Acoustic output device

Abstract

The embodiment of the invention provides at least one acoustic driver, a first cavity and a second cavity which are acoustically coupled with the at least one acoustic driver, the first cavity is provided with a first acoustic hole, and the second cavity is provided with a second acoustic hole. The at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, in the 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 is smaller than 6dB, and in the 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 smaller than 6dB. The sound radiated to the far field by the acoustic output device shows directivity, and the sound radiated from the first acoustic hole and the second acoustic hole has far-field sound pressure level difference which is not less than 3dB in at least one pair of opposite directions.

Description

Acoustic output device

[0001] Cross-references

[0002] This application claims priority to international application No. PCT / CN2023 / 083553, filed on March 24, 2023, and priority to international application No. PCT / CN2023 / 083554, filed on March 24, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This specification relates to the field of acoustics, and in particular to an acoustic output device. Background Art

[0004] In the process of sound output by the acoustic output device, most of the sound waves are radiated toward the user's ear canal opening. At the same time, it is inevitable that some sound waves will be radiated in other directions (for example, away from the ear canal opening), which will cause a certain amount of sound leakage in the acoustic output device. Therefore, in order to reduce the sound leakage of the acoustic output device, the directional propagation of sound waves of the acoustic output device is of great significance. Existing acoustic output devices usually use a dipole composed of two sound sources with the same amplitude and opposite phase to form a directional radiation sound field, thereby realizing the directional propagation of sound. However, in this way, while realizing the propagation of sound waves in a specific direction, a larger sound field intensity will also be formed in the opposite direction of the specific direction, which means that when someone is located directly in front of or to the side of the listener, obvious sound leakage can also be heard.

[0005] Therefore, it is necessary to design an acoustic output device so that the volume is maximized in the direction of the listener's ear canal opening while minimizing sound leakage in other directions, thereby better achieving listening privacy.

[0006] Summary of the Invention

[0007] One of the embodiments of the present specification provides an acoustic output device, the 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 being opened in the first cavity, and a second acoustic hole being opened in the second cavity, the at least one acoustic driver radiating sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, wherein, within 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, and the near-field sound pressure level difference is less than 6 dB, and, within the target frequency band, the sound radiated to the far field by the acoustic output device exhibits directionality, as manifested in that the sound radiated from the first acoustic hole and the second acoustic hole have a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions.

[0008] In some embodiments, the target frequency band is 200 Hz-5000 Hz.

[0009] 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 not less than 6 dB.

[0010] In some embodiments, within a frequency range of 1 kHz to 8 kHz, the rate of change of the phase difference is less than 30° / oct.

[0011] In some embodiments, within the frequency range of 1 kHz-8 kHz, the rate of change of the phase difference is less than 20° / oct.

[0012] In some embodiments, 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 less than 30°.

[0013] In some embodiments, the target frequency band includes target frequencies of 500 Hz, 1 kHz, 2 kHz, and 4 kHz.

[0014] In some embodiments, a ratio of an opening area of ​​the first acoustic hole to an opening area of ​​the second acoustic hole ranges from 0.5 to 2.

[0015] In some embodiments, a ratio of an opening area of ​​the first acoustic hole to an opening area of ​​the second acoustic hole ranges from 0.8 to 1.25.

[0016] In some embodiments, a difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.15.

[0017] In some embodiments, a difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.1.

[0018] In some embodiments, a ratio of the surface acoustic loads of the first acoustic hole to the surface acoustic loads of the second acoustic hole ranges from 0.5 to 3.5.

[0019] In some embodiments, a ratio of surface acoustic loads of the first acoustic hole to surface acoustic loads of the second acoustic hole ranges from 0.8 to 2.

[0020] In some embodiments, the at least one acoustic driver has a front side and a rear side distinguished by a diaphragm, and radiates sound into the first cavity and the second cavity through the front side and the rear side, respectively.

[0021] 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.

[0022] In some embodiments, the acoustic output device further comprises: a support structure for being mounted on the head or upper torso of a user, and for allowing the acoustic output device to be worn on the user's ear without blocking the ear canal.

[0023] One embodiment of the present specification provides an acoustic 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 being defined in the first cavity, and a second acoustic hole being defined in the second cavity, wherein the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, wherein, within a target frequency band, the sound radiated to the far field by the acoustic output device exhibits directionality, as manifested in that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions, and the difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.15.

[0024] One embodiment of the present specification provides an acoustic 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 being provided in the first cavity, and a second acoustic hole being provided in the second cavity, the at least one acoustic driver radiating sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, wherein, within a target frequency band, the sound radiated to the far field by the acoustic output device exhibits directionality, as manifested in that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions, and the ratio of the surface acoustic load of the first acoustic hole to that of the second acoustic hole is in a range of 0.5-3.5.

[0025] One embodiment of the present specification provides an acoustic 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 being provided in the first cavity, and a second acoustic hole being provided in the second cavity, wherein the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, wherein the rate of change of the phase difference is less than 30° / oct within a frequency range of 1 kHz to 8 kHz, and wherein, within a target frequency band, the sound radiated to the far field by the acoustic output device exhibits directionality, such that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions.

[0026] One embodiment of the present specification provides an acoustic 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 being provided in the first cavity, and a second acoustic hole being provided in the second cavity, the at least one acoustic driver radiating sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, wherein, within a target frequency band, the sound radiated to the far field by the acoustic output device exhibits directionality, as manifested in that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions, and the ratio of the opening area of ​​the first acoustic hole to that of the second acoustic hole is in a range of 0.5-2. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present application will be further described in the form of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, and in these embodiments, like numbers represent like structures, wherein:

[0028] FIG1 is a schematic diagram of an exemplary directional radiation sound field of an acoustic output device according to some embodiments of this specification;

[0029] FIG2A is a structural block diagram of an exemplary acoustic output device according to some embodiments of the present specification;

[0030] FIG2B is a graph showing how the near-field sound pressure levels of the first acoustic hole and the second acoustic hole vary with frequency according to some embodiments of the present specification;

[0031] FIG3A is a schematic diagram of a directional radiation sound field of an exemplary acoustic output device according to some embodiments of this specification;

[0032] FIG3B is a schematic diagram of a directional radiation sound field of an exemplary acoustic output device according to other embodiments of this specification;

[0033] FIG3C is a schematic diagram of a method for calculating the distance between acoustic centers according to some embodiments of this specification;

[0034] FIG4 is a schematic diagram of exemplary dual-sound source radiation according to some embodiments of this specification;

[0035] Figure 5 shows the phase difference between the first sound source AS1 and the second sound source AS2 corresponding to formula (5) Schematic diagram of the relationship between frequency f and spacing l;

[0036] FIG6 is a schematic diagram of directional radiation sound fields at different frequencies according to some embodiments of this specification;

[0037] FIG7A is a schematic diagram of an exemplary sound-producing part according to some embodiments of the present specification;

[0038] FIG7B is a schematic diagram of an exemplary sound-producing part according to other embodiments of the present specification;

[0039] FIG7C is a schematic diagram of an exemplary sound-producing part according to other embodiments of this specification;

[0040] FIG8 is a schematic diagram of another exemplary sound-producing part according to some embodiments of this specification;

[0041] FIG9 is a schematic diagram of another exemplary sound-producing part according to some embodiments of this specification;

[0042] FIG10A is a schematic diagram of another exemplary sound-producing part according to some embodiments of the present specification;

[0043] FIG10B is a schematic diagram of the frequency response of the Helmholtz resonant cavity;

[0044] FIG11 is an exemplary structural diagram of a sound-emitting portion having two acoustic drivers according to some embodiments of the present specification;

[0045] FIG. 12 is an exemplary structural diagram of a sound-emitting part having two acoustic drivers according to other embodiments of the present specification. DETAILED DESCRIPTION

[0046] To more clearly illustrate the technical solutions of the embodiments of this application, the following is a brief introduction to the drawings required for describing the embodiments. Obviously, the drawings described below are merely examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without inventive effort. Unless otherwise apparent from the context or otherwise noted, the same reference numerals in the figures represent the same structure or operation.

[0047] It should be understood that the terms "system," "device," "unit," and / or "module" used herein are a method for distinguishing different components, elements, parts, portions, or assemblies at different levels. However, if other terms can achieve the same purpose, the terms may be replaced by other expressions.

[0048] As used in this application and the claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not intended to refer to the singular but may include the plural. Generally speaking, the terms "comprises" and "include" only indicate the inclusion of the steps and elements specifically identified, and these steps and elements do not constitute an exclusive list. A method or apparatus may also include other steps or elements.

[0049] Flowcharts are used in this application to illustrate the operations performed by the systems according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps may be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0050] FIG1 is a schematic diagram of an exemplary directional radiation sound field of an acoustic output device according to some embodiments of the present specification.

[0051] The acoustic output device outputs sound near the listener's ear, so that the listener hears the sound while also radiating the sound to the surrounding environment, which causes a large degree of sound leakage in the acoustic output device. In order to reduce the sound leakage of the acoustic output device and enable more sound to be transmitted to the listener's ear canal opening, in some embodiments, the acoustic output device can use two sound sources with equal amplitudes and opposite phases (the first sound source AS1 and the second sound source AS2 as shown in Figure 1) to form a dipole 1, and the dipole 1 can form a directional radiation sound field similar to the shape of "8" as shown in Figure 1. The directional radiation sound field similar to the shape of "8" can include two directions of extremely strong radiation, and it can also be understood that the directional radiation sound field similar to the shape of "8" has two main lobes. In order to improve the listening effect of the listener, the positions of the two sound sources can be adjusted so that one main lobe points to the listener's ear canal opening, so that the sound transmitted by the acoustic output device to the listener's ear canal opening is large enough. At the same time, as can be seen from the schematic diagram of the directional radiation sound field of dipole 1 in Figure 1, when one main lobe points toward the listener's ear canal opening R1, the other main lobe usually points directly in front of or to the side of the listener. This means that even other people in front of or to the side of the listener can clearly hear the sound leakage from the acoustic output device.

