An open earphone

Abstract

The embodiment of the specification provides an open earphone, comprising a sound generating part and an ear hook. The sound generating part comprises a transducer comprising a diaphragm for generating sound under the action of an excitation signal, and a shell forming a cavity for accommodating the transducer, wherein the shell is provided with a sound hole on the inner side of the auricle of the user, for guiding the sound generated in front of the diaphragm out of the shell and then to the ear canal, and at least two pressure relief holes are provided on the other side wall of the shell, the at least two pressure relief holes comprising a first pressure relief hole away from the ear canal and a second pressure relief hole close to the ear canal, and the sound pressure at the first pressure relief hole is greater than that at the second pressure relief hole. The sound generating part and the ear hook jointly hold the ear region from the front and back of the concha cavity corresponding to the ear region of the auricle.

Description

[0001] Cross-referencing This specification is a divisional application of Chinese application No. 202310237166.4, filed on March 2, 2023, entitled "An Open-Type Headphone," which claims priority to Chinese applications No. 202211336918.4, filed on October 28, 2022; Chinese application No. 202223239628.6, filed on December 1, 2022; and international application No. PCT / CN2022 / 144339, filed on December 30, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This manual relates to the field of acoustic technology, specifically to an open-back headphone. Background Technology

[0003] With the development of acoustic output technology, headphones have become widely used in people's daily lives. They can be used with electronic devices such as mobile phones and computers to provide users with an auditory feast. According to the way users wear them, acoustic devices can generally be divided into over-ear, ear-hook, and in-ear types. The output performance of headphones has a significant impact on user comfort.

[0004] Therefore, it is necessary to propose an open-back headphone to improve its output performance. Summary of the Invention

[0005] This specification provides an open-back headphone, which may include a sound-generating part. The sound-generating part may include a transducer, which may include a diaphragm for generating sound under the action of an excitation signal; and a housing, the housing forming a cavity for accommodating the transducer. In the wearing state, a sound outlet may be formed on the inner side of the housing facing the user's auricle to guide the sound generated by the front side of the diaphragm through the housing and into the ear canal. At least two pressure relief holes may be formed on other sidewalls of the housing, including a first pressure relief hole away from the ear canal and a second pressure relief hole near the ear canal. The sound pressure at the first pressure relief hole may be greater than the sound pressure at the second pressure relief hole. In some embodiments, the at least two pressure relief holes may be used to guide the sound generated by the rear side (or rear cavity) of the diaphragm through the housing and cancel out the sound emitted by the sound outlet (e.g., far-field sound), thereby eliminating or reducing sound leakage generated by the sound-generating part. In some embodiments, the sound waves emitted from the second pressure relief hole near the ear canal are more likely to cancel out the sound waves emitted from the sound outlet in the near field (e.g., the ear canal) compared to the first pressure relief hole away from the ear canal. Therefore, the sound pressure at the first pressure relief hole is greater than that at the second pressure relief hole, which can reduce the near-field interference between the sound output from the second pressure relief hole and the sound output from the sound outlet hole, thereby improving the listening effect of open-back headphones.

[0006] In some embodiments, the first pressure relief hole and the second pressure relief hole may be located on different sides of the housing. This arrangement can disrupt the standing waves in the rear cavity (i.e., the cavity corresponding to the back of the diaphragm) of the open-back headphones, allowing the resonant frequency of the sound emitted from the two pressure relief holes to the outside of the housing to be as high as possible. This results in a wider, flatter frequency response area for the rear cavity and better sound leakage reduction in the mid-to-high frequency range (e.g., 2 kHz-6 kHz).

[0007] In some embodiments, the ratio between the area of ​​the first pressure relief hole and the area of ​​the second pressure relief hole can be in the range of 1-5. This configuration allows the frequency response curve of the rear cavity to have a large flat area while maintaining sufficient sound volume in the ear canal.

[0008] In some embodiments, the ratio between the major axis and minor axis of the first pressure relief hole can be in the range of 1.3-8. This configuration allows the frequency response curve corresponding to the rear cavity to have a larger flat area, improving the sound output performance of the open-back headphone 10.

[0009] In some embodiments, the ratio between the major axis and minor axis of the second pressure relief hole can be in the range of 1-6. This configuration allows the frequency response curve corresponding to the rear cavity 116 to have a larger flat region, improving the sound output performance of the open-back headphone 10.

[0010] In some embodiments, the ratio between the area of ​​the sound outlet hole and the total area of ​​the first pressure relief hole and the second pressure relief hole can be in the range of 0.1-0.99.

[0011] In some embodiments, the diaphragm divides the cavity into a front cavity and a rear cavity corresponding to the front and rear sides of the diaphragm, respectively, wherein the ratio between the volume of the rear cavity and the volume of the front cavity can be in the range of 0.1-10, and the diaphragm divides the cavity into a front cavity and a rear cavity corresponding to the front and rear sides of the diaphragm, respectively, wherein the ratio between the resonant frequency of the front cavity and the resonant frequency of the rear cavity can be in the range of 0.1-5.

[0012] In some embodiments, the ratio between the area of ​​the sound outlet and the total area of ​​the first pressure relief hole and the second pressure relief hole can be in the range of 1-10.

[0013] In some embodiments, the diaphragm divides the cavity into a front cavity and a rear cavity corresponding to the front and rear sides of the diaphragm, respectively, wherein the ratio between the volume of the rear cavity and the volume of the front cavity can be in the range of 0.1-10, and the diaphragm divides the cavity into a front cavity and a rear cavity corresponding to the front and rear sides of the diaphragm, respectively, wherein the ratio between the resonant frequency of the front cavity and the resonant frequency of the rear cavity can be in the range of 0.5-10.

[0014] With the above settings, the ratio of the volume of the rear cavity to the volume of the front cavity can be determined based on the ratio of the area of ​​the sound outlet to the total area of ​​the first and second pressure relief holes. Alternatively, the ratio of the area of ​​the sound outlet to the total area of ​​the first and second pressure relief holes can be determined based on the ratio of the volume of the rear cavity to the volume of the front cavity. This ensures that the ratio of the resonant frequency of the rear cavity to the resonant frequency of the front cavity is within a preset range. For example, the resonant frequency of the rear cavity can be close to or equal to the resonant frequency of the front cavity. This allows the sound leakage formed by the pressure relief holes (e.g., the first and / or the second pressure relief holes) to better cancel out the sound leakage formed by the sound outlet in the far field, thus improving the output effect of the open-back headphones.

[0015] In some embodiments, the ratio between the area of ​​the sound outlet and the depth of the sound outlet can be in the range of 0.31-512.2. This configuration allows for the improvement of the resonant frequency of the front cavity while ensuring the sound quality of the sound outlet, without affecting the appearance, structural strength, or other aspects of the open-back headphones.

[0016] In some embodiments, the ratio between the major axis and minor axis of the sound outlet can be in the range of 1-10. This setting ensures good low-frequency output from the sound outlet while simultaneously increasing the volume of the sound output.

[0017] In some embodiments, within the range of 3.5 kHz to 4.5 kHz, the ratio between the sound pressure at the sound outlet and the total sound pressure at the first and second pressure relief holes can be in the range of 0.4 to 0.6. This setting effectively reduces far-field sound leakage. Attached Figure Description

[0018] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein: Figure 1 This is a schematic diagram of an exemplary ear according to some embodiments of this specification; Figure 2 These are exemplary structural diagrams of open-back headphones according to some embodiments of this specification; Figure 3 These are exemplary wearing diagrams of open-back headphones according to some embodiments of this specification; Figure 4 This is an exemplary wearing diagram of another open-back headphone shown according to some embodiments of this specification; Figure 5 yes Figure 4 Another exemplary external outline diagram of the open-back headphones shown; Figure 6 yes Figure 4 Another exemplary external outline diagram of the open-back headphones shown; Figure 7 yes Figure 4 Another exemplary external outline diagram of the open-back headphones shown; Figure 8 This is an exemplary distribution diagram of a cavity structure arranged around one of the dipole sound sources according to some embodiments of this specification; Figure 9 This is a schematic diagram illustrating the listening principle of a dipole sound source structure and a cavity structure built around one of the dipole sound sources, as shown in some embodiments of this specification. Figure 10 This is a schematic diagram illustrating the sound leakage principle of a dipole sound source structure and a cavity structure built around one of the dipole sound sources, as shown in some embodiments of this specification. Figure 11 This is a schematic diagram of the exemplary internal structure of the sound-generating part according to some embodiments of this specification; Figure 12 This is an exemplary structural diagram of the inner shell according to some embodiments of this specification; Figure 13AThis is a schematic diagram illustrating exemplary positions of the sound outlet according to some embodiments of this specification; Figure 13B This is a frequency response curve diagram corresponding to the sound outlet at different positions as shown in some embodiments of this specification; Figure 14A This is a schematic diagram illustrating an exemplary location of the first pressure relief hole according to some embodiments of this specification; Figure 14B These are frequency response curves corresponding to the first pressure relief hole at different locations as shown in some embodiments of this specification; Figure 15A This is a schematic diagram illustrating an exemplary location of the second pressure relief hole according to some embodiments of this specification; Figure 15B These are frequency response curves corresponding to the second pressure relief holes at different locations as shown in some embodiments of this specification; Figure 16 These are frequency response curves of the front cavity corresponding to different aspect ratios of the sound outlet, as shown in some embodiments of this specification. Figure 17 This is a frequency response curve of the front cavity corresponding to different lengths of the sound outlet hole, as shown in some embodiments of this specification. Figure 18 These are frequency response curves corresponding to different aspect ratios of the sound outlet holes, as shown in some embodiments of this specification. Figure 19 These are frequency response curves corresponding to different lengths of sound outlet holes as shown in some embodiments of this specification; Figure 20 These are frequency response curves for racetrack-shaped and circular sound holes of different lengths, as shown in some embodiments of this specification. Figure 21 This is an exemplary structural diagram of a portion of the rear cavity structure shown in some embodiments of this specification; Figure 22 These are frequency response curves of the rear cavity corresponding to different included angles α as shown in some embodiments of this specification; Figure 23A This is a schematic diagram showing the acoustic impedance changes corresponding to different area ratios of the first and second pressure relief holes, as illustrated in some embodiments of this specification. Figure 23B This is a schematic diagram showing the acoustic quality changes corresponding to different area ratios of the first and second pressure relief holes, as illustrated in some embodiments of this specification. Figure 23C This is a schematic diagram showing the changes in radiated acoustic impedance corresponding to different area ratios of the first and second pressure relief holes, as illustrated in some embodiments of this specification. Figure 23DThis is a schematic diagram showing the changes in radiated acoustic quality corresponding to different area ratios of the first and second pressure relief holes, as illustrated in some embodiments of this specification. Figures 24A-24E This is a frequency response curve of the rear cavity corresponding to different area ratios of the first and second pressure relief holes as shown in some embodiments of this specification; Figure 25 This is a frequency response curve diagram of the first pressure relief hole with different length values ​​as shown in some embodiments of this specification; Figure 26 This is a frequency response curve diagram of the second pressure relief hole with different length values ​​as shown in some embodiments of this specification; Figure 27 It is a contour map showing the ratio of the front and rear cavity volumes and the ratio of the sound outlet opening area to the acoustic hole opening area according to some embodiments of this specification; Figure 28 This is a frequency response curve diagram corresponding to different volume levels at the sound outlet, as shown in some embodiments of this specification; Figure 29 This is a frequency response curve diagram corresponding to different volume levels at the first pressure relief hole, as shown in some embodiments of this specification; Figure 30 This is a frequency response curve diagram corresponding to different volume levels at the second pressure relief hole, as shown in some embodiments of this specification; Figures 31A-31F This is a frequency response curve diagram showing the different acoustic resistive meshes set in the front and rear cavities according to some embodiments of this specification. Detailed Implementation

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0020] It should be understood that the terms “system,” “device,” “unit,” and / or “module” used herein are one way to distinguish different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0021] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0022] Figure 1 This is a schematic diagram of an exemplary ear according to some embodiments of this application. See also Figure 1 The ear 100 (also referred to as the auricle) may include the external auditory canal 101, the concha 102, the cymba concha 103, the triangular fossa 104, the antihelix 105, the scaphoid fossa 106, the helix 107, the earlobe 108, the tragus 109, and the crus of the helix 1071. In some embodiments, the acoustic device can be stably worn by supporting it with one or more parts of the ear 100. In some embodiments, the external auditory canal 101, the concha 102, the cymba concha 103, the triangular fossa 104, etc., have a certain depth and volume in three-dimensional space, which can be used to meet the wearing requirements of the acoustic device. For example, the acoustic device (e.g., an in-ear headphone) can be worn in the external auditory canal 101. In some embodiments, the acoustic device (e.g., an open-back headphone) can be worn by using other parts of the ear 100 besides the external auditory canal 101. For example, the acoustic device can be worn using parts such as the cymba conchae 103, triangular fossa 104, antihelix 105, scaphoid fossa 106, and helix 107, or combinations thereof. In some embodiments, to improve the comfort and reliability of the acoustic device during wear, parts such as the user's earlobe 108 can also be used. By using parts of the ear 100 other than the external auditory canal 101 to achieve the wearing of the acoustic device and the propagation of sound, the user's external auditory canal 101 can be "liberated". When the user wears the acoustic device (e.g., open-back headphones), the acoustic device does not block the user's external auditory canal 101 (or ear canal, ear canal opening), and the user can receive both sound from the acoustic device and sound from the environment (e.g., horn sounds, car bell sounds, surrounding voices, traffic signals, etc.), thereby reducing the probability of traffic accidents. In some embodiments, the acoustic device can be designed to fit the ear 100 according to the structure of the ear 100, so that the sound-emitting part of the acoustic device can be worn at different positions on the ear. For example, when the acoustic device is an open-back headphone, the open-back headphone may include a suspension structure (e.g., an ear hook) and a sound-producing part, the sound-producing part being physically connected to the suspension structure, and the suspension structure being adapted to the shape of the auricle to place the entire or part of the sound-producing part in front of the tragus 109 (e.g., Figure 1The area J enclosed by the dotted line. For example, when a user wears open-back headphones, the entire or partial structure of the sound-producing part can contact the upper part of the external auditory canal 101 (e.g., the location of one or more parts such as the cymba conchae 103, triangular fossa 104, antihelix 105, scaphoid 106, helix 107, and crus of helix 1071). For yet another example, when a user wears open-back headphones, the entire or partial structure of the sound-producing part can be located within the cavity formed by one or more parts of the ear 100 (e.g., the cavum conchae 102, cymba conchae 103, triangular fossa 104, etc.). Figure 1 The region M1, enclosed by the dashed line, includes at least the cymba conchae 103 and the triangular fossa 104, and the region M2, which includes at least the cavum conchae 102.

