Acoustic output device

Abstract

The embodiment of the invention provides an acoustic output device, which comprises a sound production part, and the sound production part comprises at least one acoustic driver; the first cavity and the second cavity are acoustically coupled with the at least one acoustic driver, the first cavity is provided with at least one first sound outlet hole, the second cavity is provided with at least one second sound outlet hole, and the at least one acoustic driver is connected with the at least one acoustic driver through the at least one first sound outlet hole. And the at least one first sound outlet hole radiates sound to the outside, the at least one second sound outlet hole radiates sound to the outside, in at least part of the low-frequency range, the sound radiated to the far field by the sound production part shows directivity, and the directivity shows that the sound radiated from the first sound outlet hole and the second sound outlet hole has a sound pressure difference of not less than 3dB in at least one pair of opposite directions.

Description

Acoustic output device Technical Field

[0001] This specification relates to the field of acoustics, and in particular to an acoustic output device. Background Art

[0002] 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.

[0003] 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.

[0004] Summary of the Invention

[0005] One of the embodiments of the present specification provides an acoustic output device, comprising a sound-emitting portion, the sound-emitting portion comprising: at least one acoustic driver; a first cavity and a second cavity acoustically coupled to the at least one acoustic driver, the first cavity having at least one first sound outlet hole, the second cavity having at least one second sound outlet hole, the at least one acoustic driver radiating sound to the outside through the at least one first sound outlet hole and the at least one second sound outlet hole, wherein, in at least part of the low-frequency range, the sound radiated to the far field by the sound-emitting portion exhibits directionality, and the directionality is manifested in that the sound radiated from the first sound outlet hole and the second sound outlet hole has a sound pressure difference of not less than 3dB in at least one pair of opposite directions.

[0006] In some embodiments, the at least one acoustic driver is a single acoustic driver having a front side and a rear side and radiating sound into the first cavity and the second cavity through the front side and the rear side, respectively.

[0007] 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.

[0008] In some embodiments, the acoustic driver radiates a first sound outward through the at least one first sound outlet hole, and radiates a second sound outward through the at least one second sound outlet hole; a phase difference between the first sound and the second sound is between 120° and 179°.

[0009] In some embodiments, the phase difference between the first sound and the second sound is between 170° and 179°.

[0010] In some embodiments, within a preset frequency range, the phase difference between the first sound and the second sound is negatively correlated with the magnitude of the frequency.

[0011] In some embodiments, the first sound propagates in the first cavity with a first sound path, the second sound propagates in the second cavity with a second sound path, and the first sound path and the second sound path have a sound path difference.

[0012] In some embodiments, the first cavity and / or the second cavity is provided with an acoustic structure, and the acoustic structure comprises a baffle.

[0013] In some embodiments, the first cavity or the second cavity is provided with at least one of an acoustic gauze and an acoustic porous material.

[0014] In some embodiments, the first cavity or the second cavity is provided with an expansion acoustic structure, and the expansion acoustic structure changes the cross-sectional area of ​​the first cavity or the second cavity at different positions on the sound transmission path.

[0015] In some embodiments, the first cavity or the second cavity is provided with a sound absorbing structure, and the resonance frequency of the sound absorbing structure is between 1000 Hz and 3000 Hz.

[0016] In some embodiments, the electrical driving signals corresponding to the two acoustic drivers have different phases.

[0017] In some embodiments, the acoustic output device further comprises a support structure for being mounted on the user's head or upper torso, the support structure being configured to carry the sound-emitting part and to position the sound-emitting part on the user's ear without blocking the ear canal.

[0018] An embodiment of the present specification also provides an acoustic output device, including a sound-emitting part, which includes: at least one acoustic driver; a first cavity and a second cavity acoustically coupled to the at least one acoustic driver, at least one first sound outlet hole being opened in the first cavity, and at least one second sound outlet hole being opened in the second cavity, the at least one acoustic driver radiates a first sound to the outside through the first cavity and the at least one first sound outlet hole, and radiates a second sound to the outside through the second cavity and the at least one second sound outlet hole; wherein, at 1000 Hz, the phase difference between the first sound and the second sound is between 125° and 178°.

[0019] In some embodiments, a distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole is 2 mm-60 mm.

[0020] In some embodiments, at 1000 Hz, a phase difference between the first sound and the second sound is between 174° and 178°.

[0021] In some embodiments, a distance between an acoustic center of the first sound outlet hole and an acoustic center of the second sound outlet hole is within 2 mm-4 mm.