[0052] Since the degree of cancellation of the sound output by the acoustic output device in the far field can be changed by adjusting the phase of the sound output by the acoustic output device, in order to further reduce the sound leakage of the acoustic output device, an embodiment of the present specification provides an acoustic output device that can radiate sound with a phase difference to the outside world. The acoustic 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. The first cavity is provided with a first acoustic hole, and the second cavity is provided with a second acoustic hole. The at least one acoustic driver can radiate sound with a phase difference to the outside world through the first acoustic hole and the second acoustic hole. Moreover, when the phase difference meets certain conditions, the acoustic output device can maintain a high volume in a certain direction (for example, the direction of the user's ear canal) while suppressing sound leakage output by the acoustic output device in the opposite direction. In some embodiments, the phase difference can be between 120° and 179°. In some embodiments, the phase difference can be between 90° and 179°.

[0053] In some embodiments, by regulating 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 within the target frequency band, and the sound radiated to the far field by the acoustic output device within the target frequency band is directionally (the directionality can be manifested as the sound radiated from the first acoustic hole and the second acoustic hole having a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions), thereby making the volume in the direction of the listener's ear canal opening R1 larger, and the sound leakage in the opposite direction of the listener's ear canal opening R1 and the sound leakage in other directions smaller, thereby better balancing the openness of the ear canal and the privacy of listening.

[0054] FIG2A is a block diagram of an exemplary acoustic output device according to some embodiments of the present specification.

[0055] In some embodiments, the acoustic output device may include at least one acoustic driver. As shown in FIG2A , the acoustic output device 100 may include an acoustic driver 121, a first cavity 122, and a second cavity 123. The first cavity 122 and the second cavity 123 are acoustically coupled to the acoustic driver 121, respectively. In some embodiments, a first acoustic hole may be provided at the location of the first cavity 122 in the acoustic output device 100, and the acoustic driver 121 may radiate sound (also referred to as a first sound) from the first acoustic hole through the first cavity 122 to the outside world; a second acoustic hole may be provided at the location of the second cavity 123 in the acoustic output device 100, and the acoustic driver 121 may radiate sound (also referred to as a second sound) from the second acoustic hole through the second cavity 123 to the outside world.

[0056] The acoustic driver 121 refers to a device that can convert an electrical signal into a sound signal and output it. For example, the acoustic driver 121 may have a diaphragm and a driving member (such as a coil and a magnetic circuit assembly) that can drive the diaphragm to vibrate. In some embodiments, the number of acoustic drivers 121 may be one. At this time, the acoustic driver 121 may have a front side and a rear side, and radiate sound to the first cavity 122 and the second cavity 123 from the front side and the rear side respectively. For example, taking the driving member including a coil and a magnetic circuit assembly as an example, the front side of the acoustic driver 121 may be the side of the diaphragm away from the driving member (that is, there is no driving member on the front side of the acoustic driver 121), and the rear side of the acoustic driver 121 may be the side of the diaphragm facing the driving member (that is, there is a driving member on the rear side of the acoustic driver 121) or the side of the driving member away from the diaphragm. When vibrating, the front side and the rear side bounded by the diaphragm will produce sounds with the same amplitude and opposite phases. By setting the sound transmission path of the sound in the acoustic output device 100, a specific phase difference (for example, a phase difference of 120°-179°) can be achieved 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 respectively located on either side of the diaphragm, and when the diaphragm vibrates, it can radiate sound into the first cavity 122 and the second cavity 123, respectively. The sound radiated by the diaphragm into the first cavity 122 can be transmitted to the first acoustic hole according to the first sound transmission path and radiated outward from the first acoustic hole; the sound radiated by the diaphragm into the second cavity 123 can be transmitted to the second acoustic hole according to the second sound transmission path and radiated outward from the second acoustic hole. In some embodiments, the phase of the first sound and the second sound can be controlled by setting the acoustic structure of the first cavity 122 and / or the second cavity 123.

[0057] In some embodiments, the number of acoustic drivers 121 may be two or more. The two acoustic drivers 121 may be driven by two sets of electrical signals, respectively. The two acoustic drivers 121 may radiate sound to the first cavity 122 and the second cavity 123, respectively. In some embodiments, the amplitude and phase of the electrical signals driving the two acoustic drivers 121 may be set to control the amplitude and phase of the sound radiated by the two acoustic drivers 121 to the first cavity 122 and the second cavity 123, thereby controlling the amplitude and phase of the first sound radiated from the first acoustic hole through the first cavity 122, and the amplitude and phase of the second sound radiated from the second acoustic hole through the second cavity 123. In some embodiments, the phase of the first sound and the second sound may also be controlled by setting the acoustic structure of the first cavity 122 and / or the second cavity 123.

[0058] The first cavity 122 and the second cavity 123 can be cavities acoustically coupled to the acoustic driver 121. The first cavity 122 and the second cavity 123 can be used to transmit the sound generated by the acoustic driver 121. The sound within the first cavity 122 can be radiated outward through the first acoustic hole, and the sound within the second cavity 123 can be radiated outward through the second acoustic hole. In some embodiments, the number of the first acoustic hole and / or the second acoustic hole can be one or more. The number of acoustic holes can be reasonably set according to actual needs and is not specifically limited in this specification.

[0059] In some embodiments, the acoustic structure in the cavity (the first cavity 122, the second cavity 123) can change the phase of the sound radiated from the acoustic hole of the cavity. In some embodiments, the phase of the first sound radiated by the acoustic driver 121 at the first acoustic hole and / or the phase of the second sound radiated by the second acoustic hole can be adjusted by setting the acoustic structure of the first cavity 122 and / or the second cavity 123, thereby adjusting the phase difference between the first sound and the second sound, and thus improving the sound leakage of the acoustic output device 100. For example, in the case where the front and rear sides of the acoustic driver 121 respectively generate sounds of opposite phases, baffles can be set in the first cavity 122 and / or the second cavity 123, so that the sound path of the sound propagating in the two cavities is different, so that the phase changes of the first sound and the second sound when propagating in the cavity are different, thereby adjusting the phase difference between the first sound and the second sound (that is, 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). For another example, a specific acoustic structure may be provided in the first cavity 122 and / or the second cavity 123 to change the propagation speed of the first sound and the second sound in the cavity, thereby adjusting the phase difference between the first sound and the second sound. Exemplary specific acoustic structures may include slow acoustic structures that slow down the propagation speed of sound, such as acoustic gauze, acoustic porous materials, etc. For another example, an expansion acoustic structure (for example, an expansion cavity) may be provided in the first cavity 122 and / or the second cavity 123 to change the equivalent propagation speed of the first sound and the second sound in the cavity, thereby adjusting the phase difference between the first sound and the second sound. For another example, a sound-absorbing structure (for example, a resonance cavity) may be provided in the first cavity 122 and / or the second cavity 123, and the phase difference between the first sound and the second sound may be adjusted by modulating the sound near the resonant frequency of the sound-absorbing structure. For a detailed description of regulating the phase difference between the first sound and the second sound by setting the acoustic structure of the first cavity 122 and / or the second cavity 123 , please refer to other parts of this specification, such as FIG. 7A to FIG. 10B and related descriptions.

[0060] In some embodiments, when there are two acoustic drivers 121 , the phase difference between the first sound and the second sound may also be adjusted by setting the phase of the electrical signal driving the two acoustic drivers 121 .

[0061] In some embodiments, when the phase difference between the first sound and the second sound is within a specific range (e.g., 120°-179°), within the target frequency band, even if the near-field sound radiated from the first acoustic hole and the near-field sound radiated from the second acoustic hole have similar sound pressures, the sound radiated from the acoustic output device 100 to the far field can still exhibit directionality, such that the radiation field of the sound in the far field has at least one highly directional direction (the sound pressure in the highly directional direction and in the directions adjacent thereto is sufficiently high), while the radiation intensity in other directions is relatively low. For example, the near-field sound radiated from the first cavity 122 and the second cavity 123 has a near-field sound pressure level difference of less than 6 dB, and the sound radiated from the first cavity 122 and the second cavity 123 has a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions (e.g., a direction toward the ear canal opening R1 and a direction away from the ear canal opening R1 when the user is wearing the acoustic output device 100). For another example, the near-field sound radiated from the first cavity 122 and the second cavity 123 has a near-field sound pressure level difference of less than 3dB, and the sound radiated from the first cavity 122 and the second cavity 123 has a far-field sound pressure level difference of not less than 6dB in at least one pair of opposite directions. It can be understood that the smaller the near-field sound pressure level difference, the more significant the cancellation of sound waves with the same amplitude and opposite phase in the far field, and the better the effect of reducing sound leakage; further, the greater the far-field sound pressure level difference, the stronger the far-field sound directivity, the smaller the sound leakage in the direction away from the ear canal opening (for example, the direction away from the ear canal opening R1) and the sound leakage in other directions, that is, the better the effect of reducing far-field sound leakage. In some embodiments, when the user wears the acoustic output device 100, the strong directivity direction can be directed toward the user's ear canal opening R1. In this way, when the user wears the acoustic output device 100, the sound transmitted to the user's ear canal opening R1 can be sufficiently loud while reducing sound leakage in other directions (eg, away from the ear canal opening), thereby improving the user's listening experience and privacy.