[0023] Individual differences may exist among users, resulting in variations in ear shape, size, and other dimensional differences. For ease of description and understanding, unless otherwise specified, this specification will primarily use an ear model with a "standard" shape and size as a reference to further describe how the acoustic device in different embodiments is worn on this ear model. For example, a simulator containing a head and its (left and right) ears, such as the GRAS 45BC KEMAR, can be manufactured based on ANSI: S3.36, S3.25, and IEC: 60318-7 standards as a reference for wearing the acoustic device, thus representing the scenario of most users normally wearing the acoustic device. As an example only, the reference ear may have the following characteristics: the projection of the auricle in the sagittal plane in the vertical axis direction can be in the range of 49.5mm-74.3mm, and the projection of the auricle in the sagittal plane in the sagittal axis direction can be in the range of 36.6mm-55mm. Therefore, in this application, descriptions such as "user wearing," "in wearing state," and "under wearing state" can refer to the acoustic device described in this application being worn on the ear of the aforementioned simulator. Of course, considering the individual differences among different users, the structure, shape, size, thickness, etc. of one or more parts of the ear 100 may have certain differences. In order to meet the needs of different users, the acoustic device can be designed differently. These differentiated designs can be manifested in that the characteristic parameters of one or more parts of the acoustic device (e.g., the sound-emitting part, ear hook, etc. mentioned below) can have different ranges of values ​​to adapt to different ears.

[0024] It should be noted that in medicine, anatomy, and other fields, the human body can be defined by three basic planes: the sagittal plane, the coronal plane, and the horizontal plane; and three basic axes: the sagittal axis, the coronal axis, and the vertical axis. The sagittal plane is a section perpendicular to the ground along the anteroposterior direction of the body, dividing the body into left and right parts. The coronal plane is a section perpendicular to the ground along the left and right direction of the body, dividing the body into anterior and posterior parts. The horizontal plane is a section parallel to the ground along the vertical direction of the body, dividing the body into superior and inferior parts. Correspondingly, the sagittal axis is the axis along the anteroposterior direction of the body and perpendicular to the coronal plane; the coronal axis is the axis along the left and right direction of the body and perpendicular to the sagittal plane; and the vertical axis is the axis along the vertical direction of the body and perpendicular to the horizontal plane. Furthermore, the "front side of the ear" mentioned in this application is a concept relative to "back side of the ear," the former referring to the side of the ear away from the head, and the latter referring to the side of the ear facing the head. Specifically, by observing the ear of the simulator along the direction of the human coronal axis, one can obtain... Figure 1 A schematic diagram of the front outline of the ear is shown.

[0025] Figure 2 These are exemplary structural diagrams of open-back headphones shown in some embodiments of this specification. Figure 3 These are exemplary wearing diagrams of open-back headphones according to some embodiments of this specification. Figure 4 This is an exemplary wearing diagram of another open-back headphone shown according to some embodiments of this specification. Figures 2-4 As shown, the open-back headphones 10 may include a speaker 11 and an ear hook 12. In some embodiments, the speaker 11 of the open-back headphones 10 can be worn on the user's body (e.g., the head, neck, or upper torso) via the ear hook 12.

[0026] In some embodiments, when the open-back headphones 10 are worn, the first part of the ear hook 12 is hung between the user's auricle and head, and the second part extends towards the side of the auricle away from the head and connects to the sound-emitting part 11, for fixing the sound-emitting part 11 in a position near the ear canal without blocking the ear canal. In some embodiments, the ear hook 12 can be an arc structure adapted to the user's auricle, so that the ear hook 12 can be suspended on the user's upper auricle. In some embodiments, the ear hook 12 can also be a clamping structure adapted to the user's auricle, so that the ear hook 12 can be clamped on the user's auricle. In some embodiments, the ear hook 12 can include, but is not limited to, a hook structure, an elastic band, etc., so that the open-back headphones 10 can be better fixed to the user and prevent the headphones from falling off during use.

[0027] In some embodiments, to improve the stability of the open-back headphones 10 during wear, the open-back headphones 10 may employ any one or a combination of the following methods: First, at least a portion of the ear hook 12 is configured as a conformal structure that conforms to at least one of the back of the ear and the head, thereby increasing the contact area between the ear hook 12 and the ear and / or the head, thus increasing the resistance to the open-back headphones 10 falling off the ear. Second, at least a portion of the ear hook 12 is configured as an elastic structure, allowing it to have a certain deformation during wear, thereby increasing the positive pressure of the ear hook 12 on the ear and / or the head, thus increasing the resistance to the open-back headphones 10 falling off the ear. Third, at least a portion of the ear hook 12 is configured to rest against the head during wear, creating a reaction force that presses against the ear, causing the sound-emitting part 11 to press against the front of the ear, thereby increasing the resistance to the open-back headphones 10 falling off the ear. Fourth, the sound-emitting part 11 and the ear hook 12 are configured to clamp the physiological parts such as the antihelix and conchae from the front and back sides of the ear when worn, thereby increasing the resistance to the open-back headphones 10 falling off the ear. Fifth, the sound-emitting part 11 or the auxiliary structure connected to it is configured to extend at least partially into the physiological parts such as the conchae, cymba conchae, triangular fossa, and scaphoid fossa, thereby increasing the resistance to the open-back headphones 10 falling off the ear.

[0028] In some embodiments, such as Figure 2 As shown, the sound-generating part 11 can be worn on a user's body to generate sound input to the user's ear 100. In some embodiments, the sound-generating part 11 may include a transducer 112. The transducer 112 may include a diaphragm (e.g., as shown in the image). Figure 11 The diaphragm 1121 shown is used to generate sound under the action of an excitation signal. In some embodiments, the sound-generating part 11 may further include a housing 111. The housing 111 may form a cavity for accommodating the transducer 112. In some embodiments, the housing 111 faces the inner surface of the auricle (e.g., Figure 6 A sound hole (e.g., as shown) can be formed on the inner surface IS. Figure 6 The sound outlet 111a shown is used to guide the sound generated on the front side of the diaphragm out of the housing 111 and into the ear canal. In some embodiments, at least two pressure relief holes may be provided on other sidewalls of the housing 111 to guide the sound generated on the rear side of the diaphragm out of the housing 111 and cancel out the sound (e.g., far-field sound) emanating from the sound outlet 111a. Exemplarily, the sound-generating part 11 can emit sound with a phase difference (e.g., opposite phase) through the sound outlet and the two pressure relief holes. The sound with a phase difference can interfere with each other in the far field, thereby reducing sound leakage. In some embodiments, the at least two pressure relief holes may include a first pressure relief hole (e.g., Figure 12 The first pressure relief hole 111c shown) and the second pressure relief hole (e.g., Figure 12 The second pressure relief hole 111d is shown. When a user wears the open-back headphones 10, the second pressure relief hole can be closer to the ear canal than the first pressure relief hole. In some embodiments, the sound waves emitted from the second pressure relief hole, which is closer to the ear canal than the first pressure relief hole, are more likely to cancel out the sound waves emitted from the sound outlet in the near field (e.g., the ear canal). Therefore, the sound pressure of the second pressure relief hole can be lower than that of the first pressure relief hole to reduce the near-field interference cancellation between the sound emitted from the second pressure relief hole and the sound emitted from the sound outlet, thereby improving the listening effect of the open-back headphones 10.

[0029] In some embodiments, the open-back headphones 10 can be combined with products such as glasses, headphones, head-mounted displays, and AR / VR helmets. In this case, the sound-emitting part 11 can be fixed near the user's ear 100 by suspension or clamping. In some embodiments, the housing 111 can be a housing structure with a shape adapted to the human ear 100, such as annular, elliptical, polygonal (regular or irregular), U-shaped, V-shaped, or semi-circular, so that the sound-emitting part 11 can be directly attached to the user's ear 100. In some embodiments, the sound-emitting part 11 can have a major axis direction Y and a minor axis (or width) direction Z that are perpendicular to the thickness direction X and orthogonal to each other. The major axis direction Y can be defined as the direction with the maximum extension dimension in the shape of the two-dimensional projection surface of the sound-emitting part 11 (e.g., the projection of the sound-emitting part 11 on the plane where its outer side is located, or the projection on the sagittal plane). (For example, when the projection shape is rectangular or approximately rectangular, the major axis direction is the length direction of the rectangle or approximately rectangular shape.) The minor axis direction Z can be defined as the direction perpendicular to the major axis direction Y in the shape of the two-dimensional projection surface of the sound-emitting part 11 (for example, when the projection shape is a rectangle or approximately a rectangle, the minor axis direction is the width direction of the rectangle or approximately a rectangle). The thickness direction X can be defined as the direction perpendicular to the two-dimensional projection surface (for example, consistent with the direction of the coronal axis, both pointing in the left-right direction of the body). In some embodiments, when the sound-emitting part 11 is in a horizontal state in the wearing state, the major axis direction Y can be consistent with the direction of the sagittal axis, both pointing in the front-back direction of the body, and the minor axis direction Z can be consistent with the direction of the vertical axis, both pointing in the up-down direction of the body, such as... Figure 3 As shown. In other embodiments, when the sound-emitting part 11 is tilted in the wearing state, the major axis direction Y and the minor axis direction Z can still be parallel to or approximately parallel to the sagittal plane. The major axis direction Y can have a certain angle with the direction of the sagittal axis, that is, the major axis direction Y is also tilted accordingly. The minor axis direction Z can have a certain angle with the direction of the vertical axis, that is, the minor axis direction Z is also tilted, such as... Figure 4 As shown.

[0030] In some embodiments, when a user wears open-back headphones 10, the sound-emitting part 11 may be located above, below, in front of (e.g., in front of the tragus) or inside the auricle (e.g., in the concha cavity) of the user's ear 100.

[0031] In some embodiments, the open-back headphones 10 may include, but are not limited to, air conduction headphones, bone conduction headphones, etc. In some embodiments, when the open-back headphones 10 are in a wearing state, they may not obstruct the user's external auditory canal 101, such as... Figure 3 and Figure 4 As shown. In some embodiments, the projection of the open-back earphone 10 onto the user's ear plane can partially or completely cover but not block the user's external auditory canal 101, such as... Figure 4 As shown. In some embodiments, the projection of the open-back headphone 10 onto the user's ear plane may not cover the user's external auditory canal 101, such as... Figure 3 As shown.

[0032] The following is Figure 4 Taking the open-back headphone 10 shown as an example, the open-back headphone 10 will be described in detail. It should be noted that, without violating the corresponding acoustic principles, Figure 4 The structure and parameters of the open-back headphone 10 can also be applied to other open-back headphone configurations mentioned above.

[0033] Please refer to Figure 3 and Figure 4 In some embodiments, the sound-emitting part 11 may have a connecting end CE connected to the ear hook 12 and a free end FE not connected to the ear hook 12. In some embodiments, such as Figure 4 As shown, in the wearing state, at least a portion of the free end FE of the sound-producing part 11 can extend into the concha cavity. When viewed along the direction of the human coronal axis in the wearing state, the connecting end CE can be closer to the top of the head than the free end FE (e.g., ...). Figure 4 and Figure 6 As shown), so that the free end FE can extend into the concha cavity. In some embodiments, such as Figure 3 As shown, in the wearing state, the free end FE of the sound-producing part 11 does not extend into the concha cavity. When worn, viewed along the direction of the human coronal axis, the distance between the connecting end CE and the top of the head can be approximately equal to the distance between the free end FE and the top of the head. For example, the line connecting the connecting end CE and the free end FE can be parallel to the horizontal plane (e.g., ...). Figure 3 In some embodiments, when worn, the free end FE of the sound-emitting part 11 may not extend into the concha cavity. When viewed along the direction of the human coronal axis, the connecting end CE may be further away from the top of the head than the free end FE, so as to avoid the sound-emitting part 11 from obstructing the user's external auditory canal and concha cavity.

[0034] In some embodiments, the sound-generating part 11 and the ear hook 12 can be configured to clamp the aforementioned ear region from both the front and rear sides of the ear region corresponding to the concha cavity, thereby increasing the resistance to the open-back headphones 10 falling off the ear and improving the stability of the open-back headphones 10 in the wearing state. For example, the free end FE can be pressed into the concha cavity in the thickness direction X. As another example, the free end FE abuts against the concha cavity in the major axis direction Y and the minor axis direction Z. It should be noted that, in the wearing state, the free end FE of the sound-generating part 11 can not only extend into the concha cavity, but can also be orthographically projected onto the antihelix, or orthographically projected onto the left and right sides of the head and located at the front of the ear on the sagittal axis of the human body. In other words, the ear hook 12 can support the sound-generating part 11 to be worn in the concha cavity, antihelix, front of the ear, etc.

[0035] Figure 5 yes Figure 4 Another exemplary external outline diagram of the open-back headphones shown. Figure 6 yes Figure 4 Another exemplary external outline diagram of the open-back headphones shown. Figure 7 yes Figure 4 Another exemplary external outline diagram of the open-back headphones shown.

[0036] like Figures 4-7As shown, in some embodiments, the sound-emitting part 11 may have an inner surface IS facing the ear along the thickness direction X and an outer surface OS facing away from the ear when worn, as well as a connecting surface connecting the inner surface IS and the outer surface OS. When viewed along the direction of the coronal axis (i.e., the thickness direction X) when worn, the sound-emitting part 11 may be configured as a circle, an ellipse, a rounded square, a rounded rectangle, or the like. When the sound-emitting part 11 is configured as a circle, an ellipse, or the like, the connecting surface may refer to the arcuate side of the sound-emitting part 11; while when the sound-emitting part 11 is configured as a rounded square, a rounded rectangle, or the like, the connecting surface may include the lower surface LS, the upper surface US, and the rear surface RS mentioned later. Therefore, for ease of description, this embodiment uses a rounded rectangle as an example for illustrative explanation. In some embodiments, the sound-generating part 11 may have an upper side US and a lower side LS arranged along the minor axis direction Z, and a rear side RS connecting the upper side US and the lower side LS. The upper side US is located at the end facing the top of the head along the minor axis direction Z when worn, and the rear side RS is located at the end facing the back of the head along the major axis direction Y when worn. The free end FE is located on the rear side RS. In some embodiments, the positive direction of the major axis direction Y may point to the free end FE, the positive direction of the minor axis direction Z may point to the upper side US, and the positive direction of the thickness direction X may point to the outer side OS. In some embodiments, the inner side IS of the housing 111 facing the ear when worn has a sound outlet 111a. The sound waves generated by the transducer 112 propagate through the sound outlet 111a to facilitate transmission into the external auditory canal 101. It is worth noting that the sound outlet 111a may also be located on the lower side LS of the housing 111, or at the corner between the aforementioned inner side IS and the lower side LS.

[0037] In some embodiments, the first pressure relief hole and the second pressure relief hole can be disposed on different sides of the housing 111. For example, in the Z direction, the first pressure relief hole can be disposed on the upper side US of the housing 111, and the second pressure relief hole can be disposed on the lower side LS of the housing 111. The above arrangement can disrupt the standing waves in the rear cavity (i.e., the cavity corresponding to the rear side of the diaphragm), so that the resonant frequency of the sound vented to the outside of the housing 111 by the two pressure relief holes is as high as possible, thereby making the frequency response of the rear cavity have a wider flat region (e.g., the region before the resonance peak), and obtaining better sound leakage reduction effect in the mid-high frequency range (e.g., 2 kHz-6 kHz).

