Audio output device

Abstract

An acoustic output device according to an embodiment of the present specification includes at least one acoustic driver, and a first cavity and a second cavity acoustically coupled to the at least one acoustic driver, wherein a first acoustic hole is formed in the first cavity and a second acoustic hole is formed in the second cavity, and the at least one acoustic driver radiates sound having a phase difference to the outside via the first acoustic hole and the second acoustic hole, and in a target frequency band, the near-field sound radiated from the first acoustic hole and the near-field sound radiated from the second acoustic hole have a near-field sound pressure level difference, the near-field sound pressure level difference being less than 6 dB, and the sound radiated from the acoustic output device to the far field in the target frequency band exhibits directivity that can be expressed as the sound radiated from the first acoustic hole and the second acoustic hole having a far-field sound pressure level difference of 3 dB or more in at least a pair of opposite directions.

Description

Technical Field

[0001] This specification relates to the field of acoustics, and particularly to acoustic output devices.

[0002] [Incorporation by Reference] This application claims the priority of International Application No. PCT / CN2023 / 083553 filed on March 24, 2023, and International Application No. PCT / CN2023 / 083554 filed on March 24, 2023, and all of its contents are incorporated herein by reference.

Background Art

[0003] In the process of an acoustic output device outputting sound, most sound waves are radiated to the entrance of the user's ear canal, and it is inevitable that some sound waves are radiated in other directions (for example, in the direction away from the entrance of the ear canal). As a result, a certain amount of sound leakage occurs in the acoustic output device. Therefore, in order to reduce the sound leakage of the acoustic output device, the directional propagation of sound waves of the acoustic output device has very important significance. Conventional acoustic output devices usually use a dipole composed of two sound sources with the same amplitude and opposite phases to form a directional radiation sound field to achieve the directional propagation of sound. However, in such a method, while realizing the propagation of sound waves in a specific direction, a large sound field intensity is also formed in the direction opposite to the specific direction, which means that obvious sound leakage can be heard when there is a person in front of or on the side of the listener.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, it is necessary to design an acoustic output device that can maximize the volume in the direction of the entrance of the listener's ear canal and reduce sound leakage in other directions to better realize listening privacy.

Means for Solving the Problems

[0005] An acoustic output device according to one embodiment of this specification includes at least one acoustic driver and a first cavity and a second cavity acoustically coupled to the at least one acoustic driver, wherein a first acoustic hole is formed in the first cavity and a second acoustic hole is formed in the second cavity, the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, and in the target frequency band, there is a near-field sound pressure level difference between the near-field sound radiated from the first acoustic hole and the near-field sound radiated from the second acoustic hole, the near-field sound pressure level difference being less than 6 dB, and in the target frequency band, the sound radiated from the acoustic output device into the far field exhibits directivity such that the sound radiated from the first acoustic hole and the second acoustic hole have a far-field sound pressure level difference of 3 dB or more in at least one pair of opposite directions.

[0006] In some embodiments, the target frequency band is 200Hz to 5000Hz.

[0007] In some embodiments, the near-field sound pressure level difference is less than 3 dB, and / or the far-field sound pressure level difference is 6 dB or more.

[0008] In some embodiments, the rate of change of the phase difference is less than 30° / octave in the frequency range of 1kHz to 8kHz.

[0009] In some embodiments, the rate of change of the phase difference is less than 20° / octave in the frequency range of 1kHz to 8kHz.

[0010] In some embodiments, the absolute difference between the phase difference at 1 kHz and the phase difference at 2 kHz between the near-field sound emitted from the first acoustic hole and the near-field sound emitted from the second acoustic hole is less than 30°.

[0011] In some embodiments, the target frequency band includes target frequencies of 500 Hz, 1 kHz, 2 kHz, and 4 kHz.

[0012] In some embodiments, the ratio of the opening areas of the first acoustic hole to the second acoustic hole is in the range of 0.5 to 2.

[0013] In some embodiments, the ratio of the opening areas of the first acoustic hole to the second acoustic hole is in the range of 0.8 to 1.25.

[0014] In some embodiments, the difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.15.

[0015] In some embodiments, the difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.1.

[0016] In some embodiments, the ratio of the surface acoustic load between the first acoustic hole and the second acoustic hole is in the range of 0.5 to 3.5.

[0017] In some embodiments, the ratio of the surface acoustic load between the first acoustic hole and the second acoustic hole is in the range of 0.8 to 2.

[0018] In some embodiments, the at least one acoustic driver has a front side and a rear side separated by a diaphragm, and radiates sound from the front side and the rear side to the first cavity and the second cavity, respectively.

[0019] In some embodiments, the at least one acoustic driver comprises two acoustic drivers, the two acoustic drivers each radiating sound into the first cavity and the second cavity, respectively.

[0020] In some embodiments, the sound output device is suspended on the user's head or upper body and further includes a support structure that positions the sound output device so as not to obstruct the ear canal of the user's ear.

[0021] An acoustic output device according to one embodiment of this specification includes at least one acoustic driver and a first cavity and a second cavity acoustically coupled to the at least one acoustic driver, wherein a first acoustic hole is formed in the first cavity and a second acoustic hole is formed in the second cavity, the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, and in the target frequency band, the sound radiated into the far field from the acoustic output device exhibits directivity such that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of 3 dB or more in at least one pair of opposite directions, and the difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.15.

[0022] An acoustic output device according to one embodiment of this specification includes at least one acoustic driver and a first cavity and a second cavity acoustically coupled to the at least one acoustic driver, wherein a first acoustic hole is formed in the first cavity and a second acoustic hole is formed in the second cavity, the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, and in the target frequency band, the sound radiated into the far field from the acoustic output device exhibits directivity such that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of 3 dB or more in at least one pair of opposite directions, and the range of the surface acoustic load ratio between the first acoustic hole and the second acoustic hole is 0.5 to 3.5.

[0023] An acoustic output device according to an embodiment of the present specification includes at least one acoustic driver, and a first cavity and a second cavity acoustically coupled to the at least one acoustic driver. A first acoustic hole is formed in the first cavity, and a second acoustic hole is formed in the second cavity. The at least one acoustic driver radiates sound having a phase difference to the outside through the first acoustic hole and the second acoustic hole. The change rate of the phase difference is less than 30° / oct in a frequency range of 1 kHz to 8 kHz. In a target frequency band, the sound radiated from the acoustic output device to the far field exhibits a directivity such that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of 3 dB or more in at least one pair of opposite directions.

[0024] An acoustic output device according to an embodiment of the present specification includes at least one acoustic driver, and a first cavity and a second cavity acoustically coupled to the at least one acoustic driver. A first acoustic hole is formed in the first cavity, and a second acoustic hole is formed in the second cavity. The at least one acoustic driver radiates sound having a phase difference to the outside through the first acoustic hole and the second acoustic hole. In a target frequency band, the sound radiated from the acoustic output device to the far field exhibits a directivity such that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of 3 dB or more in at least one pair of opposite directions. The range of the ratio of the aperture areas of the first acoustic hole and the second acoustic hole is 0.5 to 2.

[0025] The present application will be further described by way of exemplary embodiments, and these exemplary embodiments will be described in detail with reference to the drawings. These embodiments are not limiting, and in these embodiments, the same numbers represent the same structures.

Brief Description of the Drawings

[0026] [Figure 1] It is a schematic diagram of an exemplary directional radiation sound field of an acoustic output device according to some embodiments of the present specification. [Figure 2A]This is a structural block diagram of an exemplary acoustic output device according to some embodiments of this specification. [Figure 2B] This is a curve diagram showing the frequency-dependent change in the near-field sound pressure level of an exemplary first acoustic hole and a second acoustic hole according to some embodiments of this specification. [Figure 3A] This is a schematic diagram of the directional radiated sound field of an exemplary acoustic output device according to some embodiments of this specification. [Figure 3B] This is a schematic diagram of the directional radiated sound field of an exemplary acoustic output device according to some other embodiments of this specification. [Figure 3C] This is a schematic diagram illustrating a method for calculating the distance between acoustic centers according to some embodiments of this specification. [Figure 4] This is a schematic diagram of an exemplary dual-source emission according to some embodiments of this specification. [Figure 5] This is a schematic diagram showing the relationship between the phase difference φ between the first sound source AS1 and the second sound source AS2, corresponding to equation (5), the frequency f, and the interval ι. [Figure 6] This is a schematic diagram of directional radiated sound fields at different frequencies according to some embodiments of this specification. [Figure 7A] This is a schematic diagram of an exemplary sound generating unit according to some embodiments of this specification. [Figure 7B] This is a schematic diagram of an exemplary sound generating unit according to some other embodiments of this specification. [Figure 7C] This is a schematic diagram of an exemplary sound generating unit according to some other embodiments of this specification. [Figure 8] This is a schematic diagram of another exemplary sound generating unit relating to some embodiments of this specification. [Figure 9] This is a schematic diagram of another exemplary sound generating unit relating to some embodiments of this specification. [Figure 10A] This is a schematic diagram of another exemplary sound generating unit relating to some embodiments of this specification. [Figure 10B] This is a schematic diagram of the frequency response of a Helmholtz resonant cavity. [Figure 11]This is an illustrative configuration diagram of an acoustic generating unit having two acoustic drivers according to some embodiments of this specification. [Figure 12] This is an illustrative configuration diagram of an acoustic generating unit having two acoustic drivers according to some other embodiments of this specification. [Modes for carrying out the invention]

[0027] To more clearly illustrate the technical means of the embodiments of this application, the drawings necessary for describing the embodiments are briefly described below. Clearly, the drawings described below are only a part of the examples or embodiments of this application, and those skilled in the art can apply this application to other similar scenarios based on these drawings without requiring any creative effort. Unless otherwise stated or otherwise evident from the context, the same reference numerals in the figures represent the same structure or operation.

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

[0029] As shown in the present application and claims, unless the context explicitly indicates otherwise, terms such as “one,” “one,” “one kind,” and / or “the” do not specifically refer to the singular form, but may include the plural form. Generally, the terms “includes” and “contains” merely indicate the inclusion of clearly identified steps and elements, and these steps and elements are not an exclusive list; the method or apparatus may include other steps or elements.

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

[0031] Figure 1 is a schematic diagram of an exemplary directional radiated sound field of an acoustic output device according to some embodiments of this specification.