[0062] It should be noted that the phase of the sound radiated from the acoustic hole (including the first acoustic hole and the second acoustic hole) described in the embodiments of this specification may refer to the phase measured at a distance of 4 mm from the acoustic hole (or the geometric center of the acoustic hole) (for example, 4 mm in front of the acoustic hole). In some embodiments, the phase difference test method may be to measure the phase of the sound radiated from the first acoustic hole and the second acoustic hole (respectively, the first sound and the second sound), and then calculate the phase difference between the first sound and the second sound. When testing the sound of the first acoustic hole (or the second acoustic hole), a baffle can be used to separate the first acoustic hole and the second acoustic hole 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 the line connecting the first acoustic hole and the second acoustic hole and 4 mm from the first acoustic hole (or the second acoustic hole) to collect the first sound, further preventing the second acoustic hole (or the first acoustic hole) from interfering with the test. For exemplary purposes only, the size of the baffle can be a standard size. For example, the length, width and height dimensions of the baffle may be 1650 mm, 1350 mm and 30 mm, respectively. It should be further explained that when the number of first acoustic holes (or second acoustic holes) is two or more, any one of them may be selected for testing. For example, a first acoustic hole and a second acoustic hole located at a specific relative position (e.g., the minimum or maximum relative distance) may be selected to test the phase of the sound emitted by each of them, and calculate the phase difference. In addition, the sound measurement within a specific frequency band (e.g., 1000 Hz-8000 Hz) does not have to be achieved through exhaustive enumeration, but can be achieved by setting multiple (e.g., 20-30) frequency sampling points with equal step sizes and endpoints as the frequency band endpoints, and measuring the sound at each sampling point separately.

[0063] In some embodiments, the acoustic output device 100 may include a supporting structure 110 and a sound-emitting portion 120 , and an acoustic driver 121 and a first cavity 122 and a second cavity 123 acoustically coupled to the acoustic driver 121 may be disposed in the sound-emitting portion 120 .

[0064] The sound-emitting portion 120 can be used to generate and radiate sound outward. In some embodiments, the acoustic output device 100 can fix the sound-emitting portion 120 near the user's ear but without blocking the user's ear canal through the support structure 110. In some embodiments, the projection of the sound-emitting portion 120 on the user's ear plane can partially or completely cover the user's ear canal but does not block the user's ear canal. In some embodiments, the projection of the sound-emitting portion 120 on the user's ear plane may not cover the user's ear canal, thereby allowing the user's ear to remain open. When the user's ear remains open, the user can hear the sound output by the sound-emitting portion 120 while also receiving sounds from the external environment.

[0065] The support structure 110 can be used to support the sound-emitting portion 120. In some embodiments, when a user wears the acoustic output device 100, the support structure 110 can be mounted on the user's ear, head, or upper torso. In some embodiments, the support structure 110 can include an arc structure that adapts to the user's auricle R2. By way of example only, the arc structure may include, but is not limited to, a hook shape, a C shape, etc. When a user wears the acoustic output device 100, the support structure 110 can be mounted or clamped on the user's auricle R2, thereby enabling the acoustic output device 100 to be worn. In some embodiments, the support structure 110 may also include an ear hook structure that adapts to the user's head or upper torso. When a user wears the acoustic output device 100, the ear hook structure can be hung on the user's auricle R2 via the user's head or neck, thereby enabling the acoustic output device 100 to be worn.

[0066] In some embodiments, the support structure 110 can be made of a softer material, a harder material, or a combination thereof. A softer material refers to 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 the softer material can be 45-85A, 30-60D. A harder material refers to a material having a hardness (e.g., Shore hardness) greater than a second hardness threshold (e.g., 65D, 70D, 80D, 85D, 90D, etc.). Materials with a softer texture may include, but are not limited to, polyurethanes (PU) (e.g., thermoplastic polyurethanes (TPU)), polycarbonate (PC), polyamides (PA), acrylonitrile butadiene styrene (ABS), polystyrene (PS), high impact polystyrene (HIPS), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyurethanes (PU), polyethylene (PE), phenolic resin (PF), urea-formaldehyde resin (UF), melamine-formaldehyde resin (MF), silicone, etc., or a combination thereof. Harder materials may include, but are not limited to, polyethersulfones (PES), polyvinylidenechloride (PVDC), polymethyl methacrylate (PMMA), polyether-ether-ketone (PEEK), or combinations thereof, or mixtures thereof with reinforcing agents such as glass fiber and carbon fiber. In some embodiments, the material of the support structure 110 can be selected based on the specific circumstances. For example, a softer material can improve the user's comfort when wearing the acoustic output device 100 and its fit with the user's ear, while a harder material can increase the strength of the acoustic output device 100.

[0067] In some embodiments, the acoustic output device 100 may also include only the sound-emitting portion 120. For example, when the acoustic output device 100 is worn, the sound-emitting portion 120 may be directly positioned in the ear cavity without blocking the ear canal. In this case, the acoustic output device 100 does not need to be provided with a support structure 110 to support the sound-emitting portion 120.

[0068] In some embodiments of the present specification, the acoustic output device can ensure that, within the 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 small sound pressure level difference by regulating the phase difference between the two sounds generated by the sound-emitting part, while also ensuring that the sound radiated to the far field by the acoustic output device is directional, so that the sounds radiated to the outside world through the first acoustic hole and the second acoustic hole can cancel each other in the far field in a specific direction, thereby reducing sound leakage in the far field.

[0069] The target frequency band can be a frequency range to which the human ear is most sensitive. In some embodiments, since the human ear is more sensitive within the 200Hz-5000Hz frequency range, the target frequency band can be 200Hz-5000Hz or a portion thereof. For example, to minimize sound leakage in the primary frequency range of human voices, the target frequency band can be 200Hz-800Hz. For another example, the target frequency band can be 2000Hz-4000Hz, to which the human ear is most sensitive. For another example, the target frequency band can also be 500Hz-4000Hz, 500Hz-3000Hz, 500Hz-2000Hz, 500Hz-1000Hz, 1000Hz-4000Hz, 1500Hz-3000Hz, 1500Hz-2000Hz, and so on. In some embodiments, the target frequency band can include a continuous frequency range or can be composed of multiple discrete frequency points. For example, the target frequency band may include target frequency points such as 500Hz, 1000Hz, 2000Hz and 4000Hz, so that the sound of the acoustic output device 100 at the above frequency points can meet the purpose of close near-field sound pressure and far-field directivity (for example, cardioid directivity).

[0070] Since the human ear is more sensitive to the frequency range of 200Hz-5000Hz, by setting the target frequency band to this frequency range, far-field sound leakage can be more effectively reduced in this frequency range, thereby meeting actual needs.

[0071] The near-field sound pressure level difference refers to the difference in sound pressure levels of the sounds radiated into the near-field by two or more sound sources generated by the acoustic output device 100. In this application, the near-field location of a sound source may refer to a location 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 in sound pressure level between the first acoustic hole and the second acoustic hole of the acoustic output device 100.

[0072] In some embodiments, the near-field sound pressure level can be measured by measuring the sound pressure of the sounds radiated from the first acoustic hole and the second acoustic hole (the first sound and the second sound, respectively) at a specific frequency (e.g., 1000 Hz), and then calculating (e.g., taking the common logarithm of the ratio of the measured sound pressure to the reference sound pressure and multiplying it by 20 to obtain the sound pressure level) the sound pressure level difference between the first sound and the second sound. In some embodiments, when testing the sound from the first acoustic hole (or the second acoustic hole), a baffle can be used to separate the first acoustic hole and the second acoustic hole to prevent interference from the second acoustic hole (or the first acoustic hole) in the test. The sound pressure at the first acoustic hole can be understood as the sound pressure at a position close to the first acoustic hole, and the sound pressure at the second acoustic hole can be understood as the sound pressure at a position close to the second acoustic hole. For example, a sound collection device can be set 4 mm from the first acoustic hole (or the second acoustic hole) to collect the first sound (or the second sound) as the sound pressure at the first acoustic hole (or the second acoustic hole).

[0073] In some embodiments, when testing the sound of the first and second acoustic holes, the locations 4 cm from the first and second acoustic holes (i.e., the collection locations) can be located in opposite directions of the acoustic output device 100 (for example, the location 4 cm from the first acoustic hole is in the direction of the second acoustic hole pointing toward the first acoustic hole, and the location 4 cm from the second acoustic hole is in the direction of the first acoustic hole pointing toward the second acoustic hole). The sound collection device is placed at the two collection locations to collect the sound pressure level of the acoustic output device 100, and the difference between the two sound pressure levels is calculated, which is the near-field sound pressure level difference between the first and second acoustic holes.

[0074] For a detailed description of the acoustic center, please refer to FIG. 3A to FIG. 3C and their related descriptions.

[0075] In some embodiments of the present specification, by controlling the near-field sound pressures of the sounds radiated from the first acoustic hole and the second acoustic hole to be similar, it is possible to ensure that the first sound and the second sound effectively interfere with each other in a specific direction of the far field, thereby effectively reducing sound leakage of the acoustic output device 100 in the far field.

[0076] For example, Figure 2B is a graph showing how the near-field sound pressure levels of the first and second acoustic holes vary with frequency, according to some embodiments of this specification. As shown in Figure 2B , the near-field sound pressure levels of the first and second acoustic holes of the acoustic output device 100 maintain a substantially consistent trend within the 200 Hz-20 kHz frequency range, with a difference of less than 5 dB. This effectively reduces far-field sound leakage from the acoustic output device 100 within the 200 Hz-20 kHz frequency range.

[0077] The near-field sound pressure level difference can be adjusted in a variety of ways. In some embodiments, the near-field sound pressure level difference can be adjusted by adjusting the opening area ratio of the first acoustic hole and the second acoustic hole.

[0078] The opening area ratio refers to the ratio of the area S1 of the first acoustic hole to the area S2 of the second acoustic hole, that is, the opening area ratio is equal to S1 / S2. It can be understood that when the number of the first acoustic holes (or second acoustic holes) is two or more, the opening area ratio can refer to the total area of ​​the first acoustic holes (S1=S2). 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 Wherein, n and m are integers greater than 1.

