Sound 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] TECHNICAL FIELD This disclosure relates to the field of audio, and in particular to audio output devices.

[0002] [Incorporated by reference] This application claims priority to International Application No. PCT / CN2023 / 083553, filed March 24, 2023, and International Application No. PCT / CN2023 / 083554, filed March 24, 2023, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] When an audio output device outputs sound, most of the sound waves are radiated toward the user's ear canal, and some sound waves are inevitably radiated in other directions (e.g., away from the ear canal), resulting in a certain amount of sound leakage from the audio output device. Therefore, directional propagation of sound waves from the audio output device is extremely important in order to reduce sound leakage from the audio output device. Conventional audio output devices typically achieve directional sound propagation by forming a directional radiation sound field using a dipole consisting of two sound sources with the same amplitude but opposite phase. However, this method only achieves sound wave propagation in a specific direction, and also creates a large sound field intensity in the direction opposite to the specific direction, which means that obvious sound leakage can be heard when there is someone directly in front of or to the side of the listener. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, there is a need to design an audio output device that can maximize the volume in the direction of the listener's ear canal and reduce sound leakage in other directions to provide better listening privacy. [Means for solving the problem]

[0005] An audio output device according to one embodiment of the present specification includes at least one audio driver, and a first cavity and a second cavity acoustically coupled to the at least one audio driver, wherein a first audio hole is formed in the first cavity and a second audio hole is formed in the second cavity, the at least one audio driver radiates audio having a phase difference to the outside via the first audio hole and the second audio hole, and in a target frequency band, the near-field audio radiated from the first audio hole and the near-field audio radiated from the second audio hole have a near-field sound pressure level difference, the near-field sound pressure level difference being less than 6 dB, and the audio radiated from the audio output device to the far field exhibits directivity that can be expressed as the audio radiated from the first audio hole and the second audio hole having a far-field sound pressure level difference of 3 dB or more in at least a pair of opposite directions in the target frequency band.

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

[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 greater than or equal to 6 dB.

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

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

[0010] In some embodiments, 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 radiated from the first acoustic hole and the near-field sound radiated 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 open area of the first acoustic hole to the open area of the second acoustic hole is in the range of 0.5 to 2.

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

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

[0015] In some embodiments, the difference in acoustic loading 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 loads of the first acoustic hole to the second acoustic hole is in the range of 0.5 to 3.5.

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

[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 into the first cavity and the second cavity, respectively.

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

[0020] In some embodiments, the acoustic output device further includes a support structure that is hung on the head or upper body of the user and that positions the acoustic output device in a position that does not block the ear canal of the user's ear.

[0021] An acoustic output device according to one 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, 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 sound radiated into the far field from the acoustic output device 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, 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 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, 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 sound radiated into the far field from the acoustic output device 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, and the range of the ratio of the surface acoustic loads of the first acoustic hole and the second acoustic hole is 0.5 to 3.5.

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

[0024] An acoustic output device according to one 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, 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, the sound radiated into the far field from the acoustic output device in a 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, and 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.

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

[0026] [Figure 1] FIG. 1 is a schematic diagram of an exemplary directional radiation sound field of an acoustic output device according to some embodiments of the present disclosure. [Figure 2A]FIG. 1 is a structural block diagram of an exemplary acoustic output device in accordance with some embodiments of the present disclosure. [Figure 2B] FIG. 10 is a curve diagram of the variation with frequency of near-field sound pressure levels of exemplary first and second acoustic holes in accordance with some embodiments of the present disclosure. [Figure 3A] FIG. 1 is a schematic diagram of a directional radiation sound field of an exemplary acoustic output device according to some embodiments of the present disclosure. [Figure 3B] FIG. 10 is a schematic diagram of a directional radiation sound field of an exemplary acoustic output device according to some further embodiments of the present disclosure. [Figure 3C] FIG. 1 is a schematic diagram of a method for calculating the distance between acoustic centers according to some embodiments herein. [Figure 4] FIG. 1 is a schematic diagram of an exemplary dual source radiation according to some embodiments herein. [Figure 5] 10 is a schematic diagram showing the relationship between the phase difference φ between the first sound source AS1 and the second sound source AS2, the frequency f, and the interval ι, which corresponds to equation (5). FIG. [Figure 6] 1A-1C are schematic diagrams of directional radiation sound fields at different frequencies according to some embodiments herein. [Figure 7A] 1 is a schematic diagram of an exemplary sound-generating unit according to some embodiments of the present disclosure. [Figure 7B] FIG. 10 is a schematic diagram of an exemplary sound-generating unit according to some other embodiments herein. [Figure 7C] FIG. 10 is a schematic diagram of an exemplary sound-generating unit according to some other embodiments herein. [Figure 8] FIG. 10 is a schematic diagram of another example sound-generating unit according to some embodiments herein. [Figure 9] FIG. 10 is a schematic diagram of another example sound-generating unit according to some embodiments herein. [Figure 10A] FIG. 10 is a schematic diagram of another example sound-generating unit according to some embodiments herein. [Figure 10B] FIG. 1 is a schematic diagram of the frequency response of a Helmholtz resonant cavity. [Figure 11]FIG. 2 is an exemplary block diagram of an acoustic generating unit having two acoustic drivers in accordance with some embodiments of the present disclosure. [Figure 12] FIG. 10 is an exemplary block diagram of an acoustic generating unit having two acoustic drivers according to some other embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

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

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

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

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

[0031] FIG. 1 is a schematic diagram of an exemplary directional radiation sound field of an acoustic output device according to some embodiments of the present disclosure.

[0032] Acoustic output devices output sound near the listener's ears, allowing the listener to hear the sound while also radiating the sound to the surrounding environment, resulting in significant sound leakage from the audio output device. To reduce sound leakage from the audio output device and transmit more sound to the listener's ear canal, in some embodiments, the audio output device can use two sound sources (a first sound source AS1 and a second sound source AS2 shown in FIG. 1 ) with the same amplitude but opposite phase to form a dipole 1, which can generate a directional radiation sound field resembling an "8" shape, as shown in FIG. 1 . The directional radiation sound field resembling an "8" shape may include two directions with extremely strong radiation, and the directional radiation sound field resembling an "8" shape may be understood to have two main lobes. To enhance the listener's listening experience, the audio output device can sufficiently amplify the sound propagated to the listener's ear canal by adjusting the positions of the two sound sources so that one main lobe is directed toward the listener's ear canal. At the same time, as can be seen from the schematic diagram of the directional radiation sound field of the dipole 1 in Figure 1, when one main lobe is directed toward 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 when there is another person in front of or to the side of the listener, sound leakage from the audio output device can be clearly heard.

[0033] By adjusting the phase of the sound output from the sound output device, the degree of cancellation in the far field of the sound output from the sound output device can be changed. Therefore, to further reduce sound leakage from the sound output device, an embodiment of the present specification provides an sound output device capable of emitting sounds with a phase difference to the outside. The sound output device may include at least one acoustic driver and a first cavity and a second cavity 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 can radiate sounds with a phase difference to the outside via the first acoustic hole and the second acoustic hole. When the phase difference satisfies a certain condition, the sound output device can maintain a high volume output in a certain direction (e.g., toward the user's ear canal) while suppressing sound leakage output from the sound 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 the two sounds generated by the acoustic output device, the near-field sound radiated from the first acoustic hole and the near-field sound radiated from the second acoustic hole can have a near-field sound pressure level difference of less than 6 dB in the target frequency band, and the sound radiated into the far field from the acoustic output device can exhibit directionality (directivity can be expressed as the sounds 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), thereby making it possible to increase the volume in the direction of the listener's ear canal opening R1 and reduce sound leakage in the direction opposite to the listener's ear canal opening R1 and in other directions, thereby better achieving both openness of the ear canal and privacy for listening.