[0038] Because the concha has a certain volume and depth, after the free end FE extends into the concha, there can be a certain distance between the inner surface IS of the sound-generating part 11 and the concha. In other words, when worn, the sound-generating part 11 and the concha can cooperate to form a cavity-like structure communicating with the external auditory canal. The sound outlet on the shell 111 can be at least partially located within the cavity-like structure, while the first and second pressure relief holes can be located outside the cavity-like structure. Thus, when worn, the sound waves generated by the diaphragm of the transducer 112 and propagated through the sound outlet are restricted by the aforementioned cavity-like structure. That is, the cavity-like structure can concentrate the sound waves, allowing more sound waves to propagate into the external auditory canal, thereby improving the volume and sound quality of the sound heard by the user in the near field, which is beneficial to improving the acoustic effect of the open-back headphones 10. Furthermore, since the sound-generating part 11 can be configured not to block the external auditory canal when worn, the cavity-like structure can be semi-open. Thus, the sound waves generated by the transducer 112 and propagated through the sound outlet can propagate to the outside of the open-back headphones 10 and the ear through the gap between the sound-emitting part 11 and the ear (e.g., a part of the concha not covered by the sound-emitting part 11), thereby forming a first sound leakage in the far field; in addition, the sound waves propagated through the first pressure relief hole and / or the second pressure relief hole on the housing 111 can form a second sound leakage in the far field. The phases of the first sound leakage and the second sound leakage are (close) to each other, so that the two can cancel each other out of phase in the far field, thereby helping to reduce the sound leakage of the open-back headphones 10 in the far field.

[0039] Figure 8 This is an exemplary distribution diagram of a cavity structure surrounding one of the dipole sound sources shown in some embodiments of this specification. Figure 8 As shown, when a cavity structure 41 is provided between the dipole sound sources, one dipole sound source and the listening position are located inside the cavity structure 41, while the other dipole sound source is located outside the cavity structure 41. In this specification, "cavity structure" can be understood as a semi-enclosed structure formed by the sidewalls of the sound-generating part 11 and the concha cavity structure. This semi-enclosed structure ensures that the interior is not completely sealed off from the external environment, but rather has a leakage structure 42 (e.g., an opening, a gap, a pipe, etc.) that acoustically communicates with the external environment. Exemplary leakage structures may include, but are not limited to, openings, gaps, pipes, etc., or any combination thereof.

[0040] In some embodiments, the cavity structure 41 may include a listening position and at least one sound source. Here, "including" can mean that at least one of the listening position and the sound source is inside the cavity, or it can mean that at least one of the listening position and the sound source is at the edge of the cavity. In some embodiments, the listening position may be the entrance to the ear canal or an acoustic reference point of the ear.

[0041] Figure 9This is a schematic diagram illustrating the listening principle of a dipole sound source structure and a cavity structure built around one of the dipole sound sources, as shown in some embodiments of this specification. Figure 10 This is a schematic diagram illustrating the sound leakage principle of a dipole sound source structure and a cavity structure built around one of the dipole sound sources, as shown in some embodiments of this specification.

[0042] For near-field listening, such as Figure 9 The diagram shows a dipole with a cavity structure surrounding one of the sound sources. Because sound source A is enclosed by the cavity structure, most of the sound radiated from it reaches the listening position through direct or reflected rays. Conversely, without the cavity structure, most of the sound radiated from the source would not reach the listening position. Therefore, the cavity structure significantly increases the volume of the sound reaching the listening position. Simultaneously, only a small portion of the antiphase sound radiated from the antiphase sound source B outside the cavity structure enters the cavity structure through its leakage structure. This is equivalent to generating a secondary sound source B' at the leakage structure, whose intensity is significantly less than both sound source B and sound source A. The sound generated by the secondary sound source B' has a weak destructive effect on sound source A within the cavity, significantly increasing the listening volume at the listening position.

[0043] Regarding sound leakage, such as Figure 10 As shown, sound source A radiates sound to the outside through the leakage structure of the cavity, which is equivalent to generating a secondary sound source A' at the leakage structure. Since almost all the sound radiated by sound source A is output from the leakage structure, and the structural scale of the cavity is much smaller than the spatial scale for evaluating sound leakage (by at least one order of magnitude), the intensity of the secondary sound source A' can be considered comparable to that of sound source A. For the external space, the canceling effect of the sound produced by the secondary sound source A' and sound source B in the far field is comparable to the canceling effect of the sound produced by sound source A and sound source B in the far field. That is, under this cavity structure, a considerable sound leakage reduction effect is still maintained.

[0044] It should be understood that the above-described leakage structure with one opening is merely an example. A cavity structure can contain one or more openings, achieving a superior listening index. The listening index can be defined as the reciprocal of the leakage index α, 1 / α. Taking a structure with two openings as an example, the cases of equal opening size and equal opening ratio are analyzed below. Comparing this to a structure with only one opening, "equal opening size" refers to having two openings of the same size as the structure with only one opening, and "equal opening ratio" refers to having the same sum of the opening areas of the two openings as the structure with only one opening. Equal opening size is equivalent to doubling the relative opening size of the structure with only one opening (i.e., the ratio of the opening area S of the leakage structure in the cavity structure to the area S0 directly affected by the contained sound source in the cavity structure). As mentioned earlier, the overall listening index will decrease. In the case of equal opening ratio, even if S / S0 is the same as the structure with only one opening, the distances from the two openings to the external sound source are different, thus resulting in different listening indices.

[0045] Figure 11 This is a schematic diagram of the exemplary internal structure of the sound-generating part according to some embodiments of this specification. For example... Figure 11 As shown, in some embodiments, the transducer 112 may include a diaphragm 1121. A first acoustic cavity may be formed between the diaphragm 1121 and the housing 111, and a sound outlet 111a may be disposed on the housing 111 surrounding the area forming the first acoustic cavity. The first acoustic cavity may communicate with the outside of the housing 111 through the sound outlet 111a. In some embodiments, the first acoustic cavity may be located on the front side of the diaphragm 1121, that is, the first acoustic cavity may serve as a front cavity 114.

[0046] In some embodiments, a support 115 may be disposed within the cavity of the housing 111, and a second acoustic cavity (which may serve as the rear cavity 116) may be formed between the support 115 and the transducer 112, thereby isolating the second acoustic cavity from other structures within the housing 111 (e.g., the main control circuit board, etc.), which is beneficial for improving the acoustic output of the sound-generating part 11. In some embodiments, the acoustic cavity formed between the support 115 and the transducer 112 may be used together with the acoustic cavity inside the transducer 112 as the second acoustic cavity. In some embodiments, the second acoustic cavity may be located behind the diaphragm 1121. The housing 111 may be provided with acoustic holes (e.g., a first pressure relief hole 111c and / or a second pressure relief hole 111d), and the bracket 115 may be provided with an acoustic channel 1151 connecting the acoustic holes and the rear cavity 116, so that the rear cavity 116 can communicate with the external environment, that is, air can freely enter and exit the rear cavity 116, which helps to reduce the resistance of the diaphragm 1121 of the transducer 112 in the low-frequency large amplitude process and improve the low-frequency output capability of the transducer.

[0047] Figure 12This is an exemplary structural schematic diagram of the inner shell of the sound-emitting part 11 of an open-back headphone according to some embodiments of this specification. In some embodiments, the inner shell 1111 may include a bottom wall 1113 and a first side wall 1114 connected to the bottom wall 1113. Wherein, viewed along the minor axis direction Z, the reference direction pointing from the connecting end CE to the free end FE (e.g.) Figure 11 and Figure 12 In the opposite direction of the middle arrow Y), the portion of the first sidewall 1114 near the free end FE gradually approaches the bottom wall 1113 in the thickness direction X, so that the scoring surface 111b is inclined towards the side where the inner shell 1111 is located in the direction near the free end FE. In some embodiments, the sound outlet 111a may be provided on the bottom wall 1113. In some embodiments, the sound outlet 111a may also be provided on the side of the first sidewall 1114 corresponding to the lower surface LS, and may also be provided at the corner between the first sidewall 1114 and the bottom wall 1113. Figure 12 In the direction of arrow Z, the first pressure relief hole 111c is located on one side of the upper surface US of the first sidewall 1114 corresponding to the housing 111, and the second pressure relief hole 111d is located on one side of the first sidewall 1114 corresponding to the lower surface LS of the housing 111.

[0048] In some embodiments, the first pressure relief hole 111c has a first center, the second pressure relief hole 111d has a second center, and the sound outlet hole 111a has a third center. In the major axis direction Y, the second center can be further away from the third center than the first center. In some embodiments, the third center of the sound outlet hole 111a can be located on or near the perpendicular bisector of the line connecting the first center of the first pressure relief hole 111c and the second center of the second pressure relief hole 111d, to maximize the distance between the first pressure relief hole 111c, the second pressure relief hole 111d, and the sound outlet hole 111a. It should be noted that since the acoustic holes, such as the sound outlet hole 111a, the first pressure relief hole 111c, and the second pressure relief hole 111d, are provided on the housing 111, and each sidewall of the housing 111 has a certain thickness, the acoustic holes are all holes with a certain depth. In this case, each acoustic hole has an inner opening and an outer opening. For ease of description, in this application, the center of the sound outlet hole mentioned above and below can indicate the centroid of the outer opening of the sound outlet hole, the center of the first pressure relief hole mentioned above and below can indicate the centroid of the outer opening of the first pressure relief hole, and the center of the second pressure relief hole mentioned above and below can indicate the centroid of the outer opening of the second pressure relief hole.

[0049] In some embodiments, the first pressure relief hole 111c and the second pressure relief hole 111d may be offset in the Y direction so that the first pressure relief hole 111c and the second pressure relief hole 111d are not blocked by the tragus. In some embodiments, the first pressure relief hole 111c may be further away from the connection end CE than the second pressure relief hole 111d. The third center of the sound outlet hole 111a may be located on the perpendicular bisector of the line connecting the first center of the first pressure relief hole 111c and the second center of the second pressure relief hole 111d, so that each pressure relief hole is as far away from the sound outlet hole as possible. In some embodiments, in order to make the sound outlet hole 111a closer to the ear canal, the sound outlet hole 111a may be located on the side of the housing 111 closer to the second pressure relief hole 111d rather than in the middle in the Z direction, such as... Figure 12 As shown.

[0050] Figure 13A This is a schematic diagram illustrating exemplary positions of the sound outlet according to some embodiments of this specification. Figure 13B This is a frequency response graph corresponding to the sound outlet at different positions, as shown in some embodiments of this specification. In some embodiments, Figure 13B The curves shown are simulation curves. Please refer to them. Figure 13A In the inner surface IS of the sound-emitting part 11, a coordinate system is established with the center of the inner surface IS (i.e., the midpoint of the inner surface IS in the Y and Z directions) as the origin, the positive direction of the Z direction as the positive direction of the Px1 axis, and the positive direction of the Y direction as the positive direction of the Py1 axis. The position of the third center of the sound outlet 111a on the inner surface IS can then be represented as (Px1, Py1), in mm. For example, (0, -4) indicates that the distance between the third center of the sound outlet 111a and the center of the inner surface IS is 0 mm in the positive direction of the Px1 axis, and 4 mm in the opposite direction of the Py1 axis. In some embodiments, based on the coordinates of the third center of the sound outlet 111a, the distance between the third center of the sound outlet 111a and the lower surface LS (or upper surface US) and the free end FE (or connecting end CE) of the sound-emitting part 11 can be determined. The distance between the third center and the lower side LS (or the upper side US) can refer to the farthest distance between the third center and the lower side LS (or the upper side US) in the Px1 axis direction; the distance between the third center and the free end FE (or the connecting end CE) can refer to the farthest distance between the third center and the free end FE (or the connecting end CE) in the Py1 axis direction.

[0051] Figure 13BThe diagram shows the simulated frequency response curves at a position 15 mm directly in front of the sound outlet 111a (i.e., in the opposite direction of the X direction) when the sound outlet 111a is located at different positions on the inner surface IS, and other structures (e.g., the first pressure relief hole 111c, the second pressure relief hole 111d, etc.) are fixed (e.g., the first pressure relief hole 111c is at the center of the upper surface US, and the second pressure relief hole 111d is located on the lower surface LS near the connection end CE (e.g., in the long axis direction Y of the sound-emitting part 11, the distance between the second pressure relief hole 111d and the connection end CE is no greater than 1 / 3 of the total length of the sound-emitting part 11)). Please refer to... Figure 13B When the sound outlet 111a is located at different positions on the inner surface IS, the frequency response curve of the sound-emitting part 11 has a first resonance peak in the range of 4 kHz-6 kHz and a second resonance peak at around 4.5 kHz. The first resonance peak is generated by the resonance of the front cavity 114, and the second resonance peak is generated by the resonance of the rear cavity 116. Comparing the frequency response curves corresponding to positions (0, 0), (0, 5), and (0, 7), it can be seen that when the position of the sound outlet 111a moves towards the positive direction of the Py1 axis, the first resonance peak of the sound-emitting part 11 shifts from high frequency to low frequency, and the amplitude of the corresponding frequency response curve decreases in the mid-low frequency range (e.g., 100 Hz-1500 Hz). However, since the position and structure of the pressure relief hole remain unchanged, the vibration characteristics of the rear cavity 116 remain essentially unchanged. Figure 13BThe second resonant peak shown does not change significantly. Furthermore, when the position of the sound outlet 111a is moved towards the positive direction of the Py1 axis, for example, when the position of the sound outlet 111a is (0, 7), the frequency response curve of the sound-emitting part 11 still has a relatively low resonance valley V in the range of 4kHz-6kHz. Therefore, in order to make the frequency of the first resonant peak as high as possible and to have a higher amplitude in the mid-low frequency response of the front cavity, the sound outlet 111a can be located on the side opposite to the positive direction of the Py1 axis from the center of the inner surface IS; for example, the sound outlet 111a can be closer to the free end FE of the sound-emitting part 11. By setting the distance between the sound outlet 111a and the free end FE of the sound-emitting part 11, the amplitude of the sound-emitting part 11 in the mid-low frequency range can be increased, and the sound-emitting part 11 can have a smooth frequency response curve over a wider frequency range, improving the overall output effect of the sound-emitting part 11 (e.g., in the range of 100Hz-10000Hz). In some embodiments, to enhance the amplitude of the sound-generating part 11 in the mid-to-low frequencies and to ensure a smooth frequency response curve over a wider frequency range, the distance between the third center of the sound outlet 111a and the rear side RS (or the free end FE) can be in the range of 8 mm to 12 mm. In some embodiments, the distance between the third center of the sound outlet 111a and the rear side RS (free end FE) can be in the range of 10 mm to 11 mm. In some embodiments, to improve the aesthetics and wearing comfort of the headphones, the rear side RS of the sound-generating part 11 can be a curved surface. When the rear side RS is curved, the distance from a certain position (e.g., the third center of the sound outlet 112) to the rear side RS can refer to the distance from that position to the tangent plane of the rear side RS that is furthest from the center of the sound-generating part 11 and parallel to the minor axis of the sound-generating part 11. Comparing the frequency response curves corresponding to positions (0, 0), (2, 0), and (4, 0), it can be seen that when the position of the sound outlet 111a moves towards the positive direction of the Px1 axis, the resonant peak of the sound-emitting part 11 shifts from high frequency to low frequency, and the amplitude of the corresponding frequency response curve in the mid-low frequency range (e.g., 100 Hz-1500 Hz) decreases. Therefore, in order to make the frequency of the first resonant peak as high as possible and to have a higher amplitude in the mid-low frequency range of the corresponding frequency response of the front cavity, the sound outlet 111a can be located on the side opposite to the positive direction of the Px1 axis from the center of the inner surface IS. For example, the sound outlet 111a can be closer to the lower surface LS of the sound-emitting part 11. By setting the distance between the sound outlet 111a and the lower surface LS, the amplitude of the sound-emitting part 11 in the mid-low frequency range can be increased, and the sound-emitting part 11 can have a smooth frequency response curve over a wider frequency range, improving the overall output effect of the sound-emitting part 11 (e.g., in the range of 100 Hz-10000 Hz).In some embodiments, in order to increase the amplitude of the sound-emitting part 11 in the mid-low frequency range and to make the sound-emitting part 11 have a smooth frequency response curve over a wider frequency range, the distance between the third center of the sound outlet 111a and the lower surface LS of the sound-emitting part 11 can be in the range of 3 mm to 8 mm. In some embodiments, the distance between the third center of the sound outlet 111a and the lower surface LS of the sound-emitting part 11 can be in the range of 4.5 mm to 5.5 mm.