[0079] In some embodiments, the ratio of the opening area of ​​the first acoustic hole to the second acoustic hole (i.e., the opening area ratio) can be 0.2, 0.5, 1, 1.5, 2, 2.5, etc. In some embodiments, the ratio of the opening area of ​​the first acoustic hole to the second acoustic hole can be in the range of 0.5-2. 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 are made close, and the acoustic impedance of the first acoustic hole and the second acoustic hole can be made close, thereby reducing the near-field sound pressure level difference between the first acoustic hole and the second acoustic hole, thereby making the far-field sound leakage cancellation more significant, and improving the effect of reducing far-field sound leakage.

[0080] Furthermore, the ratio of the opening area of ​​the first acoustic hole to the second acoustic hole can be in the range of 0.8-1.25, 0.9-1.1, or 0.95-1.1. By further reducing the ratio of the opening area of ​​the first acoustic hole to the second acoustic hole, the near-field sound pressure level difference is reduced, which can further improve the effect of reducing far-field sound leakage.

[0081] In some embodiments, the near-field sound pressure level difference can also be adjusted by adjusting the difference between the acoustic loads of the first acoustic hole and the second acoustic hole.

[0082] Acoustic load refers to the ratio of the sound pressure value P1 after passing through the first acoustic hole (or second acoustic hole) to the sound pressure value P0 before passing through the first acoustic hole (or second acoustic hole). In other words, acoustic load equals P1 / P0. It should be noted that for a particular acoustic hole, the greater the acoustic load (or the closer it is to 1), the lower its acoustic resistance.

[0083] In some embodiments, the acoustic load can be based on measuring the sound pressure value of the first acoustic hole (or the second acoustic hole) when it is covered with a gauze (equivalent to P1) and the sound pressure value when it is not covered with a gauze (equivalent to P0) at a specific distance, and determining the acoustic load of the first acoustic hole (or the second acoustic hole) by calculating the ratio of P1 to P0. Specifically, when testing the sound of the first acoustic hole (or the second acoustic hole), the sound collection device can be set at a distance of 4-5 mm from the first acoustic hole (or the second acoustic hole), and then the sound pressure value of the first acoustic hole (or the second acoustic hole) when it is covered with a gauze (equivalent to P1) and the sound pressure value when it is not covered with a gauze (equivalent to P0) are collected respectively, and finally the acoustic load of the first acoustic hole (or the second acoustic hole) is calculated. It should be noted that the test signal of the acoustic load can be a single-frequency signal, where one or more frequency points can be selected, including but not limited to 100Hz, 200Hz, 300Hz, 500Hz, 1000Hz, 2000Hz, 5000Hz and the resonant frequency f0 point of the acoustic output device 100; the test signal can also be selected as white noise, pink noise, and swept frequency signal. It should be noted that in some embodiments, the measured sound pressure level needs to be converted into a sound pressure value first, and then the acoustic load is calculated. Alternatively, the sound pressure levels measured before and after the first acoustic hole (or the second acoustic hole) is covered with the gauze can be subtracted, and then the acoustic load value of the first acoustic hole (or the second acoustic hole) can be inversely calculated by the logarithmic formula.

[0084] In some embodiments, the difference in acoustic load between the first acoustic hole and the second acoustic hole can be 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 can be less than 0.15. It is understood that the smaller the difference in acoustic load between the first acoustic hole and the second acoustic hole, the closer the acoustic impedance of the first acoustic hole and the second acoustic hole, thereby reducing the difference in near-field sound pressure levels between the first acoustic hole and the second acoustic hole, and thus significantly reducing far-field sound leakage.

[0085] Furthermore, the difference in acoustic load between the first and second acoustic holes can be less than 0.1. By further narrowing the range of the difference in acoustic load between the first and second acoustic holes, the near-field sound pressure level difference between the first and second acoustic holes can be further reduced, thereby further improving the effect of reducing far-field sound leakage.

[0086] In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 200 Hz to 5000 Hz, the difference in acoustic load between the first and second acoustic holes may be 0-0.05. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 500 Hz to 4000 Hz, the difference in acoustic load between the first and second acoustic holes may be 0-0.07. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 1000 Hz to 3000 Hz, the difference in acoustic load between the first and second acoustic holes may be 0-0.1. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 1500 Hz to 2500 Hz, the difference in acoustic load between the first and second acoustic holes may be 0-0.12.

[0087] In some embodiments, the near-field sound pressure level difference can also be adjusted by adjusting the ratio of the surface acoustic loads of the first acoustic hole to the surface acoustic loads of the second acoustic hole.

[0088] The surface acoustic load refers to 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 without passing through the first acoustic hole (or the second acoustic hole) and the area S of the first acoustic hole (or the second acoustic hole), that is, the surface acoustic load is equal to S×P1 / P0.

[0089] In some embodiments, the ratio of the surface acoustic loads of the first acoustic hole to the second acoustic hole can be 0.5, 1, 2.5, etc. In some embodiments, the ratio of the surface acoustic loads of the first acoustic hole to the second acoustic hole can range from 0.5 to 3.5. By adjusting the surface acoustic load ratio of the first acoustic hole to the second acoustic hole to maintain it within an appropriate ratio range, the acoustic impedances 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, thereby improving the effect of reducing far-field sound leakage.

[0090] Furthermore, the ratio of the surface acoustic load of the first acoustic hole to that of the second acoustic hole may be in the range of 0.8 to 2. It is understandable that by further reducing the range of the surface acoustic load ratio of the first acoustic hole to that of the second acoustic hole, the effect of reducing far-field sound leakage may be more significant.

[0091] In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 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 minimize far-field sound leakage of the acoustic output device 100 within the 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 minimize far-field sound leakage of the acoustic output device 100 within the 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 minimize far-field sound leakage of the acoustic output device 100 within the 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, in order to reduce far-field sound leakage of the acoustic output device 100 in the range of 1500 Hz-2000 Hz, the ratio of the surface acoustic load of the first acoustic hole to the surface acoustic load of the second acoustic hole may be in the range of 0.5-3.5.

[0092] The far-field sound pressure level difference refers to the difference in sound pressure levels of the sound radiated in the far field by the first acoustic hole and the second acoustic hole, respectively. In this application, the far field of the first acoustic hole (or the second acoustic hole) can refer to a position more than 10 cm 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 long distance (or symmetrical position) from the first acoustic hole and the second acoustic hole, respectively, in the direction of the line connecting the two holes.

[0093] It should be noted that the far-field sound pressure level difference test method is similar to the near-field sound pressure level difference test method, and the similarities are not repeated here. The difference is that when measuring the far-field sound pressure level, for example, when collecting sound from the first acoustic hole (or second acoustic hole), the sound collection device can be placed 30 cm away from the first acoustic hole (or second acoustic hole) for collection.

[0094] In some embodiments, the at least one pair of opposite directions may include two opposite directions in the direction of the line connecting the first acoustic hole and the second acoustic hole. For example, when the user wears the acoustic output device 100, the direction toward the ear canal opening R1 and the direction away from the ear canal opening R1 are a pair of opposite directions.

[0095] In some embodiments, at least one pair of opposite directions may also include two directions within a preset angle range relative to a certain point. For example, these directions may be formed by connecting two points in the far field, respectively near the first acoustic hole and the second acoustic hole, and the midpoint of the line connecting the first acoustic hole and the second acoustic hole, and satisfying the preset angle range. The preset angle range may include, but is not limited to, 150°-180°. This allows for comprehensive consideration of various potential scenarios in actual applications, thereby ensuring a more robust far-field sound leakage cancellation effect. For example, in actual products, a highly directional sound field, such as a cardioid directional sound field, may exhibit tilt or distortion. This tilt or distortion may result in significant sound leakage from the acoustic output device 100 in multiple directions, thereby impacting the performance of the acoustic output device 100. In this case, a set of relative directions may be defined to account for potential tilt or distortion, thereby ensuring that the highly directional sound field becomes a more standardized highly directional sound field. For example, when the highly directional radiation sound field is tilted or distorted, one direction in at least one pair of opposite directions can still be the direction of the line connecting the first acoustic hole and the second acoustic hole, and the other direction can form an angle of 10° with the opposite direction of the line connecting the first acoustic hole and the second acoustic hole; or, each direction in at least one pair of opposite directions can form a certain angle (for example, 5°, 10°, 15°, 20°) with the direction of the line connecting the first acoustic hole and the second acoustic hole, etc.

[0096] In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 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 no less than 12 dB. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 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 no less than 10 dB. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 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 no less than 8 dB. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 1500 Hz to 2500 Hz, the near-field sound pressure level difference may be less than 3 dB, and the far-field sound pressure level difference may be no less than 4 dB. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 1500 Hz-2000 Hz, the near-field sound pressure level difference may be less than 2 dB, and the far-field sound pressure level difference may be no less than 3 dB.

[0097] In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 200Hz-5000Hz range, the far-field sound pressure level difference is no less than 12dB. In this case, the difference in acoustic load between the first and second acoustic holes can be 0-0.03. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 500Hz-4000Hz range, the far-field sound pressure level difference is no less than 10dB. In this case, the difference in acoustic load between the first and second acoustic holes can be 0-0.05. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 1000Hz-3000Hz range, the far-field sound pressure level difference is no less than 6dB. In this case, the difference in acoustic load between the first and second acoustic holes can be 0-0.1. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 1500 Hz-2500 Hz range and maintain a far-field sound pressure level difference of no less than 4 dB, the difference in acoustic load between the first and second acoustic holes can be 0-0.12. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 1500 Hz-2000 Hz range and maintain a far-field sound pressure level difference of no less than 3 dB, the difference in acoustic load between the first and second acoustic holes can be 0-0.15.