[0035] FIG. 2A is a structural block diagram of an exemplary acoustic output device according to some embodiments of the present disclosure.

[0036] In some embodiments, the acoustic output device may include at least one acoustic driver. As shown in FIG. 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 each acoustically coupled to the acoustic driver 121. In some embodiments, a first acoustic hole may be formed in the acoustic output device 100 at the position of the first cavity 122, and the acoustic driver 121 may radiate sound (also referred to as a first sound) to the outside through the first acoustic hole via the first cavity 122. Alternatively, a second acoustic hole may be formed in the acoustic output device 100 at the position of the second cavity 123, and the acoustic driver 121 may radiate sound (also referred to as a second sound) to the outside through the second acoustic hole via the second cavity 123.

[0037] Acoustic driver 121 is a device that can convert an electrical signal into an audio signal and output it. Exemplarily, acoustic driver 121 may include a diaphragm and a driving member (e.g., a coil and a magnetic circuit assembly) that can vibrate the diaphragm. In some embodiments, the number of acoustic driver 121 may be one. In this case, acoustic driver 121 may have a front side and a rear side, and may radiate sound from the front side and the rear side to first cavity 122 and second cavity 123, respectively. For example, assuming that the driving member includes a coil and a magnetic circuit assembly, the front side of acoustic driver 121 may be the side of the diaphragm that is far from the driving member (i.e., no driving member is present in front of acoustic driver 121), and the rear side of acoustic driver 121 may be the side of the diaphragm that faces the driving member (i.e., a driving member is present behind acoustic driver 121) or the side of the driving member that is far from the diaphragm. During vibration, sounds with the same amplitude but opposite phases are generated on the front side and the rear side of the diaphragm. By setting the sound transmission path in the sound output device 100, a specific phase difference (e.g., 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 either side of the vibrating membrane, respectively, and the vibrating membrane can radiate sound to the first cavity 122 and the second cavity 123, respectively, when vibrating. The sound radiated from the vibrating membrane to the first cavity 122 may be transmitted to the first acoustic hole along the first sound transmission path and radiated to the outside from the first acoustic hole, and the sound radiated from the vibrating membrane to the second cavity 123 may be transmitted to the second acoustic hole along the second sound transmission path and radiated to the outside from the second acoustic hole. In some embodiments, the acoustic structure of the first cavity 122 and / or the second cavity 123 can be configured to adjust the phase of the first sound and the second sound.

[0038] In some embodiments, the number of acoustic drivers 121 may be two or more. The two acoustic drivers 121 may each be driven by two sets of electrical signals. The two acoustic drivers 121 can radiate sound to the first cavity 122 and the second cavity 123, respectively. In some embodiments, by setting the amplitude and phase of the electrical signals driving the two acoustic drivers 121, 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, and 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 phase of the first sound and the second sound can also be controlled by configuring the acoustic structures 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. The sound in the first cavity 122 may be radiated to the outside through the first acoustic hole, and the sound in the second cavity 123 may be radiated to the outside through the second acoustic hole. In some embodiments, the number of the first acoustic hole and / or the second acoustic hole may be one or more. The number of the acoustic holes may be reasonably set according to actual needs and is not specifically limited in this specification.

[0040] In some embodiments, the acoustic structure in the cavity (first cavity 122, second cavity 123) can change the phase of the sound radiated from the acoustic hole of the cavity. In some embodiments, by installing the acoustic structure in the first cavity 122 and / or the second cavity 123, the phase of the first sound radiated from the acoustic driver 121 through the first acoustic hole and / or the phase of the second sound radiated from the second acoustic hole can be adjusted, thereby adjusting the phase difference between the first sound and the second sound and further improving sound leakage from the audio output device 100. For example, if sounds of opposite phases are generated at the front and rear of the acoustic driver 121, a baffle can be installed in the first cavity 122 and / or the second cavity 123 to vary the acoustic distances the sounds travel through the two cavities, thereby varying the phase changes the first and second sounds experience as they propagate through the cavities. This can adjust the phase difference between the first and second sounds (i.e., the difference between the phase of the first sound at the first acoustic hole and the phase of the second sound at the second acoustic hole). Furthermore, for example, a specific acoustic structure can be installed in the first cavity 122 and / or the second cavity 123 to change the propagation speed of the first and second sounds through the cavities, thereby adjusting the phase difference between the first and second sounds. An exemplary specific acoustic structure may include a low-speed acoustic structure that slows the propagation speed of sound, such as acoustic gauze or an acoustic porous material. Also, for example, the phase difference between the first sound and the second sound can be adjusted by changing the equivalent propagation speed of the first sound and the second sound in the cavity by installing an extended acoustic structure (e.g., an extended cavity) in the first cavity 122 and / or the second cavity 123. Furthermore, for example, the phase difference between the first sound and the second sound can be adjusted by 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 set up the acoustic structure of the first cavity 122 and / or the second cavity 123 to adjust the phase difference between the first sound and the second sound, please refer to other parts of this specification, for example, Figures 7A to 10B and their related descriptions.

[0041] In some embodiments, when the number of acoustic drivers 121 is two, 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 acoustic hole and the near-field sound radiated from the second acoustic hole is close in the target frequency band, the sound radiated into the far field from the acoustic output device 100 can exhibit directionality, so that the radiation field of the sound in the far field has at least one strong directional direction (the sound pressure in the strong directional direction and its nearby directions is sufficiently large), and the radiation intensity in all other directions is relatively small. For example, the near-field sounds radiated from the first cavity 122 and the second cavity 123 have a near-field sound pressure level difference of less than 6 dB, and the sounds radiated from the first cavity 122 and the second cavity 123 have a far-field sound pressure level difference of 3 dB or more in at least a pair of opposite directions (for example, a direction toward the ear canal R1 and a direction away from the ear canal R1 when the user wears the acoustic output device 100). Also, for example, the near-field sounds radiated from the first cavity 122 and the second cavity 123 have a near-field sound pressure level difference of less than 3 dB, and the sounds radiated from the first cavity 122 and the second cavity 123 have a far-field sound pressure level difference of 6 dB or more in at least a pair of opposite directions. As can be seen, the smaller the near-field sound pressure level difference, the more pronounced sound waves with the same amplitude and opposite phase in the far field are canceled out, resulting in a greater effect of reducing sound leakage. Furthermore, the larger the far-field sound pressure level difference, the stronger the directionality of the far-field sound, resulting in less sound leakage in directions away from the ear canal opening (e.g., directions away from the ear canal opening R1) and in other directions, i.e., a greater effect of reducing far-field sound leakage. In some embodiments, when a user wears the audio output device 100, a strong directional direction may be directed toward the user's ear canal opening R1. In this way, when a user wears the audio output device 100, the sound transmitted to the user's ear canal opening R1 can be sufficiently loud, while sound leakage in other directions (e.g., directions away from the ear canal opening) can be reduced, thereby improving the user's listening experience and privacy.