[0052] Figure 14A This is a schematic diagram illustrating an exemplary location of the first pressure relief hole according to some embodiments of this specification. Figure 14B This is a frequency response graph corresponding to the first pressure relief hole at different locations as shown in some embodiments of this specification. In some embodiments, Figure 14B The curves shown are simulation curves. In some embodiments, the first pressure relief hole 111c and the second pressure relief hole 111d can be disposed in the region on the housing 111 corresponding to the rear cavity 116. Therefore, the position of the first pressure relief hole 111c and the second pressure relief hole 111d in the X direction is related to the size of the rear cavity 116. In some embodiments, the distance between the first center of the first pressure relief hole 111c (or the second center of the second pressure relief hole 111d) and the inner surface IS can be in the range of 4 mm to 8 mm. In some embodiments, the distance between the first center of the first pressure relief hole 111c and the inner surface IS can be in the range of 5 mm to 6 mm. In some embodiments, in the X direction, the positions of the first center of the first pressure relief hole 111c and the second center of the second pressure relief hole 111d can be considered relatively fixed, considering only the different positions of the first center of the first pressure relief hole 111c and the second center of the second pressure relief hole 111d in the Y direction. Accordingly, Figure 14A and 14B The positions of the first pressure relief hole 111c and the second pressure relief hole 111d can refer to different positions of the first pressure relief hole 111c and the second pressure relief hole 111d along the Y direction.

[0053] Please refer to Figure 14A In the upper side US, a coordinate system is established with the midpoint of the dimension of the upper side US in the Y direction as the origin, the opposite direction of the Y direction as the positive direction of the Px2 axis, and the opposite direction of the X direction as the positive direction of the Py2 axis. The Py2 of the first center of the first pressure relief hole 111c can be considered a fixed value, and only the different positions corresponding to different Px2 values ​​are considered. The position of the first center of the first pressure relief hole 111c on the upper side US can be represented as (Px2, Py2), in mm. For example, (4, Py2) indicates that the distance between the first center of the first pressure relief hole 111c and the origin in the positive direction of the Px2 axis is 4 mm. In some embodiments, based on the Px2 of the first center of the first pressure relief hole 111c, the distance between the first center of the first pressure relief hole 111c and the free end FE of the sound-generating part 11 can be determined.

[0054] Figure 14B The diagram shows the simulated frequency response curves at a position 15 mm directly in front of the sound outlet 111a (i.e., in the opposite direction of the X direction) when the first pressure relief hole 111c is located at different positions on the upper side US, and other structures (e.g., the sound outlet 111a, the second pressure relief hole 111d, etc.) are fixed (e.g., the sound outlet 111a is located at the center of the inner side IS, and the second pressure relief hole 111d is located on the lower side LS near the connection end CE). Figure 14B As shown, when the first pressure relief hole 111c is located at different positions on the upper side US, the frequency response curve of the sound-generating part 11 has a first resonance peak at around 4.5 kHz (as shown). Figure 14B (As shown by the dashed coil A) and has a second resonance peak around 5.5 kHz (as shown by...) Figure 14B (As shown by the dashed circle B). The first resonant peak is generated by the rear cavity 116, and the second resonant peak is generated by the front cavity 114. When the Px2 of the first pressure relief hole 111c gradually increases from -3.2 mm to 3.2 mm (i.e., the first pressure relief hole 111c moves in the opposite direction of the Y direction), the first resonant peak of the frequency response curve of the sound-generating part 11 shifts slightly from low frequency to high frequency. Since the position of the sound outlet hole 111a remains unchanged, the vibration characteristics of the front cavity 114 remain essentially unchanged, and the second resonant peak shows little change. Therefore, in order to make the frequency of the first resonant peak as high as possible, the first pressure relief hole 111c can be located on the side facing the positive direction of Px2 from the center of the upper side US. For example, the first pressure relief hole 111c can be located at the midpoint of the dimension of the upper side US in the Y direction or closer to the free end FE of the sound-generating part 11, thereby enabling the sound-generating part 11 to have a smooth frequency response curve over a wider frequency range and improving the overall output effect of the sound-generating part 11 (e.g., in the range of 100 Hz-10000 Hz). In some embodiments, in order to make the sound-generating part 11 have a smooth frequency response curve over a wider frequency range and improve the overall output effect of the sound-generating part 11 (e.g., in the range of 100 Hz-10000 Hz), the distance between the first center of the first pressure relief hole 111c and the rear side RS (free end FE) can be in the range of 11 mm-15 mm. In some embodiments, the distance between the first center of the first pressure relief hole 111c and the rear side RS (free end FE) can be in the range of 13 mm-14 mm.

[0055] Figure 15A This is a schematic diagram illustrating an exemplary location of the second pressure relief hole according to some embodiments of this specification. Figure 15B This is a frequency response graph corresponding to the second pressure relief hole at different locations as shown in some embodiments of this specification. In some embodiments, Figure 15B The curves shown are simulation curves.

[0056] Please refer to Figure 15A In the lower side LS, a coordinate system is established with the midpoint of the dimension of the lower side LS in the Y direction as the origin, the opposite direction of the Y direction as the positive direction of the Px3 axis, and the opposite direction of the X direction as the positive direction of the Py3 axis. The Py3 of the second center of the second pressure relief hole 111d can be considered a fixed value, and only the different positions corresponding to different Px3 values ​​are considered. The position of the second center of the second pressure relief hole 111d on the lower side LS can be represented as (Px3, Py3), in mm. For example, (-2, Py2) indicates that the second center of the second pressure relief hole 111d is 2 mm away from the origin in the negative direction of the Px3 axis. In some embodiments, the distance between the second center of the second pressure relief hole 111d and the free end FE of the sound-generating part 11 can be determined based on the Px3 of the second center of the second pressure relief hole 111d.

[0057] Figure 15B The diagram shows the simulated frequency response curves at a position 15 mm directly in front of the sound outlet 111a (i.e., in the opposite direction of the X direction) when the second pressure relief hole 111d is located at different positions on the lower side LS, and other structures (e.g., the sound outlet 111a, the first pressure relief hole 111c, etc.) are fixed (e.g., the sound outlet 111a is located at the center of the inner side IS, and the first pressure relief hole 111c is located at the center of the upper side US). Figure 15B As shown, when the second pressure relief hole 111d is located at different positions on the lower side LS, the frequency response curve of the sound-generating part 11 has a first resonance peak at around 4.5 kHz (as shown). Figure 15B (As shown by the dashed coil C) and has a second resonance peak around 5.5 kHz (as shown by...) Figure 15B (As shown by the dashed circle D). When the Px3 of the second center of the second pressure relief hole 111d gradually increases from -4.5 mm to -1 mm (i.e., the second pressure relief hole 111d moves in the opposite direction of the Y direction), the first resonant peak of the frequency response curve of the sound-emitting part 11 shifts slightly from low frequency to high frequency, while the second peak value does not change much. When the Px3 of the second center of the second pressure relief hole 111d gradually increases from -1 mm to 4.5 mm (i.e., the second pressure relief hole 111d continues to move in the opposite direction of the Y direction), the first resonant peak of the frequency response curve of the sound-emitting part 11 shifts slightly from high frequency to low frequency, while the second peak value does not change much. In some embodiments, combined with Figure 11 and Figure 12As described, the first pressure relief hole 111c can be further away from the connection end CE than the second pressure relief hole 111d. That is, the second pressure relief hole 111d can be further away from the free end FE than the first pressure relief hole 111c. Therefore, by setting the distance between the second pressure relief hole 111d and the free end FE, the overall output effect of the sound-generating part 11 (e.g., in the range of 100 Hz-10000 Hz) can be guaranteed while satisfying the structural design. For example, the first pressure relief hole 111c can be located at the midpoint of the upper side US in the Y direction or closer to the connection end CE of the sound-generating part 11. In some embodiments, in order to guarantee the overall output effect of the sound-generating part 11 (e.g., in the range of 100 Hz-10000 Hz) while satisfying the structural design, the distance between the second center of the second pressure relief hole 111d and the rear side RS (free end FE) can be in the range of 15 mm-18 mm. In some embodiments, the distance between the second center of the second pressure relief hole 111d and the rear side RS (free end FE) can be in the range of 16 mm to 17 mm.

[0058] In some embodiments, the front cavity 114 and the sound outlet 111a (or the rear cavity 116 and the first pressure relief hole 111c and / or the second pressure relief hole 111d) can be approximated as a Helmholtz resonant cavity model. Taking the front cavity 114 as an example, the front cavity 114 can be the cavity body of the Helmholtz resonant cavity model, and the sound outlet 111a is the neck of the Helmholtz resonant cavity model. The resonant frequency of this Helmholtz resonant cavity model is the resonant frequency of the front cavity 114. f 1.

[0059] In the Helmholtz resonant cavity model, the size of the neck (e.g., the outlet 111a) can affect the resonant frequency of the cavity (e.g., the front cavity 114). f The specific relationship is shown in formula (1): (1) in, c Represents the speed of sound. S The opening area (or cross-sectional area) of the neck (e.g., the sound outlet 111a). V Represents the volume of a cavity (e.g., anterior cavity 114). L This represents the depth of the neck (e.g., the sound outlet 111a). For the front cavity 114, its resonant frequency is... f 1. Then the opening area of ​​the sound outlet 111a can be... S 1. The volume of the anterior cavity 114 can be V 1. The depth of the sound outlet 111a can be L1. It should be noted that each sidewall of the housing 111 has a certain thickness; therefore, the acoustic holes are all holes with a certain depth. Each acoustic hole has an inner opening and an outer opening. For ease of description, in this specification, the opening area of ​​the sound outlet hole can refer to the area of ​​the inner opening of the sound hole, and the area of ​​the pressure relief hole can refer to the area of ​​the inner opening of the pressure relief hole.

[0060] To improve the sound output of the open-back headphones 10, the frequency response curve of the sound-emitting part 11 needs to have a wide flat region; therefore, the resonant frequency of the front cavity 114... f 1 can be set higher to increase the range of the flat region of the frequency response curve of the front cavity 114. In some embodiments, in order to increase the range of the flat region of the frequency response curve of the front cavity 114, the resonant frequency of the front cavity 114 is... f 1 can be in the range of 1 kHz to 10 kHz. In some embodiments, the resonant frequency of the front cavity 114 is... f 1 can be above 6 kHz.

[0061] As can be seen from formula (1), when the opening area of ​​the sound outlet 111a is increased... S 1. Or reduce the depth of the sound outlet 111a L At time 1, the resonant frequency of the front cavity 114 is... f 1. Move towards higher frequencies.

[0062] During the vibration of the diaphragm 1121, the air in the front cavity 114 is compressed or expanded along with the vibration of the diaphragm 1121. The compressed or expanded air can drive the air column at the sound outlet to move back and forth, thereby causing the air column to radiate sound outward. In some embodiments, the air column in the sound outlet 111a has mass, which can correspond to the acoustic mass of the sound outlet 111a. The acoustic mass can be part of the acoustic impedance, thereby affecting the acoustic output of the sound-generating part 11. Therefore, the size of the sound outlet 111a also affects the acoustic mass of the sound outlet 111a. Ma The specific relationship that causes the impact is shown in formula (2): (2) in, ρ Represents air density.

[0063] From formula (2), we can see that the opening area of ​​the sound outlet 111a is... S 1. Increase or deepen L 1. Reduce the sound quality of the sound outlet 111a Ma Decrease.

[0064] Figure 16 This is a frequency response curve diagram of the sound-emitting part 11 corresponding to different cross-sectional areas of the sound outlet shown in some embodiments of this specification. For example... Figure 16As shown, when the cross-sectional area of ​​the sound outlet 111a... S From 2.875 mm 2 Increased to 46 mm 2 At that time, the sound quality of the sound outlet 111a M a From 800 kg / m 4 Reduced to 50 kg / m 4 The resonant frequency of the front cavity 114 f 1. The frequency gradually increases from around 4 kHz to around 8 kHz. It should be noted that... Figure 16 The 200 kg / m shown 4 and 800 kg / m 4 These parameters only represent the theoretical sound quality of the sound outlet 111a, and there may be errors compared with the actual sound quality of the sound outlet 111a.

[0065] In order to increase the resonant frequency of the front cavity 114 f While ensuring the sound quality of the sound outlet 111a, 1. Ma The opening area of ​​the sound outlet 111a S 1. It needs to be within a suitable value range. Additionally, if the opening area of ​​the sound outlet 111a is too large, it may have a certain impact on the appearance, structural strength, and other aspects of the open-back headphone 100. Therefore, in some embodiments, in order to increase the resonant frequency of the front cavity 114... f While ensuring the sound quality of the sound outlet 111a, 1. Ma And without affecting the appearance, structural strength, etc. of the open-back headphone 100, the opening area of ​​the sound outlet 111a S The value of 1 can range from 2.875 mm. 2 -46 mm 2 For example only, the opening area of ​​the sound outlet 111a... S The value of 1 can be 11 mm. 2 -15 mm 2 (For example, 11.49 mm) 2 For example, the opening area of ​​the sound outlet 111a. S The value of 1 can be 25 mm. 2 -26 mm 2 (For example, 25.29 mm) 2 ).