[0098] In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 200 Hz to 5000 Hz and ensure a far-field sound pressure level difference of no less than 12 dB, the opening area ratio of the first acoustic hole to the second acoustic hole may be 0.75-1.1. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 500 Hz to 4000 Hz and ensure a far-field sound pressure level difference of no less than 10 dB, the opening area ratio of the first acoustic hole to the second acoustic hole may be 0.7-1.2. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 1000 Hz to 3000 Hz and ensure a far-field sound pressure level difference of no less than 6 dB, the opening area ratio of the first acoustic hole to the second acoustic hole may be 0.6-1.5. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 1500 Hz-2500 Hz range and maintain a far-field sound pressure level difference of no less than 4 dB, the opening area ratio of the first acoustic hole to the second acoustic hole may be 0.6-1.7. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 1500 Hz-2000 Hz range and maintain a far-field sound pressure level difference of no less than 3 dB, the opening area ratio of the first acoustic hole to the second acoustic hole may be 0.5-1.9.

[0099] In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 200 Hz to 5000 Hz and to ensure a far-field sound pressure level difference of no less than 12 dB, the surface acoustic load ratio of the first acoustic hole to the second acoustic hole may be in the range of 0.9 to 1.2. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 500 Hz to 4000 Hz and to ensure a far-field sound pressure level difference of no less than 10 dB, the surface acoustic load ratio of the first acoustic hole to the second acoustic hole may be in the range of 0.8 to 1.5. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 1000 Hz to 3000 Hz and to ensure a far-field sound pressure level difference of no less than 6 dB, the surface acoustic load ratio of the first acoustic hole to the second acoustic hole may be in the range of 0.7 to 2. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 1500 Hz-2500 Hz range and maintain a far-field sound pressure level difference of no less than 4 dB, the surface acoustic load ratio of the first acoustic hole to the second acoustic hole may be in the range of 0.6-2.7. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the 1500 Hz-2000 Hz range and maintain a far-field sound pressure level difference of no less than 3 dB, the surface acoustic load ratio of the first acoustic hole to the second acoustic hole may be in the range of 0.5-3.5.

[0100] Figure 3A is a schematic diagram of the directional radiation sound field of an exemplary acoustic output device according to some embodiments of this specification; Figure 3B is a schematic diagram of the directional radiation sound field of an exemplary acoustic output device according to other embodiments of this specification; Figure 3C is a schematic diagram of a method for calculating the distance between acoustic centers according to some embodiments of this specification.

[0101] As shown in Figures 3A and 3B, AS1 and AS2 represent the first and second sound sources, respectively, formed by the sound-emitting portion 120 of the acoustic 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 specific phase difference (e.g., 120°-179°), the first sound source AS1 and the second sound source AS2 can form a highly directional sound field, such as a cardioid directional sound field (as shown in Figure 3A) or a supercardioid directional sound field (as shown in Figure 3B). It should be noted that 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.

[0102] The acoustic center of an acoustic hole (for example, the first acoustic hole or the second acoustic hole) refers to the equivalent sound emission position of the acoustic hole, which can be determined based on the shape, size and number of the acoustic holes. When the number of acoustic holes is one, the acoustic center can be the geometric center of the acoustic hole (for example, 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 the number of acoustic holes is two, the acoustic center can be the midpoint of the line connecting the geometric centers of the two acoustic holes. When the number of acoustic holes is three, the acoustic center can be the center of the circumscribed circle of the geometric centers of the three acoustic holes, or the acoustic center can also be the centroid of the triangle formed by the line connecting the geometric centers of the three acoustic holes. When the number of acoustic holes is four (or more), the acoustic center can be the centroid of a quadrilateral (or polygon) formed by the line connecting the geometric centers of the four (or more) acoustic holes.

[0103] The distance between the first acoustic hole and the second acoustic hole refers to the distance between the acoustic center of the first acoustic hole and the acoustic center of the second acoustic hole. For example, if there is one first acoustic hole and two second acoustic holes, the one first acoustic hole and the two second acoustic holes can form a triangle with three sides. The lengths of the three sides of the triangle can be measured, and the distance from the acoustic center of the first acoustic hole to the acoustic center of the second acoustic hole can be calculated (when there are two second acoustic holes, the acoustic center can 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.

[0104] As shown in FIG3C , the geometric center A of the first acoustic hole, the geometric center B1 of one second acoustic hole, and the geometric center B2 of another second acoustic hole can form a triangle 300. The lengths of the three sides of the triangle 300 can be obtained by measurement, namely a, b, and c. The acoustic center of the first acoustic hole is the geometric center A of the first acoustic hole, and the equivalent acoustic centers of the two second acoustic holes are 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). The value of x can be calculated according to the following formula: cosβ=-cos(180°-β) (1)

[0105] Here, β represents the angle formed by line segment AB3 and line segment B1B3.

[0106] According to formula (1)-formula (3), it can be deduced and calculated:

[0107] As shown in Figures 3A and 3B, it can be seen from the figures that the directional radiation sound field of the cardioid (Figure 3A) or supercardioid (Figure 3B) has only one main lobe, and the sound field radiation of the main lobe and its vicinity is strong, while the sound field radiation in other directions is weak (the sound field intensity in the opposite direction of the main lobe is also relatively weak). When the user wears the acoustic output device 100, the main lobe can be directed to the listener's ear canal opening R1. At this time, only the radiation directed to the ear canal opening R1 and its vicinity is strong, while the other directions are all weakly directional directions. Thus, the sound leakage of the acoustic output device 100 can be reduced. It can be understood that the phase difference between the first sound and the second sound in Figures 3A and 3B is different (but both are within a specific range), so the radiation sound fields presented in Figures 3A and 3B are also different. The following describes 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.

[0108] FIG4 is a schematic diagram of an exemplary dual-sound source radiation according to some embodiments of the present specification.

[0109] As shown in Figure 4, the first sound source AS1 and the second sound source AS2 can respectively represent two equivalent sound sources formed by the first acoustic hole and the second acoustic hole of the sound-emitting part 120 of the acoustic output device 100. 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 the point P, r2 represents the distance from the second sound source AS2 to the 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 the point P, and θ represents the angle formed by the line connecting the first sound source AS1 and the second sound source AS2 and the line connecting the midpoint O and the point P.

[0110] The sound pressures at the first sound source AS1 and the second sound source AS2 can be respectively:

[0111] Where A represents the intensity of the point sound source, ω represents the angular frequency, j represents the imaginary part, and t represents the time. represents the phase difference between the first sound source AS1 and the second sound source AS2, and k represents the wave vector. Under far-field conditions (r>>l, kl<<1), the distances r1 and r2 can be expressed as:

[0112] Therefore, the sound pressure amplitude |p| at the far-field point P can be expressed as the superposition of the sound fields of the first sound source AS1 and the second sound source AS2:

[0113] When a cardioid directional sound field is required, that is, when θ=180°, the sound pressure amplitude |p| at a point P in the far field reaches a minimum. Taking the derivative of |p|, we have:

[0114] Solving the above equation (7), we can get the phase difference between the first sound source AS1 and the second sound source AS2 Relationships that need to be satisfied:

[0115] From formula (8), we can see that in order for the first sound source AS1 and the second sound source AS2 to form a cardioid directional radiation sound field, the phase difference between the two sound sources is There is a certain relationship between kl and wave vector k. Since wave vector k is related to frequency f, the phase difference between the two sound sources is It also depends on the frequency.

[0116] Figure 5 shows the phase difference between the first sound source AS1 and the second sound source AS2 corresponding to formula (8) Schematic diagram of the relationship between frequency f and spacing l.

[0117] As shown in Figure 5, the horizontal axis represents the frequency f, the unit is Hz; the vertical axis represents the distance l between the two sound sources, the unit is mm, and each curve represents the required phase difference under different conditions (i.e., different frequencies f and different distances l). Comparing the various curves in Figure 5, it can be seen that to achieve a cardioid directional sound field, when the spacing l is constant, within a preset frequency range, the phase difference between the first sound source AS1 and the second sound source AS2 is negatively correlated with the frequency. For example, within the 200Hz-2000Hz range, higher frequencies require a smaller phase difference between the first sound source AS1 and the second sound source AS2; lower frequencies require a larger 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 spacing between the two sound sources. A larger spacing requires a smaller phase difference between the first sound source AS1 and the second sound source AS2; a smaller spacing requires a larger phase difference between the first sound source AS1 and the second sound source AS2. It should be noted that in actual measurements, when the phase difference is negatively correlated with the magnitude of multiple consecutive frequencies within a certain frequency range and / or multiple consecutive spacings within a certain dual-source spacing range, it can be considered that the phase difference is negatively correlated with the frequency and / or the spacing between the two sound sources. As an example only, multiple (for example, 5, 10, etc.) frequencies and their corresponding phase differences can be measured at equal step frequencies (for example, every 1 Hz, 10 Hz, 50 Hz, 100 Hz, 200 Hz, etc.). When the multiple frequencies and their corresponding phase differences satisfy a negative correlation relationship, it can be considered that the phase difference is negatively correlated with the magnitude of the frequency.

[0118] In practical applications, the spacing l is usually fixed, and the phase difference The correspondence between and kl can be simplified to the correspondence between frequency and phase difference. That is, under the premise of a certain distance l, when the phase difference between the first sound source AS1 and the second sound source AS2 and the frequency satisfy a certain correspondence, a cardioid directional radiation sound field can be formed between the first sound source AS1 and the second sound source AS2. For example, as shown in the table below, when the distance l is 3mm, in order for the first sound source AS1 and the second sound source AS2 to form a cardioid directional radiation sound field, the required phase difference is (It can also be understood as the optimal phase difference that can achieve a cardioid directional radiation sound field) and the corresponding relationship table of frequency f can be:

[0119]

[0120] As can be seen from the table, at different frequencies, in order for the first sound source AS1 and the second sound source AS2 to form a cardioid directional radiation sound field, the required phase difference between the first sound source AS1 and the second sound source AS2 is At the same time, it can be seen from the table that even if the phase difference corresponding to different frequencies Different, but not much difference. For example, the phase difference corresponding to 200Hz shown in the table is 179°, and the phase difference corresponding to 2000Hz is 173°, and the difference between the two phase differences is only 6°. Therefore, when determining a fixed phase difference When the phase difference range is within a certain range (e.g., 176°) or a phase difference range (e.g., 120°-179°), in a wide frequency band (e.g., 200Hz-2000Hz), even if a cardioid directional radiation sound field (as shown in FIG3A ) cannot be formed at certain frequencies, a quasi-cardioid directional radiation sound field can be formed, such as a super-cardioid directional radiation sound field as shown in FIG3B .

