane 321 may be the side toward the drive system (e.g., magnetic circuit assembly) of the vibrating membrane 321. The sound waves on the front side of the vibrating membrane 321 may pass through a first acoustic cavity and be emitted from a first acoustic hole, and the sound waves on the rear side of the vibrating membrane 321 may pass through a second acoustic cavity and be emitted from a second acoustic hole. When the vibrating membrane 321 vibrates, a pair of sound waves with a phase difference can be generated simultaneously on the front and rear sides of the vibrating membrane 321.

[0075] In some embodiments, a pair of sound waves with a phase difference are simultaneously generated on the front and rear sides of the vibrating membrane 321. The first sound wave passes through the first acoustic cavity and emerges from the first acoustic hole, and the second sound wave passes through the second acoustic cavity and emerges from the second acoustic hole. The two sound waves overlap and cancel each other out at a specific spatial point (e.g., the far field) outside the acoustic device, thereby reducing far-field sound leakage. The first and second acoustic holes 111 and 112 that output the sound waves in this manner form a dipole sound source. When the positions, phase differences, etc. between the dipole sound sources satisfy certain conditions, the acoustic device can exhibit different sound effects in the near and far fields. For example, when the point sound sources corresponding to the two acoustic holes have opposite phases and the same or nearly the same amplitudes, i.e., when the absolute value of the phase difference between the two point sound sources is 180° or close to 180°, the principle of anti-phase cancellation of sound waves can be used to reduce far-field sound leakage. Further, for example, if the phases of the point sound sources corresponding to the two acoustic holes are approximately opposite, it is also possible to achieve a reduction in far-field sound leakage. By way of example only, the absolute value of the phase difference between the two point sound sources that achieves a reduction in far-field sound leakage may be in the range of 120° to 240°.

[0076] 1 to 2B, the dipole may disturb the 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 330 may be installed in the second acoustic cavity of the acoustic device. The sound absorbing structure 330 absorbs sound waves within a target frequency range of the second acoustic cavity, reducing or avoiding the overlap of the first and second sound waves at a specific spatial point (e.g., the far field) outside the acoustic device, reducing the amplitude of the sound waves within the target frequency range at the spatial point, adjusting the directivity of the acoustic output device, and achieving a far-field sound leakage reduction effect.

[0077] The sound absorbing structure 330 is 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 330 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 330 is not installed may be greater than the sound pressure level at the second acoustic hole when the sound absorbing structure 330 is installed.

[0078] 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 330 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 of the second acoustic cavity near the resonant frequency, thereby reducing the amplitude of the sound waves near the resonant frequency and reducing sound leakage. 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 1 kHz to 10 kHz. In some embodiments, in the high frequency range, the distance between the dipole sound sources formed by the first acoustic hole and the second acoustic hole is not negligible relative to the wavelength. Therefore, the first sound wave and the second sound wave 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 the 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 and reducing the amplitude of the sound waves in the target frequency range at that spatial point. For example, the target frequency range may be 1 kHz to 20 kHz. The resonant frequency of the second acoustic cavity may be obtained using various measurement methods. For example, when measuring the frequency response curve of a second acoustic cavity without or without the sound absorbing structure 330, 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. For a specific method for measuring the frequency response curve of the second acoustic cavity without or with the sound absorbing structure 330 removed, please refer to FIG. 18 and the accompanying description.

[0079] 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, resulting in 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, another sound-absorbing structure 330 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 reinforcing at spatial points (e.g., in the far field), thereby reducing the amplitude of the sound waves near the resonance frequency of the first acoustic cavity received at the spatial point. 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 also 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 of the acoustic device (i.e., transmitted to the user's ear). 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 ranges and low-frequency ranges, respectively, to absorb sounds in different frequency ranges.

[0080] In some embodiments, in a 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 of the dipole sound source formed by the two acoustic holes in the high-frequency range. 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 330 can absorb the high-frequency sound waves and improve the problem that the sound leakage reduction effect of the dipole sound source in the high-frequency range is not ideal.

[0081] 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 of 3 kHz to 6 kHz to achieve more directional and effective sound leakage reduction. In some embodiments, the target frequency range may include 4 kHz to 6 kHz. In some embodiments, the target frequency range may include 5 kHz to 6 kHz. Note that the resonant frequency here mainly refers to the resonant frequency of the second acoustic cavity, and in some embodiments, may be the resonant frequency of either the second acoustic cavity or the first acoustic cavity, and will hereinafter be referred to as the resonant frequency.

[0082] 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 a dipole sound source, 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 effect of reducing sound leakage in a wideband band.

[0083] The sound absorption effect of the sound absorbing structure 330 is the amount of sound that the sound absorbing structure 330 can absorb in a target frequency range, and can be expressed in terms of the sound pressure level of the sound. For example, the sound absorption effect of the sound absorbing structure 330 can be expressed as the difference between the sound pressure levels measured at the same frequency and at the same position corresponding to the second acoustic cavity in the target frequency range with and without the sound absorbing structure 330. By way of example only, the difference between the sound pressure levels of the second acoustic cavity in the presence and absence of the sound absorbing structure 330 can be expressed as the difference between the sound pressure levels of the second acoustic cavity in the presence and absence of the sound absorbing structure 330. As merely an example, the sound pressure level of the second acoustic hole when the sound absorbing structure 330 is present and when the sound absorbing structure 330 is absent can be measured by placing a measurement 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 level of the second acoustic hole when the sound absorbing structure 330 is present and when the sound absorbing structure 330 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 when the sound absorbing structure 330 is present and when the sound absorbing structure 330 is absent may be 3 dB or more. For example, the difference between the sound pressure levels of the second acoustic hole when the sound absorbing structure 330 is present and when the sound absorbing structure 330 is absent 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 330. When the sound absorption bandwidth is in the range of 3 kHz to 6 kHz, the sound absorbing structure 330 can effectively absorb sound waves in the range of 3 kHz to 6 kHz, with a sound absorption effect of 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 330 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 330 may be 6 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 330 may be 8 dB or more within the target frequency range to further reduce sound leakage of the acoustic device.In some embodiments, the sound absorbing effect of the sound absorbing structure 330 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 330 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 330 may be 3 dB or more. Alternatively, within the range of 4 kHz to 6 kHz, the sound absorbing effect of the sound absorbing structure 330 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 330 may be 8 dB or more, thereby more effectively reducing sound leakage within higher frequency ranges.