[0066] Figure 17 This is a frequency response curve diagram of the front cavity 114 corresponding to different depths of the sound outlet hole, as shown in some embodiments of this specification. For example... Figure 17 As shown, the depth of the sound outlet 111a L1. When the diameter of the sound outlet 111a increases from 0.3 mm to 3 mm, the sound quality of the sound outlet 111a... M a From 100 kg / m 4 Increase to 1000 kg / m 4 The resonant frequency of the front cavity 114 f 1. The frequency decreased from around 7 kHz to around 3.7 kHz.

[0067] To ensure that the front cavity 114 has a sufficiently large resonant frequency, the depth of the sound outlet 111a is... L A smaller value for 1 is better. However, since the sound outlet 111a is located on the housing 111, the depth of the sound outlet 111a is the same as the thickness of the housing 111. If the thickness of the housing 111 is too small, it may affect the structural strength of the open-back headphone 10, and the corresponding manufacturing process will be more difficult. In some embodiments, in order to ensure that the front cavity 114 has a sufficiently large resonant frequency without affecting the structural strength of the open-back headphone 10, the depth of the sound outlet 111a is... L The value of 1 can range from 0.3 mm to 3 mm. In some embodiments, the depth of the sound outlet 111a... L The value of 1 can be between 0.3 mm and 1 mm.

[0068] In some embodiments, in order to increase the resonant frequency of the front cavity 114 f While ensuring the sound quality of the sound outlet 111a, 1. Ma And without affecting the appearance, structural strength, etc. of the open-back headphone 100, the cross-sectional area of ​​the sound outlet 111a S The value of 1 ranges from 2.875 mm. 2 -46 mm 2 The depth of the sound outlet 111a L When the value of 1 can be in the range of 0.3 mm to 3 mm, the corresponding cross-sectional area of ​​the sound outlet 111a is... S 1 and depth L The ratio of the squares of 1 The value range can be 0.31-512.2. In some embodiments, the cross-sectional area of ​​the sound outlet 111a is... S 1 and depth L The ratio of the squares of 1 The value can range from 10 to 50.

[0069] In some embodiments, the shape of the sound outlet 111a also affects its acoustic impedance. For example, the narrower and longer the sound outlet 111a, the greater its acoustic impedance, which is detrimental to the acoustic output of the front cavity 114. Therefore, in order to ensure that the sound outlet 111a produces good low-frequency output and to increase the volume of the sound output from the sound outlet 111a, the major axis dimension of the sound outlet 111a (i.e., the length of the cross-section of the sound outlet 111a) is... L f ) and the minor axis dimension (i.e., the width of the cross-section of the sound outlet 111a) W f The ratio of the length to the width of the sound outlet 111a (or the aspect ratio of the sound outlet 111a) needs to be within a preset appropriate range. In some embodiments, the shape of the sound outlet 111a may include, but is not limited to, a circle, an ellipse, a racetrack shape, etc. In some embodiments, the sound outlet 111a may be racetrack shaped (e.g., Figure 12 As shown in the figure, the two ends of the racetrack shape can be minor arcs or semicircles. In this case, the major axis dimension of the sound outlet 111a can be the maximum dimension of the sound outlet 111a in the Y direction, and the minor axis dimension of the sound outlet 111a can be the maximum dimension of the sound outlet 111a in the Z direction.

[0070] Figure 18 These are frequency response curves corresponding to different aspect ratios of the sound outlet holes, as shown in some embodiments of this specification. Figure 18 The image shown shows the sound outlet 111a in the same cross-sectional area (e.g., S 1 = 22.5mm 2 Frequency response curves corresponding to different aspect ratios under ( ). Figure 18 The curves shown are simulation curves. In some embodiments, such as... Figure 18 As shown, the aspect ratio of the sound outlet 111a is ( L f / W f With different values ​​of the aspect ratio, as the width-to-length ratio gradually increases from 1 to 10, the sound pressure of the front cavity 114 in the low-frequency and mid-high-frequency range (e.g., 100 Hz to 3.5 kHz) gradually decreases (e.g., the sound pressure at 3 kHz is 2.3 dB lower when the aspect ratio of the sound outlet is 10 than when the aspect ratio of the sound outlet is 1). Its resonant frequency in the high-frequency range gradually shifts towards higher frequencies, and the amplitude of the resonant peak gradually decreases. In some embodiments, when the cross-sectional area of ​​the sound outlet 111a is constant, in order to ensure a strong low-frequency response in the front cavity 114, the length of the cross-section of the sound outlet 111a is... L f With width W fThe ratio between them can be in the range of 1-10. In some embodiments, the length of the cross-section of the sound outlet 111a is... L f With width W f The ratio between them can be 2-3.

[0071] Figure 19 This is a frequency response graph showing the different lengths of the sound outlet hole according to some embodiments of this specification. For ease of explanation, the length of the cross-section of the sound outlet hole 111a is shown here. L f With width W f The ratio between them is set to 2, and the shape of the sound outlet 111a is racetrack-shaped. When the width of the sound outlet 111a is fixed, the length passing through the sound outlet 111a... L f The corresponding opening area can be determined. S 1. By Figure 19 It can be seen that the frequency response curve of the sound-emitting part 11 has a first resonant peak at around 4.5 kHz and a second resonant peak that varies in the range of 3.5 kHz to 10 kHz. The first resonant peak corresponds to the resonant peak generated by the rear cavity 116, and the second resonant peak corresponds to the resonant peak generated by the front cavity 114. With the length of the sound outlet 111a... L f The opening area of ​​the sound outlet 111a gradually increases from 3 mm to 11 mm. S 1 also increases accordingly), the second resonant peak of the frequency response curve gradually shifts to higher frequencies, while the first resonant peak remains basically unchanged. Among these, when the length of the sound outlet 111a... L f Increased to 4 mm (opening area of ​​sound outlet 111a) S 1 increased to 7.1416 mm 2 After that, continue to increase the length of the sound outlet 111a. L f (Opening area of ​​sound outlet 111a) S As 1 increases, the peak value of the second resonant peak in the frequency response curve decreases, while the peak value of the first resonant peak remains around 4.5 kHz. In some embodiments, shifting the resonant peak to higher frequencies can increase the range of the flat region of the frequency response curve. Simultaneously, a larger resonant peak also makes the high frequencies of the open-back headphone 10 more abundant, resulting in better sound quality. In some embodiments, to maximize the frequency of the second resonant peak, the length of the sound outlet 111a... L f It can have a relatively large value, but at the same time, in order not to reduce the high-frequency output corresponding to the second resonant peak and considering the structural stability of the sound-emitting part 11, the length of the sound outlet 111a is...L f The width of the sound outlet 111a can be no greater than 17 mm. W f It can be no greater than 10 mm. In some embodiments, in order to make the frequency of the second resonant peak as high as possible, while not reducing the high-frequency output corresponding to the second resonant peak and considering the structural stability of the sound-emitting part 11, the length of the sound outlet 111a is... L f It can be 2 mm to 11 mm. In some embodiments, the length of the sound outlet 111a is... L f It can be 6 mm to 9 mm.

[0072] In some embodiments, based on length L f and length L f With width W f The ratio between them can determine the width of the sound hole 111a. W f For example, the length of the cross-section of the sound outlet 111a L f With width W f If the ratio between them can be 2, then the width of the sound outlet 111a is... W f The diameter can range from 1.5 mm to 5.5 mm. The corresponding area of ​​the racetrack-shaped sound outlet 111a can be 4.02 mm². 2 -54 mm 2 By setting the length of the sound hole 111a L f This range allows for an increase in the flat area of ​​the frequency response curve, thereby improving the sound quality of the open-back headphones 10, while also taking into account the structural design of the sound-emitting part 11. For example, the racetrack-shaped sound outlet 111a has an area of ​​11.5 mm². 2 The length of the sound hole 111a can be determined accordingly from the left and right sides. L f The width of the sound outlet 111a is 5 mm-6 mm. W f It is 2.5 mm to 3 mm. (Combined) Figure 19 It can be seen that within this size range, the open-back headphone 10 can have a flat frequency response curve and sufficient high-frequency output over a wide frequency range; in addition, the relatively small value of this area is also beneficial to the stability of the structure.

[0073] Figure 20These are frequency response curves corresponding to racetrack-shaped and circular sound holes of different lengths, as shown in some embodiments of this specification. Figure 20 The length of the circular sound outlet shown can refer to the diameter of the circle. According to... Figure 20 It can be seen that the frequency response curve of the circular sound outlet follows a similar trend to that of the racetrack-shaped sound outlet. Therefore, in order to increase the range of the flat region of the frequency response curve, while considering the structural design of the sound-generating part 11, the length of the circular sound outlet can be 2 mm-17 mm. In some embodiments, the length of the circular sound outlet can be 6 mm-9 mm. Continuing to refer to... Figure 20 When the lengths are the same, compared to a racetrack-shaped sound outlet, the frequency response curve of a circular sound outlet shifts towards lower frequencies, and the sound pressure amplitude of a circular sound outlet is slightly greater than that of a racetrack-shaped sound outlet. In some embodiments, to enable the open-back headphone 10 to have a flat frequency response curve over a wider frequency range, the shape of the sound outlet can be racetrack-shaped. Furthermore, the width of a racetrack-shaped sound outlet is narrower than that of a circular sound outlet, which facilitates the design of the appearance and structure of the sound-emitting part 11.

[0074] Figure 21 This is an exemplary structural diagram of a portion of the rear cavity structure according to some embodiments of this specification. Please refer to... Figure 11 and Figure 21 In some embodiments, a second acoustic cavity may be formed between the support 115 and the transducer 112, and the second acoustic cavity may serve as the rear cavity 116.

[0075] In some embodiments, in order to improve the acoustic output performance of the open-back headphone 10, the frequency response curve of the rear cavity 116 needs to have a wide flat region; therefore, the resonant frequency of the rear cavity 116... f 2 can be set to a relatively large value. In some embodiments, the resonant frequency of the rear cavity 116 is... f 2 can be in the range of 2 kHz to 8 kHz. In some embodiments, the resonant frequency of the rear cavity 116 is... f 2 can be 4.5 kHz. In some embodiments, in order to better cancel out the second sound leakage formed by the aforementioned acoustic aperture with the first sound leakage formed by the sound outlet 111a in the far field, the resonant frequency of the rear cavity 116 is... f 2 can resonate with the resonant frequency of the front cavity 114. f 1. Approximately equal to or equal to the resonant frequency of the rear cavity 116. In some embodiments, the resonant frequency of the rear cavity 116 is... f 2 can resonate with the resonant frequency of the front cavity 114. f The difference of 1 may not exceed 2 kHz. In some embodiments, the resonant frequency of the rear cavity 116 f 2 can resonate with the resonant frequency of the front cavity 114. f The difference of 1 can be no greater than 200 Hz.

[0076] In some embodiments, the combination of the rear cavity 116 and the acoustic holes (e.g., the first pressure relief hole 111c and / or the second pressure relief hole 111d) provided on the aforementioned housing 111 can also be regarded as a Helmholtz resonant cavity model. The rear cavity 116 can serve as the body of the Helmholtz resonant cavity model, and the acoustic holes can serve as the neck of the Helmholtz resonant cavity model. The resonant frequency of the Helmholtz resonant cavity model is the resonant frequency of the rear cavity 116. f 2. The opening area of ​​the acoustic aperture can be S 2. The volume of the rear cavity can be V 2. The depth of the acoustic aperture can be L 2. Among them, S 2 can be related to the opening areas of the first pressure relief hole 111c and the second pressure relief hole 111d. L 2. The depths of the first pressure relief hole 111c and the second pressure relief hole 111d can be related.

[0077] As can be seen from formula (1) above, when the volume of the rear cavity 116... V Reduce the resonant frequency of the rear cavity 116 f 2. Increase. Therefore, in order to make the rear cavity 116 have a sufficiently large resonant frequency. f 2. The volume of the rear cavity 116 can be small enough.

[0078] However, the volume of the rear cavity 116 will also affect the acoustic capacity of the rear cavity 116. C a This has an impact on the acoustic volume of the posterior cavity 116. C a Changes in these characteristics will alter the capacitive reactance of the rear cavity 116, thereby affecting its vibration characteristics. The volume and acoustic-capacitive ratio of the rear cavity 116... C a The specific relationship is shown in formula (3): (3) in, ρ Represents air density, c Represents the speed of sound. V This represents the volume of the rear cavity 116.

[0079] Combining formulas (1) and (3), it can be seen that when the volume of the rear cavity 116... V Increase the acoustic capacity of the posterior cavity 116 C a Increase, corresponding to the resonant frequency of the rear cavity 116 f 2. Reduce. In order to reduce the resonant frequency of the rear cavity 116. f Since 2 is relatively large, the volume and acoustic capacity of the rear cavity 116 should be relatively small; that is to say, the volume of the rear cavity 116...V It needs to have an appropriate range of values.

[0080] like Figure 21 As shown, in some embodiments, the cross-section of the rear cavity 116 can be formed by two perpendicular sides and a curved side. Connecting the two endpoints of the curved side, the cross-section (e.g., cross-section ABC) can be approximated as a triangle. The hypotenuse AC is formed by the line connecting the two endpoints of the curved surface formed on the support 115 and the two straight sides. The two straight sides AB and BC are formed by the frame 1123 of the transducer 112, with an included angle α between the hypotenuse AC and the straight side BC. In some embodiments, since the frame 1123 of the transducer 112 needs to have a sound-permeable hole (not shown) in the area where the straight side BC is located, the length of the straight side BC can be considered constant to ensure acoustic performance. The included angle α can be adjusted by adjusting the length of the straight side AB, thereby changing the area of ​​triangle ABC to adjust the volume of the rear cavity 116. In some embodiments, due to the limitation of the sound-permeable hole, the length of the straight side BC is not less than 0.67 mm. In some embodiments, since the value of the included angle α is limited, the volume of the rear cavity 116... V The value of is also subject to range limitations.

[0081] Figure 22 These are frequency response curves of the rear cavity corresponding to different included angles α, as shown in some embodiments of this specification. Figure 22 As shown, when the length of the straight side AB is reduced to decrease the included angle α from 67.6° to 45°, the volume of the rear cavity 116... V The acoustic volume of the corresponding rear cavity 116 is reduced. C a From 7×10 -12 m 3 / Pa decreased to 2.88×10 -12 m 3 / Pa, but the resonant frequency of the rear cavity 116 f 2. The kHz value increases from approximately 4.5 kHz to approximately 6 kHz. When the length of the straight side AB is increased so that the included angle α increases from 67.6° to 79.11°, the volume of the rear cavity 116... V Increase, corresponding to the acoustic volume of the rear cavity 116 C a From 7×10 -12 m 3 / Pa increased to 15×10 - 12 m 3 / Pa, but the resonant frequency of the rear cavity 116 f 2. The frequency decreased from approximately 4.5 kHz to approximately 3 kHz. It should be noted that... Figure 22 The 7×10 shown -12m 3 / Pa, 15 ×10 -12 m 3 Parameters such as / Pa only represent the theoretical acoustic capacitance value corresponding to the volume of the rear cavity 116, and may have errors compared to actual data. In some embodiments, in order to make the rear cavity 116 have a relatively large resonant frequency... f 2. The included angle α in the rear cavity 116 can range from 45° to 80°. In some embodiments, the included angle α in the rear cavity 116 can range from 67° to 68°.