[0121] FIG6 is a schematic diagram of directional radiation sound field at different frequencies according to some embodiments of this specification. It should be noted that FIG6 corresponds to a spacing of l = 3 mm and a phase difference of , the sound field radiation corresponding to different frequencies under far-field conditions at a distance of 0.5m from the sound source. As shown in Figure 6, curve 610, curve 620, curve 630, and curve 640 are the directional radiation sound field curves corresponding to frequencies of 200Hz, 500Hz, 1000Hz, and 2000Hz under far-field conditions, respectively. It can be seen from Figure 6 that the sound field intensity in the opposite direction (180° direction) of the main lobe (the sound field intensity is the largest) of the radiated sound field of curve 630 is the smallest. Therefore, the sound field radiation directivity (cardioid directivity) of curve 630 is the best compared to the other three curves (that is, the phase difference is 0.01). The directional radiation sound field is optimal at a frequency of 1000Hz). The sound field intensity in the opposite direction of the main lobe of the radiation sound field corresponding to curves 610, 620, and 640 is larger than that of curve 630, which forms a cardioid directivity. When the phase difference is within a certain range, for example, 120°-179°, both sound sources can also form a strong directional radiation sound field within the frequency range of 200Hz to 2000Hz.

[0122] The sound leakage reduction effect of the acoustic output device 100 in the far field can be affected by the rate of change of the near-field phase difference of the sound radiated by the sound source. The rate of change of the phase difference may refer to 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 with frequency. In some embodiments, the rate of change of the phase difference can be expressed based on the phase difference and the octave. An octave (oct) refers to the interval between two frequencies with a frequency ratio of 2 or 1 / 2 on the frequency response curve. For example, 1000Hz-2000Hz is an octave, 2000Hz-4000Hz is an octave; for another example, 1500Hz-3000Hz is an octave, 3000Hz-6000Hz is an octave, and so on.

[0123] By controlling the rate of change of the near-field phase difference to exhibit a slow change trend, distortion of the sound radiated from the far-field of the acoustic output device can be avoided, thereby allowing the two sound sources to tend to form a highly directional radiation sound field (for example, a cardioid or supercardioid directional radiation sound field) over a wider frequency range. In some embodiments, within the frequency range of 1000 Hz to 8000 Hz, 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 can be less than 30° / oct.

[0124] In some embodiments, within the frequency range of 1000 Hz to 8000 Hz, the rate of change of the near-field phase difference can be less than 20° / oct. By further controlling the rate of change of the near-field phase difference, the two sound sources can further form a more standardized, highly directional sound field (e.g., a cardioid or supercardioid directional sound field), minimizing sound leakage in the direction opposite to the ear canal and in other directions, thereby better balancing ear canal openness and listening privacy.

[0125] Furthermore, in some embodiments, to enable the acoustic output device 100 to form a relatively standard, highly directional sound radiation field within the range of 1000 Hz-5000 Hz, the rate of change of the near-field phase difference may be less than 25° / oct. In some embodiments, to enable the acoustic output device 100 to form a relatively standard, highly directional sound radiation field within the range of 3000 Hz-4000 Hz, the rate of change of the near-field phase difference may be less than 20° / oct. In some embodiments, to enable the acoustic output device 100 to form a relatively standard, highly directional sound radiation field within the range of 2000 Hz-3000 Hz, the rate of change of the near-field phase difference may be less than 15° / oct. In some embodiments, to enable the acoustic output device 100 to form a relatively standard, highly directional sound radiation field within the range of 1000 Hz-2000 Hz, the rate of change of the near-field phase difference may be less than 10° / oct.

[0126] In some embodiments, the absolute value of the difference between the phase difference between the sound radiated from the first acoustic hole and the sound radiated from the second acoustic hole at 1000 Hz and the phase difference at 2000 Hz may be less than 30°. For example, if the phase difference between the sound radiated from the first acoustic hole and the sound radiated from the second acoustic hole at 1000 Hz is 159°-178°, and the phase difference between the sound radiated from the first acoustic hole and the sound radiated from the second acoustic hole at 2000 Hz is 149°-176°, then the absolute value of the difference between the phase difference between the sound radiated from the first acoustic hole and the sound radiated from the second acoustic hole at 1000 Hz and the phase difference at 2000 Hz is between 2°-29°, which is less than 30°. Because the frequency range of 1000Hz-2000Hz is within the frequency range that the human ear is more sensitive to, based on this, within this frequency range, by controlling the absolute value of the difference between the phase difference between the sound radiated from the first acoustic hole and the sound radiated from the second acoustic hole at 1000Hz and the phase difference at 2000Hz to within 30°, the effect of reducing far-field sound leakage can be further improved.

[0127] In some embodiments, to minimize far-field sound leakage from the acoustic output device 100 within the 200 Hz-5000 Hz range, the far-field sound pressure level difference is no less than 12 dB, and the near-field phase difference change rate is less than 29° / oct. In some embodiments, to minimize far-field sound leakage from the acoustic output device 100 within the 500 Hz-4000 Hz range, the far-field sound pressure level difference is no less than 10 dB, and the near-field phase difference change rate is less than 25° / oct. In some embodiments, to minimize far-field sound leakage from the acoustic output device 100 within the 1000 Hz-3000 Hz range, the far-field sound pressure level difference is no less than 6 dB, and the near-field phase difference change rate is less than 20° / oct. In some embodiments, to minimize far-field sound leakage from the acoustic output device 100 within the 1500 Hz-2500 Hz range, the far-field sound pressure level difference is no less than 4 dB, and the near-field phase difference change rate is less than 15° / oct. In some embodiments, to minimize far-field sound leakage of the acoustic output device 100 within the range of 1500 Hz-2000 Hz, the far-field sound pressure level difference is not less than 3 dB, and the near-field phase difference change rate is less than 10° / oct.

[0128] Figure 7A is a schematic diagram of an exemplary sound-emitting part according to some embodiments of this specification; Figure 7B is a schematic diagram of an exemplary sound-emitting part according to other embodiments of this specification; Figure 7C is a schematic diagram of an exemplary sound-emitting part according to other embodiments of this specification.

[0129] As shown in FIG7A , the sound-emitting portion 700 may include at least one acoustic driver 721, 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 diaphragm, and the at least one acoustic driver 721 may have a front side and a rear side, respectively, distinguished by the diaphragm, and radiate sound into the first cavity 722 and the second cavity 723 through the front side and the rear side, respectively. In some embodiments, the at least one acoustic driver 721 may also include two acoustic drivers (i.e., the acoustic driver 721 in FIG7A may be replaced with two parallel acoustic drivers), each driven by two sets of electrical signals to radiate sound into the first cavity 722 and the second cavity 723. Sound within the first cavity 722 may be radiated to the outside world through the first acoustic hole 724, i.e., the first acoustic hole 724 radiates a first sound V1 to the outside world; sound within the second cavity 723 may be radiated to the outside world through the second acoustic hole 725, i.e., the second acoustic hole 725 radiates a second sound V2 to the outside world.

[0130] In some embodiments, in order to make the sound radiated to the far field by the sound-emitting portion 700 within the target frequency band (for example, 200Hz-5000Hz) exhibit strong directivity (for example, cardioid or supercardioid), it is necessary to make 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 be within a specific range (for example, 120°-179°). Since the initial value of the phase difference between the two sound waves radiated by the acoustic driver 721 to the first cavity 722 and the second cavity 723 respectively is 180°, an acoustic structure can be set in the first cavity 722 and / or the second cavity 723 so that the phase difference between the first sound V1 and the second sound V2 meets the conditions. In some embodiments, the sound-emitting portion 700 may include an acoustic structure 726 arranged in the first cavity 722 and / or the second cavity 723. The acoustic structure 726 can be used to control the actual output phase of the first sound V1 and / or the second sound V2, thereby adjusting the phase difference between the first sound V1 and the second sound V2. In some embodiments, the acoustic structure 726 can create a path difference between a first acoustic path of the first sound V1 propagating in the first cavity 722 and a second acoustic path of the second sound V2 propagating in the second cavity 723, thereby changing 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. In this embodiment, the acoustic structure 726 is disposed in the second cavity 723 as an example. It is understood that in other alternative embodiments, the acoustic structure 726 can also be disposed in the first cavity 722, or different acoustic structures can be disposed in the first cavity 722 and the second cavity 723.