[0084] 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 330 needs to absorb more sound at the resonant frequency. Therefore, in some embodiments, the sound absorbing effect of the sound absorbing structure 330 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 330, 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 (e.g., the phase difference is no longer equal to 180 degrees) between the first and second sound waves near the resonant frequency. This reduces or prevents the situation where the two sets of sounds not only no longer cancel but also 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 the acoustic device, the sound absorbing structure 330 has a sound absorption effect of 16 dB or more for sounds at or near the resonant frequency. In some embodiments, to further reduce sound leakage from the acoustic device, the sound absorbing structure 330 has a sound absorption effect of 18 dB or more for sounds at or near the resonant frequency. In some embodiments, to further reduce sound leakage from the acoustic device, the sound absorbing structure 330 has a sound absorption effect of 20 dB or more for sounds at or near the resonant frequency. In some embodiments, to further reduce sound leakage from the acoustic device, the sound absorbing structure 330 has a sound absorption effect of 22 dB or more for sounds at or near the resonant frequency. In some embodiments, to further reduce sound leakage from the acoustic device, the sound absorbing structure 330 has a sound absorption effect of 25 dB or more for sounds at or near the resonant frequency.

[0085] In some embodiments, sound absorbing structure 330 may include at least one of an absorptive sound absorbing structure or a reactive sound absorbing structure. For example, the function of sound absorbing structure 330 can be realized by an absorptive sound absorbing structure. Alternatively, for example, the function of sound absorbing structure 330 can be realized by a reactive sound absorbing structure. Furthermore, for example, the function of sound absorbing structure 330 can be realized by a sound absorbing structure that combines an absorptive sound absorbing structure and a reactive sound absorbing structure.

[0086] 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 located 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, or the like, or any combination thereof. In some embodiments, the absorptive-reactive composite sound absorbing structure may include both an absorptive sound absorbing structure and a reactive sound absorbing structure to achieve the functionality of sound absorbing structure 330. For example, the absorptive-reactive composite sound absorbing structure may include a perforated plate sound absorbing structure and a porous sound absorbing material or acoustic gauze, and the porous sound absorbing material or acoustic gauze may be disposed within the cavity of the perforated plate sound absorbing structure or within the sound transmission 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, and the quarter-wave resonator tube structure may be disposed within or outside the sound transmission structure, and the porous sound absorbing material or acoustic gauze may be disposed within the sound transmission structure. For example, the absorptive-reactive composite sound absorbing structure may include a perforated plate sound absorbing structure, a quarter-wave resonator tube structure, and a porous sound absorbing material or acoustic gauze.

[0087] FIG. 4 illustrates frequency response curves of an acoustic device having different sound-absorbing structures, according to some embodiments of the present disclosure. Curves 411 and 421 represent the frequency response curves of a first acoustic cavity (e.g., first acoustic cavity 130 shown in FIG. 1 ) and a second acoustic cavity (e.g., second acoustic cavity 140 shown in FIG. 1 ), respectively, when no sound-absorbing structure is installed in the acoustic device. Curves 412 and 422 represent the frequency response curves of a first acoustic cavity and a second acoustic cavity, respectively, when a quarter-wavelength resonator tube is installed in the second acoustic cavity of the acoustic device. Curves 413 and 423 represent the frequency response curves of a first acoustic cavity and a second acoustic cavity, respectively, when a micro-perforated plate sound-absorbing structure is installed in the second acoustic cavity of the acoustic device. As shown in FIG. 4 , the frequency response of the first acoustic cavity of the acoustic device with a sound-absorbing structure is less changed than that of the acoustic device without a sound-absorbing structure. The frequency response of the second acoustic cavity does not change much in the low frequency range (e.g., less than 2 kHz), but can form a dip in the high frequency range (e.g., greater than 2 kHz). That is, the sound absorbing structure can reduce the amplitude of high-frequency sound waves output from the second acoustic cavity, thereby reducing sound leakage at high frequencies. Furthermore, compared to using a quarter-wave resonator tube, an acoustic device using a micro-perforated plate sound absorbing structure has a greater effect in reducing sound leakage at high frequencies.

[0088] In some embodiments, the acoustic transmission structure (e.g., housing) of an acoustic device may include a perforated plate sound absorbing structure and an absorptive sound absorbing structure. The absorptive sound absorbing structure may include a porous sound absorbing material and / or acoustic gauze. In some embodiments, the absorptive sound absorbing structure may be disposed around one or more hole openings in the perforated plate sound absorbing structure. In some embodiments, the absorptive reactive composite sound absorbing structure not only absorbs sound through the resonance of the reactive sound absorbing structure, but also increases the frictional wear of sound waves caused by the absorptive sound absorbing structure, thereby widening the sound absorption bandwidth and further improving the sound leakage reduction effect within the target frequency range of the acoustic device. In some embodiments, the absorptive sound absorbing structure may be attached to the inner wall of a cavity in the perforated plate sound absorbing structure. In some embodiments, the absorptive sound absorbing structure may fill at least a portion of the cavity. In some embodiments, the absorptive sound absorbing structure may be disposed inside the housing or may be part of the housing.

[0089] 5 is a frequency response curve diagram of an acoustic device with different sound absorbing structures installed, according to some embodiments of the present disclosure. As shown in FIG. 5, the curve L 5-1 indicates the frequency response curve of the second acoustic cavity of an acoustic device without a sound-absorbing structure, and curve L 5-2 shows the frequency response curve of the second acoustic cavity of the acoustic device in which the micro-perforated plate sound absorbing structure is installed, and curve L 5-3 shows the frequency response curve of the second acoustic cavity of the acoustic device with the micro-perforated plate sound absorbing structure and acoustic gauze installed, and curve L 5-4 Figure 5 shows the frequency response curves of the second acoustic cavity of an acoustic device equipped with a micro-perforated plate sound absorbing structure, acoustic gauze, and N'Bass material. As can be seen from Figure 5, within the low frequency range (e.g., 1 kHz to 2 kHz), the four curves overlap to a large extent, indicating that the low frequency outputs of the acoustic devices with the four structures are nearly the same. However, within the mid-to-high frequency range (e.g., above 2 kHz), the L curves for the case without the sound absorbing structure are significantly different. 5-1 Compared to L when a sound-absorbing structure is installed, 5-2 , L 5-3 and L 5-4In other words, the sound absorbing structure can reduce the high frequency output of the second acoustic cavity of the acoustic device, thereby improving the sound leakage reduction effect at high frequencies. Within a large range (e.g., 2kHz to 5kHz), the L when three sound absorbing structures are installed is 5-4 is basically located below the other three curves and has the best sound leakage reduction effect. Therefore, by installing a sound absorbing structure (for example, an absorption-reactive composite sound absorbing structure), the high frequency output of the second acoustic cavity of the acoustic device can be reduced, which can suppress the sound field disturbance in the high frequency range of the acoustic device and improve the sound leakage reduction effect at high frequencies.