[0043] Note that the phase of the sound radiated from the acoustic holes (including the first and second acoustic holes) described in the examples 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, a position 4 mm in front of the acoustic hole). In some examples, a method for testing the phase difference may be to measure the phase of the sounds radiated from the first and second acoustic holes (the first and second sounds, respectively), and then calculate the phase difference between the first and second sounds. 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 prevent the second acoustic hole (or the first acoustic hole) from interfering with the test. Furthermore, a sound collection device can be placed on a line connecting the first sound hole and the second sound hole, and the first sound can be collected at a position 4 mm away from the first sound hole (or the second sound hole), further preventing the second sound hole (or the first sound hole) from interfering with the test. As a mere example, the dimensions of the baffle may be selected from 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 sound holes (or second sound holes), any one of them may be selected for testing. For example, one first sound hole and one second sound hole located at a specific relative position (e.g., minimum or maximum relative distance) may be selected, and the phase of the sounds emitted by each of them may be tested, and the phase difference may be calculated. Furthermore, audio measurement within a specific frequency band (e.g., 1000 Hz to 8000 Hz) does not necessarily need to be achieved comprehensively; it is sufficient to set multiple (e.g., 20 to 30) frequency sampling points with equal step sizes and whose endpoints are frequency band endpoints, and measure the audio at each sampling point.

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

[0045] The sound generating unit 120 may be used to generate and radiate sound to the outside. In some embodiments, the sound output device 100 may use the support structure 110 to fix the sound generating unit 120 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 may not block the user's ear canal, but may partially or completely cover it. In some embodiments, the projection of the sound generating unit 120 onto the plane of the user's ear may not cover the user's ear canal, thereby allowing the user's ear to remain open. When the user's ear is kept open, the user can not only hear the sound output by the sound generating unit 120 but also pick up sounds from the external environment.

[0046] The support structure 110 may be used to mount the sound generating unit 120. In some embodiments, when a user wears the audio output device 100, the support structure 110 may be hooked around the user's ear, head, or upper body. In some embodiments, the support structure 110 may include an arc structure that fits around the user's ear R2. By way of example only, the arc structure may include, but is not limited to, a hook shape, a C-shape, or the like. When a user wears the audio output device 100, the support structure 110 may be hooked or clamped around the user's ear R2, thereby achieving wearing of the audio output device 100. In some embodiments, the support structure 110 may include an ear-hook structure that fits around the user's head or upper body. When a user wears the audio output device 100, the ear-hook structure may be hooked around the user's ear R2 by the user's head or neck, thereby achieving wearing of the audio output device 100.

[0047] In some embodiments, the support structure 110 may be fabricated from a soft material, a hard material, or the like, or a combination thereof. A soft material is a material having a hardness (e.g., Shore hardness) 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, 30-60D, etc. A hard material is a material having a hardness (e.g., Shore hardness) greater than a second hardness threshold (e.g., 65D, 70D, 80D, 85D, 90D, etc.). The soft material may include, but is not limited to, polyurethanes (PU) (e.g., thermoplastic polyurethanes (TPU)), polycarbonate (PC), polyamides (PA), acrylonitrile butadiene styrene copolymers (ABS), polystyrene (PS), high impact polystyrene (HIPS), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyurethanes (PU), polyethylene (PE), phenolic resins (PF), urea-formaldehyde resins (UF), melamine-formaldehyde resins (MF), silicone rubber, and the like, or combinations thereof.The hard material may include, but is not limited to, poly(ester sulfones) (PES), polyvinylidene chloride (PVDC), polymethyl methacrylate (PMMA), polyether ether ketone (PEEK), or the like, or a combination thereof, or a mixture thereof with a reinforcing agent such as glass fiber or carbon fiber. In some embodiments, the material of the support structure 110 may be selected according to specific circumstances. For example, a soft material can improve the comfort of the audio output device 100 when worn by a user and its fit with the user's ear, while a hard material can improve the strength of the audio output device 100.

[0048] In some embodiments, the acoustic output device 100 may include only the acoustic generating unit 120. For example, when wearing the acoustic output device 100, the acoustic generating unit 120 can be directly locked in a position in the ear cavity so as not to block the ear canal. In this case, the acoustic output device 100 does not need to have a support structure 110 to mount the acoustic generating unit 120.

[0049] In some embodiments of the present specification, the acoustic output device adjusts the phase difference between the two sounds generated by the acoustic generating unit to ensure that there is a small 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 in the target frequency band, and to ensure that the sound radiated from the acoustic output device to the far field exhibits directionality, so that the sounds radiated to the outside by the first acoustic hole and the second acoustic hole are canceled 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 to which the human ear is sensitive. In some embodiments, since the human ear is sensitive within a frequency range of 200 Hz to 5000 Hz, the target frequency band may be 200 Hz to 5000 Hz or a part thereof. For example, in order to reduce sound leakage in the main frequency range of human voices from the sound output device 100, the target frequency band may be 200 Hz to 800 Hz. Furthermore, for example, the target frequency band may be 2000 Hz to 4000 Hz, which is the frequency range to which the human ear is most sensitive. Furthermore, for example, the target frequency band may be 500 Hz to 4000 Hz, 500 Hz to 3000 Hz, 500 Hz to 2000 Hz, 500 Hz to 1000 Hz, 1000 Hz to 4000 Hz, 1500 Hz to 3000 Hz, 1500 Hz to 2000 Hz, etc. In some embodiments, the target frequency band may include a continuous frequency range or may be composed of multiple independent frequency points. For example, the target frequency band may include target frequency points such as 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz, thereby achieving the objective that the sounds at the above frequency points of the acoustic output device 100 all have close near-field sound pressure and exhibit directionality in the far field (e.g., cardioid-type directionality).

[0051] Since the human ear is sensitive to the frequency range of 200Hz to 5000Hz, by setting the target frequency band in this frequency range, far-field sound leakage in this frequency range can be more effectively reduced, thereby meeting actual needs.

[0052] The near-field sound pressure level difference is the difference in sound pressure levels of sounds radiated to near-field positions from each of two or more sound sources formed by the audio output device 100. In the present application, the near-field position of a sound source may be a position within 5 mm of the sound source (e.g., the first acoustic hole or the second acoustic 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 acoustic hole and the sound pressure level at the second acoustic hole of the audio output device 100.

[0053] In some embodiments, a method for testing near-field sound pressure levels may involve measuring the sound pressures of sounds (first sound and second sound, respectively) radiated from a first sound hole and a second sound hole at a specific frequency point (e.g., 1000 Hz), and then calculating the sound pressure level difference between the first sound and the second sound (e.g., taking the common logarithm of the ratio between the measured sound pressure and 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 sound hole (or the second sound hole), a baffle can be used to separate the first sound hole and the second sound hole to prevent the second sound hole (or the first sound hole) from interfering with 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 4 mm away from the first acoustic hole (or the second acoustic hole) and collect the first sound (or the second sound) as sound pressure at the first acoustic hole (or the 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., collection positions) may be located in a pair of opposite directions from the audio output device 100 (e.g., the position 4 cm away from the first acoustic hole is in the direction from the second acoustic hole to the first acoustic hole, and the position 4 cm away from the second acoustic hole is in the direction from the first acoustic hole to the second acoustic hole). Audio collection devices are installed at the two collection positions to collect the sound pressure levels of the audio 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 specific description of the acoustic center, please refer to FIGS. 3A to 3C and the related descriptions.