[0032] An acoustic output device emits sound near the listener's ear, allowing the listener to hear the sound, but also radiating sound into the surrounding environment, causing significant sound leakage. To reduce sound leakage from the acoustic output device and transmit more sound to the listener's ear canal, in some embodiments, the acoustic output device can configure a dipole 1 using two sound sources (a first sound source AS1 and a second sound source AS2 shown in Figure 1) with the same amplitude and opposite phase, and this dipole 1 can form a directional radiating sound field similar to the "8" shape shown in Figure 1. The "8" shaped directional radiating sound field may include two directions with extremely strong radiation, and the "8" shaped directional radiating sound field may be understood as having two main lobes. To enhance the listener's listening effect, the positions of the two sound sources can be adjusted so that one main lobe is directed towards the listener's ear canal, thereby making the sound transmitted by the acoustic output device to the listener's ear canal sufficiently loud. At the same time, as can be seen from the schematic diagram of the directional sound field of dipole 1 in Figure 1, when one main lobe is directed towards the listener's ear canal R1, the other main lobe is usually directed directly in front of or to the side of the listener. This means that if there is another person in front of or to the side of the listener, the sound leakage from the sound output device will be clearly audible.

[0033] By adjusting the phase of the sound output from the acoustic output device, the degree of cancellation of the sound output from the acoustic output device in the far field can be changed. Therefore, to further reduce sound leakage from the acoustic output device, embodiments of this specification provide an acoustic output device that can radiate sound with a phase difference to the outside. The acoustic output device may include at least one acoustic driver and a first cavity and a second cavity coupled to at least one acoustic driver. A first acoustic hole is formed in the first cavity and a second acoustic hole is formed in the second cavity, and at least one acoustic driver can radiate sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole. When the phase difference satisfies certain conditions, the acoustic output device can maintain a high volume output in a certain direction (e.g., the direction of the user's ear canal) while suppressing sound leakage from the acoustic output device in the opposite direction. In some embodiments, the phase difference may be 120° to 179°. In some embodiments, the phase difference may be 90° to 179°.

[0034] In some embodiments, by adjusting the phase difference between two sounds generated by the acoustic output device, it is possible to make the near-field sound pressure level difference between the near-field sound emitted from the first acoustic hole and the near-field sound emitted from the second acoustic hole less than 6 dB in the target frequency band. In the target frequency band, the sound emitted from the acoustic output device to the far field exhibits directionality (directivity can be expressed as the sound emitted from the first and second acoustic holes having a far-field sound pressure level difference of 3 dB or more in at least one opposite direction), thereby increasing the volume in the direction of the listener's ear canal opening R1, reducing sound leakage in the opposite direction from the listener's ear canal opening R1 and in other directions, thus better balancing ear canal openness and listening privacy.

[0035] Figure 2A is a structural block diagram of an exemplary acoustic output device according to some embodiments of this specification.

[0036] In some embodiments, the acoustic output device may include at least one acoustic driver. As shown in Figure 2A, the acoustic output device 100 may include an acoustic driver 121, a first cavity 122, and a second cavity 123. The first cavity 122 and the second cavity 123 are acoustically coupled to the acoustic driver 121, respectively. In some embodiments, a first acoustic hole may be formed at the location of the first cavity 122 in the acoustic output device 100, and the acoustic driver 121 may radiate sound (also called first sound) to the outside through the first acoustic hole via the first cavity 122. A second acoustic hole may be formed at the location of the second cavity 123 in the acoustic output device 100, and the acoustic driver 121 may radiate sound (also called second sound) to the outside through the second acoustic hole via the second cavity 123.

[0037] An acoustic driver 121 is a device that can convert an electrical signal into an audio signal and output it. Exemplarily, the acoustic driver 121 may have a diaphragm and a drive member (e.g., a coil and a magnetic circuit assembly) that can vibrate the diaphragm. In some embodiments, there may be only one acoustic driver 121. In this case, the acoustic driver 121 may have a front and a rear side, and may radiate sound from the front and rear sides to a first cavity 122 and a second cavity 123, respectively. For example, taking the case where the drive member includes a coil and a magnetic circuit assembly, the front side of the acoustic driver 121 may be the side of the diaphragm away from the drive member (i.e., there is no drive member on the front side of the acoustic driver 121), and the rear side of the acoustic driver 121 may be the side of the diaphragm facing the drive member (i.e., there is a drive member on the rear side of the acoustic driver 121) or the side of the drive member away from the diaphragm. During vibration, sound with the same amplitude but opposite phase is generated on the front and rear sides of the diaphragm. By setting the sound transmission path in the acoustic output device 100, a specific phase difference (for example, a phase difference of 120° to 179°) can be established between the first sound radiated from the first acoustic hole after passing through the first cavity 122 and the second sound radiated from the second acoustic hole after passing through the second cavity 123. In some embodiments, the first cavity 122 and the second cavity 123 are located on opposite sides of the diaphragm, and when the diaphragm vibrates, it can radiate sound to the first cavity 122 and the second cavity 123, respectively. The sound radiated from the diaphragm to the first cavity 122 may be transmitted to the first acoustic hole according to the first sound transmission path and radiated to the outside from the first acoustic hole, and the sound radiated from the diaphragm to the second cavity 123 may be transmitted to the second acoustic hole according to the second sound transmission path and radiated to the outside from the second acoustic hole. In some embodiments, the phases of the first sound and the second sound can be adjusted by installing the acoustic structures of the first cavity 122 and / or the second cavity 123.

[0038] In some embodiments, the number of acoustic drivers 121 may be two or more. Each of the two acoustic drivers 121 may be driven by two sets of electrical signals. The two acoustic drivers 121 can each radiate sound into a first cavity 122 and a second cavity 123. In some embodiments, the amplitude and phase of the sound radiated from the two acoustic drivers 121 to the first cavity 122 and the second cavity 123 can be adjusted by setting the amplitude and phase of the electrical signals that drive the two acoustic drivers 121, and further, the amplitude and phase of the first sound radiated from the first acoustic hole by the first cavity 122 and the amplitude and phase of the second sound radiated from the second acoustic hole by the second cavity 123 can be adjusted. In some embodiments, the phases of the first and second sound can also be controlled by setting the acoustic structure of the first cavity 122 and / or the second cavity 123.

[0039] The first cavity 122 and the second cavity 123 may be cavities acoustically coupled to the acoustic driver 121. The first cavity 122 and the second cavity 123 may be used to transmit sound generated by the acoustic driver 121. Sound in the first cavity 122 may be radiated to the outside through the first acoustic hole, and sound in the second cavity 123 may be radiated to the outside through the second acoustic hole. In some embodiments, the number of first acoustic holes and / or second acoustic holes may be one or more. The number of acoustic holes may be reasonably determined according to the actual needs and is not specifically limited herein.

[0040] In some embodiments, the acoustic structures within the cavities (first cavity 122, second cavity 123) can alter the phase of the sound emitted from the acoustic holes of the cavities. In some embodiments, by installing the acoustic structures in the first cavity 122 and / or the second cavity 123, the phase difference between the first and second sound can be adjusted by adjusting the phase of the first sound emitted from the acoustic driver 121 through the first acoustic hole and / or the phase of the second sound emitted through the second acoustic hole, thereby further improving sound leakage from the acoustic output device 100. For example, if sound waves with opposite phases are generated on the front and rear sides of the acoustic driver 121, the phase difference between the first and second sound waves (i.e., the difference between the phase of the first sound wave at the first acoustic hole and the phase of the second sound wave at the second acoustic hole) can be adjusted by installing baffles in the first cavity 122 and / or the second cavity 123 to make the acoustic distance over which the sound waves propagate through the two cavities different, thereby making the phase changes of the first and second sound waves as they propagate through the cavities different. Alternatively, the phase difference between the first and second sound waves can be adjusted by installing specific acoustic structures in the first cavity 122 and / or the second cavity 123 to change the propagation speed of the first and second sound waves in the cavities. Exemplary specific acoustic structures may include slow acoustic structures that slow down the propagation speed of sound waves, such as acoustic gauze or acoustic porous materials. Furthermore, the phase difference between the first and second sounds can be adjusted by, for example, installing an extended acoustic structure (e.g., an extended cavity) in the first cavity 122 and / or the second cavity 123 to change the equivalent propagation speed of the first and second sounds in the cavities. In addition, the phase difference between the first and second sounds can be adjusted by, for example, installing a sound-absorbing structure (e.g., a resonant cavity) in the first cavity 122 and / or the second cavity 123 and modulating the sound near the resonant frequency of the sound-absorbing structure.For a specific description of how to adjust the phase difference between the first sound and the second sound by installing the acoustic structures of the first cavity 122 and / or the second cavity 123, refer to other parts of this specification, for example, Figures 7A to 10B and their related descriptions.

[0041] In some embodiments, when there are two acoustic drivers 121, the phase difference between the first sound and the second sound can be adjusted by setting the phase of the electrical signals that drive the two acoustic drivers 121.

[0042] In some embodiments, when the phase difference between the first sound and the second sound is within a specific range (e.g., 120° to 179°), even if the sound pressure of the near-field sound radiated from the first sound port and the near-field sound radiated from the second sound port are similar in the target frequency band, the sound radiated from the sound output device 100 into the far field can exhibit directivity. This results in the far-field sound radiation field having at least one strong directional direction (where the sound pressure in the strong directional direction and its vicinity is sufficiently large), while the radiation intensity in the other directions is relatively small. For example, the near-field sound radiated from the first cavity 122 and the second cavity 123 has a near-field sound pressure level difference of less than 6 dB, and the sound radiated from the first cavity 122 and the second cavity 123 has a far-field sound pressure level difference of 3 dB or more in at least one pair of opposite directions (for example, when a user wears the sound output device 100, the direction toward the ear canal opening R1 and the direction away from the ear canal opening R1). Also, for example, the near-field sound radiated from the first cavity 122 and the second cavity 123 has a near-field sound pressure level difference of less than 3 dB, and the sound radiated from the first cavity 122 and the second cavity 123 has a far-field sound pressure level difference of 6 dB or more in at least one pair of opposite directions. As can be understood, the smaller the near-field sound pressure level difference, the more pronounced the similar amplitude, opposite phase sound waves in the far-field cancel each other out, resulting in a greater effect in reducing sound leakage. Furthermore, the larger the far-field sound pressure level difference, the stronger the directivity of the far-field sound, reducing sound leakage in directions away from the ear canal (e.g., away from the ear canal R1) and in other directions, thus increasing the effect of reducing far-field sound leakage. In some embodiments, when the user wears the acoustic output device 100, the strong directivity direction may be directed towards the user's ear canal R1. In this way, when the user wears the acoustic output device 100, the sound transmitted to the user's ear canal R1 becomes sufficiently loud, while reducing sound leakage in other directions (e.g., away from the ear canal), thereby improving the user's listening experience and privacy.