[0090] By arranging the sound absorbing structure 330 so as to be coupled to the second acoustic cavity, sound waves within a target frequency range are absorbed by the sound absorbing structure 330, 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 (e.g., the phase difference is no longer equal to 180 degrees) between the first and second sound waves around the specific frequency of the cavity reduces the sound leakage reduction effect at the spatial point, thereby reducing or avoiding a situation in which 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 target frequency range may include a high frequency range, and the first and second sound waves outside the target frequency range can achieve dipole cancellation to reduce sound leakage at the spatial point.

[0091] FIG. 6 is a schematic diagram of an acoustic device equipped with a sound absorbing structure according to some embodiments of the present disclosure.

[0092] 6, in some embodiments, an acoustic device 600 may include a housing 610 and a speaker 620. The speaker 620 is installed in a receiving cavity defined by the housing 610, and a first acoustic cavity 630 and a second acoustic cavity 640 are installed on both the front and rear sides of the speaker 620 (or diaphragm), respectively. A first acoustic hole 611 and a second acoustic hole 612 are installed in the housing 610, and the first acoustic cavity 630 may be acoustically coupled to the first acoustic hole 611, and the second acoustic cavity 640 may be acoustically coupled to the second acoustic hole 612.

[0093] In some embodiments, as shown in FIG. 6 , acoustic device 600 may further include a sound absorbing structure 650, which may be coupled to second acoustic cavity 640. In some embodiments, sound absorbing structure 650 may include a micro-perforated board sound absorbing structure. Micro-perforated board sound absorbing structure includes a micro-perforated board 651 and a cavity 652, where micro-perforated board 651 includes through-holes, and second acoustic cavity 640 coupled to the micro-perforated board structure communicates with cavity 652 through the through-holes of the micro-perforated board. Note that acoustic device 600 shown in FIG. 6 is merely an illustrative example, and various changes or modifications may be made to the specific installation manner of sound absorbing structure 650.

[0094] The sound waves from the second acoustic cavity 640 enter the cavity 652 of the micro-perforated sound absorbing structure through one or more through holes and can cause the micro-perforated sound absorbing structure to resonate under certain conditions, for example, if the vibration frequency of the sound waves entering the cavity 652 is close to the resonant frequency of the micro-perforated sound absorbing structure, the sound waves entering the cavity 652 will cause the micro-perforated sound absorbing structure to resonate. The air in the cavity 652 resonates with the micro-perforated sound absorbing structure to consume energy and achieve a sound absorption effect, and the frequency of the sound waves absorbed by the micro-perforated sound absorbing structure is the same as or close to its resonant frequency.

[0095] In some embodiments, the material of the micro-perforated plate 651 may be metal (e.g., aluminum) or non-metal (e.g., acrylic, polycarbonate (PC), etc.). If the micro-perforated plate 651 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 651 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.

[0096] 7 is a diagram showing the sound absorption effects of acoustic devices according to some embodiments of the present disclosure when using a metallic micro-perforated plate and a non-metallic micro-perforated plate. In FIG. 7, the horizontal axis represents the sound absorption frequency, the vertical axis represents the sound absorption coefficient, and curve 71 represents the sound absorption effect of the non-metallic micro-perforated plate, while curve 72 represents the sound absorption effect of the metallic micro-perforated plate. As shown in FIG. 7, 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 a higher equivalent attenuation for sound waves passing through it.

[0097] FIG. 8 shows frequency response curves for acoustic devices according to some embodiments of the present disclosure, respectively, when using a metallic micro-perforated plate and a non-metallic micro-perforated plate. In FIG. 8, the horizontal axis represents frequency, and the vertical axis represents sound pressure level. Curve 81 shows the frequency response when using a metallic micro-perforated plate, and curve 82 shows the frequency response when using a non-metallic micro-perforated plate. The frequency response here is the frequency response of the second acoustic hole (e.g., a point 10 mm away from and directly in front of the second acoustic hole). As shown in FIG. 8, the metallic micro-perforated plate has a higher sound absorption effect than the non-metallic 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 metallic micro-perforated plate is an aluminum plate, which slightly reduces the sound absorption effect of the non-metallic micro-perforated plate. However, using a non-metallic micro-perforated plate reduces the weight of the acoustic device, which helps to improve the lightness of the acoustic device and reduce 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.

[0098] If the natural frequency of the micro-perforated plate 651 attached to the acoustic device (or referred to as the fixed state) is within the target frequency range, the micro-perforated plate 651 may resonate within the target frequency range, affecting the sound absorption effect. Therefore, the natural frequency of the micro-perforated plate 651 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 651 in the fixed state, the natural frequency of the micro-perforated plate 651 in the fixed state can be represented by the natural frequency of the micro-perforated plate 651 in its free state. The free state may be the state when the micro-perforated plate 651 is not attached to the acoustic device, and the natural frequency of the micro-perforated plate 651 in the fixed state is much greater than the natural frequency of the free state. A method for measuring the natural frequency of the free state may be as follows. The micro-perforated plate 651 is maintained in a free state, and an excitation force having a constant amplitude and a frequency that varies from low to high is applied to the micro-perforated plate 651 by a vibrator. The velocity amplitude of the micro-perforated plate 651 is measured and recorded using a laser vibrometer. The frequency at which the velocity range of the micro-perforated plate 651 first reaches a maximum is defined as the natural frequency of the free state of the micro-perforated plate 651. 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 651 may be greater than 500 Hz (e.g., 500 Hz to 3.6 kHz), thereby making the natural frequency of the fixed state much greater than the upper sound absorption frequency limit (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 651, so that the natural frequency can be determined by setting the stiffness and / or mass of the micro-perforated plate 651, thereby absorbing sound waves within a target frequency range. In some embodiments, micro-perforated plates 651 with different shapes, materials, etc., have different stiffness and / or mass, and therefore different natural frequencies. In some embodiments, the micro-perforated plate 651 may have a regular or irregular shape, such as a circle, a sector, a rectangle, a diamond, etc. In some embodiments, the material of the micro-perforated plate 651 may be a non-metallic material or a metallic material.

[0099] In some embodiments, micro-perforated plate 651 may be a racetrack-type micro-perforated plate. In some embodiments, when micro-perforated plate 651 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 free-state natural frequency of micro-perforated plate 651 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 651 can affect its natural frequency. When micro-perforated plate 651 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 free-state natural frequency of micro-perforated plate 651 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.

[0100] In some embodiments, the micro-perforated plate 651 may be a circular micro-perforated plate. Given the same parameters (e.g., hole diameter, thickness, open area ratio, and cavity (e.g., cavity 652) height), the circular micro-perforated plate 651 has a lower natural frequency than the racetrack-type micro-perforated plate 651. Therefore, the circular micro-perforated plate must use 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 651 is a circular micro-perforated plate, the Young's modulus of the material of the micro-perforated plate 651 is in the range of 50 GPa to 200 GPa to ensure that the free-state natural frequency of the micro-perforated plate 651 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 651 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 651 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.