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

[0057] 2B is a curve diagram illustrating the change in near-field sound pressure level with frequency for the first acoustic hole and the second acoustic hole according to some embodiments of the present specification. As shown in FIG. 2B, the first acoustic hole and the second acoustic hole of the audio output device 100 have almost the same change trend in near-field sound pressure level within the frequency range of 200 Hz to 20 kHz, with the difference being less than 5 dB, indicating that the audio 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 opening area ratio between the first acoustic hole and the second acoustic hole.

[0059] The open area ratio is the ratio of the area S1 of the first acoustic hole to the area S2 of the second acoustic hole, i.e., the open area ratio is S1 / S2. As will be understood, when the number of first acoustic holes (or second acoustic holes) is two or more, the open area ratio is the ratio of the total area of the first acoustic holes (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 ) where n and m are integers greater than 1.

[0060] In some embodiments, the ratio of the opening area of the first acoustic hole to the opening area of 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 area of the first acoustic hole to the opening area of the second acoustic hole may be 0.5 to 2. By controlling the range of the opening area ratio of the first acoustic hole to the second acoustic hole, the opening areas of the first acoustic hole and the second acoustic hole can be made similar, and the acoustic resistances of the first acoustic hole and the second acoustic hole can be made similar, thereby reducing the near-field sound pressure level difference between the first acoustic hole and the second acoustic hole, and further more significantly canceling out far-field sound leakage, improving the effect of reducing far-field sound leakage.

[0061] Furthermore, the ratio of the opening area of the first acoustic hole to the opening area of 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 narrowing the range of the ratio of the opening area of the first acoustic hole to the opening area of 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 loading between the first acoustic hole and the second acoustic hole.

[0063] The acoustic load is the ratio of the sound pressure value P1 after passing through the first acoustic hole (or the second acoustic hole) to the sound pressure value P0 without passing through the first acoustic hole (or the second acoustic hole), i.e., the acoustic load is P1 / P0. Note that for a certain 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 the second acoustic hole) can be determined by measuring the sound pressure value (corresponding to P1) when the first acoustic hole (or the second acoustic hole) is covered with gauze and the sound pressure value (corresponding to P0) when it is not covered with gauze at a specific distance, and calculating the ratio of P1 to P0. Specifically, when testing the sound of the first acoustic hole (or the second acoustic hole), a sound collection device is placed 4 to 5 mm away from the first acoustic hole (or the second acoustic hole), and then the sound pressure value (corresponding to P1) when the first acoustic hole (or the second acoustic hole) is covered with gauze and the sound pressure value (corresponding to P0) when it is not covered with gauze are collected, and finally the acoustic load of the first acoustic hole (or the second acoustic hole) can be calculated. The acoustic load test signal may be a single-frequency signal, or one or more frequency points may be selected therefrom, including, but not limited to, 100 Hz, 200 Hz, 300 Hz, 500 Hz, 1000 Hz, 2000 Hz, 5000 Hz, and the resonant frequency f of the acoustic output device 100. The test signal may also be white noise, pink noise, or a sweep signal. In some embodiments, the measured sound pressure level may first be converted to a sound pressure value and then calculated to obtain the acoustic load. Alternatively, the difference between the sound pressure levels measured before and after the first acoustic hole (or the second acoustic hole) is covered with gauze may be calculated, and the acoustic load value of the first acoustic hole (or the second acoustic hole) may be back-calculated using a logarithmic formula.

[0065] In some embodiments, the difference in acoustic load between the first acoustic hole and the second acoustic hole may include 0.1, 0.15, 0.2, etc. In some embodiments, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be less than 0.15. As will be understood, the smaller the difference in acoustic load between the first acoustic hole and the second acoustic hole, the closer the acoustic resistances of the first acoustic hole and the second acoustic hole will be, thereby reducing the difference in near-field sound pressure levels between the first acoustic hole and the second acoustic hole and resulting in a more significant reduction in far-field sound leakage.

[0066] Furthermore, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be less than 0.1. By further narrowing the range of the difference in acoustic load between the first acoustic hole and the second acoustic hole, the difference in near-field sound pressure level between the first acoustic hole and the second acoustic hole 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 of the audio output device 100 in a frequency range of 200 Hz to 5000 Hz, 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 of the audio output device 100 in a frequency range of 500 Hz to 4000 Hz, 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 of the audio output device 100 in a frequency range of 1000 Hz to 3000 Hz, 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 of the audio output device 100 in a frequency range of 1500 Hz to 2500 Hz, 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 loading of the first acoustic hole to 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 the second acoustic hole) to the sound pressure value P0 that does not pass through the first acoustic hole (or the second acoustic hole) and the area S of the first acoustic hole (or the second acoustic hole), i.e., the surface acoustic load is S × P1 / P0.

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

[0071] Furthermore, the range of the ratio of the surface acoustic loads of the first acoustic hole to the second acoustic hole may be 0.8 to 2. As will be understood, by further narrowing the range of the ratio of the surface acoustic loads of the first acoustic hole to the second acoustic hole, the effect of reducing far-field sound leakage can be made more significant.

[0072] In some embodiments, to reduce far-field sound leakage of the audio output device 100 in a frequency range of 200 Hz to 5000 Hz, the ratio of the surface acoustic loads of the first acoustic hole to the second acoustic hole may be in a range of 0.9 to 1.2. In some embodiments, to reduce far-field sound leakage of the audio output device 100 in a frequency range of 500 Hz to 4000 Hz, the ratio of the surface acoustic loads of the first acoustic hole to the second acoustic hole may be in a range of 0.8 to 1.5. In some embodiments, to reduce far-field sound leakage of the audio output device 100 in a frequency range of 1000 Hz to 3000 Hz, the ratio of the surface acoustic loads of the first acoustic hole to the second acoustic hole may be in a range of 0.7 to 2. In some embodiments, to reduce far-field sound leakage of the audio output device 100 in a frequency range of 1500 Hz to 2500 Hz, the ratio of the surface acoustic loads of the first acoustic hole to the second acoustic hole may be in a range of 0.6 to 2.7. In some embodiments, to reduce far-field sound leakage in the range of 1500 Hz to 2000 Hz of the acoustic output device 100, the ratio of the surface acoustic loads of the first acoustic hole to 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 between the sound pressure levels of sounds radiated in the far field from the first acoustic hole and the second acoustic hole. In the present application, the far field of the first acoustic hole (or the second acoustic hole) may be a position 10 cm or more away from the first acoustic hole (or the second acoustic hole). For ease of understanding, the far-field sound pressure level difference between the first acoustic hole and the second acoustic hole can be expressed as the difference in sound pressure levels at the same or approximately the same distance (or symmetrical positions) from the two holes in the direction of a line connecting the first acoustic hole and the second acoustic hole.

[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 here. The difference is that when measuring the far-field sound pressure level, for example, when collecting sound from the first sound hole (or the second sound hole), the sound collection device may be installed 30 cm away from the first sound hole (or the second sound hole).