[0043] In addition, the phase of sound emitted from the acoustic holes (including the first and second acoustic holes) described in the embodiments of this specification may refer to the phase measured at a position 4 mm away from the acoustic hole (or the geometric center of the acoustic hole) (for example, 4 mm in front of the acoustic hole). In some embodiments, the phase difference test method may involve measuring the phases of the sound emitted from the first and second acoustic holes (the first and second sound, respectively), and then calculating the phase difference between the first and second sound. When testing the sound from the first acoustic hole (or the second acoustic hole), a baffle can be used to separate the first and second acoustic holes to avoid interference from the second acoustic hole (or the first acoustic hole) during the test. Furthermore, the sound collection device can be positioned on the line connecting the first and second acoustic holes, and the first sound can be collected at a position 4 mm away from the first (or second) acoustic hole, further avoiding interference from the second (or first) acoustic hole during testing. For illustrative purposes only, the dimensions of the baffle may be standard dimensions. For example, the length, width, and height of the baffle may be 1650 mm, 1350 mm, and 30 mm, respectively. If there are two or more first (or second) acoustic holes, one may be selected for testing. For example, one first acoustic hole and one second acoustic hole located at specific relative positions (e.g., minimum or maximum relative distance) can be selected, and the phase of the sound emitted from each can be tested, and the phase difference can be calculated. Furthermore, audio measurements within a specific frequency band (e.g., 1000Hz to 8000Hz) do not necessarily need to be exhaustive. By setting up multiple frequency sampling points (e.g., 20 to 30) with equal step sizes and endpoints that are at the frequency band endpoints, the audio at each sampling point can be measured individually.

[0044] In some embodiments, the acoustic output device 100 may include a support structure 110 and an acoustic generating unit 120, and the acoustic driver 121 and the first cavity 122 and second cavity 123 acoustically coupled to the acoustic driver 121 may be installed within the acoustic generating unit 120.

[0045] The sound generating unit 120 may be used to generate sound and radiate it to the outside. In some embodiments, the sound output device 100 can fix the sound generating unit 120 by a support structure 110 in a position near the user's ear but not blocking the user's ear canal. In some embodiments, the projection of the sound generating unit 120 onto the plane of the user's ear canal can partially or completely cover it without blocking it. In some embodiments, the projection of the sound generating unit 120 onto the plane of the user's ear canal does not have to cover the user's ear canal, thereby maintaining an open state for the user's ear. When the user's ear is maintained in an open state, the user can not only hear the sound output by the sound generating unit 120 but also acquire sounds from the external environment.

[0046] The support structure 110 may be used to support the sound generating unit 120. In some embodiments, when a user wears the sound output device 100, the support structure 110 may be placed over the user's ear, head, or upper body. In some embodiments, the support structure 110 may include an arc structure that conforms to the user's auricle R2. For illustrative purposes only, the arc structure may include, but is not limited to, a hook shape, a C shape, etc. When a user wears the sound output device 100, the support structure 110 can be placed over or clamped onto the user's auricle R2 to achieve the attachment of the sound output device 100. In some embodiments, the support structure 110 may include an ear-hook structure that conforms to the user's head or upper body. When a user wears the sound output device 100, the ear-hook structure can be placed over the user's auricle R2 by the user's head or neck to achieve the attachment of the sound output device 100.

[0047] In some embodiments, the support structure 110 may be made of a soft material, a hard material, or a combination thereof. A soft material is a material whose hardness (e.g., Shore hardness) is less than a first hardness threshold (e.g., 15A, 20A, 30A, 35A, 40A, etc.). For example, the Shore hardness of a soft material may be 45-85A or 30-60D. A hard material is a material whose hardness (e.g., Shore hardness) is greater than a second hardness threshold (e.g., 65D, 70D, 80D, 85D, 90D, etc.). The soft material may include, but is not limited to, polyurethane (PU) (e.g., thermoplastic polyurethane elastomer rubber (TPU)), polycarbonate (PC), polyamide (PA), acrylonitrile butadiene styrene copolymer (ABS), polystyrene (PS), high impact polystyrene (HIPS), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyurethane (PU), polyethylene (PE), phenol formaldehyde (PF), urea formaldehyde (UF), melamine formaldehyde (MF), silicone rubber, or combinations thereof.The rigid material may include, but is not limited to, polyethersulfone resin (Poly(ester sulfones), PES), polyvinylidene chloride (PVDC), polymethyl methacrylate (PMMA), polyether-ether-ketone (PEEK), or combinations thereof, or mixtures thereof with reinforcing agents such as glass fibers or carbon fibers. In some embodiments, the material of the support structure 110 may be selected depending on the specific circumstances. For example, a flexible material can improve the comfort and fit of the acoustic output device 100 when worn by the user, while a rigid material can improve the strength of the acoustic output device 100.

[0048] In some embodiments, the acoustic output device 100 may include only the sound generating unit 120. For example, when the acoustic output device 100 is installed, the sound generating unit 120 can be directly secured in a position that does not obstruct the ear canal within the ear cavity, and in this case, the acoustic output device 100 does not need to install a support structure 110 on which to place the sound generating unit 120.

[0049] In some embodiments of this specification, the acoustic output device can adjust the phase difference between two sounds generated by the sound generating unit to ensure that in the target frequency band, the near-field sound emitted from the first sound port and the near-field sound emitted from the second sound port have a small sound pressure level difference, and that the sound emitted from the acoustic output device to the far field exhibits directionality. As a result, the sound emitted to the outside from the first and second sound ports cancels out in the far field in a specific direction, thereby reducing sound leakage in the far field.

[0050] The target frequency band may be a frequency range sensitive to the human ear. In some embodiments, since the human ear is sensitive within the frequency range of 200Hz to 5000Hz, the target frequency band may be 200Hz to 5000Hz or a part thereof. For example, in order to reduce sound leakage in the main frequency range of the human voice in the sound output device 100, the target frequency band may be 200Hz to 800Hz. Alternatively, for example, the target frequency band may be 2000Hz to 4000Hz, which is the frequency range to which the human ear is most sensitive. Furthermore, for example, the target frequency band may be 500Hz to 4000Hz, 500Hz to 3000Hz, 500Hz to 2000Hz, 500Hz to 1000Hz, 1000Hz to 4000Hz, 1500Hz to 3000Hz, 1500Hz to 2000Hz, etc. In some embodiments, the target frequency band may include a continuous frequency range or consist of a plurality of independent frequency points. For example, the target frequency band may include target frequency points such as 500Hz, 1000Hz, 2000Hz, and 4000Hz, thereby satisfying the objective that the sound at these frequency points of the sound output device 100 will have a near-field sound pressure and a far-field directionality (e.g., cardioid directivity).

[0051] Since the human ear is sensitive to the frequency range of 200Hz to 5000Hz, setting the target frequency band to this range allows for more effective reduction of distant sound leakage within that frequency range, thereby meeting actual needs.

[0052] The near-field sound pressure level difference is the difference in sound pressure levels of the sound radiated at a near-field position from each of the two or more sound sources formed by the sound output device 100. In this application, the near-field position of a sound source may be within 5 mm of the sound source (for example, the first sound hole or the second sound hole). For ease of understanding, the near-field sound pressure level difference can be expressed as the difference between the sound pressure level at the first sound hole and the sound pressure level at the second sound hole of the sound output device 100.

[0053] In some embodiments, the near-field sound pressure level test method may involve measuring the sound pressure of sounds (first sound and second sound, respectively) radiated from a first and second sound hole at a specific frequency point (e.g., 1000 Hz), and then calculating the sound pressure level difference between the first and second sound (e.g., by taking the common logarithm of the ratio of the measured sound pressure to the reference sound pressure and then multiplying by 20 to obtain the sound pressure level). In some embodiments, when testing the sound from the first (or second) sound hole, a baffle can be used to separate the first and second sound holes to avoid interference from the second (or first) sound hole during the test. The sound pressure at the first sound hole can be understood as the sound pressure at a position close to the first sound hole, and the sound pressure at the second sound hole can be understood as the sound pressure at a position close to the second sound hole. For example, the sound collection device may be installed at a position 4 mm away from the first acoustic hole (or second acoustic hole) and collect the first sound (or second sound) as sound pressure at the first acoustic hole (or second acoustic hole).

[0054] In some embodiments, when testing the sound from the first and second acoustic holes, the positions 4 cm away from the first and second acoustic holes (i.e., the collection positions) may be in opposite directions from the acoustic output device 100 (for example, the position 4 cm away from the first acoustic hole is in the direction from the second acoustic hole toward the first acoustic hole, and the position 4 cm away from the second acoustic hole is in the direction from the first acoustic hole toward the second acoustic hole). The sound collection device is installed at each of the two collection positions to collect the sound pressure level of the acoustic output device 100, and the difference between the two sound pressure levels is calculated, i.e., the near-field sound pressure level difference between the first and second acoustic holes.

[0055] For a detailed explanation of the acoustic center, please refer to Figures 3A to 3C and their related explanations.

[0056] In some embodiments of this specification, by controlling the near-field sound pressure of the sound emitted from the first and second acoustic holes to be close together, it is possible to ensure that the first and second sound effectively interfere and cancel each other out in a specific direction in the far field, thereby effectively reducing sound leakage in the far field from the acoustic output device 100.

[0057] Exemplary, Figure 2B is a curve diagram showing the frequency-dependent change in near-field sound pressure levels of a first and second acoustic hole according to some embodiments of this specification. As shown in Figure 2B, the first and second acoustic holes of the acoustic output device 100 show nearly identical trends in the change of near-field sound pressure levels within the frequency range of 200 Hz to 20 kHz, with a difference of less than 5 dB, indicating that the acoustic output device 100 effectively reduces far-field sound leakage within the frequency range of 200 Hz to 20 kHz.

[0058] The near-field sound pressure level difference can be adjusted in various ways. In some embodiments, the near-field sound pressure level difference may be adjusted by adjusting the ratio of the opening areas of the first acoustic hole and the second acoustic hole.

[0059] The opening area ratio is the ratio of the area S1 of the first acoustic hole to the area S2 of the second acoustic hole, that is, the opening area ratio is S1 / S2. As can be understood, when there are two or more first acoustic holes (or second acoustic holes), the opening area ratio is the total area of ​​the first acoustic hole (S1=S 11 +S 12 +S 13 …+S 1n ) and the total area of ​​the second acoustic hole (S2 = S 21 +S 22 +S 23 …+S 2m The ratio may also be given to n and m. Here, n and m are integers greater than 1.

[0060] In some embodiments, the ratio of the opening areas of the first acoustic hole to the second acoustic hole (i.e., the opening area ratio) may be 0.2, 0.5, 1, 1.5, 2, 2.5, etc. In some embodiments, the range of the ratio of the opening areas of the first acoustic hole to the second acoustic hole may be 0.5 to 2. By controlling the range of the ratio of the opening areas of the first acoustic hole to the second acoustic hole, the opening areas of the first acoustic hole to the second acoustic hole can be made closer, and the acoustic resistances of the first acoustic hole to the second acoustic hole can be made closer, thereby reducing the near-field sound pressure level difference between the first acoustic hole to the second acoustic hole, and furthermore, the far-field sound leakage can be more significantly canceled out, improving the effect of reducing far-field sound leakage.