[0082] In some embodiments, combined with Figure 11 and Figure 12 As described, the third center of the sound outlet 111a is located on or near the perpendicular plane of the line connecting the first center of the first pressure relief hole 111c and the second center of the second pressure relief hole 111d. The sound outlet 111a is located on the side of the housing 111 closer to the second pressure relief hole 111d in the Z direction, rather than in the middle. Because the sound outlet 111a is located close to the external auditory canal, the second pressure relief hole 111d is closer to the external auditory canal, while the first pressure relief hole 111c is farther away. Compared to the first pressure relief hole 111c, the sound waves emitted from the second pressure relief hole 111d are more likely to cancel out the sound waves emitted from the sound outlet 111a in the near field. Therefore, the sound pressure amplitude at the second pressure relief hole 111d can be smaller than that at the first pressure relief hole 111c, thereby increasing the listening volume in the ear canal. In some embodiments, the acoustic impedance of the second pressure relief hole 111d can be larger than that of the first pressure relief hole 111c. For example, the size of the second pressure relief hole 111d can be smaller than the size of the first pressure relief hole 111c, thereby allowing the second pressure relief hole 111d to have a relatively large acoustic resistance. For example, the area of ​​the first pressure relief hole 111c can be larger than the area of ​​the second pressure relief hole 111d.

[0083] Figure 23A This is a schematic diagram showing the acoustic impedance changes corresponding to different area ratios of the first and second pressure relief holes, as illustrated in some embodiments of this specification. Figure 23B This is a schematic diagram showing the acoustic quality changes corresponding to different area ratios of the first and second pressure relief holes, as illustrated in some embodiments of this specification. Figure 23C This is a schematic diagram showing the change in radiated acoustic impedance corresponding to different area ratios of the first and second pressure relief holes, as illustrated in some embodiments of this specification. Figure 23D This is a schematic diagram showing the changes in radiated acoustic quality corresponding to different area ratios of the first and second pressure relief holes, as illustrated in some embodiments of this specification. Figures 24A-24E This is a frequency response curve diagram of the rear cavity corresponding to different area ratios of the first and second pressure relief holes as shown in some embodiments of this specification. It should be noted that... Figures 23A-23DThe acoustic impedance, acoustic quality, radiated acoustic impedance, and radiated acoustic quality in the sound also change with frequency, therefore Figures 23A-23D The values ​​shown are acoustic impedance, acoustic mass, radiated acoustic impedance, and radiated acoustic mass at 1 kHz. Figures 23A-23D as well as Figures 24A-24E In this context, the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d changes, but the total area of ​​the first pressure relief hole 111c and the second pressure relief hole 111d remains unchanged. Radiative acoustic impedance can refer to the impedance generated by a sound source (e.g., the first pressure relief hole 111c and / or the second pressure relief hole 111d) due to outward sound radiation, and can be used to describe the radiation characteristics of the sound source. Radiative acoustic impedance can include radiation resistance and radiation reactance. Radiation resistance adds the damping effect and energy consumption when the sound source radiates sound, while radiation reactance can be equivalent to adding a radiation mass to the surface mass of the sound source, i.e., the radiated acoustic mass. In some embodiments, the larger the radiative acoustic impedance and / or radiated acoustic mass, the greater the resistance overcome and / or energy consumed by the sound source when radiating sound. In some embodiments, the radiative acoustic impedance and radiated acoustic mass can be as shown in formulas (5) and (6): (5) (6) in, Represents radiated acoustic impedance. ρ Represents air density, c Represents the speed of sound. S The area corresponding to the sound source (e.g., the area of ​​the first pressure relief hole 111c and / or the second pressure relief hole 111d). Represents the radiated sound quality. As can be seen from formulas (5) and (6), the radiated acoustic impedance and radiated sound quality can be related to the area corresponding to the sound source (e.g., negatively related).

[0084] Depend on Figures 23A-23D It can be seen that as the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d gradually increases from 1 to 5, the total acoustic resistance (i.e., the sum of the acoustic resistance of the first pressure relief hole 111c and the second pressure relief hole 111d), the total acoustic mass, the total radiated acoustic resistance, and the total radiated acoustic mass of the first pressure relief hole 111c and the second pressure relief hole 111d all gradually increase. Furthermore, the total acoustic resistance when the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d is 5 is much greater than the total acoustic resistance when the area ratio is 2.

[0085] Depend on Figures 24A-24EIt can be seen that when the area of ​​the first pressure relief hole 111c is greater than the area of ​​the second pressure relief hole 111d (for example, when the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d is greater than 1), the sound pressure amplitude at the second pressure relief hole 111d is less than the sound pressure amplitude at the first pressure relief hole 111c. Furthermore, as the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d gradually increases from 1 to 5, the frequency response curve at the second pressure relief hole 111d gradually shifts downwards, falling below the frequency response curve at the first pressure relief hole 111c, and the distance between the two curves gradually increases. That is, the difference between the sound pressure amplitude of the second pressure relief hole 111d and the sound pressure amplitude of the first pressure relief hole 111c gradually increases as the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d increases. Therefore, the range of the difference between the sound pressure amplitude of the second pressure relief hole 111d and the sound pressure amplitude of the first pressure relief hole 111c can be adjusted by adjusting the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d.

[0086] Combination Figures 23A-24E By setting the area of ​​the first pressure relief hole 111c to be larger than the area of ​​the second pressure relief hole 111d, the acoustic impedance at the second pressure relief hole 111d is greater than that at the first pressure relief hole 111c, and the sound pressure amplitude at the second pressure relief hole 111d is less than that at the first pressure relief hole 111c. This reduces sound leakage at the second pressure relief hole 111d and increases the listening volume in the ear canal. In some embodiments, if the acoustic impedance difference between the first pressure relief hole 111c and the second pressure relief hole 111d is too large, the sound pressure at the second pressure relief hole 111d may be too low, thus affecting the sound leakage reduction effect of the far field of the sound waves propagated from the second pressure relief hole 111d. In addition, if the acoustic impedance difference between the first pressure relief hole 111c and the second pressure relief hole 111d is too large, it may be detrimental to breaking the standing waves in the rear cavity, thus hindering the improvement of the resonant frequency of the sound emanating from the two pressure relief holes to the outside of the housing 111. Therefore, the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d should not be too large. In some embodiments, in order to make the frequency response curve of the rear cavity 116 have a large flat area while ensuring the listening volume at the ear canal, the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d can be less than 5. For example, in some embodiments, the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d can be in the range of 1-5. As another example, the area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d can be in the range of 1.4-1.7.

[0087] In some embodiments, the area of ​​the first pressure relief hole 111c may also be equal to the area of ​​the second pressure relief hole 111d. For example, as Figure 3As shown, when worn, the free end FE of the sound-generating part 11 does not need to extend into the concha cavity. The area ratio of the first pressure relief hole 111c to the second pressure relief hole 111d of the sound-generating part 11 can be 1.

[0088] In some embodiments, the shape of the pressure relief orifice (e.g., the first pressure relief orifice 111c and the second pressure relief orifice 111d) also affects the acoustic quality of the pressure relief orifice. On the other hand, a long and narrow pressure relief orifice also has a larger acoustic impedance, which is not conducive to the acoustic output of the rear cavity 116. Therefore, the ratio of the major axis dimension to the minor axis dimension of the pressure relief orifice needs to be within a preset appropriate range. In some embodiments, the shape of the first pressure relief orifice 111c and the second pressure relief orifice 111d may include, but is not limited to, circular, elliptical, racetrack-shaped, etc. In some embodiments, the first pressure relief orifice 111c and the second pressure relief orifice 111d may be racetrack-shaped (e.g., Figure 12 As shown in the figure, the two ends of the runway shape can be minor arcs or semicircles. In this case, the major axis dimension (i.e., the length of the corresponding cross section) of the first pressure relief hole 111c and the second pressure relief hole 111d can refer to the dimension of the first pressure relief hole 111c and the second pressure relief hole 111d in the Y direction, and the minor axis dimension (i.e., the width of the corresponding cross section) of the first pressure relief hole 111c and the second pressure relief hole 111d can refer to the dimension of the first pressure relief hole 111c and the second pressure relief hole 111d in the Z direction.

[0089] In some embodiments, the first pressure relief hole 111c and the second pressure relief hole 111d are connected to the rear cavity 116. According to formula (1), an excessively large volume of the rear cavity 116 is detrimental to increasing its resonant frequency. Due to the volume limitation of the rear cavity 116, the width of the pressure relief hole should not be too large. In some embodiments, the width of the first pressure relief hole 111c... W m The value range can be 1 mm to 3 mm, and the width of the second pressure relief hole 111d is... W n The value can range from 1 mm to 3 mm.

[0090] Figure 25 This is a frequency response curve diagram showing different lengths of the first pressure relief hole according to some embodiments of this specification. For example... Figure 25 As shown, when the length of the first pressure relief hole 111c L m When the value is 0 mm, it indicates that the first pressure relief hole 111c is blocked, and the first resonant peak of the frequency response curve corresponding to the sound-emitting part 11 (such as...) Figure 25 The frequency of the frequency response curve (shown by the dashed coil G) is around 3 kHz, the flat region of the flat region is relatively small, and the amplitude corresponding to the flat region (e.g., 300 Hz-2500 Hz) is relatively small. The second resonant peak (e.g., as shown by the dashed coil G) is also relatively small. Figure 25(As shown by the dashed coil H) around 5.5 kHz. The first resonant peak is generated by the rear cavity 116, and the second resonant peak is generated by the front cavity 114. When the length of the first pressure relief hole 111c... L m As the diameter of the first resonant peak gradually increases from 2 mm to 8 mm, it gradually shifts to higher frequencies, for example, from about 3.8 kHz to about 4.7 kHz, while the position of the second resonant peak remains basically unchanged.

[0091] In some embodiments, the resonant frequency of the rear cavity 116 can be adjusted. f 2 has a larger value, thus giving the frequency response curve a larger flat area, improving the output performance of the open-back headphone 10. In some embodiments, the length of the first pressure relief hole 111c L m It can be greater than 4 mm. This is because the length of the first pressure relief hole 111c... L m After increasing the diameter to 8 mm, the resonant frequency of the frequency response curve changes slowly towards higher frequencies, with little noticeable change. In some embodiments, to improve the stability of the housing 111 and the waterproof and dustproof properties of the first pressure relief hole 111c, the length of the first pressure relief hole 111c is... L m It can be less than 8 mm. For example, the length of the first pressure relief hole 111c L m It can be in the range of 4 mm to 8 mm. For example, the length of the first pressure relief hole 111c... L m It can be in the range of 5mm-6mm. In some embodiments, by setting the resonant frequency of the rear cavity 116... f 2 (i.e.) Figure 25 The frequency corresponding to the first resonant peak in the cavity can have a large value, which can also make the resonant frequency of the rear cavity 116... f 2. Resonant frequency with the front cavity f 1 (i.e.) Figure 25 The frequency corresponding to the second resonant peak in the sound source is close to that of the second resonant peak. On the one hand, this can achieve a better effect of reducing sound leakage in the far field. On the other hand, it can also avoid the frequency response of the sound-emitting part 11 from having too many peaks and valleys, thereby improving the sound output performance of the open-back headphones 10.

[0092] Combining the length of the first pressure relief hole 111c mentioned above L m and width W m The range of values ​​for can be used to determine the length of the first pressure relief hole 111c. L m With width W mThe ratio between them ensures that the frequency response curve corresponding to the rear cavity 116 has a larger flat area, thus improving the sound output performance of the open-back headphone 10. In some embodiments, to ensure that the frequency response curve corresponding to the rear cavity 116 has a larger flat area and improves the sound output performance of the open-back headphone 10, the length of the first pressure relief hole 111c is... L m With width W m The ratio between them can be in the range of 1.3-8. In some embodiments, the length of the first pressure relief orifice 111c L m With width W m The ratio between them can be in the range of 3-6.

[0093] In some embodiments, based on the length of the first pressure relief hole 111c L m and width W m The range of values ​​for this value can determine the range of the opening area of ​​the first pressure relief hole 111c. In some embodiments, the opening area of ​​the first pressure relief hole 111c can be 3.7 mm. 2 -23 mm 2 In some embodiments, the opening area of ​​the first pressure relief hole 111c can be in the range of 10 mm. 2 -20mm 2 .

[0094] Figure 26 This is a frequency response curve diagram showing different lengths of the second pressure relief hole according to some embodiments of this specification. For example... Figure 26 As shown, when the length of the second pressure relief hole 111d... L n When the value is 0 mm, it indicates that the second pressure relief hole 111d is blocked, and the first resonant peak of the frequency response curve corresponding to the sound-emitting part 11 (such as...) Figure 26 (As shown by the dashed coil I) The frequency is around 2.4 kHz, the flat region of the frequency response curve is relatively small, and the amplitude corresponding to the flat region (e.g., 300 Hz-2500 Hz) is relatively small. The second resonant peak (as shown by...) Figure 26 (As shown by the dashed coil J) is around 5.5 kHz. The first resonant peak is generated by the rear cavity 116, and the second resonant peak is generated by the front cavity 114. The length of the second pressure relief hole 111d... L n As the diameter of the first resonant peak gradually increases from 3 mm to 6 mm, it gradually shifts to higher frequencies, increasing from around 4.4 kHz to around 4.9 kHz, while the position of the second resonant peak remains basically unchanged.

[0095] To achieve a larger first resonant frequency and thus a flatter frequency response curve, thereby improving the output performance of the open-back headphone 10, in some embodiments, the length of the second pressure relief hole 111d is... L n It can be greater than 3 mm. This is because the length of the second pressure relief hole 111d... L n After increasing to 6 mm, the resonant frequency of the frequency response curve changes slowly towards higher frequencies, with little noticeable change. In some embodiments, to improve the stability of the housing 111 and the waterproof and dustproof properties of the second pressure relief hole, the length of the second pressure relief hole 111d is... L n It can be less than 6 mm. In some embodiments, in order to have a larger flat area in the frequency response curve, improve the output performance of the open-back headphone 10, and at the same time improve the stability of the housing 111 and the water and dust resistance of the second pressure relief hole, the length of the second pressure relief hole 111d is... L n It can be in the range of 3 mm to 6 mm. In some embodiments, the length of the second pressure relief hole 111d L n It can be in the range of 4 mm to 5 mm. In some embodiments, by setting the resonant frequency of the rear cavity 116... f 2 (i.e.) Figure 26 The frequency corresponding to the first resonant peak in the cavity can have a large value, which can also make the resonant frequency of the rear cavity 116... f 2. Resonant frequency with the front cavity f 1 (i.e.) Figure 26 The frequency corresponding to the second resonant peak in the sound is close to that of the second resonant peak in the sound source. This can achieve a better effect of reducing sound leakage in the far field, and also avoid the frequency response of the sound-emitting part 11 from having too many peaks and valleys, thereby improving the sound output performance of the open-back headphones 10.