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

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

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

[0078] In some embodiments, to reduce far-field sound leakage from the audio output device 100 within a frequency range of 200 Hz to 5000 Hz, the far-field sound pressure level difference may be 12 dB or more, and the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.03. In some embodiments, to reduce far-field sound leakage from the audio output device 100 within a frequency range of 500 Hz to 4000 Hz, the far-field sound pressure level difference may be 10 dB or more, and 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 from the audio output device 100 within a frequency range of 1000 Hz to 3000 Hz, the far-field sound pressure level difference may be 6 dB or more, and 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 from the audio output device 100 within a frequency range of 1500 Hz to 2500 Hz, the far-field sound pressure level difference may be 4 dB or more, and at this time, the difference in acoustic load between the first acoustic hole and the second acoustic hole may be 0 to 0.12. In some embodiments, to reduce far-field sound leakage from the audio output device 100 within a frequency range of 1500 Hz to 2000 Hz, the far-field sound pressure level difference may be 3 dB or more, and at this time, 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, to reduce far-field sound leakage from the audio output device 100 within a frequency range of 200 Hz to 5000 Hz, the far-field sound pressure level difference may be 12 dB or more, and the opening area ratio between the first acoustic hole and the second acoustic hole may be 0.75 to 1.1. In some embodiments, to reduce far-field sound leakage from the audio output device 100 within a frequency range of 500 Hz to 4000 Hz, the far-field sound pressure level difference may be 10 dB or more, and the opening area ratio between the first acoustic hole and the second acoustic hole may be 0.7 to 1.2. In some embodiments, to reduce far-field sound leakage from the audio output device 100 within a frequency range of 1000 Hz to 3000 Hz, the far-field sound pressure level difference may be 6 dB or more, and the opening area ratio between the first acoustic hole and the second acoustic hole may be 0.6 to 1.5. In some embodiments, in order to reduce far-field sound leakage from the audio output device 100 within a frequency range of 1500 Hz to 2500 Hz, the far-field sound pressure level difference may be 4 dB or more, and at this time, the opening area ratio 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 audio output device 100 within a frequency range of 1500 Hz to 2000 Hz, the far-field sound pressure level difference may be 3 dB or more, and at this time, the opening area ratio between the first acoustic hole and the second acoustic hole may be 0.5 to 1.9.

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

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

[0082] 3A and 3B, AS1 and AS2 respectively represent the first and second sound sources formed by the sound generating unit 120 of the sound output device 100. When the first sound generated by the first sound source AS1 and the second sound generated by the second sound source AS2 have a certain phase difference (e.g., 120° to 179°), the first sound source AS1 and the second sound source AS2 can form a strong directional radiation sound field, such as a cardioid directional radiation sound field (as shown in FIG. 3A) or a supercardioid directional radiation sound field (as shown in FIG. 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 located 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 located at the acoustic center of the second acoustic hole.

[0083] The acoustic center of an acoustic hole (e.g., the first acoustic hole or the second acoustic hole) is the equivalent sound emitting position of the acoustic hole, and the equivalent sound emitting position may be determined based on the shape, size, and number of the acoustic hole. When there is one acoustic hole, the acoustic center may be the geometric center of the acoustic hole (e.g., when the acoustic hole has an outer opening and an inner opening in the depth direction and the geometric center of the acoustic hole refers to the centroid of the outer opening). When there are two acoustic holes, the acoustic center may be the midpoint of a line connecting the geometric centers of the two acoustic holes. When there are three acoustic holes, the acoustic center may be the center of a circumscribing circle of the geometric centers of the three acoustic holes, or the acoustic center may be the centroid of a triangle enclosed by lines connecting the geometric centers of the three acoustic holes. When there are four (or more) acoustic holes, the acoustic center may be the centroid of a rectangle (or polygon) enclosed by lines 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. Taking an example in which 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 three sides, and the lengths of the three sides of the 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 (when 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), i.e., 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 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., the geometric center B1 and the 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 the line segment AB3 and the line segment B1B3.

[0090] Based on the formulas (1) to (3), the following estimation and calculation can be performed.

[0091]

number

[0092] As shown in Figures 3A and 3B, the directional radiation sound field of a cardioid type (Figure 3A) or a supercardioid type (Figure 3B) has only one main lobe, and the sound field radiation is strong at and near the main lobe and weak 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 toward the listener's ear canal R1, and in this case, only the radiation toward the ear canal R1 and its vicinity is strong, while the directionality is weak in all other directions, thereby reducing sound leakage from the acoustic output device 100. As can be seen, since the phase differences between the first sound and the second sound in Figures 3A and 3B are different (although both are within a certain range), the radiation sound fields shown in Figures 3A and 3B are also different. Hereinafter, the principle of forming a strong directional radiation sound field (for example, a cardioid or supercardioid directional radiation sound field) when the first sound and the second sound have a specific phase difference will be described.

[0093] FIG. 4 is a schematic diagram of an exemplary dual source radiation according to some embodiments herein.

[0094] As shown in FIG. 4, the first sound source AS1 and the second sound source AS2 can represent two equivalent sound sources consisting of the first and second acoustic holes of the sound generating unit 120 of the sound output device 100, respectively, where 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 included 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 pressures at the first sound source AS1 and the second sound source AS2 are as follows:

[0096]

number

[0097] where A represents the intensity of the point sound 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 condition (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 type directional radiation sound field is required, i.e., when θ=180° is required, the sound pressure amplitude |p| at point P in the far field has a minimum value. Differentiating |p| gives:

[0102]

number

[0103] By solving the above equation (7), the relationship that the phase difference φ between the first sound source AS1 and the second sound source AS2 must satisfy is obtained.

[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-type directional radiation field, the phase difference φ between the two sound sources and kι must satisfy a certain relationship. Because 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] FIG. 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, which corresponds to equation (8), and the frequency f and the interval ι.

[0107] As shown in FIG. 5, the horizontal axis represents frequency f in Hz, and the vertical axis represents the spacing ι between two sound sources in mm. Each curve represents the phase difference φ required under different conditions (i.e., different frequencies f and different spacing ι). Comparing the curves in FIG. 5 reveals that, to achieve a cardioid-type directional radiation sound field, when the spacing ι is the same, the phase difference between the first sound source AS1 and the second sound source AS2 in a given frequency range is negatively correlated with the magnitude of the frequency. 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 size of the spacing between the two sound sources. The larger the spacing, the smaller the required phase difference between the first sound source AS1 and the second sound source AS2; the smaller the spacing, the larger the required phase difference between the first sound source AS1 and the second sound source AS2. Note that in actual measurements, if the phase difference is negatively correlated with the magnitude of multiple consecutive frequencies within a certain frequency range and / or the magnitude of multiple consecutive intervals within a certain dual sound source spacing range, the phase difference is considered to be negatively correlated with the magnitude of the frequency and / or the magnitude of the interval between the two sound sources. As a mere example, multiple (e.g., 5, 10, etc.) frequencies at the same pitch (e.g., every 1 Hz, 10 Hz, 50 Hz, 100 Hz, 200 Hz, etc.) and their corresponding phase differences may be measured. If the multiple frequencies and their corresponding phase differences satisfy a negative correlation, the phase difference is considered to be negatively correlated with the magnitude of the frequency.