[0061] Furthermore, the ratio of the opening areas of the first acoustic hole to the second acoustic hole may be in the range of 0.8 to 1.25, 0.9 to 1.1, or 0.95 to 1.1. By further reducing the range of the ratio of the opening areas of the first acoustic hole to the second acoustic hole, the near-field sound pressure level difference can be reduced, and the effect of reducing far-field sound leakage can be further improved.

[0062] In some embodiments, the near-field sound pressure level difference may be adjusted by adjusting the difference in acoustic load between the first acoustic hole and the second acoustic hole.

[0063] Acoustic load is the ratio of the sound pressure value P1 after passing through the first (or second) acoustic hole to the sound pressure value P0 before passing through the first (or second) acoustic hole; that is, the acoustic load is P1 / P0. Note that for a given acoustic hole, the larger the acoustic load (or the closer it is to 1), the smaller the acoustic resistance.

[0064] In some embodiments, the acoustic load of the first acoustic hole (or second acoustic hole) can be determined by measuring the sound pressure value when the first acoustic hole (or second acoustic hole) is covered with gauze (corresponding to P1) and when it is not covered with gauze (corresponding to P0) at a specific distance, and calculating the ratio of P1 to P0. Specifically, when testing the sound of the first acoustic hole (or second acoustic hole), the sound collection device can be placed 4-5 mm away from the first acoustic hole (or second acoustic hole), and then the sound pressure value when the first acoustic hole (or second acoustic hole) is covered with gauze (corresponding to P1) and when it is not covered with gauze (corresponding to P0) can be collected, and finally the acoustic load of the first acoustic hole (or second acoustic hole) can be calculated. The test signal for the acoustic load may be a single-frequency signal, or one or more frequency points within that signal may be selected, including but not limited to 100Hz, 200Hz, 300Hz, 500Hz, 1000Hz, 2000Hz, 5000Hz, and the resonant frequency f0 point of the acoustic output device 100. The test signal may also be white noise, pink noise, or a sweep signal. In some embodiments, it is necessary to first convert the measured sound pressure level into a sound pressure value and then calculate the acoustic load. Alternatively, the difference in sound pressure levels obtained by measuring before and after the first acoustic hole (or second acoustic hole) is covered with gauze may be calculated, and the acoustic load value of the first acoustic hole (or second acoustic hole) may be calculated inversely from a logarithmic formula.

[0065] In some embodiments, the difference in acoustic load between the first and second acoustic holes may include values ​​such as 0.1, 0.15, and 0.2. In some embodiments, the difference in acoustic load between the first and second acoustic holes may be less than 0.15. As can be understood, the smaller the difference in acoustic load between the first and second acoustic holes, the closer the acoustic resistances of the first and second acoustic holes become, thereby reducing the near-field sound pressure level difference between the first and second acoustic holes and significantly reducing far-field sound leakage.

[0066] Furthermore, the difference in acoustic load between the first and second acoustic holes may be less than 0.1. By further reducing the range of the difference in acoustic load between the first and second acoustic holes, the difference in near-field sound pressure levels between the first and second acoustic holes can be further reduced, thereby further improving the effect of reducing far-field sound leakage.

[0067] In some embodiments, to reduce far-field sound leakage in the 200Hz to 5000Hz range of the sound output device 100, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.05. In some embodiments, to reduce far-field sound leakage in the 500Hz to 4000Hz range of the sound output device 100, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.07. In some embodiments, to reduce far-field sound leakage in the 1000Hz to 3000Hz range of the sound output device 100, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.1. In some embodiments, to reduce far-field sound leakage in the 1500Hz to 2500Hz range of the sound output device 100, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.12.

[0068] In some embodiments, the near-field sound pressure level difference may be adjusted by adjusting the ratio of the surface acoustic loads between the first acoustic hole and the second acoustic hole.

[0069] The surface acoustic load is the product of the ratio of the sound pressure value P1 after passing through the first acoustic hole (or second acoustic hole) to the sound pressure value P0 that does not pass through the first acoustic hole (or second acoustic hole), and the area S of the first acoustic hole (or second acoustic hole). In other words, the surface acoustic load is S × P1 / P0.

[0070] In some embodiments, the ratio of the surface acoustic loads between the first and second acoustic holes may be 0.5, 1, 2.5, etc. In some embodiments, the range of the ratio of the surface acoustic loads between the first and second acoustic holes may be 0.5 to 3.5. By adjusting the ratio of the surface acoustic loads between the first and second acoustic holes and maintaining it within an appropriate range, the acoustic resistances of the first and second acoustic holes can be made closer, thereby reducing the near-field sound pressure level difference between the first and second acoustic holes and improving the effect of reducing far-field sound leakage.

[0071] Furthermore, the ratio of the surface acoustic loads between the first and second acoustic holes may be in the range of 0.8 to 2. As can be seen, by further reducing the range of the ratio of the surface acoustic loads between the first and second acoustic holes, the effect of reducing far-field sound leakage can be made more pronounced.

[0072] In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 200Hz to 5000Hz, the range of the ratio of the surface acoustic load between the first acoustic hole and the second acoustic hole may be 0.9 to 1.2. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 500Hz to 4000Hz, the range of the ratio of the surface acoustic load between the first acoustic hole and the second acoustic hole may be 0.8 to 1.5. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 1000Hz to 3000Hz, the range of the ratio of the surface acoustic load between the first acoustic hole and the second acoustic hole may be 0.7 to 2. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 1500Hz to 2500Hz, the range of the ratio of the surface acoustic load between the first acoustic hole and the second acoustic hole may be 0.6 to 2.7. In some embodiments, in order to reduce far-field sound leakage from the acoustic output device 100 in the range of 1500Hz to 2000Hz, the ratio of the surface acoustic load between the first acoustic hole and the second acoustic hole may be in the range of 0.5 to 3.5.

[0073] The far-field sound pressure level difference is the difference in sound pressure levels of the sound radiated in the far field from the first and second sound holes, respectively. In this application, the far field of the first (or second) sound hole may be located at a distance of 10 cm or more from the first (or second) sound hole. For ease of understanding, the far-field sound pressure level difference between the first and second sound holes can be expressed as the difference in sound pressure levels at the same or approximately the same distance (or symmetrical position) from the two holes in the direction of the line connecting the first and second sound holes.

[0074] The test method for the far-field sound pressure level difference is similar to the test method for the near-field sound pressure level difference, and the similarities will not be explained. The difference is that when measuring the far-field sound pressure level, for example, when collecting sound from the first acoustic hole (or the second acoustic hole), the sound collection device may be placed 30 cm away from the first acoustic hole (or the second acoustic hole) for collection.

[0075] In some embodiments, at least one pair of opposite directions may include two opposite directions in the linear direction connecting the first acoustic hole and the second acoustic hole. For example, when a user puts on the acoustic output device 100, the direction toward the ear canal opening R1 and the direction away from the ear canal opening R1 are a pair of opposite directions.

[0076] In some embodiments, at least one pair of opposing directions may further include two directions that satisfy a predetermined angle range with respect to a given position point. For example, two directions that satisfy a predetermined angle range formed by a line connecting two position points near the first and second acoustic holes in the far field, respectively, and the midpoint of the line connecting the first and second acoustic holes. Here, the predetermined angle range may include, but is not limited to, 150° to 180°. In this way, multiple situations that may occur in the actual application process can be comprehensively considered, thereby better ensuring the cancellation effect of far-field sound leakage. For example, in an actual product, a tilt or distortion may occur in a strong directional radiated sound field, such as a cardioid directional radiated sound field. In this case, the tilt or distortion of the cardioid directional radiated sound field may increase sound leakage in multiple directions from the acoustic output device 100, which may affect the performance of the acoustic output device 100. In this case, a pair of opposing directions may be assigned to any possible tilt or distortion so that the strong directional sound field becomes a more standard strong directional sound field. For example, if tilt or distortion occurs in the strong directional sound field, at least one of the pair of opposing directions may still be the direction of the line connecting the first and second sound holes, and the other direction may form a 10° angle with the opposite direction of the line connecting the first and second sound holes, or each of the pair of opposing directions may form a certain angle (e.g., 5°, 10°, 15°, 20°) with the direction of the line connecting the first and second sound holes.

[0077] In some embodiments, in order to reduce far-field sound leakage within the 200Hz to 5000Hz range of the sound output device 100, the near-field sound pressure level difference may be less than 6dB, and the far-field sound pressure level difference may be 12dB or more. In some embodiments, in order to reduce far-field sound leakage within the 500Hz to 4000Hz range of the sound output device 100, the near-field sound pressure level difference may be less than 5dB, and the far-field sound pressure level difference may be 10dB or more. In some embodiments, in order to reduce far-field sound leakage within the 1000Hz to 3000Hz range of the sound output device 100, the near-field sound pressure level difference may be less than 4dB, and the far-field sound pressure level difference may be 8dB or more. In some embodiments, in order to reduce far-field sound leakage from the sound output device 100 in the range of 1500Hz to 2500Hz, the near-field sound pressure level difference may be less than 3dB, and the far-field sound pressure level difference may be 4dB or more. In some embodiments, in order to reduce far-field sound leakage from the sound output device 100 in the range of 1500Hz to 2000Hz, the near-field sound pressure level difference may be less than 2dB, and the far-field sound pressure level difference may be 3dB or more.

[0078] In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 200Hz to 5000Hz, the far-field sound pressure level difference is 12dB or more, and in this case, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.03. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 500Hz to 4000Hz, the far-field sound pressure level difference is 10dB or more, and in this case, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.05. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 1000Hz to 3000Hz, the far-field sound pressure level difference is 6dB or more, and in this case, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.1. In some embodiments, in order to reduce far-field sound leakage from the acoustic output device 100 in the range of 1500Hz to 2500Hz, the far-field sound pressure level difference is 4dB or more, and in this case, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.12. In some embodiments, in order to reduce far-field sound leakage from the acoustic output device 100 in the range of 1500Hz to 2000Hz, the far-field sound pressure level difference is 3dB or more, and in this case, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.15.