[0131] 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 the baffle is a free end. In some embodiments, as shown in Figure 7A, four baffles can be set in the second cavity 723, wherein two baffles are set on the first inner wall 7231 of the second cavity 723, and the remaining two baffles are set on the second inner wall 7232 (the second inner wall 7232 is set opposite to the first inner wall 7231), and the free ends of the baffles on the two inner walls are respectively set opposite to each other. At this time, there is a gap between the free ends of the two baffles set opposite to each other, and sound can bypass the baffle and be transmitted from the gap to the second acoustic hole 725. In some embodiments, the number and / or position of the baffles in the second cavity 723 can also be set in other ways. For example, as shown in FIG7B , a baffle may be provided on only one inner wall of the second cavity 723 (e.g., the second inner wall 7232), with one end of the baffle connected to the second inner wall 7232 and the free end of the baffle extending to the vicinity of the first inner wall 7231 (forming a gap between the free end of the baffle and the first inner wall 7231). Sound can bypass the baffle and be transmitted to the second acoustic hole 725 through the gap between the free end of the baffle and the first inner wall 7231. For another example, as shown in FIG7C , the two ends of the baffle may be connected to the first inner wall 7231 and the second inner wall 7232, respectively. In this case, a hole may be provided in the baffle, allowing sound to bypass the baffle and be transmitted to the second acoustic hole 725 through the hole. As the sound bypasses the baffle and is transmitted to the second acoustic hole 725, the distance traveled by the sound (i.e., the sound path) changes compared to when no baffle is provided. The sound waves radiated from the front side of the acoustic driver 721 are radiated from the first acoustic hole 724 to the outside through the first cavity 722. The distance traveled by the sound wave is the first sound path L1. The sound waves radiated from the rear side of the acoustic driver 721 are radiated from the second acoustic hole 725 to the outside through the second cavity 723 and the acoustic structure 726. The distance traveled by the sound wave is the second sound path L2. There is a sound path difference between the first sound path L1 and the second sound path L2.

[0132] The phase delay between the first sound V1 radiated from the first acoustic hole 724 and the second sound V2 radiated from the second acoustic hole 725 can be:

[0133] Here, c represents the speed of sound. Therefore, the phase difference between the first sound V1 and the second sound V2 is for:

[0134] It can be seen therefrom that the actual output phase difference between the first sound V1 and the second sound V2 can be controlled by controlling the path difference between the first path L1 and the second path L2 (for example, the path difference can be made to be within the range of 1 mm to 57 mm), so that the phase difference between the first sound V1 and the second sound V2 is within 120° - 179°, and further making the sound radiated by the sound generating part 700 to the far field exhibit strong directivity (for example, heart-shaped or super-heart-shaped).

[0135] It can be understood that the number, position, size, and setting method of the baffle can affect the second path L2 that the sound wave travels in the second cavity 723, thereby affecting the phase difference between the first sound V1 and the second sound V2. Therefore, the number, position, size, and setting method of the baffle can be reasonably set according to the requirement of the phase difference between the first sound V1 and the second sound V2.

[0136] In addition, it can also be seen in this embodiment that, when other parameters (for example, the first path and the second path) are the same, the phase difference between the first sound V1 and the second sound V2 is negatively correlated with the frequency. The higher the frequency, the smaller the phase difference between the first sound V1 and the second sound V2; the lower the frequency, the larger the phase difference between the first sound V1 and the second sound V2.

[0137] FIG. 8 is a schematic diagram of another exemplary sound generating part shown according to some embodiments of this specification.

[0138] As shown in FIG. 8, an acoustic structure for changing the sound propagation speed can be provided in the first cavity 822 and / or the second cavity 823 of the sound generating part 800. For example, the acoustic structure can be a slow acoustic structure that can slow down the speed of sound when it propagates in itself. The speed of sound wave propagating in air is faster than the speed of sound wave propagating in the slow acoustic structure. In some embodiments, the slow acoustic structure can include at least one of acoustic mesh, acoustic porous material, etc. When the sound wave passes through the micropores in the mesh or porous material, due to the viscous effect of the micropores on air, the speed of the sound wave becomes slower when passing through the micropores, so as to achieve the effect of slowing down. Specifically, the speed of sound wave propagating in air (also called normal sound speed) is c, and the speed of sound wave propagating in the slow acoustic structure (also called equivalent sound speed) is c'. From the above description, it can be known that c' < c. Therefore, by setting a slow acoustic structure in the cavity to change the sound propagation speed, the actual output phase of the first sound V1 and / or the second sound V2 can be regulated, and thus the phase difference between the first sound V1 and the second sound V2 can be adjusted.

[0139] In this embodiment, the slow acoustic structure 826 is set in the second cavity 823 as an example. As shown in Figure 8, a slow acoustic structure 826 can be set in the second cavity 823. The sound waves radiated from the front side of the acoustic driver 821 are radiated to the outside world from the first acoustic hole 824. The distance traveled by the sound wave is the first sound path L1. The sound waves radiated from the rear side of the acoustic driver 821 are radiated to the outside world from the second acoustic hole 825. The distance traveled by the sound wave can include the second sound path L2 propagated through the air and the third sound path L3 propagated through the slow acoustic structure 826.

[0140] The phase delay between the first sound V1 radiated from the first acoustic hole 824 and the second sound V2 radiated from the second acoustic hole 825 can be:

[0141] Where c represents the normal sound speed, and c' represents the equivalent sound speed in the slow acoustic structure 826. Therefore, the phase difference between the first sound V1 and the second sound V2 is for:

[0142] It can be seen from this that the actual output phase difference between the first sound V1 and the second sound V2 can be controlled by controlling the equivalent sound speed and / or the third sound path L3 of the sound wave propagating in the slow acoustic structure 826 (for example, the ratio of the equivalent sound speed to the normal sound speed in the slow acoustic structure can be made to be in the range of 0.02 to 0.5), so that the phase difference between the first sound V1 and the second sound V2 is between 120° and 179°, thereby making the sound radiated to the far field by the sound-emitting part 800 exhibit strong directivity (for example, cardioid or supercardioid).

[0143] Furthermore, this embodiment also shows that, when other parameters (e.g., equivalent sound velocity, first sound path, second sound path, and third sound path) remain the same, the phase difference between the first sound V1 and the second sound V2 is negatively correlated with frequency. The higher the frequency, the smaller the phase difference between the first sound V1 and the second sound V2; the lower the frequency, the larger the phase difference between the first sound V1 and the second sound V2.

[0144] FIG9 is a schematic diagram of another exemplary sound-producing part according to some embodiments of the present specification.

[0145] As shown in Figure 9, an expanded acoustic structure 926 can be provided in the first cavity 922 and / or the second cavity 923 of the sound-emitting part 900. The expanded acoustic structure 926 can change (for example, expand) the cross-sectional area of ​​the first cavity 922 or the second cavity 923 at different positions on the sound transmission path. When a sound wave propagates in a waveguide (that is, an air waveguide formed by the first cavity 922 or the second cavity 923), if the cross-sectional area of ​​the waveguide at different positions on the sound wave transmission path changes, 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 has changed. Accordingly, the parameters related to the equivalent impedance (such as equivalent sound speed, equivalent density, etc.) will also change accordingly, thereby causing the phase of the sound wave to change. For example, the effect of the expanded acoustic structure 926 on the change in equivalent sound speed is mainly related to the ratio of the cross-sectional area of ​​the second cavity 923 after expansion by the expanded acoustic structure 926 to the original cross-sectional area of ​​the second cavity 923. In some embodiments, the actual equivalent speed of sound may be obtained through simulation or experimental testing.

[0146] In this embodiment, the expanded acoustic structure 926 is provided in the second cavity 923 as an example for explanation. As shown in FIG9 , the expanded acoustic structure 926 can be provided on two opposite side walls of the second cavity 923. The expanded acoustic structure 926 causes a sudden change in the cross-sectional area of ​​the second cavity 923 before and after a specific position on the sound transmission path. In some embodiments, the expanded acoustic structure 926 can be an expanded cavity. The structural shape of the expanded cavity can be a rectangle as shown in FIG9 . In other embodiments, the cross-sectional area of ​​the expanded acoustic structure 926 can also be other shapes, for example, a triangle, a trapezoid, etc. The structural shape of the expanded cavity can be reasonably set according to the phase difference between the first sound V1 and the second sound V2.

[0147] As shown in Figure 9, the sound waves radiated from the front side of the acoustic driver 921 radiate from the first acoustic hole 924 to the outside world, and the distance traveled by the sound waves is the first acoustic path L1. The sound waves radiated from the rear side of the acoustic driver 921 pass through the expanded acoustic structure 926 and the second cavity 923 and radiate from the second acoustic hole 925 to the outside world, and the distance traveled by the sound waves is the second acoustic path L2. Among them, the sound speed in the first acoustic path L1 is the normal sound speed c, and the sound speed in the second acoustic path L2 is the equivalent sound speed c'. The phase delay between the first sound V1 radiated from the first acoustic hole 924 and the second sound radiated from the second acoustic hole 925 is:

[0148] Where c represents the normal sound speed, and c' represents the equivalent sound speed in the expanded acoustic structure 926. Thus, the phase difference between the first sound V1 and the second sound V2 is for:

[0149] It can be seen from this that the actual output phase difference between the first sound V1 and the second sound V2 can be controlled by setting an expanded acoustic structure 926 in the cavity to control the equivalent sound velocity of the sound wave propagating in the cavity, so that the phase difference between the first sound V1 and the second sound V2 is between 120° and 179°, thereby making the sound radiated to the far field by the sound-emitting part 900 exhibit strong directivity (for example, cardioid or supercardioid).

[0150] Furthermore, this embodiment also shows that, when other parameters (e.g., first sound range, second sound range, equivalent sound speed) remain the same, the phase difference between the first sound V1 and the second sound V2 is negatively correlated with frequency. The higher the frequency, the smaller the phase difference between the first sound V1 and the second sound V2; the lower the frequency, the larger the phase difference between the first sound V1 and the second sound V2.

[0151] FIG10A is a schematic diagram of another exemplary sound-producing part according to some embodiments of the present specification.