[0101] By setting the Young's modulus and / or thickness of the micro-perforated plate 651 and adjusting its natural frequency, it is possible to prevent the natural frequency of the micro-perforated plate 651 in a fixed state from being within the sound absorption bandwidth and affecting its sound absorption effect.

[0102] In some embodiments, a waterproof ventilation structure may be installed on the side of the micro-perforated plate 651 facing the speaker 620 (or diaphragm), and the waterproof ventilation structure can provide waterproofing and dustproofing. Specifically, the through-holes in the micro-perforated plate 651 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 651 and the second acoustic cavity 640. In some embodiments, the waterproof ventilation structure may cover the entire side where the micro-perforated plate 651 and the second acoustic cavity 640 come into contact. In some embodiments, the waterproof ventilation structure may cover all of the through-holes in the micro-perforated plate 651 so that the through-holes communicate with the second acoustic cavity 640 via the waterproof ventilation structure.

[0103] In some embodiments, the waterproof breathable structure may be gauze. FIG. 9 is a frequency response curve diagram of the second acoustic hole 612 measured when an 025HY-type gauze is placed on the side of the micro-perforated plate 651 facing the speaker 620 (or diaphragm) and when no gauze is placed, according to some embodiments of the present disclosure. In FIG. 9, the horizontal axis represents frequency, and the vertical axis represents sound pressure level. Curve 91 represents the frequency response curve measured at the second acoustic hole 612 (e.g., 10 mm away from the second acoustic hole 612) when an 025HY-type gauze is placed, and curve 92 represents the frequency response curve measured at the second acoustic hole 612 (e.g., 10 mm away from the second acoustic hole 612) when no gauze is placed. As shown in FIG. 9, curve 91 is slightly higher than curve 92, and the difference in sound pressure level between the two is not significant. As is apparent, the sound absorption effect of the micro-perforated plate 651 provided with 025HY-type gauze is slightly reduced compared to the sound absorption effect of the micro-perforated plate 651 without gauze, but the effect is not significant and the micro-perforated plate 651 can still provide a certain level of waterproof and dustproof performance (for example, an acoustic device using 025HY-type gauze can pass the IPX7 waterproof test). Therefore, in some embodiments, to achieve the waterproof and dustproof purpose of the micro-perforated plate sound absorbing structure, 025HY-type gauze may be provided on the side of the micro-perforated plate 651 facing the diaphragm. In some embodiments, the acoustic resistance of the 025HY-type gauze is less than 50 MKS Rayls. Thus, the micro-perforated plate 651 may be provided with gauze on the side facing the diaphragm, and the acoustic resistance of the gauze may be less than 50 MKS Rayls, thereby providing waterproof and dustproof performance while having little effect on the output effect of the acoustic device (e.g., the second acoustic hole).

[0104] Cavity 652 is a cavity separated from second acoustic cavity 640 and communicates with the outside only through the through-holes in micro-perforated plate 651. In some embodiments, the shape of cavity 652 includes, but is not limited to, the rectangular parallelepiped shown in FIG. 6 , and may include regular shapes such as a sphere or a cylinder, or irregular shapes such as a racetrack. In some embodiments, cavity 652 has a constant height D (see FIG. 6 ), and the larger the cavity height D, the wider its sound absorption bandwidth. Thus, in some embodiments, increasing the cavity height D can improve the sound absorption effect of the micro-perforated plate sound absorbing structure.

[0105] 10 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. 10, 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.

[0106] FIG. 11 is a comparison diagram of the change trends of the maximum sound absorption coefficient and 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. 11, 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.

[0107] As described above, the greater the height D of the cavity 652, the wider the sound absorption bandwidth can be obtained near the desired resonant sound absorption frequency. However, the greater the height of the cavity, 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 range of the cavity height D may be 0.5 mm to 10 mm. For example, the range of the cavity height D may be 2 mm to 9 mm. Furthermore, for example, the range of the cavity height D may be 4 mm to 9 mm. Furthermore, for example, the range of the cavity height D may be 7 mm to 10 mm.

[0108] In some embodiments, multiple through-holes may be provided in the micro-perforated plate 651, and the multiple through-holes may be distributed at intervals. In some embodiments, the multiple through-holes may be distributed arbitrarily as a whole. For example, the multiple through-holes may be distributed in an array. Also, for example, the multiple through-holes may be distributed in a circular pattern around a center 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.

[0109] In some embodiments, the hole spacing between the through-holes may be much larger than the hole diameter of the through-holes (where hole diameter is the diameter of the through-hole), 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 properties of the sound waves transmitted between each hole do not affect each other.

[0110] In some embodiments, the hole spacing of 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 56 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 651 between the edge of a through-hole and the edge of an adjacent through-hole) can be negligible, thereby avoiding the influence of the reflection of the hole spacing on the sound wave propagation process.

[0111] 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 processing, 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.

[0112] FIG. 12 illustrates the sound absorption effect of micro-perforated plate 651 having through-hole diameters of 0.15 mm and 0.3 mm, respectively, according to some embodiments of the present disclosure. In FIG. 12, the horizontal axis represents sound absorption frequency, and the vertical axis represents sound absorption coefficient. Curve 121 represents the sound absorption effect of micro-perforated plate 651 having a hole diameter of 0.15 mm, and curve 122 represents the sound absorption effect of micro-perforated plate 651 having a hole diameter of 0.3 mm. As shown in FIG. 12, curve 121 is wider than curve 122, but their heights are similar. As can be seen, the sound absorption bandwidth and sound absorption effect of micro-perforated plate 651 having a hole diameter of 0.15 mm are significantly better than those of micro-perforated plate 651 having a hole diameter of 0.3 mm.

[0113] FIG. 13 is a frequency response curve diagram for a micro-perforated plate 651 having a hole diameter of 0.15 mm and a micro-perforated plate 651 having a hole diameter of 0.3 mm according to some embodiments of the present disclosure. In FIG. 13, the horizontal axis represents frequency, and the vertical axis represents sound pressure level. Curve 131 represents the frequency response for a micro-perforated plate 651 having a hole diameter of 0.15 mm, and curve 132 represents the frequency response for a micro-perforated plate 651 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. 13, the sound leakage of curve 131 in the frequency range of 2 kHz to 4 kHz is approximately 6 dB lower than that of curve 132. As can be seen, the sound absorption effect of the micro-perforated plate 651 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 651 having a hole diameter of 0.3 mm. Therefore, in some embodiments, to achieve a higher sound absorption effect, a micro-perforated plate 651 with a hole diameter of 0.15 mm or close to 0.15 mm may be used. For example, a micro-perforated plate 651 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 micro-perforated plate 651 with a hole diameter of 0.3 mm or close to 0.3 mm (e.g., 0.28 mm to 0.35 mm) may be used.