[0079] In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 200Hz to 5000Hz, the far-field sound pressure level difference is 12dB or more, and in this case, the ratio of the opening area of ​​the first sound hole to the second sound hole may be 0.75 to 1.1. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 500Hz to 4000Hz, the far-field sound pressure level difference is 10dB or more, and in this case, the ratio of the opening area of ​​the first sound hole to the second sound hole may be 0.7 to 1.2. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 1000Hz to 3000Hz, the far-field sound pressure level difference is 6dB or more, and in this case, the ratio of the opening area of ​​the first sound hole to the second sound hole may be 0.6 to 1.5. In some embodiments, in order to reduce far-field sound leakage from the acoustic output device 100 in the range of 1500Hz to 2500Hz, the far-field sound pressure level difference is 4dB or more, and in this case, the ratio of the opening area between the first acoustic hole and the second acoustic hole may be 0.6 to 1.7. In some embodiments, in order to reduce far-field sound leakage from the acoustic output device 100 in the range of 1500Hz to 2000Hz, the far-field sound pressure level difference is 3dB or more, and in this case, the ratio of the opening area between the first acoustic hole and the second acoustic hole may be 0.5 to 1.9.

[0080] In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 200Hz to 5000Hz, the far-field sound pressure level difference is 12dB or more, and in this case, the range of the ratio of surface acoustic load between the first acoustic hole and the second acoustic hole may be 0.9 to 1.2. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 500Hz to 4000Hz, the far-field sound pressure level difference is 10dB or more, and in this case, the range of the ratio of surface acoustic load between the first acoustic hole and the second acoustic hole may be 0.8 to 1.5. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 1000Hz to 3000Hz, the far-field sound pressure level difference is 6dB or more, and in this case, the range of the ratio of surface acoustic load between the first acoustic hole and the second acoustic hole may be 0.7 to 2. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 1500Hz to 2500Hz, the far-field sound pressure level difference is 4dB or more, and in this case, the range of the ratio of surface acoustic load between the first acoustic hole and the second acoustic hole may be 0.6 to 2.7. In some embodiments, in order to reduce far-field sound leakage of the sound output device 100 in the range of 1500Hz to 2000Hz, the far-field sound pressure level difference is 3dB or more, and in this case, the range of the ratio of surface acoustic load between the first acoustic hole and the second acoustic hole may be 0.5 to 3.5.

[0081] Figure 3A is a schematic diagram of the directional radiated sound field of an exemplary acoustic output device according to some embodiments of this specification, Figure 3B is a schematic diagram of the directional radiated sound field of an exemplary acoustic output device according to some other embodiments of this specification, and Figure 3C is a schematic diagram of a method for calculating the distance between acoustic centers according to some embodiments of this specification.

[0082] As shown in Figures 3A and 3B, AS1 and AS2 represent a first sound source and a second sound source formed by the sound generating unit 120 of the sound output device 100, respectively. When the first sound generated by the first sound source AS1 and the second sound generated by the second sound source AS2 have a specific phase difference (e.g., 120° to 179°), the first sound source AS1 and the second sound source AS2 can form a strong directional radiated sound field, for example, a cardioid directional radiated sound field (as shown in Figure 3A) or a supercardioid directional radiated sound field (as shown in Figure 3B). The first acoustic hole can constitute the first sound source AS1, and the position of the first sound source AS1 can be considered to be at the acoustic center of the first acoustic hole. The second acoustic hole can constitute the second sound source AS2, and the position of the second sound source AS2 can be considered to be at the acoustic center of the second acoustic hole.

[0083] The acoustic center of an acoustic hole (for example, a first or second acoustic hole) is the equivalent sound emission position of the acoustic hole, which may be determined based on the shape, dimensions, and number of acoustic holes. If there is one acoustic hole, the acoustic center may be the geometric center of the acoustic hole (for example, if the acoustic hole has an outer opening and an inner opening in the depth direction, the geometric center of the acoustic hole points to the centroid of the outer opening). If there are two acoustic holes, the acoustic center may be the midpoint of the line connecting the geometric centers of the two acoustic holes. If there are three acoustic holes, the acoustic center may be the center of the circumscribed circle of the geometric centers of the three acoustic holes, or the acoustic center may be the centroid of the triangle enclosed by the line connecting the geometric centers of the three acoustic holes. If there are four (or more) acoustic holes, the acoustic center may be the centroid of the quadrilateral (or polygon) enclosed by the line connecting the geometric centers of the four (or more) acoustic holes.

[0084] The distance between the first acoustic hole and the second acoustic hole is the distance between the acoustic center of the first acoustic hole and the acoustic center of the second acoustic hole. As an example, if there is one first acoustic hole and two second acoustic holes, the one first acoustic hole and the two second acoustic holes can form a triangle determined by the three sides. The side lengths of the three sides of this triangle can be obtained by measurement. Furthermore, the distance from the acoustic center of the first acoustic hole to the acoustic center of the second acoustic hole (if there are two second acoustic holes, the acoustic center may be the midpoint of the line connecting the geometric centers of the two acoustic holes), that is, the distance between the first sound source AS1 and the second sound source AS2 can be calculated.

[0085] As shown in Figure 3C, the geometric center A of the first acoustic hole, the geometric center B1 of one second acoustic hole, and the geometric center B2 of the other second acoustic hole can form a triangle 300, and the side lengths of the three sides of triangle 300 are obtained by measurement and are a, b, and c, respectively. The acoustic center of the first acoustic hole is the geometric center A of the first acoustic hole, and the equivalent acoustic center of the two second acoustic holes is the midpoint B3 of the line connecting the geometric centers of the two second acoustic holes (i.e., geometric center B1 and geometric center B2). The distance from the acoustic center of the first acoustic hole to the equivalent acoustic center of the second acoustic hole is the length of the line segment AB3 (denoted as x), and the value of x can be calculated based on the following formula.

[0086]

number

[0087]

number

[0088]

number

[0089] Here, β represents the included angle between line segment AB3 and line segment B1B3.

[0090] Based on equations (1) to (3), the following estimations and calculations can be made.

[0091]

number

[0092] As can be seen from Figures 3A and 3B, a cardioid (Figure 3A) or supercardioid (Figure 3B) directional radiated sound field has only one main lobe, with strong sound field radiation in and around the main lobe, and weak sound field radiation in other directions (the sound field intensity in the opposite direction of the main lobe is also relatively weak). When a user wears the acoustic output device 100, the main lobe can be directed towards the listener's ear canal R1. In this case, only the radiation directed towards the ear canal R1 and its vicinity is strong, and the directivity is weak in all other directions, thereby reducing sound leakage from the acoustic output device 100. As can be understood, the phase difference between the first and second sounds in Figures 3A and 3B is different (although both are within a specific range), and therefore the radiated sound fields shown in Figures 3A and 3B are also different. The following explains the principle by which a strong directional radiated sound field (for example, a cardioid or supercardioid directional radiated sound field) is formed when the first sound and the second sound have a specific phase difference.

[0093] Figure 4 is a schematic diagram of an exemplary dual-source emission according to some embodiments of this specification.

[0094] As shown in Figure 4, the first sound source AS1 and the second sound source AS2 can represent two equivalent sound sources consisting of the first and second sound holes of the sound generating section 120 of the sound output device 100, respectively. P is a point in the far field, l represents the distance between the first sound source AS1 and the second sound source AS2, r1 represents the distance from the first sound source AS1 to point P, r2 represents the distance from the second sound source AS2 to point P, r represents the distance from the midpoint O of the line connecting the first sound source AS1 and the second sound source AS2 to point P, and θ represents the angle between the line connecting the first sound source AS1 and the second sound source AS2 and the line connecting the midpoint O and point P.

[0095] The sound pressure levels of the first sound source AS1 and the second sound source AS2 are as follows:

[0096]

number

[0097] Here, A represents the intensity of the point source, ω represents the angular frequency, j represents the imaginary part, t represents time, φ represents the phase difference between the first sound source AS1 and the second sound source AS2, and k represents the wave vector. Under the far-field conditions (r>>ι, kι<<1), the distances r1 and r2 can be expressed as follows.

[0098]

number

[0099] Therefore, the sound pressure amplitude |p| at point P in the far field can be expressed as a superposition of the sound fields of the first sound source AS1 and the second sound source AS2.

[0100]

number

[0101] When a cardioid directional sound field is required, i.e., when θ = 180° is needed, the sound pressure amplitude |p| at point P in the far field has a local minimum. Differentiating |p| yields the following:

[0102]

number

[0103] Solving equation (7) above yields the relationship that the phase difference φ between the first sound source AS1 and the second sound source AS2 must satisfy.

[0104]

number

[0105] As can be seen from equation (8), in order for the first sound source AS1 and the second sound source AS2 to form a cardioid directional radiated sound field, the phase difference φ between the two sound sources and kι must satisfy a certain relationship. Since the wave vector k is related to the frequency f, the phase difference φ between the two sound sources is also related to the frequency.

[0106] Figure 5 is a schematic diagram showing the relationship between the phase difference φ between the first sound source AS1 and the second sound source AS2, corresponding to equation (8), the frequency f, and the interval ι.

[0107] As shown in Figure 5, the horizontal axis represents frequency f in Hz, the vertical axis represents the distance ι between the two sound sources in mm, and each curve represents the phase difference φ required under different conditions (i.e., different frequencies f and different distances ι). As can be seen by comparing the curves in Figure 5, in order to realize a cardioid directional radiated sound field, when the distance ι is the same, the phase difference between the first sound source AS1 and the second sound source AS2 is negatively correlated with the magnitude of the frequency in a given frequency range. For example, in the range of 200 Hz to 2000 Hz, the higher the frequency, the smaller the required phase difference between the first sound source AS1 and the second sound source AS2, and the lower the frequency, the larger the required phase difference between the first sound source AS1 and the second sound source AS2. Similarly, when the frequency is the same, the phase difference between the first sound source AS1 and the second sound source AS2 is negatively correlated with the magnitude of the distance between the two sound sources. The larger the interval, the smaller the phase difference between the required first sound source AS1 and second sound source AS2; and the smaller the interval, the larger the phase difference between the required first sound source AS1 and second sound source AS2. In actual measurements, if the phase difference is negatively correlated with the magnitude of multiple consecutive frequencies within a certain frequency range and / or multiple consecutive intervals within a certain dual sound source interval range, then it can be considered that the phase difference is negatively correlated with the magnitude of the frequency and / or the magnitude of the interval between the two sound sources. As a simple example, multiple frequencies (e.g., 5, 10, etc.) and their corresponding phase differences can be measured at the same pitch (e.g., every 1Hz, 10Hz, 50Hz, 100Hz, 200Hz, etc.), and if the above multiple frequencies and their corresponding phase differences satisfy a negative correlation, then it can be considered that the phase difference is negatively correlated with the magnitude of the frequency.