[0108] In practical applications, the distance ι is usually constant, and the correspondence relationship between the phase difference φ and kι can be simplified to the correspondence relationship between frequency and phase difference. That is, assuming that the distance ι is constant, if the phase difference and frequency between the first sound source AS1 and the second sound source AS2 satisfy a certain correspondence relationship, a cardioid-type directional radiation sound field can be formed between the first sound source AS1 and the second sound source AS2. For illustrative purposes, when the distance ι shown in the table below is 3 mm, in order for the first sound source AS1 and the second sound source AS2 to form a cardioid-type directional radiation sound field, the correspondence table between the required phase difference φ (which may be understood as the optimal phase difference that can realize a cardioid-type directional radiation sound field) and frequency f may be as follows:

[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-type directional radiation sound field varies at different frequencies. At the same time, as can be seen from the table, the difference between the phase differences φ corresponding to different frequencies is not significant. 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°, with the difference between the two phase differences being only 6°. Therefore, when a certain phase difference φ (e.g., 176°) or a phase difference range (e.g., 120° to 179°) is determined, even if a cardioid-type directional radiation sound field (such as that shown in FIG. 3A) cannot be formed at a certain frequency within a wide frequency band range (e.g., 200 Hz to 2000 Hz), a cardioid-like directional radiation sound field, such as a supercardioid-type directional radiation sound field as shown in FIG. 3B, can be formed.

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

[0112] The sound leakage reduction effect in the far field of the acoustic output device 100 may be affected by the rate of change of the near-field phase difference of the sound emitted from the sound source. The rate of change of the phase difference may be the rate of change of the phase difference between the sound emitted from the first acoustic hole and the sound emitted from the second acoustic hole with frequency. 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 is the interval between two frequencies whose frequency ratio is 2 or 1 / 2 on a frequency response curve. For example, 1000 Hz to 2000 Hz is one octave, 2000 Hz to 4000 Hz is one octave, and 1500 Hz to 3000 Hz is one octave, and 3000 Hz to 6000 Hz is one octave.

[0113] When the rate of change of the near-field phase difference is controlled to exhibit a gradual change trend, distortion of the sound radiated from the acoustic output device to the far field can be avoided, and the two sound sources tend to form a strong directional radiation sound field (e.g., a cardioid or supercardioid directional radiation sound field) within 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 smaller than 30° / octave in the frequency range of 1000 Hz to 8000 Hz.

[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 1000 Hz to 8000 Hz. By further controlling the rate of change of the near-field phase difference, the two sound sources can form a stronger standard directional radiation sound field (e.g., a cardioid or supercardioid directional radiation sound field), and sound leakage in the direction opposite to the ear canal and in other directions can be reduced, thereby better achieving both openness of the ear canal and privacy for listening.

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

[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 radiated from the first acoustic hole and the sound radiated from the second acoustic hole may be smaller than 30°. For example, the phase difference at 1000 Hz between the sound radiated from the first acoustic hole and the sound radiated from the second acoustic hole is 159° to 178°, and the phase difference at 2000 Hz between the sound radiated from the first acoustic hole and the sound radiated from the second acoustic hole is 149° to 176°, and 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 radiated from the first acoustic hole and the sound radiated from the second acoustic hole is 2° to 29°, which is smaller than 30°. Since the frequency range of 1000Hz to 2000Hz is within the frequency range to which the human ear is sensitive, the effect of reducing far-field sound leakage can be further improved by controlling the absolute value of the difference between the phase difference at 1000Hz and the phase difference at 2000Hz between the sound radiated from the first acoustic hole and the sound radiated from the second acoustic hole to within 30° in this frequency range.

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

[0118] FIG. 7A is a schematic diagram of an exemplary sound-generating unit according to some embodiments of the present disclosure, FIG. 7B is a schematic diagram of an exemplary sound-generating unit according to some other embodiments of the present disclosure, and FIG. 7C is a schematic diagram of an exemplary sound-generating unit according to some other embodiments of the present disclosure.

[0119] 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 the at least one acoustic driver. In some embodiments, the at least one acoustic driver 721 may include a vibrating membrane, having a front side and a rear side separated by the vibrating membrane, and radiating sound from the front side to the first cavity 722 and the second cavity 723, respectively. In some embodiments, the at least one acoustic driver 721 may include two acoustic drivers (i.e., the acoustic driver 721 in FIG. 7A may be replaced with two parallel acoustic drivers), and the two acoustic drivers are driven by two sets of electrical signals to radiate sound to the first cavity 722 and the second cavity 723, respectively. The sound in the first cavity 722 may be radiated to the outside by the first acoustic hole 724, i.e., 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 by the second acoustic hole 725, i.e., 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 radiated from the first acoustic hole 724 and the second sound V2 radiated from the second acoustic hole 725 needs to be within a specific range (e.g., 120° to 179°) so that the sound radiated into the far field from the sound generating unit 700 can exhibit strong directionality (e.g., cardioid or supercardioid) within a target frequency band (e.g., 200 Hz to 5000 Hz). Since the initial value of the phase difference between the two sound waves radiated from the acoustic driver 721 to the first cavity 722 and the second cavity 723, respectively, is 180°, the acoustic structures within the first cavity 722 and / or the second cavity 723 can be set so 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 disposed 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 a first acoustic distance over which the first sound V1 propagates in the first cavity 722 and a second acoustic distance over which the second sound V2 propagates in the second cavity 723. In this embodiment, the acoustic structure 726 is described as being installed in the second cavity 723 as an example, but it will be understood that 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 FIG. 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 are installed on the second inner wall 7232 (the second inner wall 7232 is installed opposite the first inner wall 7231), with the free ends of the baffles on the two inner walls facing each other. In this case, a gap is formed between the free ends of the two baffles, allowing sound to bypass the baffle and pass through the gap to the second acoustic hole 725. In some embodiments, the number and / or positions of the baffles in the second cavity 723 may be different. 7B, a baffle may be installed on only one inner wall (e.g., second inner wall 7232) of second cavity 723, with one end of the baffle connected to second inner wall 7232 and the free end of the baffle extending near first inner wall 7231 (a gap is formed between the free end of the baffle and first inner wall 7231), allowing sound to bypass the baffle and be transmitted through the gap between the free end of the baffle and first inner wall 7231 to second acoustic hole 725. Alternatively, for example, as shown in FIG. 7C, both ends of the baffle may be connected to first inner wall 7231 and second inner wall 7232, respectively, and in this case, an opening may be formed in the baffle, allowing sound to bypass the baffle and be transmitted through the opening to second acoustic hole 725. In the process of sound bypassing the baffle and being transmitted to the second acoustic hole 725, the distance the sound travels (i.e., acoustic distance) changes compared to when no baffle is installed. Sound waves emitted from the front side of the acoustic driver 721 are radiated to the outside from the first acoustic hole 724 by the first cavity 722, and the distance the sound waves travel is a first acoustic distance L1. Sound waves emitted from the rear side of the acoustic driver 721 are radiated to the outside from the second acoustic hole 725 by the second cavity 723 and the acoustic structure 726, and the distance the sound waves travel is a second acoustic distance L2, and there is an acoustic distance difference between the first acoustic distance L1 and the second acoustic distance L2.

[0122] The time delay 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 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 set 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 into the far field from the sound generating unit 700 can exhibit strong directivity (for example, cardioid or supercardioid).