[0114] In some embodiments, the aperture ratio of the micro-perforated plate 651 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 a proportional relationship between the total area of ​​the through-holes and the area of ​​the side of the micro-perforated plate 651 that is adjacent to the second acoustic cavity 640.

[0115] As can be seen from the above, the cavity height D, the thickness of the micro-perforated plate 651, 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 651, and the comprehensive value of the above parameters can be seen from the following explanation.

[0116] In general, the acoustic impedance of a single through-hole in the micro-perforated plate 651 is:

[0117]

number

[0118] 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 corresponds to 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 651, the acoustic resistance is equivalent to the acoustic resistance of the multiple through-holes connected in parallel. That is, the acoustic impedance of the micro-perforated plate 651 is obtained by dividing the acoustic impedance of a single through-hole by the aperture ratio.

[0119]

number

[0120] In equation (2), σ is the aperture ratio, k is the wave number, and the expression is:

[0121]

number

[0122] 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:

[0123]

number

[0124] 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:

[0125]

number

[0126] After normalization:

[0127]

number

[0128] In equation (5), r is the relative acoustic impedance, and m is the relative sound quality, specifically as follows:

[0129]

number

[0130]

number

[0131] When sound waves are incident perpendicularly, the sound absorption coefficient α of the finely perforated plate sound absorbing structure can be calculated as follows:

[0132]

number

[0133] The resonant frequency of the sound absorbing structure 650 is:

[0134]

number

[0135] As can be seen from equations (1) to (9), the sound absorption bandwidth and sound absorption coefficient of the sound absorbing structure 650 can be controlled by adjusting the hole diameter, aperture ratio, thickness, and cavity height of the finely perforated plate 651.

[0136] In addition, parameter values ​​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 parameter combination. For example, the sound absorption bandwidth and maximum sound absorption coefficient of the sound-absorbing structure 650 are mutually constrained and can be balanced according to actual needs. For example, the smaller the hole diameter of the micro-perforated panel 651, 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.

[0137] In some embodiments, the hole diameter may be in the range of 0.1 mm to 0.2 mm, the open area ratio may be in the range of 2% to 5%, the thickness may be in the range of 0.2 mm to 0.7 mm, and the cavity height may be in the range of 7 mm to 10 mm. By way of example only, micro-perforated plate 651 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, micro-perforated plate 651 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 9 mm. For example, the micro-perforated plate 651 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 7.5 mm. For example, the micro-perforated plate 651 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.

[0138] 14 is a diagram illustrating the sound absorption effect of micro-perforated plate 651 with different cavity heights, where the hole diameter is 0.15 mm, the aperture ratio is 2.18%, and the thickness is 0.3 mm, according to some embodiments of the present disclosure. In FIG. 14, the horizontal axis represents frequency, the vertical axis represents sound absorption coefficient, and curve 141 represents the sound absorption effect of micro-perforated plate 651 with a cavity height of 9 mm, curve 142 represents the sound absorption effect of micro-perforated plate 651 with a cavity height of 7.5 mm, and curve 143 represents the sound absorption effect of micro-perforated plate 651 with a cavity height of 5 mm. 14, there is not much difference in sound absorption effect between when the cavity height is 7.5 mm and when it is 9 mm, and when the cavity height is reduced to 5 mm, the sound absorption center frequency (the frequency corresponding to the point where the sound absorption coefficient is highest) of the finely perforated plate 651 shifts from 4 kHz to 4.9 kHz, and the sound absorption coefficient decreases significantly in the frequency band below the sound absorption center frequency (e.g., 2 kHz to 4.9 kHz). As a result, the sound absorption effect can meet the need for reducing sound leakage whether the cavity height is 9 mm, 7.5 mm, or 5 mm, but the sound absorption effect when the cavity height is 5 mm is lower than the sound absorption effect when the cavity height is 9 mm and 7.5 mm.

[0139] In some embodiments, the hole diameter may be in the range of 0.2 mm to 0.4 mm, the open area ratio may be in the range of 1% to 5%, the thickness of the micro-perforated plate 651 may be in the range of 0.2 mm to 0.7 mm, and the cavity height may be in the range of 4 mm to 9 mm. By way of example only, the micro-perforated plate 651 may have a hole diameter in the range of 0.25 mm to 0.3 mm, an open area ratio in the range of 1.11% to 4.06%, a thickness in the range of 0.3 mm to 0.6 mm, and a cavity height in the range of 4 mm to 8.5 mm. For example, the micro-perforated plate 651 may have a hole diameter of 0.3 mm, an open area ratio of 2.18%, a thickness in the range of 0.5 mm, and a cavity height in the range of 5 mm. For example, the micro-perforated plate 651 may have a hole diameter of 0.25 mm, a hole ratio of 3.41%, a thickness of 0.6 mm, and a cavity height of 8.5 mm. For example, the micro-perforated plate 651 may have a hole diameter of 0.3 mm, a hole ratio of 2.45%, a thickness of 0.5 mm, and a cavity height of 6 mm.

[0140] 15 is a graph showing the sound absorption effects of micro-perforated plates 651 of different thicknesses, where the hole diameter is 0.3 mm, the aperture ratio is 2.18%, and the cavity height is 5 mm, according to some embodiments of the present disclosure. In FIG. 15, the horizontal axis represents frequency, and the vertical axis represents sound absorption coefficient. Curve 151 shows the sound absorption effect of the micro-perforated plate 651 with a thickness of 0.6 mm, curve 152 shows the sound absorption effect of the micro-perforated plate 651 with a thickness of 0.5 mm, and curve 153 shows the sound absorption effect of the micro-perforated plate 651 with a thickness of 0.4 mm. As shown in FIG. 15, the sound absorption center frequencies of curves 151, 152, and 153 gradually increase, and the maximum sound absorption coefficients gradually decrease. Although the sound absorption effect can meet the need for sound leakage reduction whether the thickness is 0.4 mm, 0.5 mm, or 0.6 mm, the sound absorption effect when the thickness is 0.4 mm is lower than the sound absorption effects when the thickness is 0.5 mm or 0.6 mm. In some embodiments, a micro-perforated plate 651 with a thickness of 0.4 mm can be used to reduce the mass of the acoustic device. Therefore, a micro-perforated plate with a thickness of 0.4 mm may be used in consideration of the user's wearing experience.