[0152] The structure of the sound-emitting portion 1000 shown in FIG10A is similar to that of the sound-emitting portion 700 shown in FIG7A . For example, the sound-emitting portion 1000 may include at least one acoustic driver 1021, a first cavity 1022, and a second cavity 1023. The first cavity 1022 may be provided with at least one first acoustic hole 1024, and the second cavity 1023 may be provided with at least one second acoustic hole 1025. For details regarding 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 description of FIG7A . The difference between the sound-emitting portion 1000 and the sound-emitting portion 700 lies in the difference in acoustic structure. As shown in FIG10A , a sound-absorbing structure 1026 may be provided within the first cavity 1022 and / or the second cavity 1023 of the sound-emitting portion 1000. In some embodiments, the sound-absorbing structure 1026 may have a resonant frequency. The actual output phase difference between the two sound waves can be controlled by modulating the sound near the resonant frequency of the sound absorbing structure 1026 (e.g., phase modulation). In some embodiments, the sound absorbing structure 1026 can be a Helmholtz resonator. In some embodiments, the sound absorbing structure 1026 can be a microperforated plate resonator. In some embodiments, the sound absorbing structure 1026 can be a quarter-wavelength tube resonator.

[0153] In this embodiment, the sound absorbing structure 1026 is provided in the second cavity 1023 as an example for description. The sound absorbing structure 1026 can be provided on the side wall of the second cavity 1023 and be acoustically connected to the second cavity 1023. Taking the Helmholtz resonant cavity as an example, its resonant frequency f0 can be:

[0154] Wherein, M represents the acoustic mass (mainly related to the nozzle parameters of the Helmholtz resonator), and C represents the acoustic capacity (mainly related to the cavity parameters at the rear end of the Helmholtz resonator).

[0155] FIG10B is a schematic diagram showing the frequency response of the Helmholtz resonant cavity.

[0156] Wherein, the horizontal axis represents the frequency, the unit is Hz, and the vertical axis represents the amplitude response (the unit is dB) or the phase response (the unit is ° (deg)). The solid line is the amplitude response of the frequency response, and the dotted line is the phase response of the frequency response. As shown in Figure 10B, when the resonance frequency f0 of the Helmholtz resonator is 2000Hz, the amplitude response has a resonance peak at 2000Hz, and the phase response is around 2000Hz. As the frequency increases, the phase gradually changes from 180° and eventually approaches 0°. It can be seen that in the low-frequency range (for example, between 40Hz-1000Hz), the phase difference varies in the range of 179° to 150°, which basically meets the phase difference requirements for achieving cardioid directivity or supercardioid directivity described in the embodiments of this specification. Therefore, a sound-absorbing structure 1026 can be set in the cavity to adjust the phase of the sound radiated from the acoustic hole corresponding to the cavity, thereby controlling the actual output phase difference between the first sound and the second sound, so that the sound radiated to the far field by the sound-emitting part 900 can show strong directivity (for example, cardioid or supercardioid).

[0157] In some embodiments, when at least one acoustic driver of the sound-emitting portion is a single driver or includes two acoustic drivers, the phase difference between the first sound V1 and the second sound V2 can be adjusted using the method described in Figures 7A to 10A. Under this control method, the phase difference between the sound radiated by the acoustic driver to the first cavity and the second cavity can be 180°. By setting different types of acoustic structures in the cavity (for example, baffles, slow acoustic structures, expansion acoustic structures, sound-absorbing structures), the phase of the first sound V1 or the second sound V2 is changed, thereby achieving the adjustment of the phase difference between the first sound V1 and the second sound V2. In some embodiments, when at least one acoustic driver includes two acoustic drivers, the phase difference between the first sound V1 and the second sound V2 can also be adjusted by regulating the electrical drive signals corresponding to the two acoustic drivers. In some embodiments, the phases of the two electrical drive signals can be set separately so that the phase of the sound radiated by one acoustic driver to the first cavity is not completely opposite to the phase of the sound radiated by the other acoustic driver to the second cavity.

[0158] FIG11 is an exemplary structural diagram of a sound-emitting part having two acoustic drivers according to some embodiments of the present specification; FIG12 is an exemplary structural diagram of a sound-emitting part having two acoustic drivers according to other embodiments of the present specification.

[0159] As shown in FIG11 , the sound-emitting unit 1100 may include a first acoustic driver 1121A, a second acoustic driver 1121B, a first cavity 1122, and a second cavity 1123. The first cavity 1122 may have a first acoustic hole 1124, through which the first acoustic driver 1121A may radiate a first sound V1 to the outside world. The second cavity 1123 may have a second acoustic hole 1125, through which the second acoustic driver 1121B may radiate a second sound V2 to the outside world. In some embodiments, the first acoustic driver 1121A and the second acoustic driver 1121B may be driven by two sets of electrical signals. By setting the phases of the two sets of electrical drive signals to be different, the phase difference between the first sound V1 and the second sound V2 may be set between 120° and 179°. For example, as shown in Figure 11, the phase difference between the electrical driving signal for driving the first acoustic driver 1121A and the electrical driving signal for driving the second acoustic driver 1121B can be set to 120°-179°. Under this setting, no other acoustic structures need to be set in the first cavity 1122 and the second cavity 1123, and the sound path of the sound propagation in their respective cavities is also roughly the same, thereby achieving a phase difference of 120°-179° between the first sound V1 and the second sound V2. For another example, as shown in FIG12 , the phase difference between the electrical driving signal for driving the first acoustic driver 1121A and the driving electrical signal for the second acoustic driver 1121B may be set not to be between 120° and 179°. Under this setting, an acoustic structure may be set in the first cavity 1122 and / or the second cavity 1123 (for example, as shown in FIG12 , a slow acoustic structure 1126 may be set in the second cavity 1123) so that the phase difference between the first sound V1 and the second sound V2 is between 120° and 179°.

[0160] The beneficial effects that may be brought about by the acoustic output device described in the embodiments of this specification include but are not limited to: (1) by adjusting the phase difference of the two sounds generated by the sound-emitting part, the near-field sound pressure level difference between the first acoustic hole and the second acoustic hole is made smaller and the far-field sound pressure level difference is made larger, so that within the target frequency band, the sound radiated to the far field by the acoustic output device presents a stronger directionality, so that when the listener wears the acoustic output device, the volume in the direction of the ear canal opening is the largest, and the sound leakage in the opposite direction of the listener's ear canal opening and the sound leakage in other directions are smaller, thereby better taking into account the opening of the ear canal. (1) The acoustic output device is characterized in that the phase difference between the two sounds generated by the sound-emitting part is adjusted by arranging a variety of acoustic structures (e.g., baffles, slow acoustic structures, expansion acoustic structures, and sound-absorbing structures) in the sound-emitting part of the acoustic output device, thereby making the adjustment of the phase difference more flexible and more precise, thereby improving the practicality of the acoustic output device; (2) By arranging a variety of acoustic structures (e.g., baffles, slow acoustic structures, expansion acoustic structures, and sound-absorbing structures) in the sound-emitting part of the acoustic output device, the adjustment of the phase difference can be made more flexible and more precise, thereby improving the practicality of the acoustic output device; (3) When at least one acoustic driver in the sound-emitting part includes two acoustic drivers, the adjustment of the phase difference between the two sounds can be achieved by directly adjusting the two electrical drive signals, thereby making the structure of the acoustic output device simpler and the cost lower.

[0161] While the basic concepts have been described above, it will be apparent to those skilled in the art that the detailed disclosure is merely illustrative and does not limit this specification. Although not explicitly stated herein, various modifications, improvements, and revisions to this specification may be made by those skilled in the art. Such modifications, improvements, and revisions are suggested in this specification and remain within the spirit and scope of the exemplary embodiments of this specification.

Claims

1. An acoustic 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 provided in the first cavity, a second acoustic hole is provided in the second cavity, and the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, wherein: In the 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, and the near-field sound pressure level difference is less than 6 dB, and, in the target frequency band, the sound radiated to the far field by the acoustic output device presents directionality, which is manifested as the sound radiated from the first acoustic hole and the second acoustic hole having a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions.

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

3. The acoustic output device according to claim 1, wherein: The near-field sound pressure level difference is less than 3 dB, and / or the far-field sound pressure level difference is not less than 6 dB.

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

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

6. 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 less than 30°.

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

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

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

25.

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

15.

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

1.

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

5.

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

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

15. The acoustic output device according to claim 1, wherein: The at least one acoustic driver includes two acoustic drivers, and the two acoustic drivers radiate sound to the first cavity and the second cavity, respectively.

16. The acoustic output device according to claim 1, wherein: The acoustic output device further comprises: The support structure is used to be mounted on the head or upper torso of the user, and the acoustic output device is worn on the user's ear without blocking the ear canal.

17. An acoustic 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 provided in the first cavity, a second acoustic hole is provided in the second cavity, and the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, wherein: In the target frequency band, the sound radiated to the far field by the acoustic output device exhibits directivity, which is manifested in that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions, and The difference in acoustic load between the first acoustic hole and the second acoustic hole is less than 0.

15.

18. An acoustic 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 provided in the first cavity, a second acoustic hole is provided in the second cavity, and the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, wherein: In the target frequency band, the sound radiated to the far field by the acoustic output device exhibits directivity, which is manifested in that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions, and The ratio of the surface acoustic load of the first acoustic hole to the surface acoustic load of the second acoustic hole is in the range of 0.5-3.

5.

19. An acoustic 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 provided in the first cavity, a second acoustic hole is provided in the second cavity, the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, and within a frequency range of 1kHz-8kHz, the rate of change of the phase difference is less than 30° / oct, wherein, In the target frequency band, the sound radiated to the far field by the acoustic output device exhibits directivity, which is manifested in that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of not less than 3dB in at least one pair of opposite directions.

20. An acoustic 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 provided in the first cavity, a second acoustic hole is provided in the second cavity, and the at least one acoustic driver radiates sound with a phase difference to the outside through the first acoustic hole and the second acoustic hole, wherein: In the target frequency band, the sound radiated to the far field by the acoustic output device exhibits directivity, which is manifested in that the sound radiated from the first acoustic hole and the second acoustic hole has a far-field sound pressure level difference of not less than 3 dB in at least one pair of opposite directions, and The ratio of the opening area of ​​the first acoustic hole to the opening area of ​​the second acoustic hole is in the range of 0.5-2.

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