[0127] As can be understood, the number, position, size, installation method, etc. of the baffles can affect the second acoustic distance L2 that the sound waves pass through the second cavity 723, and thereby affect the phase difference between the first sound V1 and the second sound V2. Therefore, the number, position, size, installation method, etc. of the baffles can be reasonably 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 generation 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 generation 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 air in the micropores, 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, an example is taken of the low-speed acoustic structure 826 being installed in the second cavity 823. As shown in FIG. 8, the low-speed acoustic structure 826 may be installed in the second cavity 823, and the sound waves emitted from the front side of the acoustic driver 821 are radiated to the outside through the first acoustic hole 824, and the distance traveled by the sound waves is the first acoustic distance L1. The sound waves emitted from the rear side of the acoustic driver 821 are radiated to the outside through the second acoustic hole 825, and the distance traveled by the sound waves may include the second acoustic distance L2 propagated by the air and the third acoustic distance L3 propagated by the low-speed acoustic structure 826.

[0132] The time delay difference 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 given as follows:

[0135]

number

[0136] As can be seen from this, by controlling the equivalent sound speed at which sound waves propagate within the low-speed acoustic structure 826 and / or the third acoustic distance L3 (for example, the ratio of the equivalent sound speed in the low-speed acoustic structure to the normal sound speed can be set within 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 into the far field from the sound generating unit 800 can exhibit strong directionality (for example, cardioid or supercardioid).

[0137] Furthermore, in this embodiment, when other parameters (e.g., equivalent sound speed, first acoustic distance, second acoustic distance, third acoustic distance) are the same, it can be seen that the phase difference between the first sound V1 and the second sound V2 has a negative correlation 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] FIG. 9 is a schematic diagram of another example sound-generating unit according to some embodiments herein.

[0139] As shown in Fig. 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., expand) the cross-sectional area at different positions in the sound transmission path of the first cavity 922 or the second cavity 923. When a sound wave propagates in 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 positions in the sound wave transmission path, the sound wave will be reflected at the position where the cross-sectional area suddenly changes, which means that the equivalent impedance of the medium will change. Accordingly, parameters related to the equivalent impedance (e.g., equivalent sound speed, equivalent density, etc.) will also change correspondingly, thereby changing the phase of the sound wave. For example, the effect of the extended acoustic structure 926 on the equivalent sound speed change is mainly related to the ratio of the cross-sectional area of the second cavity 923 after being extended by the extended acoustic structure 926 to the original cross-sectional area of the second cavity 923. In some embodiments, the actual equivalent sound speed can be obtained by means such as simulation or experimental testing.

[0140] In this embodiment, the extended acoustic structure 926 is installed in the second cavity 923 as an example. As shown in FIG. 9 , the extended acoustic structure 926 may be installed on two opposing side walls of the second cavity 923, and the extended acoustic structure 926 causes a sudden 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 extended acoustic structure 926 may be an extended cavity. The structural shape of the extended cavity may be rectangular as shown in FIG. 9 . In other embodiments, the cross-sectional area of the extended acoustic structure 926 may have other shapes, such as a triangle or a trapezoid. The structural shape of the extended cavity may be reasonably set based on the phase difference between the first sound V1 and the second sound V2.

[0141] 9, sound waves emitted from the front side of acoustic driver 921 are radiated to the outside through first acoustic hole 924, and the distance traveled by the sound waves is a first acoustic distance L1. Sound waves emitted from the rear side of acoustic driver 921 are radiated to the outside through second acoustic hole 925 by extended acoustic structure 926 and second cavity 923, and the distance traveled by the sound waves is a second acoustic distance L2. Here, the sound speed at first acoustic distance L1 is the normal sound speed c, and the sound speed at second acoustic distance L2 is the equivalent sound speed c'. The time delay difference between the first sound V1 radiated from first acoustic hole 924 and the second sound radiated from second acoustic hole 925 is given by:

[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 given as follows:

[0144]

number

[0145] As can be seen from this, by installing the extended acoustic structure 926 in 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, and by setting the phase difference between the first sound V1 and the second sound V2 to 120° to 179°, the sound radiated into the far field from the sound generating unit 900 can exhibit strong directionality (for example, cardioid or supercardioid).

[0146] Furthermore, in this embodiment, when other parameters (e.g., the first acoustic distance, the second acoustic distance, and the equivalent sound speed) are the same, it can be seen that the phase difference between the first sound V1 and the second sound V2 has a negative correlation with the 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] FIG. 10A is a schematic diagram of another example sound-generating unit according to some embodiments herein.

[0148] The structure of the sound generating unit 1000 shown in Fig. 10A is similar to the structure of the sound generating unit 700 shown in Fig. 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 description of Fig. 7A. The sound generating unit 1000 and the sound generating unit 700 differ in their acoustic structures. As shown in FIG. 10A , an acoustic absorbing structure 1026 may be disposed within the first cavity 1022 and / or the second cavity 1023 of the sound-generating unit 1000. In some embodiments, the acoustic absorbing structure 1026 may have a resonant frequency. The actual output phase difference between the two sound waves can be controlled by modulating (e.g., phase modulating) the sound near the resonant frequency of the acoustic absorbing structure 1026. In some embodiments, the acoustic absorbing structure 1026 may be a Helmholtz resonator cavity. In some embodiments, the acoustic absorbing structure 1026 may be a micro-perforated plate resonator. In some embodiments, the acoustic absorbing structure 1026 may be a quarter-wave tube resonator.

[0149] In this embodiment, the sound absorbing structure 1026 is installed in the second cavity 1023 as an example, and 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] where M represents the acoustic mass (mainly related to the nozzle parameters of the Helmholtz resonator) and C represents the acoustic capacitance (mainly related to the cavity parameters at the rear end of the Helmholtz resonator).

[0152] FIG. 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). 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 FIG. 10B, when the resonant frequency f0 of the Helmholtz resonator cavity is 2000 Hz, the amplitude response exhibits a resonant peak at 2000 Hz. As for the phase response, as the frequency increases around 2000 Hz, the phase gradually changes from 180° and finally approaches 0°. As can be seen from this, in the low frequency range (e.g., between 40 Hz and 1000 Hz), the phase difference varies within a range of 179° to 150°, which basically satisfies the phase difference requirement necessary to realize 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 radiated from the acoustic hole corresponding to the cavity, the actual output phase difference between the first sound and the second sound can be controlled, and the sound radiated into the far field from the sound generating unit 900 can exhibit strong directionality (e.g., cardioid or supercardioid).

[0154] In some embodiments, when at least one acoustic driver of the sound generating 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 methods shown in Figures 7A to 10A. In such an adjustment method, the phase difference between the sounds radiated from the acoustic driver to the first cavity and the second cavity may be 180°, and the adjustment of the phase difference between the first sound V1 and the second sound V2 is achieved by changing the phase of the first sound V1 or the second sound V2 by installing different types of acoustic structures (e.g., baffles, low-speed acoustic structures, expansion acoustic structures, sound-absorbing structures) in the cavities. 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 electrical drive signals corresponding to the two acoustic drivers. In some embodiments, the phases of the two electrical drive signals may be set such that the phase of the sound radiated from one acoustic driver into a first cavity is not completely opposite to the phase of the sound radiated from the other acoustic driver into a second cavity.