[0108] In practical applications, the spacing ι is usually constant, and the correspondence between the phase difference φ and kι can be simplified to the correspondence between frequency and phase difference. That is, assuming that the spacing ι is constant, if the phase difference and frequency of the first sound source AS1 and the second sound source AS2 satisfy a constant correspondence, a cardioid directional radiated sound field can be formed between the first sound source AS1 and the second sound source AS2. As a purely illustrative explanation, if the spacing ι shown in the table below is 3 mm, the following table may represent the correspondence between the necessary phase difference φ (which may be understood as the optimal phase difference that can realize a cardioid directional radiated sound field) and frequency f so that the first sound source AS1 and the second sound source AS2 can form a cardioid directional radiated sound field.

[0109] [Table 1]

[0110] As can be seen from the table, the phase difference φ required between the first sound source AS1 and the second sound source AS2 to form a cardioid directional radiated sound field differs at different frequencies. At the same time, as can be seen from the table, even if the phase difference φ corresponding to different frequencies is different, the difference is not large. For example, the phase difference corresponding to 200 Hz shown in the table is 179°, and the phase difference corresponding to 2000 Hz is 173°, and the two phase differences differ by only 6°. Therefore, if a constant phase difference φ (e.g., 176°) or phase difference range (e.g., 120° to 179°) is determined, even if a cardioid directional radiated sound field (as shown in Figure 3A) cannot be formed at a certain frequency in a wide frequency band range (e.g., 200 Hz to 2000 Hz), a directional radiated sound field similar to a cardioid, such as a supercardioid directional radiated sound field as shown in Figure 3B, can be formed.

[0111] Figure 6 is a schematic diagram of directional radiated sound fields at different frequencies according to some embodiments of this specification. Note that Figure 6 corresponds to sound field radiation at different frequencies under far-field conditions, 0.5 m away from the sound source, when the spacing ι = 3 mm and the phase difference φ = 176°. As shown in Figure 6, curves 610, 620, 630, and 640 are directional radiated sound field curves corresponding to frequencies of 200 Hz, 500 Hz, 1000 Hz, and 2000 Hz, respectively, under far-field conditions. As can be seen from Figure 6, the sound field intensity in the opposite direction (180° direction) of the main lobe (maximum sound field intensity) of the radiated sound field of curve 630 is minimal; therefore, the sound field radiation directivity (cardioid directivity) of curve 630 is optimal compared to the other three curves (i.e., the directional radiated sound field is optimal when the phase difference φ = 176° and the frequency is 1000 Hz). The sound field intensity in the opposite direction of the main lobe of the radiated sound field corresponding to curves 610, 620, and 640 is slightly greater than that of curve 630, forming a directivity similar to a cardioid pattern. As can be seen from this, when the phase difference φ = 176°, both sound sources can form a strong directional radiated sound field in the frequency range of 200Hz to 2000Hz. Also, as can be seen from the above explanation (the difference in the optimal phase difference corresponding to different frequencies is not large), when the phase difference is within a certain range, for example, 120° to 179°, both sound sources can form a strong directional radiated sound field in the frequency range of 200Hz to 2000Hz.

[0112] The far-field sound leakage reduction effect of the sound output device 100 may be influenced by the rate of change of the near-field phase difference of the sound radiated from the sound source. The rate of change of the phase difference may be the frequency-dependent rate of change of the phase difference between the sound radiated from the first sound hole and the sound radiated from the second sound hole. In some embodiments, the rate of change of the phase difference can be expressed based on the phase difference and the octave. Here, an octave (oct) is the interval between two frequencies in the frequency response curve where the ratio of the frequencies is 2 or 1 / 2. For example, 1000Hz to 2000Hz is one octave, 2000Hz to 4000Hz is one octave, and also, for example, 1500Hz to 3000Hz is one octave, and 3000Hz to 6000Hz is one octave.

[0113] When the rate of change of the near-field phase difference is controlled to show a gradual trend, distortion can be avoided in the sound radiated from the acoustic output device to the far field, thereby causing the two sound sources to tend to form a strong directional radiated sound field (e.g., a cardioid or supercardioid directional radiated sound field) over a wider frequency range. In some embodiments, the rate of change of the phase difference between the sound radiated from the first acoustic hole and the sound radiated from the second acoustic hole may be less than 30° / oct in the frequency range of 1000Hz to 8000Hz.

[0114] In some embodiments, the rate of change of the near-field phase difference may be less than 20° / octave in the frequency range of 1000Hz to 8000Hz. By further controlling the rate of change of the near-field phase difference, the two sound sources can form a standard, stronger directional radiated sound field (e.g., a cardioid or supercardioid directional radiated sound field), reducing sound leakage in the opposite direction to the ear canal and in other directions, thereby better balancing ear canal openness with listening privacy.

[0115] Furthermore, in some embodiments, the rate of change of the near-field phase difference may be less than 25° / oct in order for the acoustic output device 100 to form a standard strong directional radiated sound field in the range of 1000Hz to 5000Hz. In some embodiments, the rate of change of the near-field phase difference may be less than 20° / oct in order for the acoustic output device 100 to form a standard strong directional radiated sound field in the range of 3000Hz to 4000Hz. In some embodiments, the rate of change of the near-field phase difference may be less than 15° / oct in order for the acoustic output device 100 to form a standard strong directional radiated sound field in the range of 2000Hz to 3000Hz. In some embodiments, the rate of change of the near-field phase difference may be less than 10° / oct in order for the acoustic output device 100 to form a standard strong directional radiated sound field in the range of 1000Hz to 2000Hz.

[0116] In some embodiments, the absolute value of the difference between the phase difference at 1000 Hz and the phase difference at 2000 Hz between the sound emitted from the first sound hole and the sound emitted from the second sound hole may be less than 30°. For example, the phase difference at 1000 Hz between the sound emitted from the first sound hole and the sound emitted from the second sound hole is 159° to 178°, and the phase difference at 2000 Hz between the sound emitted from the first sound hole and the sound emitted from the second sound hole is 149° to 176°. In this case, the absolute value of the difference between the phase difference at 1000 Hz and the phase difference at 2000 Hz between the sound emitted from the first sound hole and the sound emitted from the second sound hole is 2° to 29°, which is less than 30°. Since the frequency range of 1000Hz to 2000Hz is within the range of sensitivity to the human ear, by controlling the absolute value of the difference between the phase difference at 1000Hz and the phase difference at 2000Hz between the sound emitted from the first acoustic hole and the sound emitted from the second acoustic hole to within 30°, the effect of reducing distant sound leakage can be further improved.

[0117] In some embodiments, in order to reduce far-field sound leakage within the 200Hz to 5000Hz range of the sound output device 100, the far-field sound pressure level difference is 12dB or more, and in this case, the rate of change of the near-field phase difference is less than 29° / oct. In some embodiments, in order to reduce far-field sound leakage within the 500Hz to 4000Hz range of the sound output device 100, the far-field sound pressure level difference is 10dB or more, and in this case, the rate of change of the near-field phase difference is less than 25° / oct. In some embodiments, in order to reduce far-field sound leakage within the 1000Hz to 3000Hz range of the sound output device 100, the far-field sound pressure level difference is 6dB or more, and in this case, the rate of change of the near-field phase difference is less than 20° / oct. In some embodiments, in order to reduce far-field sound leakage from the sound output device 100 in the range of 1500Hz to 2500Hz, the far-field sound pressure level difference is 4dB or more, and in this case, the rate of change of the near-field phase difference is less than 15° / oct. In some embodiments, in order to reduce far-field sound leakage from the sound output device 100 in the range of 1500Hz to 2000Hz, the far-field sound pressure level difference is 3dB or more, and in this case, the rate of change of the near-field phase difference is less than 10° / oct.

[0118] Figure 7A is a schematic diagram of an exemplary sound generating unit according to some embodiments of this specification, Figure 7B is a schematic diagram of an exemplary sound generating unit according to some other embodiments of this specification, and Figure 7C is a schematic diagram of an exemplary sound generating unit according to some other embodiments of this specification.

[0119] As shown in Figure 7A, the sound generating unit 700 may include at least one acoustic driver 721 and a first cavity 722 and a second cavity 723 acoustically coupled to at least one acoustic driver. In some embodiments, at least one acoustic driver 721 may include a diaphragm, and the at least one acoustic driver 721 has a front side and a rear side separated by the diaphragm, and radiates sound from the front side and the rear side to the first cavity 722 and the second cavity 723, respectively. In some embodiments, at least one acoustic driver 721 may include two acoustic drivers (i.e., the acoustic driver 721 in Figure 7A may be replaced by two parallel acoustic drivers), and the two acoustic drivers are each driven by two sets of electrical signals to radiate sound to the first cavity 722 and the second cavity 723. The sound in the first cavity 722 may be radiated to the outside through the first acoustic hole 724, that is, the first acoustic hole 724 radiates a first sound V1 to the outside, and the sound in the second cavity 723 may be radiated to the outside through the second acoustic hole 725, that is, the second acoustic hole 725 radiates a second sound V2 to the outside.

[0120] In some embodiments, the phase difference between the first sound V1 emitted from the first acoustic hole 724 and the second sound V2 emitted from the second acoustic hole 725 must be within a specific range (e.g., 120° to 179°) so that the sound emitted from the acoustic generator 700 to the far field within a target frequency band (e.g., 200 Hz to 5000 Hz) exhibits strong directivity (e.g., cardioid or supercardioid). Since the initial value of the phase difference between the two sound waves emitted from the acoustic driver 721 to the first cavity 722 and the second cavity 723, respectively, is 180°, the acoustic structures in the first cavity 722 and / or the second cavity 723 can be positioned such that the phase difference between the first sound V1 and the second sound V2 satisfies the condition. In some embodiments, the sound generating unit 700 may include an acoustic structure 726 installed in the first cavity 722 and / or the second cavity 723. The acoustic structure 726 may be used to adjust the phase difference between the first sound V1 and the second sound V2 by adjusting the actual output phase of the first sound V1 and / or the second sound V2. In some embodiments, the acoustic structure 726 can change the phase difference between the first sound V1 radiated from the first acoustic hole 724 and the second sound V2 radiated from the second acoustic hole 725 by creating an acoustic distance difference between the first acoustic distance over which the first sound V1 propagates within the first cavity 722 and the second acoustic distance over which the second sound V2 propagates within the second cavity 723. In this embodiment, the acoustic structure 726 was described as being installed in the second cavity 723 as an example, but as can be understood, in other alternative embodiments, the acoustic structure 726 may be installed in the first cavity 722, or different acoustic structures may be installed in the first cavity 722 and the second cavity 723.