[0096] Combining the length of the second pressure relief hole 111d mentioned above L n and width W n The range of values ​​for can be used to determine the length of the second pressure relief hole 111d. L n With width W n The ratio between them makes the frequency response curve corresponding to the rear cavity 116 have a larger flat area, improving the sound output performance of the open-back headphone 10. In some embodiments, the length of the second pressure relief hole 111d L n With width W nThe ratio between them can be in the range of 1-6. In some embodiments, the length of the second pressure relief orifice 111d... L n With width W n The ratio between them can be in the range of 3-4.

[0097] In some embodiments, based on the length of the second pressure relief hole 111d L n and width W n The range of values ​​for this value can determine the range of the opening area of ​​the second pressure relief hole 111d. In some embodiments, the opening area range of the second pressure relief hole 111d can be 2.5 mm. 2 -17 mm 2 In some embodiments, the opening area of ​​the second pressure relief hole 111d can be in the range of 6 mm. 2 -10mm 2 .

[0098] In some embodiments, the length of the first pressure relief hole 111c L m With width W m The ratio between them can be greater than the length of the second pressure relief hole 111d. L n With width W n The ratio between them. For example, the width of the first pressure relief hole 111c. W m Width of the second pressure relief hole 111d W n Under similar conditions, the length of the first pressure relief hole 111c L m With width W m The ratio between them is greater than the length of the second pressure relief hole 111d. L n With width W n The ratio between them allows the area of ​​the first pressure relief hole 111c to be larger than the area of ​​the second pressure relief hole 111d, thereby making the acoustic impedance of the first pressure relief hole 111c relatively small. Correspondingly, the sound pressure amplitude at the second pressure relief hole 111d can be smaller than the sound pressure amplitude at the first pressure relief hole 111c, thereby reducing sound leakage at the second pressure relief hole 111d and increasing the listening volume in the ear canal.

[0099] In some embodiments, the length of the first pressure relief hole 111c L m With width W mThe ratio between them can be less than the length of the second pressure relief hole 111d. L n With width W n The ratio between them. For example, in the length of the first pressure relief hole 111c. L m Length of the second pressure relief hole 111d L n Under similar conditions, the length of the first pressure relief hole 111c L m With width W m The ratio between them is less than the length of the second pressure relief hole 111d. L n With width W n The ratio between them allows the area of ​​the first pressure relief hole 111c to be larger than the area of ​​the second pressure relief hole 111d, thereby making the acoustic impedance of the first pressure relief hole 111c relatively small. Correspondingly, the sound pressure amplitude at the second pressure relief hole 111d can be smaller than the sound pressure amplitude at the first pressure relief hole 111c, thereby reducing sound leakage at the second pressure relief hole 111d and increasing the listening volume in the ear canal.

[0100] In some embodiments, the length of the first pressure relief hole 111c L m With width W m The ratio between them can be equal to the length of the second pressure relief hole 111d. L n With width W n The ratio between them. For example, such as Figure 3 As shown, when worn, the free end FE of the sound-generating part 11 does not need to extend into the concha cavity. The length of the first pressure relief hole 111c of the sound-generating part 11... L m With width W m The ratio between them can be equal to the length of the second pressure relief hole 111d. L n With width W n The ratio between them. Accordingly, the acoustic resistance of the first pressure relief hole 111c can be equal to the acoustic resistance of the second pressure relief hole 111d.

[0101] In some embodiments, in order to better cancel out the second sound leakage formed by the acoustic aperture with the first sound leakage formed by the sound outlet 111a in the far field, the resonant frequency of the rear cavity 116 is... f 2 can resonate with the resonant frequency of the front cavity 114. f1. Approximately equal to. According to formula (1), the resonant frequency of the front cavity 114 is... f The resonant frequency of 1 and the rear cavity 116 f The ratio of 2 for: (4) According to formula (4), the resonant frequency of the front cavity 114 is... f The resonant frequency of 1 and the rear cavity 116 f The ratio between 2 can be related to the ratio of the volumes of the front and rear cavities, the ratio of the area of ​​the sound outlet opening to the area of ​​the acoustic hole opening, and the ratio of the depth of the sound outlet to the depth of the acoustic hole. The range of other parameters (e.g., the ratio of the area of ​​the sound outlet opening to the area of ​​the acoustic hole) can be set based on some of these parameters (e.g., the ratio of the areas of the sound outlet opening to the area of ​​the acoustic hole opening) so that the second sound leakage formed by the acoustic hole can better cancel out the first sound leakage formed by the sound outlet 111a in the far field, thus improving the output performance of the open-back headphone 10.

[0102] Figure 27 This is a contour map showing the ratio of the front and rear cavity volumes and the ratio of the sound outlet opening area to the acoustic aperture opening area, according to some embodiments of this specification. In some embodiments, such as Figure 27 As shown, the range of the ratio between the resonant frequencies of the front and rear cavities can be related to the ratio between the area of ​​the sound outlet and the area of ​​the pressure relief hole, as well as the ratio between the volumes of the front and rear cavities. Therefore, by setting the ratio between the areas of the sound outlet and the pressure relief hole, and the ratio between the volumes of the front and rear cavities, the ratio between the resonant frequencies of the front and rear cavities can be kept within a target range. For example, please refer to... Figure 27 If the resonant frequency of the front cavity 114 is made... f The resonant frequency of 1 and the rear cavity 116 f The ratio of 2 f 1 / f The value of 2 ranges from 0.1 to 3, and the opening area of ​​the sound outlet 111a is... S 1 can be smaller than the total opening area of ​​the first pressure relief hole 111c and the second pressure relief hole 111d, for example, the opening area of ​​the sound outlet hole 111a. S 1. Total opening area of ​​the first pressure relief hole 111c and the second pressure relief hole 111d S The ratio between 2 S 1 / S 2. The volume of the rear cavity 116 can be in the range of 0.1-0.99. V 2 and the volume of the anterior cavity 114 V The ratio of 1 V 2 / V The value of 1 can range from 0.1 to 10. For example, if the resonant frequency of the front cavity 114 is... fThe resonant frequency of 1 and the rear cavity 116 f The ratio of 2 f 1 / f The value of 2 can range from 0.5 to 2, so the opening area of ​​the sound outlet 111a is... S 1. Total opening area of ​​the first pressure relief hole 111c and the second pressure relief hole 111d S The ratio between 2 S 1 / S 2 can be between 0.2 and 0.7, with a volume of 116 in the rear cavity. V 2 and the volume of the anterior cavity 114 V The ratio of 1 V 2 / V The value of 1 can range from 1 to 7.

[0103] In some embodiments, the opening area of ​​the sound outlet 111a S 1 can be greater than the total opening area of ​​the first pressure relief hole 111c and the second pressure relief hole 111d. For example, the opening area of ​​the sound outlet hole 111a. S 1. Total opening area of ​​the first pressure relief hole 111c and the second pressure relief hole 111d S The ratio between 2 S 1 / S 2 can be in the range of 1-10, with a volume of 116 in the rear cavity. V 2 and the volume of the anterior cavity 114 V The ratio of 1 V 2 / V The value of 1 can range from 0.1 to 10, according to... Figure 27 The corresponding resonant frequency of the front cavity 114 f The resonant frequency of 1 and the rear cavity 116 f The ratio of 2 f 1 / f The value of 2 can range from 0.5 to 10. For example, the opening area of ​​the sound outlet 111a... S 1. Total opening area of ​​the first pressure relief hole 111c and the second pressure relief hole 111d S The ratio between 2 S 1 / S 2 can be between 3 and 9, with a rear cavity volume of 116. V 2 and the volume of the anterior cavity 114 V The ratio of 1 V 2 / V The value of 1 can range from 2 to 6, according to Figure 27 The resonant frequency of the front cavity 114 f The resonant frequency of 1 and the rear cavity 116 f The ratio of 2 f 1 / f The value of 2 can be between 1 and 8.

[0104] In some embodiments, reference Figure 27 The contour lines shown can be based on V 2 / V 1. Confirm S 1 / S The range of values ​​for 2, or, can be based on S 1 / S 2. Confirm V 2 / V The range of values ​​for 1 determines the resonant frequency of the rear cavity 116. f 2 can resonate with the resonant frequency of the front cavity 114. f 1. When the sound leakage from the acoustic aperture is close to or equal to that from the sound outlet 111a in the far field, the second sound leakage can be better canceled out by the first sound leakage from the sound outlet 111a, thus improving the output performance of the open-back headphone 10. For example, according to formula (1), in order to make the rear cavity 116 have a sufficiently large resonant frequency, f 2. Volume of the rear cavity 116 V 2 can be relatively small, for example, V 2 / V 1 can be less than 1. (Combined) Figure 27 If the resonant frequency of the rear cavity 116 is made... f 2 can resonate with the resonant frequency of the front cavity 114. f 1. Close to or equal to (e.g., f 1 / f The value of 2 is approximately 1). S 1 / S The value of 2 can range from 1 to 2.5.

[0105] For example only, the volume of the anterior cavity 114 V 1 can be 190 mm 3 -220 mm 3 Within the range; the volume of the rear cavity 116 V 2 can be in 60 mm 3 -80 mm 3 Within the scope. Accordingly, in some embodiments, V 2 / V The value of 1 can be in the range of 0.2-0.4. In some embodiments, V 2 / V The value of 1 can be in the range of 0.25-0.45.

[0106] In some embodiments, combined with Figures 16-26 The relevant description allows for adjustment of the opening area of ​​the sound hole 111a. S 1. Total opening area of ​​the first pressure relief hole 111c and the second pressure relief hole 111d S The ratio between 2 S 1 / SThe range of 2 allows open-back headphones to have good output performance. For example, the length of the sound outlet 111a L f The cross-sectional length of the sound outlet 111a can be 3 mm-11 mm. L f With width W f The ratio between them is 2, and the area of ​​the corresponding racetrack-shaped sound outlet 111a can be 4.02 mm². 2 -54 mm 2 The length of the first pressure relief hole 111c L m It can be 6 mm wide. W m The diameter can be 1.5 mm, and the area of ​​the corresponding first pressure relief hole 111c can be 8.51 mm². 2 The length of the second pressure relief hole 111d L n It can be 3 mm wide. W n The diameter can be 1.5 mm, and the corresponding area of ​​the second pressure relief hole 111d can be 4.02 mm². 2 Therefore, the opening area of ​​the sound outlet a S 1. Total opening area of ​​the first pressure relief hole 111c and the second pressure relief hole 111d S The ratio between 2 S 1 / S 2 can be between 0.32 and 4.31. For example, the length of the first pressure relief hole 111c... L m It can be 2 mm-8 mm, width W m The diameter can be 1.5 mm, and the area of ​​the first pressure relief hole 111c is 2.517 mm². 2 -11.5171 mm 2 ; Length of the second pressure relief hole 111d L n It can be 3 mm-6 mm, width W n The diameter can be 1.5mm, and the area of ​​the second pressure relief hole 111d is 4.017 mm². 2 -8.5171 mm 2 The length of the sound outlet 111a L f It can be 5 mm wide. W f It can be 2.5 mm, corresponding to the area. S 1 is 11.16 mm 2 Therefore, the opening area of ​​the sound outlet aS 1. Total opening area of ​​the first pressure relief hole 111c and the second pressure relief hole 111d S The ratio between 2 is 0.56-1.71.

[0107] Combination Figure 27 ,when V 2 / V 1. Within the range of 0.25-0.45, S 1 / S 2 When it is in the range of 0.32-4.31, f 1 / f 2 is within the range of 0.5-1.5; when V 2 / V 1. Within the range of 0.25-0.45, S 1 / S 2. When the value is in the range of 0.56-1.71, f 1 / f The value is in the range of 0.5-0.9. It can be seen that the volume ratio and / or area ratio can be determined based on the above range, so that the resonant frequency of the rear cavity 116 is... f 2 can resonate with the resonant frequency of the front cavity 114. f 1. Close to or equal to.

[0108] Figure 28 This is a frequency response curve diagram corresponding to different volume levels at the sound outlet, based on some embodiments of this specification. Figure 29 This is a frequency response curve diagram corresponding to different volume levels at the first pressure relief hole, as shown in some embodiments of this specification. Figure 30 This is a frequency response curve diagram showing the different volume levels at various locations of the second pressure relief hole, as illustrated in some embodiments of this specification. For example... Figures 28-30 As shown, as the volume gradually decreases from the maximum volume, the sound pressure at the sound outlet 111a, the sound pressure at the first pressure relief hole 111c, and the sound pressure at the second pressure relief hole 111d all gradually decrease.

[0109] It should be noted that the sound pressure at the sound outlet 111a, the sound pressure at the first pressure relief hole 111c, and the sound pressure at the second pressure relief hole 111d refer to the sound pressure at distances of 4 mm from the sound outlet 111a, 4 mm from the first pressure relief hole 111c, and 4 mm from the second pressure relief hole 111d, respectively. During the measurement of the sound pressure at each hole, no other holes are blocked. For example, when measuring the sound pressure at the sound outlet 111a, the first pressure relief hole 111c and the second pressure relief hole 111d are not obstructed or blocked.

[0110] In some embodiments, combined with Figures 8-10As described, by setting a cavity-like structure, the sound waves emitted from the pressure relief holes (first pressure relief hole 111c or second pressure relief hole 111d) can cancel out the sound leakage generated by the sound outlet hole 111a in the far field, thereby helping to reduce far-field sound leakage, and the sound waves emitted from the pressure relief holes have little impact on near-field hearing. Therefore, in some embodiments, the sound pressure amplitude at the pressure relief holes (first pressure relief hole 111c or second pressure relief hole 111d) can be close to the sound pressure amplitude at the sound outlet hole 111a, thereby effectively reducing far-field sound leakage without affecting near-field hearing. In some embodiments, to effectively reduce far-field sound leakage, within a specific frequency range (e.g., in the range of 3.5 kHz to 4.5 kHz), the ratio between the sound pressure at the sound outlet hole 111a and the sound pressure at the first pressure relief hole 111c can be in the range of 0.8 to 1.2. In some embodiments, the ratio between the sound pressure at the sound outlet 111a and the sound pressure at the first pressure relief hole 111c can be in the range of 0.95-1.05. In some embodiments, to effectively reduce far-field sound leakage, the ratio between the sound pressure at the sound outlet 111a and the sound pressure at the second pressure relief hole 111d can be in the range of 0.8-1.2. In some embodiments, the ratio between the sound pressure at the sound outlet 111a and the sound pressure at the second pressure relief hole 111d can be in the range of 0.95-1.05. In some embodiments, to effectively reduce far-field sound leakage, the ratio between the sound pressure at the sound outlet 111a and the total sound pressure at the first pressure relief hole 111c and the second pressure relief hole 111d can be in the range of 0.4-0.6. It should be noted that the sound pressure at the sound outlet 111a, the sound pressure at the first pressure relief hole 111c, and the sound pressure at the second pressure relief hole 111d refer to the sound pressure at the corresponding frequency at the same volume.