[0155] FIG. 11 is an exemplary block diagram of an acoustic generating unit having two acoustic drivers according to some embodiments of the present specification, and FIG. 12 is an exemplary block diagram of an acoustic generating unit having two acoustic drivers according to some other embodiments of the present specification.

[0156] 11, the sound generating unit 1100 may include a first acoustic driver 1121A, a second acoustic driver 1121B, a first cavity 1122, and a second cavity 1123. A first acoustic hole 1124 may be formed in the first cavity 1122, and the first acoustic driver 1121A can radiate a first sound V1 to the outside through the first cavity 1122 and the first acoustic hole 1124. A second acoustic hole 1125 is formed in the second cavity 1123, and the second acoustic driver 1121B can radiate a second sound V2 to the outside through the second cavity 1123 and the second acoustic hole 1125. In some embodiments, the first acoustic driver 1121A and the second acoustic driver 1121B may be driven by two sets of electric signals, and by making the phases of the two sets of electric drive signals 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 Fig. 11, the phase difference between the electric drive signal driving the first acoustic driver 1121A and the electric drive signal driving the second acoustic driver 1121B can be set to 120° to 179°. In this setting method, no other acoustic structure is required to be installed in the first cavity 1122 and the second cavity 1123, and the acoustic distances that the sounds propagate within each cavity are approximately the same, thereby achieving a phase difference between the first sound V1 and the second sound V2 of 120° to 179°. Furthermore, for example, as shown in FIG. 12, 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 so as not to be between 120° and 179°. In such a setting method, by installing an acoustic structure in the first cavity 1122 and / or the second cavity 1123 (for example, by installing a low-speed acoustic structure 1126 in the second cavity 1123 as shown in FIG. 12), the phase difference between the first sound V1 and the second sound V2 can be set to be between 120° and 179°.

[0157] Beneficial effects that can be achieved by the acoustic output device 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 acoustic generating unit, the near-field sound pressure level difference between the first acoustic hole and the second acoustic hole is reduced and the far-field sound pressure level difference is increased, thereby allowing the sound radiated into the far field from the acoustic output device to exhibit stronger directionality in the target frequency band, thereby maximizing the volume in the direction of the listener's ear canal opening when the listener wears the acoustic output device and reducing sound leakage in the direction opposite the listener's ear canal opening and in other directions, thereby better achieving both openness of the ear canal and listening privacy. (2) By installing multiple types of acoustic structures (e.g., baffles, low-speed acoustic structures, extended acoustic structures, sound-absorbing structures) in the acoustic generating unit of the acoustic output device to adjust the phase difference between two sounds generated by the acoustic generating unit, the phase difference can be adjusted more flexibly and accurately, thereby improving the practicality of the acoustic output device. (3) When at least one acoustic driver in the sound generating unit includes two acoustic drivers, the two electric driving signals can be directly controlled to realize the control of the phase difference between the two sounds, which can simplify the structure of the sound output device and reduce the cost.

[0158] Although the basic concepts have been described above, it will be apparent to those skilled in the art that the detailed disclosure above is merely provided by way of example and is not intended to limit the present specification. Although not expressly described herein, those skilled in the art may make various changes, improvements, and modifications to the present specification. These changes, improvements, and modifications are intended to be suggested by the present specification and are therefore within the spirit and scope of the exemplary embodiments of the present specification. [Explanation of symbols]

[0159] 100 Sound output device 120, 700, 800, 900, 1000, 1100 Sound generating 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 hole 725, 825, 925, 1025, 1125 Second acoustic hole 1026 Sound-absorbing structure 110 Support structure R1 auditory canal opening R2 Auricle AS1 first sound source AS2 second sound source

Claims

1. An audio output device, comprising: at least one acoustic driver; 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, a second acoustic hole is formed in the second cavity, and the at least one acoustic driver radiates sounds having a phase difference to the outside through the first acoustic hole and the second acoustic hole; an acoustic output device in which, 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 smaller than 6 dB, and the sound radiated into the far field from the acoustic output device in the target frequency band exhibits directivity that can be expressed as the sounds 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.

2. The sound 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 smaller than 3 dB and / or the far-field sound pressure level difference is 6 dB or greater.

4. 2. The sound output device according to claim 1, wherein the rate of change of the phase difference is smaller than 30° / oct in a frequency range of 1 kHz to 8 kHz.

5. 2. The sound output device according to claim 1, wherein the rate of change of the phase difference is smaller than 20° / oct in a frequency range of 1 kHz to 8 kHz.

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

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

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

9. 9. The sound output device according to claim 8, wherein a ratio of the open area of the first sound hole to the open area of the second sound hole is in a range of 0.8 to 1.

25.

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

15.

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

1.

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

5.

13. 13. The acoustic output device according to claim 12, wherein a ratio of the surface acoustic loads of the first acoustic hole and the second acoustic hole is in a range of 0.8 to 2.

14. 2. 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 vibrating membrane, and radiates sound from the front side and the rear side into the first cavity and the second cavity, respectively.

15. The acoustic output device of claim 1 , wherein the at least one acoustic driver includes two acoustic drivers, the two acoustic drivers radiating sound into the first cavity and the second cavity, respectively.

16. The sound output device according to claim 1 , further comprising a support structure that is hung on the head or upper body of a user and that mounts the sound output device in a position that does not block the ear canal of the user's ear.

17. An audio output device, comprising: at least one acoustic driver; 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, a second acoustic hole is formed in the second cavity, and the at least one acoustic driver radiates sounds 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 into the far field from the acoustic output device exhibits directivity that can be expressed as a far-field sound pressure level difference of 3 dB or more between the sounds radiated from the first acoustic hole and the second acoustic hole in at least a pair of opposite directions, An acoustic output device, wherein a difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.

15.

18. An audio output device, comprising: at least one acoustic driver; 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, a second acoustic hole is formed in the second cavity, and the at least one acoustic driver radiates sounds 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 into the far field from the acoustic output device exhibits directivity that can be expressed as a far-field sound pressure level difference of 3 dB or more between the sounds radiated from the first acoustic hole and the second acoustic hole in at least a pair of opposite directions, An acoustic output device, wherein the ratio of the surface acoustic loads of the first acoustic hole to the second acoustic hole is in the range of 0.5 to 3.

5.

19. An audio output device, comprising: at least one acoustic driver; 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, 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, and a rate of change of the phase difference is smaller than 30° / oct in a frequency range of 1 kHz to 8 kHz; an acoustic output device in which, in a target frequency band, sound radiated into the far field from the acoustic output device exhibits directivity that can be expressed as a far-field sound pressure level difference of 3 dB or more between sounds radiated from the first acoustic hole and the second acoustic hole in at least a pair of opposite directions.

20. An audio output device, comprising: at least one acoustic driver; 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, a second acoustic hole is formed in the second cavity, and the at least one acoustic driver radiates sounds 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 into the far field from the acoustic output device exhibits directivity that can be expressed as a far-field sound pressure level difference of 3 dB or more between the sounds radiated from the first acoustic hole and the second acoustic hole in at least a pair of opposite directions, An acoustic output device, wherein the ratio of the open area of the first acoustic hole to the open area of the second acoustic hole is in the range of 0.5 to 2.

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