[0121] In some embodiments, the acoustic structure 726 may include a baffle, one end of which is connected to the inner wall of the second cavity 723, and the other end of which is a free end. In some embodiments, as shown in Figure 7A, four baffles may be installed in the second cavity 723, two of which are installed on the first inner wall 7231 of the second cavity 723, and the remaining two baffles are installed on the second inner wall 7232 (the second inner wall 7232 is installed opposite the first inner wall 7231), and the free ends of the baffles on the two inner walls are installed opposite each other. In this case, there is a gap between the free ends of the two opposing baffles, and sound can bypass the baffles and be transmitted through the gap to the second acoustic hole 725. In some embodiments, the number and / or position of the baffles in the second cavity 723 may have other installation configurations. For example, as shown in Figure 7B, a baffle may be installed on only one inner wall of the second cavity 723 (for example, the second inner wall 7232), with one end of the baffle connected to the second inner wall 7232 and the free end of the baffle extending near the first inner wall 7231 (forming a gap between the free end of the baffle and the first inner wall 7231). Sound can bypass the baffle and be transmitted to the second acoustic hole 725 through the gap between the free end of the baffle and the first inner wall 7231. Alternatively, as shown in Figure 7C, for example, both ends of the baffle may be connected to the first inner wall 7231 and the second inner wall 7232, respectively. In this case, an opening may be formed in the baffle, and sound can bypass the baffle and be transmitted to the second acoustic hole 725 through the opening. In the process by which sound waves bypass the baffle and are transmitted to the second acoustic hole 725, the distance the sound waves travel (i.e., the acoustic distance) changes compared to when the baffle is not installed. Sound waves radiated from the front of the acoustic driver 721 are radiated to the outside from the first acoustic hole 724 by the first cavity 722, and the distance these sound waves travel is the first acoustic distance L1. Sound waves radiated from the rear of the acoustic driver 721 are radiated to the outside from the second acoustic hole 725 by the second cavity 723 and acoustic structure 726, and the distance these sound waves travel is the second acoustic distance L2. There is an acoustic distance difference between the first acoustic distance L1 and the second acoustic distance L2.

[0122] The difference in time delay between the first sound V1 emitted from the first acoustic hole 724 and the second sound V2 emitted from the second acoustic hole 725 may be as follows:

[0123]

number

[0124] Here, c represents the speed of sound. Then, the phase difference φ between the first sound V1 and the second sound V2 is as follows:

[0125]

number

[0126] As can be seen from this, by controlling the acoustic distance difference between the first acoustic distance L1 and the second acoustic distance L2 (for example, the acoustic distance difference can be within the range of 1 mm to 57 mm), the actual output phase difference between the first sound V1 and the second sound V2 can be controlled, and by setting the phase difference between the first sound V1 and the second sound V2 to 120° to 179°, the sound radiated from the sound generation unit 700 into the far field can exhibit strong directivity (for example, cardioid or supercardioid type).

[0127] As can be understood, the number, position, dimensions, and installation method of the baffles can affect the phase difference between the first sound V1 and the second sound V2 by influencing the second acoustic distance L2 through which the sound waves pass the second cavity 723. Therefore, the number, position, dimensions, and installation method of the baffles can be rationally set according to the needs of the phase difference between the first sound V1 and the second sound V2.

[0128] Also, in this embodiment, when other parameters (for example, the first acoustic distance, the second acoustic distance) are the same, it can be understood that the phase difference between the first voice V1 and the second voice V2 has a negative correlation with the frequency. The higher the frequency, the smaller the phase difference between the first voice V1 and the second voice V2, and the lower the frequency, the larger the phase difference between the first voice V1 and the second voice V2.

[0129] FIG. 8 is a schematic diagram of another exemplary acoustic generating unit according to some embodiments of this specification.

[0130] As shown in FIG. 8, an acoustic structure for changing the propagation speed of sound may be installed in the first cavity 822 and / or the second cavity 823 of the acoustic generating unit 800. For example, the acoustic structure may be a low-speed acoustic structure that can slow down the speed at which sound transmits itself. The speed at which sound waves propagate in air is faster than the speed at which sound waves propagate in the low-speed acoustic structure. In some embodiments, the low-speed acoustic structure may include at least one of acoustic gauze, acoustic porous material, etc. When sound waves pass through the micropores in the gauze or porous material, due to the viscous action of the micropores on the air, the speed at which the sound waves pass through the micropores becomes slower, thereby achieving the effect of low speed. Specifically, the speed at which sound waves propagate in air (also called the normal sound speed) is c, and the speed at which sound waves propagate in the low-speed acoustic structure (also called the equivalent sound speed) is c'. As can be seen from the above description, c' < c. Therefore, by installing a low-speed acoustic structure in the cavity so as to change the propagation speed of sound, the actual output phase of the first voice V1 and / or the second voice V2 can be adjusted, and the phase difference between the first voice V1 and the second voice V2 can be adjusted.

[0131] In this embodiment, the low-speed acoustic structure 826 is described as being installed in the second cavity 823 as an example. Alternatively, as shown in Figure 8, the low-speed acoustic structure 826 may be installed in the second cavity 823. Sound waves radiated from the front of the acoustic driver 821 are radiated to the outside from the first acoustic hole 824, and the distance the sound waves travel is the first acoustic distance L1. Sound waves radiated from the rear of the acoustic driver 821 are radiated to the outside from the second acoustic hole 825, and the distance the sound waves travel may include the second acoustic distance L2 propagated by air and the third acoustic distance L3 propagated by the low-speed acoustic structure 826.

[0132] The difference in time delay between the first sound V1 emitted from the first acoustic hole 824 and the second sound V2 emitted from the second acoustic hole 825 may be as follows.

[0133]

number

[0134] Here, c represents the normal speed of sound, and c' represents the equivalent speed of sound in the low-speed acoustic structure 826. Then, the phase difference φ between the first sound V1 and the second sound V2 is as follows.

[0135]

number

[0136] As can be seen from this, by controlling the equivalent sound velocity and / or third acoustic distance L3 as the sound waves propagate within the low-speed acoustic structure 826 (for example, the ratio of the equivalent sound velocity to the normal sound velocity in the low-speed acoustic structure can be set to the range of 0.02 to 0.5), the actual output phase difference between the first sound V1 and the second sound V2 can be controlled, and by setting the phase difference between the first sound V1 and the second sound V2 to 120° to 179°, the sound radiated from the sound generation unit 800 into the far field can exhibit strong directivity (for example, cardioid or supercardioid).

[0137] Furthermore, in this embodiment, it can be seen that, given the same other parameters (e.g., equivalent sound velocity, first acoustic distance, second acoustic distance, third acoustic distance), the phase difference between the first sound V1 and the second sound V2 is negatively correlated with frequency. The higher the frequency, the smaller the phase difference between the first sound V1 and the second sound V2, and the lower the frequency, the larger the phase difference between the first sound V1 and the second sound V2.

[0138] Figure 9 is a schematic diagram of another exemplary sound generating unit according to some embodiments of this specification.

[0139] As shown in Figure 9, an extended acoustic structure 926 may be installed in the first cavity 922 and / or the second cavity 923 of the sound generating unit 900. The extended acoustic structure 926 can change (e.g., enlarge) the cross-sectional area at different locations in the sound transmission path of the first cavity 922 or the second cavity 923. When sound waves propagate through a waveguide (i.e., an air waveguide formed by the first cavity 922 or the second cavity 923), if the cross-sectional area of ​​the waveguide changes at different locations in the sound wave transmission path, the sound waves will reflect at the locations of abrupt changes in cross-sectional area, which means that the equivalent impedance of the medium changes. Accordingly, parameters related to the equivalent impedance (e.g., equivalent sound velocity, equivalent density, etc.) also change accordingly, thereby changing the phase of the sound wave. For example, the effect of the extended acoustic structure 926 on the change in equivalent sound velocity is mainly related to the ratio of the cross-sectional area of ​​the second cavity 923 after expansion by the extended acoustic structure 926 to the original cross-sectional area of ​​the second cavity 923. In some embodiments, the actual equivalent sound velocity can be obtained by means of simulation or experimental testing.

[0140] In this embodiment, the extension acoustic structure 926 is described as being installed in the second cavity 923 as an example. As shown in Figure 9, the extension acoustic structure 926 may also be installed on two opposing side walls of the second cavity 923, and the extension acoustic structure 926 causes a rapid change in the cross-sectional area before and after a specific position in the sound transmission path of the second cavity 923. In some embodiments, the extension acoustic structure 926 may be an extension cavity. The structural shape of the extension cavity may be a rectangle as shown in Figure 9, and in other embodiments, the cross-sectional area of ​​the extension acoustic structure 926 may be other shapes, such as a triangle or a trapezoid. The structural shape of the extension cavity can be reasonably set based on the phase difference between the first sound V1 and the second sound V2.

[0141] As shown in Figure 9, sound waves radiated from the front of the acoustic driver 921 are radiated to the outside from the first acoustic hole 924, and the distance these sound waves travel is the first acoustic distance L1. Sound waves radiated from the rear of the acoustic driver 921 are radiated to the outside from the second acoustic hole 925 by the extended acoustic structure 926 and the second cavity 923, and the distance these sound waves travel is the second acoustic distance L2. Here, the speed of sound at the first acoustic distance L1 is the normal speed of sound c, and the speed of sound at the second acoustic distance L2 is the equivalent speed of sound c'. The difference in time delay between the first sound V1 radiated from the first acoustic hole 924 and the second sound radiated from the second acoustic hole 925 is as follows.

[0142]

number

[0143] Here, c represents the normal speed of sound, and c' represents the equivalent speed of sound in the extended acoustic structure 926. Then, the phase difference φ between the first sound V1 and the second sound V2 is as follows.

[0144]

number

[0145] As can be seen from this, by installing an extended acoustic structure 926 inside the cavity and controlling the equivalent sound speed at which sound waves propagate within the cavity, the actual output phase difference between the first sound V1 and the second sound V2 can be controlled. By setting the phase difference between the first sound V1 and the second sound V2 to 120° to 179°, the sound radiated from the sound generation unit 900 into the far field can exhibit strong directivity (for example, cardioid or supercardioid).

[0146] Furthermore, in this embodiment, it can be seen that, given the same other parameters (e.g., first acoustic distance, second acoustic distance, equivalent sound velocity), the phase difference between the first sound V1 and the second sound V2 is negatively correlated with frequency. The higher the frequency, the smaller the phase difference between the first sound V1 and the second sound V2, and the lower the frequency, the larger the phase difference between the first sound V1 and the second sound V2.

[0147] Figure 10A is a schematic diagram of another exemplary sound generating unit according to some embodiments of this specification.