[0141] By setting the above parameter combinations, it is possible to achieve both the sound absorption bandwidth and the sound absorption coefficient, so that the sound absorbing structure can effectively absorb sound waves within the target frequency range and improve the sound leakage reduction effect within the target frequency range. In addition, different parameter combinations can meet the needs of different application scenarios.

[0142] In some embodiments, the sound absorbing effect of the micro-perforated board sound absorbing structure can be improved by using an absorbing-type sound absorbing structure, because a too small micro-perforation size can increase the processing difficulty and a large cavity depth D can increase the size of the acoustic device. FIG. 16 is a schematic diagram of an acoustic device equipped with a sound absorbing structure, according to some embodiments herein. As shown in FIG. 16 , the absorbing-type sound absorbing structure can be installed in a cavity 652 of the micro-perforated board sound absorbing structure. In some embodiments, the absorbing-type sound absorbing structure can further include a filler material 654 (e.g., N'Bass particles or a porous sound absorbing material). The filler material 654 increases the equivalent height of the cavity 652 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 1600. Specifically, the filler material 654 has a "sponge" effect, and when sound waves propagate, air molecules are adsorbed into and desorbed from the voids in the filler material 654, which can be considered to reduce the sound speed in the filler material 654, which is equivalent to increasing the volume of the cavity 652, thereby achieving the purpose of widening the sound absorption bandwidth of the micro-perforated plate 651 and increasing the sound absorption coefficient (without affecting the sound absorption center frequency), further improving the sound absorption effect of the micro-perforated plate sound absorption structure, and reducing the design size of the acoustic device.

[0143] In some embodiments, cavity 652 may be filled with N'Bass (aluminosilicate) sound-absorbing particles. In some embodiments, N'Bass sound-absorbing particles may be filled into cavity 652 in a number of ways. By way of example only, N'Bass sound-absorbing particles may be filled directly into cavity 652; N'Bass sound-absorbing particles may be filled into a powder pack and the powder pack placed into cavity 652; N'Bass sound-absorbing particles may be potted into a shaped gauze and the powder pack placed into cavity 652; or N'Bass sound-absorbing particles may be filled into cavity 652 using at least two of the above filling methods.

[0144] 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.

[0145] In some embodiments, the filling rate of the N'Bass sound-absorbing particles in cavity 652 gradually increases, such that the more N'Bass sound-absorbing particles there are in cavity 652, the greater 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 652. However, if the N'Bass sound-absorbing particles completely fill cavity 652, 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.

[0146] FIG. 17 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. 17, 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. 17), indicating a high volume output at 2 kHz from the second acoustic cavity. 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 the 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 the 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 60% 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., 2 kHz to 3 kHz). In some embodiments, the fill rate may be in the range of 70% to 95%. For example, the fill rate may be in the range of 75% to 90%. For example, the fill rate may be in the range of 80% to 90%. In some embodiments, considering the cost of filling 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%.

[0147] 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.

[0148] 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 653 may be placed between the N'Bass sound-absorbing particles and micro-perforated plate 651 to prevent the N'Bass sound-absorbing particles from blocking the through-holes, as shown in FIG. 16 . In some embodiments, gauze 653 may be coated on the side of micro-perforated plate 651 that faces away from second acoustic cavity 640 (or the diaphragm), and gauze 653 covers all of the through-holes in micro-perforated plate 651. In some embodiments, gauze 653 may be placed in cavity 652 between N'Bass sound-absorbing particles and micro-perforated plate 651. Specifically, gauze 653 may be connected to the inner wall of cavity 652 between N'Bass sound-absorbing particles and micro-perforated plate 651.

[0149] In some embodiments, cavity 652 may include a porous sound-absorbing material. In some embodiments, the porous sound-absorbing material may include, but is not limited to, polyurethane, polypropylene, melamine sponge, wood wool board, wool felt, etc. In some embodiments, the filling method of the porous sound-absorbing material may be similar to the filling method of N'Bass sound-absorbing particles. In some embodiments, to achieve a better sound absorption effect, the porous sound-absorbing material may fill the entire cavity 652 uniformly. In some embodiments, to achieve a better sound absorption effect, the porosity of the porous sound-absorbing material may be greater than 70%. The porosity refers to the percentage of the void volume of the porous sound-absorbing material compared to the total volume of the porous sound-absorbing material.

[0150] In some embodiments, the micro-perforated sound absorbing structure can effectively reduce sound pressure levels by 4 dB to 20 dB within the 4 kHz to 6 kHz frequency range. After the cavity 652 of the micro-perforated sound absorbing structure is filled with a porous sound absorbing material or N'Bass sound absorbing particles, the sound absorption frequency range can be further extended to lower frequencies. Both the porous sound absorbing material and the N'Bass sound absorbing particles have excellent sound absorption effects. For an explanation of the sound absorption effects of the porous sound absorbing material and the N'Bass sound absorbing particles, please refer to FIG. 18.

[0151] 18 illustrates frequency response curves for the cases where a micro-perforated plate 651 is not used, a micro-perforated plate 651 is used alone, a micro-perforated plate 651 is used in combination with N′Bass sound-absorbing particles, and a micro-perforated plate 651 is used in combination with a porous sound-absorbing material, according to certain embodiments of the present disclosure. In FIG. 18, the horizontal axis represents frequency, and the vertical axis represents sound pressure level. Curve 181 represents the frequency response for the case where a micro-perforated plate 651 is not used, curve 182 represents the frequency response for the case where a micro-perforated plate 651 is used alone, curve 183 represents the frequency response for the case where a micro-perforated plate 651 is used and a porous sound-absorbing material is used to fill the cavity 652, and curve 184 represents the frequency response for the case where a micro-perforated plate 651 is used and a porous sound-absorbing material is used to fill the cavity 652, where the frequency responses are those of sound emanating from the second acoustic hole. 18, without the micro-perforated plate 651 (curve 181), there is a very high resonance peak around 3.9 kHz, and 4.2 kHz corresponds to the resonance frequency of the second acoustic cavity 640. After adding the micro-perforated plate sound absorbing structure (curve 182), the sound pressure level is effectively reduced by 4 dB to 20 dB in the frequency band of 3 kHz to 6 kHz. It is clear that the micro-perforated plate sound absorbing structure can effectively absorb sound waves within the range of 3 kHz to 6 kHz, and the sound absorption effect of the micro-perforated plate sound absorbing structure on sound waves at the resonance frequency is about 20 dB. This can reduce or prevent sound waves from resonating near the resonance frequency under the action of the second acoustic cavity 640, thereby reducing sound leakage at the resonance frequency. After the cavity 652 of the micro-perforated plate sound-absorbing structure is filled with porous sound-absorbing material (curve 183) or N'Bass sound-absorbing particles (curve 184), the sound absorption frequency range can be extended to lower frequencies, and both of these combined sound-absorbing methods have excellent sound-absorbing effects.