[0111] Combination Figures 28-30 At maximum volume, at 4000 Hz, the sound pressure level at the outlet 111a is 103.54 dB, the sound pressure level at the first pressure relief port 111c is 104.5 dB, and the sound pressure level at the second pressure relief port 111d is 100.74 dB. At this point, the sound pressure level at the outlet 111a is close to the sound pressure levels at the first pressure relief port 111c and the second pressure relief port 111d, respectively, thus effectively reducing far-field sound leakage.

[0112] Please refer to Figure 11 and Figure 12In some embodiments, one or more recessed areas 1119 may be provided on the inner side of the housing 111, and the first pressure relief hole 111c and / or the second pressure relief hole 111d and / or the sound outlet hole 111a may be respectively provided at the bottom of the recessed area 1119. In some embodiments, an acoustic barrier 118 may be provided in the recessed area 1119. The acoustic barrier 118 provided in the front cavity 114 (i.e., the acoustic barrier 118 provided in the recessed area 1119 corresponding to the sound outlet hole 111a) can be used to adjust the amplitude of the corresponding resonance peak of the front cavity 114, and the acoustic barrier 118 provided in the rear cavity 116 (i.e., the acoustic barrier 118 provided in the recessed area 1119 corresponding to the first pressure relief hole 111c and the second pressure relief hole 111d) can be used to adjust the amplitude of the resonance peak of the rear cavity 116. In some embodiments, the acoustic barrier 118 can also serve as a waterproof and dustproof device. For the acoustic barrier 118 disposed in the rear cavity 116, the bracket 115 can press the acoustic barrier 118 onto the bottom of the recessed area 1119. This not only helps to prevent the bracket 115 from scraping the acoustic barrier 118 during assembly, but also helps to reduce the assembly gap between the bracket 115, the acoustic barrier 118, and the housing 111, preventing the acoustic barrier 118 from shaking. In some embodiments, the acoustic barrier 118 may include a mesh, a steel mesh, or a combination thereof. In some embodiments, the acoustic barrier 118 may be pre-fixed to the bottom of the recessed area 1119 by means of adhesive or other methods. In some embodiments, the acoustic impedance of the acoustic barrier 118 disposed in the front cavity 114 and the acoustic impedance of the acoustic barrier 118 disposed in the rear cavity 116 may be the same, that is, the acoustic impedance of the acoustic barrier 118 disposed at the sound outlet 111a may be the same as that of the acoustic barrier 118 disposed at at least two pressure relief holes (e.g., the first pressure relief hole 111c and the second pressure relief hole 111d). For example, to facilitate structural assembly (e.g., reduce the variety of materials and / or avoid mixing) and increase appearance consistency, the same acoustic barrier 118 can be provided at the sound outlet 111a and at least two pressure relief holes. In some embodiments, the acoustic impedance of the acoustic barrier 118 provided in the front cavity 114 and the acoustic barrier 118 provided in the rear cavity 116 can also be different, that is, the acoustic impedance of the acoustic barrier 118 provided in the sound outlet 111a can be different from that of the acoustic barrier 118 provided in at least two pressure relief holes (e.g., the first pressure relief hole 111c and the second pressure relief hole 111d). For example, based on other parameters of the front cavity 114 and the rear cavity 116 (e.g., the area (or area ratio) of the sound outlet 111a and / or the pressure relief hole, the depth of each hole, the aspect ratio, etc.), a preset output effect can be achieved by setting acoustic barrier meshes 118 with different acoustic impedance ratios in the front cavity 114 and the rear cavity 116. (For example, by setting acoustic barrier meshes 118 with different acoustic impedance ratios, the sound pressure output at the sound outlet 111a and the pressure relief hole can be made close, thereby effectively reducing far-field sound leakage.)

[0113] In some embodiments, different acoustic resistive meshes 118 may have different thicknesses. In some embodiments, the acoustic resistive mesh 118 may have a certain thickness to maintain structural stability between it and the sound-generating part 11. However, when the thickness of the acoustic resistive mesh 118 is too large, the corresponding acoustic resistance is large, and the acoustic output performance of the corresponding acoustic holes (e.g., sound outlet 111a, first pressure relief hole 111c, second pressure relief hole 111d) will be greatly affected. Therefore, the thickness of the acoustic resistive mesh 118 needs to be set within a certain range. Taking the rear cavity 116 as an example, in some embodiments, in order to maintain structural stability between the acoustic resistive mesh 118 and the sound-generating part 11 and reduce the impact on acoustic output performance, the thickness range of the acoustic resistive mesh 118 disposed at the first pressure relief hole 111c and the second pressure relief hole 111d can be 40μm-150μm. In some embodiments, the thickness range of the acoustic resistive mesh 118 disposed at the first pressure relief hole 111c and the second pressure relief hole 111d can be 55μm-62μm. In some embodiments, the distance between the upper surface of the acoustic barrier 118 disposed at the first pressure relief hole 111c and the outer surface of the housing 1111 can be 0.8 mm-0.9 mm, and the distance between the upper surface of the acoustic barrier 118 disposed at the second pressure relief hole 111d and the outer surface of the housing 1111 can be 0.7 mm-0.8 mm. In some embodiments, the mesh density of different types of acoustic barrier 118 may also be different, resulting in different acoustic resistance of the corresponding acoustic holes, thereby affecting the output of the corresponding acoustic cavity. Therefore, it is necessary to design the composition and type of the acoustic barrier 118.

[0114] In some embodiments, in order to improve structural stability while providing waterproofing and dustproofing, steel mesh can be used at the first pressure relief hole 111c and / or the second pressure relief hole 111d and / or the sound outlet hole 111a, or a combination of mesh and steel mesh can be used. Figures 31A-31F These are frequency response curves corresponding to different acoustic impedance meshes installed in the front and rear cavities according to some embodiments of this specification. Figure 31A The figure shows the frequency response curves when only different steel meshes are used in the front cavity. Figure 31B The figure shows the frequency response curves when the front cavity is equipped with 006 mesh and different steel meshes. Figure 31C The figure shows the frequency response curves when the front cavity is equipped with 010 mesh and different steel meshes. Figure 31D The figure shows the frequency response curves when the front cavity is equipped with an etched steel mesh and different types of mesh. Figure 31E The figure shows the frequency response curves when the front cavity is equipped with 006 mesh and etched steel mesh, the rear cavity is equipped with 010 mesh, and different steel meshes. Figure 31FThe diagram shows the frequency response curves for the front cavity with 006 mesh and etched steel mesh, the rear cavity with etched steel mesh, and different mesh types. For different meshes, the nominal acoustic impedance ratios, from smallest to largest, are: 006 mesh, 010 mesh; for steel meshes of the same mesh count but different types, the nominal acoustic impedance ratios, from smallest to largest, are: etched steel mesh, steel mesh 12, steel mesh 14. Here, 006 and 010 are acoustic impedance parameters; for example, 006 can represent an acoustic impedance ratio of approximately 6 MKS rayls. The mesh count refers to the number of openings per unit area of ​​the acoustic resistive mesh; for the same type of acoustic resistive mesh, a larger mesh count corresponds to a larger acoustic impedance ratio.

[0115] like Figures 31A-31E As shown, as the overall acoustic impedance of the acoustic barrier 118 increases, the frequency response curve gradually shifts downward, corresponding to a decrease in output sound pressure, but the decrease is not significant. When the etched steel mesh is set in the current cavity 114, the frequency response curve in the corresponding low-frequency range exhibits less fluctuation, fewer peaks and valleys, and a smoother curve. Furthermore, as... Figure 31CAs shown in Figure 31D, when the front cavity 114 uses an etched steel mesh and is equipped with a 010 mesh or a 006 mesh, the frequency response curve in the corresponding low-frequency range has relatively small fluctuations, fewer peaks and valleys, and a smoother curve. In some embodiments, to improve the smoothness of the frequency response curve of the sound-generating part 11 and to give the sound-generating part 11 a larger output sound pressure, the acoustic barrier 118 provided in the front cavity 114 may include a steel mesh (e.g., an etched steel mesh), and the mesh count of the steel mesh can be in the range of 60-100. In some embodiments, the acoustic barrier 118 provided in the front cavity 114 may include a steel mesh, and the mesh count of the steel mesh can be in the range of 70-90. In some embodiments, to improve the smoothness of the frequency response curve of the sound-generating part 11 and to give the sound-generating part 11 a larger output sound pressure, the acoustic barrier 118 provided in the front cavity 114 may include a mesh and a steel mesh (e.g., an etched steel mesh), the acoustic impedance of the mesh can be in the range of 2 MKS rayls-50 MKS rayls, and the mesh count of the steel mesh can be in the range of 60-100. In some embodiments, to improve the smoothness of the frequency response curve of the sound-generating part 11 and to give the sound-generating part 11 a larger output sound pressure, the acoustic barrier 118 provided in the front cavity 114 may include a mesh and a steel mesh. The acoustic impedance of the mesh can be in the range of 6 MKS rayls-10 MKS rayls, and the mesh count of the steel mesh can be in the range of 75-85. In some embodiments, when the acoustic barrier 118 provided in the front cavity 114 includes a steel mesh (e.g., etched steel mesh) or a combination of mesh and steel mesh, the acoustic impedance of the steel mesh can be in the range of 0.1 MKS rayls-10 MKS rayls. In some embodiments, the acoustic impedance of the steel mesh can be in the range of 0.1 MKS rayls-3 MKS rayls.

[0116] This specification uses frequency response curves obtained through simulation to illustrate the sound-producing characteristics of the sound-generating part 11 under different configurations. It should be noted that in some embodiments, the frequency response curves can also be measured using testing equipment (e.g., an electroacoustic tester). The testing equipment may include a signal excitation device and a sound acquisition device (e.g., a microphone). The testing equipment can be connected to the headphones via wired or wireless means (e.g., Bluetooth, WiFi, etc.), and the sound acquisition device can be positioned near the sound-generating part 11 (e.g., 15 mm directly in front of the sound outlet 111a). During measurement, the testing equipment can send an excitation signal to the headphones to generate sound, and the sound is acquired by the sound acquisition device.

[0117] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore remain within the spirit and scope of the exemplary embodiments of this application.

Claims

1. An open-back headphone, characterized in that, include: Vocal parts, including: A transducer, including a diaphragm, is used to generate sound under the action of an excitation signal; and The housing forms a cavity for accommodating the transducer, wherein, in the wearing state, the housing has a sound outlet on its inner surface facing the user's auricle for discharging sound generated on the front side of the diaphragm through the housing. At least two pressure relief holes are provided on the other side walls of the housing. The at least two pressure relief holes include a first pressure relief hole away from the user's ear canal and a second pressure relief hole close to the ear canal. The sound pressure at the first pressure relief hole is greater than the sound pressure at the second pressure relief hole. The ear hook, together with the sound-producing part, clamps the ear region from both the front and back sides of the ear region corresponding to the concha cavity of the auricle.

2. The open-back headphone according to claim 1, characterized in that, The sound-emitting part has a connecting end connected to the ear hook and a free end not connected to the ear hook. In the wearing state, at least a portion of the free end extends into the concha cavity. There is a gap between the inner surface of the sound-emitting part and the concha cavity so that the sound-emitting part and the concha cavity form a cavity-like structure communicating with the ear canal. The sound outlet is at least partially located inside the cavity-like structure, and the first pressure relief hole and the second pressure relief hole are located outside the cavity-like structure.

3. The open-back headphone according to claim 2, characterized in that, The free end is pressed against the concha cavity in the thickness direction of the sound-producing part. or, The free end abuts against the concha cavity in the long axis and short axis directions of the sound-producing part.

4. The open-back headphone according to any one of claims 1-3, characterized in that, The first pressure relief hole is located on the upper side of the housing, and the second pressure relief hole is located on the lower side of the housing.

5. The open-back headphone according to any one of claims 1-3, characterized in that, The ratio between the area of ​​the first pressure relief hole and the area of ​​the second pressure relief hole is in the range of 1-5.

6. The open-back headphone according to claim 5, characterized in that, Both the first pressure relief hole and the second pressure relief hole are racetrack-shaped. In the long axis direction of the sound-generating part, the length of the first pressure relief hole is in the range of 4mm-8mm, and the length of the second pressure relief hole is in the range of 2mm-6mm.

7. The open-back headphone according to claim 5, characterized in that, The ratio between the length of the first pressure relief hole in the long axis direction of the sound-emitting part and the width of the first pressure relief hole in the short axis direction of the sound-emitting part is in the range of 1.3-8.

8. The open-back headphone according to claim 5, characterized in that, The ratio between the length of the second pressure relief hole in the long axis direction of the sound-emitting part and the width of the second pressure relief hole in the short axis direction of the sound-emitting part is in the range of 1-6.

9. The open-back headphone according to claim 2, characterized in that, Within the range of 3.5 kHz to 4.5 kHz, the ratio between the sound pressure at the sound outlet and the total sound pressure at the first and second pressure relief holes is in the range of 0.4 to 0.

6.

10. The open-back headphone according to claim 2, characterized in that, Within the range of 3.5 kHz to 4.5 kHz, the ratio between the sound pressure at the sound outlet and the sound pressure at the first pressure relief hole is in the range of 0.95 to 1.05, and the ratio between the sound pressure at the sound outlet and the sound pressure at the second pressure relief hole is in the range of 0.95 to 1.

05.

11. The open-back headphone according to any one of claims 1-3, characterized in that, The diaphragm divides the cavity into a front cavity and a rear cavity, which correspond to the front and rear sides of the diaphragm, respectively. The ratio between the resonant frequency of the front cavity and the resonant frequency of the rear cavity is in the range of 0.1-3, and the ratio between the area of ​​the sound outlet hole and the total area of ​​the first pressure relief hole and the second pressure relief hole is in the range of 0.1-0.

99.

12. The open-back headphone according to any one of claims 1-3, characterized in that, The diaphragm divides the cavity into a front cavity and a rear cavity, which correspond to the front and rear sides of the diaphragm, respectively. The ratio between the resonant frequency of the front cavity and the resonant frequency of the rear cavity is in the range of 0.5-10, and the ratio between the area of ​​the sound outlet hole and the total area of ​​the first pressure relief hole and the second pressure relief hole is in the range of 1-10.

13. The open-back headphone according to any one of claims 1-3, characterized in that, Acoustic blocking meshes are respectively provided at the sound outlet and at the at least two pressure relief holes, wherein the acoustic impedance of the acoustic blocking mesh at the sound outlet is different from that at the at least two pressure relief holes.

14. The open-back headphone according to claim 13, characterized in that, The acoustic barrier mesh installed at the sound outlet is a steel mesh, and the acoustic impedance of the steel mesh is in the range of 0.1 MKS rayls-10 MKS rayls.

15. The open-back headphone according to claim 13, characterized in that, The thickness of the acoustic barrier at at least two pressure relief holes is in the range of 40 μm to 150 μm.

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