[0148] The structure of the sound generating unit 1000 shown in Figure 10A is similar to the structure of the sound generating unit 700 shown in Figure 7A. For example, the sound generating unit 1000 may include at least one acoustic driver 1021, a first cavity 1022, and a second cavity 1023. At least one first acoustic hole 1024 may be formed in the first cavity 1022, and at least one second acoustic hole 1025 may be formed in the second cavity 1023. For specific details of the acoustic driver 1021, the first cavity 1022, the second cavity 1023, the first acoustic hole 1024, and the second acoustic hole 1025, please refer to the related explanation in Figure 7A. The difference between the sound generating unit 1000 and the sound generating unit 700 is that their acoustic structures are different. As shown in Figure 10A, a sound-absorbing structure 1026 may be installed in the first cavity 1022 and / or the second cavity 1023 of the sound-generating unit 1000. In some embodiments, the sound-absorbing structure 1026 may have a resonant frequency. The actual output phase difference of the two sound waves can be controlled by modulating the sound (e.g., phase modulation) near the resonant frequency of the sound-absorbing structure 1026. In some embodiments, the sound-absorbing structure 1026 may be a Helmholtz resonant cavity. In some embodiments, the sound-absorbing structure 1026 may be a micro-perforated plate resonator. In some embodiments, the sound-absorbing structure 1026 may be a quarter-wavelength tube resonator.

[0149] In this embodiment, the sound-absorbing structure 1026 is described as being installed inside the second cavity 1023, but the sound-absorbing structure 1026 may be installed on the side wall of the second cavity 1023 and be in acoustic communication with the second cavity 1023. Taking a Helmholtz resonant cavity as an example, its resonant frequency f0 may be as follows.

[0150]

number

[0151] Here, M represents the acoustic mass (primarily related to the nozzle parameters of the Helmholtz resonator), and C represents the acoustic capacitance (primarily related to the cavity parameters at the rear end of the Helmholtz resonator).

[0152] Figure 10B is a schematic diagram of the frequency response of a Helmholtz resonant cavity.

[0153] Here, the horizontal axis represents frequency in Hz, and the vertical axis represents amplitude response (in dB) or phase response (in degrees (deg)). The solid line represents the amplitude response of the frequency response, and the dashed line represents the phase response of the frequency response. As shown in Figure 10B, when the resonant frequency f0 = 2000 Hz of the Helmholtz resonant cavity, the amplitude response shows a resonant peak at 2000 Hz, and regarding the phase response, around 2000 Hz, the phase gradually changes from 180° with increasing frequency, eventually approaching 0°. As can be seen from this, in the low frequency range (e.g., between 40 Hz and 1000 Hz), the phase difference changes within the range of 179° to 150°, which basically satisfies the phase difference requirements necessary to achieve the cardioid or supercardioid directivity described in the examples of this specification. Therefore, by installing a sound-absorbing structure 1026 in the cavity and adjusting the phase of the sound emitted from the acoustic holes corresponding to the cavity, the actual output phase difference between the first sound and the second sound can be controlled, and the sound emitted from the sound generation unit 900 into the far field can exhibit strong directivity (for example, cardioid or supercardioid).

[0154] In some embodiments, when at least one acoustic driver in the sound generation unit is a single driver or includes two acoustic drivers, the phase difference between the first sound V1 and the second sound V2 can be adjusted using the method shown in Figures 7A to 10A. In such an adjustment method, the phase difference of the sound radiated from the acoustic driver to the first cavity and the second cavity may be 180°, and the phase of the first sound V1 or the second sound V2 can be changed by installing different types of acoustic structures (e.g., baffles, slow acoustic structures, extended acoustic structures, sound-absorbing structures) within the cavities, thereby adjusting the phase difference between the first sound V1 and the second sound V2. In some embodiments, when at least one acoustic driver includes two acoustic drivers, the phase difference between the first sound V1 and the second sound V2 can be adjusted by adjusting the electrically driven signals corresponding to the two acoustic drivers. In some embodiments, the phases of the two electrically driven signals may be set such that the phase of the sound radiated from one acoustic driver into the first cavity is not completely inverse to the phase of the sound radiated from the other acoustic driver into the second cavity.

[0155] Figure 11 is an exemplary configuration diagram of a sound generating unit having two acoustic drivers according to some embodiments of this specification, and Figure 12 is an exemplary configuration diagram of a sound generating unit having two acoustic drivers according to some other embodiments of this specification.

[0156] As shown in Figure 11, the sound generating unit 1100 may include a first sound driver 1121A, a second sound driver 1121B, a first cavity 1122, and a second cavity 1123. A first sound hole 1124 may be formed in the first cavity 1122, and the first sound driver 1121A can radiate a first sound V1 to the outside through the first cavity 1122 and the first sound hole 1124. A second sound hole 1125 may be formed in the second cavity 1123, and the second sound driver 1121B can radiate a second sound V2 to the outside through the second cavity 1123 and the second sound hole 1125. In some embodiments, the first acoustic driver 1121A and the second acoustic driver 1121B may be driven by two sets of electrical signals, and by setting the phases of the two sets of electrical drive signals to be different, the phase difference between the first sound V1 and the second sound V2 can be set to 120° to 179°. For example, as shown in Figure 11, the phase difference between the electrical drive signal that drives the first acoustic driver 1121A and the electrical drive signal that drives the second acoustic driver 1121B can be set to 120° to 179°. In such a setting method, it is not necessary to install other acoustic structures in the first cavity 1122 and the second cavity 1123, and the acoustic distance over which sound propagates within each cavity is approximately the same, thereby enabling a phase difference of 120° to 179° between the first sound V1 and the second sound V2. Furthermore, as shown in Figure 12, for example, the phase difference between the electrical drive signal that drives the first acoustic driver 1121A and the electrical signal that drives the second acoustic driver 1121B may be set not to 120° to 179°. In such a setting method, the phase difference between the first sound V1 and the second sound V2 can be set to 120° to 179° by installing an acoustic structure in the first cavity 1122 and / or the second cavity 1123 (for example, installing a low-speed acoustic structure 1126 in the second cavity 1123 as shown in Figure 12).

[0157] The beneficial effects that can be achieved by the acoustic output devices described in the embodiments of this specification include, but are not limited to, the following: (1) By adjusting the phase difference between two sounds generated by the sound generating unit, the near-field sound pressure level difference between the first and second sound holes can be reduced and the far-field sound pressure level difference can be increased, so that in the target frequency band, the sound radiated from the acoustic output device into the far field can exhibit stronger directivity, thereby maximizing the volume in the direction of the ear canal opening when the listener wears the acoustic output device, and reducing sound leakage in the direction opposite to the listener's ear canal opening and in other directions, thereby better balancing ear canal openness and listening privacy. (2) By installing multiple types of acoustic structures (e.g., baffles, slow-speed acoustic structures, extended acoustic structures, sound-absorbing structures) in the sound generating unit of the acoustic output device and adjusting the phase difference between two sounds generated by the sound generating unit, the phase difference can be adjusted more flexibly and accurately, thereby improving the practicality of the acoustic output device. (3) If at least one acoustic driver in the sound generation unit includes two acoustic drivers, the two electrically driven signals can be directly controlled to achieve control of the phase difference between the two sounds, which can simplify the structure of the acoustic output device and lower the cost.

[0158] Having explained the basic concepts above, it will be clear to those skilled in the art that the above detailed disclosures are merely examples and do not limit this specification. Although not explicitly stated herein, those skilled in the art can make various changes, improvements, and modifications to this specification. These changes, improvements, and modifications are intended to be suggested herein and are therefore within the spirit and scope of the exemplary embodiments herein. [Explanation of symbols]

[0159] 100 Audio output device 120, 700, 800, 900, 1000, 1100 Sound generation unit 121, 721, 821, 921, 1021 Acoustic Drivers 122, 722, 822, 922, 1022, 1122 First Cavity 123, 723, 823, 923, 1023, 1123 Second Cavity 724, 824, 924, 1024, 1124 First acoustic holes 725, 825, 925, 1025, 1125 Second acoustic opening 1026 Sound-absorbing structure 110 Support structure R1 auditory canal opening R2 Auricle AS1 First Sound Source AS2 2nd sound source

Claims

1. It is an audio output device, At least one acoustic driver, It includes a first cavity and a second cavity acoustically coupled to at least one acoustic driver, A first acoustic hole is formed in the first cavity, a second acoustic hole is formed in the second cavity, and the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole. An acoustic output device wherein, in the target frequency band, the near-field sound emitted from the first acoustic hole and the near-field sound emitted from the second acoustic hole have a near-field sound pressure level difference, the near-field sound pressure level difference is less than 6 dB, and in the target frequency band, the sound emitted from the acoustic output device into the far field exhibits a directivity such that the sound emitted from the first acoustic hole and the second acoustic hole have a far-field sound pressure level difference of 3 dB or more in at least one pair of opposite directions.

2. The acoustic output device according to claim 1, wherein the target frequency band is 200 Hz to 5000 Hz.

3. The sound output device according to claim 1, wherein the near-field sound pressure level difference is less than 3 dB, and / or the far-field sound pressure level difference is 6 dB or more.

4. The acoustic output device according to claim 1, wherein the rate of change of the phase difference is less than 30° / octave in the frequency range of 1 kHz to 8 kHz.

5. The acoustic output device according to claim 1, wherein the rate of change of the phase difference is less than 20° / octave in the frequency range of 1 kHz to 8 kHz.

6. The acoustic output device according to claim 4, wherein the absolute value of the difference between the phase difference at 1 kHz and the phase difference at 2 kHz between the near-field sound emitted from the first acoustic hole and the near-field sound emitted from the second acoustic hole is less than 30°.

7. The acoustic output device according to claim 1, wherein the target frequency band includes target frequencies of 500 Hz, 1 kHz, 2 kHz, and 4 kHz.

8. The acoustic output device according to claim 1, wherein the ratio of the opening areas of the first acoustic hole and the second acoustic hole is in the range of 0.5 to 2.

9. The acoustic output device according to claim 8, wherein the ratio of the opening areas of the first acoustic hole to the second acoustic hole is in the range of 0.8 to 1.

25.

10. The acoustic output device according to claim 1, wherein the difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.

15.

11. The acoustic output device according to claim 10, wherein the difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.

1.

12. The acoustic output device according to claim 1, wherein the ratio of the surface acoustic load between the first acoustic hole and the second acoustic hole is in the range of 0.5 to 3.

5.

13. The acoustic output device according to claim 1, wherein the at least one acoustic driver has a front side and a rear side separated by a diaphragm, and radiates sound from the front side and the rear side to the first cavity and the second cavity, respectively.

14. The acoustic output device according to claim 1, wherein the at least one acoustic driver comprises two acoustic drivers, the two acoustic drivers each radiating sound into the first cavity and the second cavity, respectively.

15. The acoustic output device according to claim 1, further comprising a support structure that is hung on the user's head or upper body and is positioned so as not to obstruct the ear canal of the user's ear.

Images