[0152] When measuring a frequency response curve without a micro-perforated board sound absorbing structure, the through-holes of the micro-perforated board 651 of an acoustic device including the micro-perforated board sound absorbing structure can be blocked to simulate the frequency response of sound emitted from the second acoustic hole without the micro-perforated board sound absorbing structure. For example, opening the back panel of the cavity 652 away from the second acoustic cavity 640 and changing the cavity 652 from a closed state to an open state is equivalent to removing the cavity 652 from the micro-perforated board sound absorbing structure. Furthermore, blocking the through-holes of the micro-perforated board 651 with a material such as rubber clay or adhesive is equivalent to removing the micro-perforated board 651 from the micro-perforated board sound absorbing structure. This method is equivalent to removing the micro-perforated board sound absorbing structure and has little effect on the volume of the second acoustic cavity 640, thereby avoiding any impact on the frequency response of the second acoustic cavity 640. Furthermore, the frequency response of sound emitted from the second acoustic hole can be measured. For example, the measurement microphone is placed directly facing the second acoustic hole at a distance of about 2 mm to 5 mm from the second acoustic hole, and the method for measuring the frequency response of the first acoustic hole is similar to the method for measuring the frequency response of the second acoustic hole.

[0153] 19 and 20 are diagrams illustrating the internal structure of an acoustic device according to some embodiments of the present disclosure.

[0154] As shown in FIGS. 19 and 20, the speaker divides the accommodating cavity of a housing 1910 into a first acoustic cavity 1930 and a second acoustic cavity 1940, and the speaker includes a diaphragm 1921, a coil 1922, a frame 1923, and a magnetic circuit assembly 1924. The frame 1923 is installed around the diaphragm 1921, the coil 1922, and the magnetic circuit assembly 1924 to provide a mounting and fixing platform. The speaker may be connected to the housing 1910 by the frame 1923. The diaphragm 1921 covers the coil 1922 and the magnetic circuit assembly 1924 in the Z direction. At least a portion of the coil 1922 enters the magnetic gap formed by the magnetic circuit assembly 1924 and is connected to the diaphragm 1921. The magnetic field generated when the coil 1922 is energized interacts with the magnetic field formed by the magnetic circuit assembly 1924 to drive the diaphragm 1921 to generate mechanical vibrations, which then propagate through a medium such as air to generate sound. The sound is output through holes in the housing 1910. A micro-perforated sound-absorbing structure may be installed in the second acoustic cavity 1940. For example, a micro-perforated board sound absorbing structure may be disposed around the magnetic circuit assembly 1924, and the micro-perforated board sound absorbing structure may include a micro-perforated board 1951 and a packing layer 1953, with the side of the micro-perforated board 1951 away from the diaphragm 1921 in the Z direction connected to the packing layer 1953. The micro-perforated board 1951 has an annular structure and is disposed around the magnetic circuit assembly 1924. The packing layer 1953 is filled with N'Bass sound absorbing particles or a porous sound absorbing material. In some embodiments, the housing 1910 (e.g., back plate 1952) and the magnetic circuit assembly 1924 may form a sealed cavity, i.e., the cavity of the micro-perforated board sound absorbing structure, and the packing layer 1953 may be filled into the cavity.

[0155] In some embodiments, the magnetic circuit assembly 1924 includes a magnetically permeable plate 19241, a magnet 19242, and a magnetically permeable cover 19243, where the magnetically permeable plate 19241 and the magnet 19242 are connected to each other, and the side of the magnet 19242 away from the magnetically permeable plate 19241 is attached to the bottom wall of the magnetically permeable cover 19243, forming a magnetic gap between the peripheral side of the magnet 19242 and the peripheral inner wall of the magnetically permeable cover 19243. In some embodiments, the peripheral outer wall of the magnetically permeable cover 19243 is connected and fixed to the frame 1923. In some embodiments, both the magnetically permeable cover 19243 and the magnetically permeable plate 19241 can be made of a magnetically permeable material (e.g., iron).

[0156] In some embodiments, the micro-perforated plate 1951 may be provided with multiple through-holes, which are positioned around the magnet assembly to help ensure proper hole spacing and aperture ratio.

[0157] In some embodiments, since it is necessary to install a sealed cavity of a certain height on the side of the micro-perforated plate 1951 away from the diaphragm, if the entire micro-perforated plate 1951 is installed on the side of the magnetic circuit assembly away from the diaphragm, the micro-perforated plate 1951 and the filling layer 1953 may occupy too much space in the housing 1910, making it difficult to meet the design requirements for a compact acoustic device. In the acoustic device 1900 according to this embodiment, the micro-perforated plate 1951 has an annular structure centered on the magnetic circuit assembly, which not only makes effective use of the space in the circumferential direction of the magnetic circuit assembly but also does not increase the thickness of the acoustic device (i.e., the dimension along the Z direction), which is useful for designing a compact acoustic device.

[0158] In some embodiments, the micro-perforated plate may be installed on the side of the magnetic circuit assembly 1924 away from the diaphragm 1921, i.e., the micro-perforated plate 1951 and the magnetic circuit assembly are installed with a gap in the Z direction (the vibration direction of the diaphragm). Specific installation methods can be seen in FIG. 4. In some embodiments, the micro-perforated plate may be a panel (e.g., racetrack-shaped, circular, etc.) that conforms to the shape of the second acoustic cavity 1940 or the housing 1910. The parameters of the micro-perforated plate, such as the hole diameter, aperture ratio, and hole spacing, may be matched with the relevant parameters of the micro-perforated plate 1951. In this way, the area of ​​the micro-perforated plate in the panel structure may be larger, the number of through-holes may be larger, the sound absorption effect may be better, the structure may be simpler, and it may be easier to assemble.

[0159] Fig. 21 is a diagram showing the internal structure of an acoustic device according to some embodiments of the present disclosure. The acoustic device 2100 and its speaker shown in Fig. 21 are similar to the acoustic device 1900 and its speaker shown in Fig. 19 and Fig. 20, except that they do not have a separate micro-perforated plate.

[0160] At least a portion of the magnetic permeable element of the acoustic device 2100 may be a micro-perforated plate. For example, as shown in FIG. 21 , a plurality of through holes may be provided at the bottom of the magnetic permeable cover 21243, which is away from the vibration membrane, to form a micro-perforated plate. The side of the magnetic permeable cover 21243 away from the vibration membrane along the Z direction is connected to a cavity. In some embodiments, a filling layer may be provided in the cavity. In this embodiment, by directly forming a part of the magnetic circuit assembly as a sound-absorbing structure, it is possible to achieve a sound-absorbing effect, reduce costs, and simplify the process.

[0161] FIG. 22 is a frequency response curve diagram of the acoustic device 1900 shown in FIGS. 19 and 20 and the acoustic device 2100 shown in FIG. In Figure 22, the horizontal axis represents frequency, the vertical axis represents sound pressure level, curve a1 represents the frequency response of the first acoustic hole of acoustic device 2100, curve a2 represents the frequency response of the first acoustic hole of acoustic device 1900, curve b1 represents the frequency response of the first decompression hole of acoustic device 2100, curve b2 represents the frequency response of the first decompression hole of acoustic device 1900, curve c1 represents the frequency response of the second decompression hole of acoustic device 2100, curve c2 represents the frequency response of the second decompression hole of acoustic device 1900, curve d1 represents the frequency response of sound emitted from the third decompression hole of acoustic device 2100, and curve d2 represents the frequency response of sound emitted from the third decompression hole of acoustic device 1900, and the first decompression hole, second decompression hole, and third decompression hole are acoustic holes (i.e., second acoustic holes) located at different positions on the housing corresponding to the second acoustic cavity. 22, for the acoustic device, curves a1, a2, b1, b2, c1, c2, d1, and d2 all reach a low point around 3.9 kHz, and within the frequency band around 3.9 kHz, curves a2, b2, c2, and d2 are all lower than the corresponding curves a1, b1, c1, and d1. As can be seen, the sound absorption center frequencies of the two types of micro-perforated panel installation methods corresponding to acoustic device 1900 and acoustic device 2100 are both 3.9 kHz, and the sound absorption effect of the micro-perforated panel corresponding to acoustic device 1900 is superior to that of the micro-perforated panel corresponding to acoustic device 2100. The reason is that when the magnetic permeable cover 21243 is a micro-perforated plate, the micro-perforated plate sound absorbing structure accordingly acts on the magnetic gap cavity between the magnetic permeable cover 21243 and the corresponding magnet (not shown), rather than on the second acoustic cavity (not shown) of the acoustic device 2100, so the micro-perforated plate sound absorbing structure has limited effect on absorbing sound waves in the second acoustic cavity. In some embodiments, both the micro-perforated plate 1951 shown in Figures 19 and 20 and the magnetic permeable cover 21243 shown in Figure 21 can be installed to form the sound absorbing structure of the acoustic device, and in this case, the number of through holes in the sound absorbing structure will be greater, resulting in a higher sound absorbing effect.

[0162] 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.

[0163] Furthermore, certain terms are used herein to describe embodiments herein. For example, "one embodiment," "one embodiment," and / or "some embodiments" refer to particular features, structures, or characteristics associated with at least one embodiment herein. Therefore, it is emphasized and understood that references to "one embodiment" or "one embodiment" or "one alternative embodiment" in various parts of this specification do not necessarily all refer to the same embodiment. Furthermore, particular features, structures, or characteristics in one or more embodiments herein may be combined as appropriate.

[0164] 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 described through various examples what are presently believed to be various useful embodiments of the invention, it should be understood that such details are for illustrative purposes only, 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.

[0165] 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.

[0166] In some embodiments, numbers describing the number of components and attributes are used, and 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. In some embodiments, the numerical ranges and parameters used to determine ranges are approximations; however, in specific embodiments, such numerical values ​​are set as precisely as possible.

[0167] 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.

[0168] 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]

[0169] 100 Sound equipment 110 Housing 111 1st acoustic hole 112 2nd acoustic hole 120 speakers 130 First Acoustic Cavity 140 Second Acoustic Cavity

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, the diaphragm radiating sound to the first acoustic cavity and the second acoustic cavity, respectively, and emitting 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 comprising a micro-perforated plate coupled to the second acoustic cavity, the sound absorbing structure absorbing sound that passes through the second acoustic cavity and is transmitted to the second acoustic hole within a target frequency range that includes a resonant frequency of the second acoustic cavity; a magnetic circuit assembly; 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 when energized to generate sound, and the micro-perforated plate includes an annular structure disposed around the magnetic circuit assembly.

2. 2. The acoustic device of claim 1, wherein the target frequency range further includes a resonant frequency of the first acoustic cavity.

3. 2. The acoustic device according to claim 1, wherein the target frequency range includes 3 kHz to 6 kHz, and the sound absorbing effect of the sound absorbing structure for sounds within the target frequency range is 3 dB or more.

4. 4. The acoustic device according to claim 3, wherein the sound absorbing effect of the sound absorbing structure with respect to the sound at the resonant frequency is 14 dB or more.

5. 2. The acoustic device of claim 1, wherein the sound absorbing structure includes a cavity, the micro-perforated plate includes at least one through hole, and the second acoustic cavity coupled to the sound absorbing structure communicates with the cavity via the at least one through hole.

6. The cavity is filled with a filler material, the filler material comprising: The diameter is in the range of 0.15 mm to 0.7 mm; The filling rate of the cavity is in the range of 70% to 95%; 6. The acoustic device according to claim 5, wherein at least one of the following is satisfied: a gauze is placed between the acoustic device and the micro-perforated plate.

7. 7. The acoustic device according to claim 6, wherein a ratio of a hole spacing between the at least one through-hole to a hole diameter of the at least one through-hole is greater than 5.

8. 6. The acoustic device of claim 5, wherein the diameter of the at least one through-hole 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.

9. 6. The acoustic device of claim 5, wherein the hole diameter of the at least one through-hole 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.

10. 6. The acoustic device of claim 5, wherein the height of the cavity is in the range of 0.5 mm to 10 mm.

11. 6. The acoustic device according to claim 5, wherein a waterproof and breathable structure is provided on the side of the finely perforated plate facing the vibration membrane.

12. An acoustic device as described in claim 5, characterized in that the finely perforated plate and the magnetic circuit assembly are installed at a distance in the vibration direction of the vibration membrane.

13. An acoustic device as described in claim 5, characterized in that the finely perforated plate includes a magnetically permeable element of the magnetic circuit assembly.

14. 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, the diaphragm radiating sound to the first acoustic cavity and the second acoustic cavity, respectively, and emitting 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 including a micro-perforated plate coupled to the second acoustic cavity, the sound absorbing structure absorbing sound within a target frequency range that passes through the second acoustic cavity and is transmitted to the second acoustic hole; a sound pressure level of the second acoustic hole when the sound absorbing structure is not installed is greater than a sound pressure level of the second acoustic hole when the sound absorbing structure is installed, within the target frequency range; further comprising 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 when energized to generate sound, and the micro-perforated plate includes an annular structure disposed around the magnetic circuit assembly.

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