[0022] In some embodiments, at 1000 Hz, the phase difference between the first sound and the second sound is between 170° and 177°.

[0023] In some embodiments, a distance between an acoustic center of the first sound outlet hole and an acoustic center of the second sound outlet hole is within a range of 4 mm to 8 mm.

[0024] In some embodiments, at 1000 Hz, the phase difference between the first sound and the second sound is between 162° and 173°.

[0025] In some embodiments, a distance between an acoustic center of the first sound outlet hole and an acoustic center of the second sound outlet hole is within a range of 8 mm to 16 mm.

[0026] In some embodiments, at 1000 Hz, the phase difference between the first sound and the second sound is between 158° and 165°.

[0027] In some embodiments, a distance between an acoustic center of the first sound outlet hole and an acoustic center of the second sound outlet hole is within a range of 16 mm to 20 mm.

[0028] In some embodiments, at 2000 Hz, the phase difference between the first sound and the second sound is between 138° and 177°.

[0029] In some embodiments, a distance between an acoustic center of the first sound outlet hole and an acoustic center of the second sound outlet hole is within a range of 2 mm to 20 mm.

[0030] In some embodiments, at 2000 Hz, the phase difference between the first sound and the second sound is between 170° and 175°.

[0031] In some embodiments, a distance between an acoustic center of the first sound outlet hole and an acoustic center of the second sound outlet hole is within 2 mm-4 mm.

[0032] In some embodiments, there are multiple frequency values ​​within the frequency band of 500 Hz-3000 Hz, and at any one of the multiple frequency values, the phase difference between the first sound and the second sound is between 121° and 179°.

[0033] In some embodiments, a distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 20 mm.

[0034] In some embodiments, there are multiple frequency values ​​within the frequency band of 500 Hz-3000 Hz, and at any one of the multiple frequency values, the phase difference between the first sound and the second sound is between 175° and 179°.

[0035] In some embodiments, a distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 4 mm.

[0036] In some embodiments, in the frequency band of 500 Hz-3000 Hz, the phase difference between the first sound and the second sound is between 145° and 179°.

[0037] In some embodiments, a distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 10 mm.

[0038] In some embodiments, in the frequency band of 500 Hz-3000 Hz, the phase difference between the first sound and the second sound is between 175° and 179°.

[0039] In some embodiments, a distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 4 mm.

[0040] In some embodiments, at 200 Hz, a phase difference between the first sound and the second sound is greater than 175° and less than 179.8°.

[0041] In some embodiments, a distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 20 mm.

[0042] In some embodiments, at 200 Hz, a phase difference between the first sound and the second sound is between 177° and 179.8°.

[0043] In some embodiments, a distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 4 mm.

[0044] In some embodiments, within a preset frequency range, the phase difference between the first sound and the second sound is negatively correlated with the magnitude of the frequency.

[0045] In some embodiments, the at least one acoustic driver is a single acoustic driver having a front side and a rear side and radiating sound into the first cavity and the second cavity through the front side and the rear side, respectively.

[0046] 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.

[0047] In some embodiments, the electrical driving signals corresponding to the two acoustic drivers have different phases.

[0048] In some embodiments, the first sound propagates in the first cavity with a first sound path, the second sound propagates in the second cavity with a second sound path, and the first sound path and the second sound path have a sound path difference.

[0049] In some embodiments, the first cavity and / or the second cavity is provided with an acoustic structure, and the acoustic structure comprises a baffle.

[0050] In some embodiments, the first cavity or the second cavity is provided with at least one of an acoustic gauze and an acoustic porous material.

[0051] In some embodiments, the first cavity or the second cavity is provided with an expansion acoustic structure, and the expansion acoustic structure changes the cross-sectional area of ​​the first cavity or the second cavity at different positions on the sound transmission path.

[0052] In some embodiments, the first cavity or the second cavity is provided with a sound absorbing structure, and the resonance frequency of the sound absorbing structure is between 1000 Hz and 3000 Hz.

[0053] In some embodiments, the acoustic output device further comprises: a support structure for being mounted on the head or upper torso of a user, the support structure being configured to carry the sound-emitting part and to place the sound-emitting part on the user's ear without blocking the ear canal.

[0054] The acoustic output device provided in the embodiments of this specification can make the sound radiated from the sound-emitting part to the far field in the low-frequency range present directionality by adjusting the phase difference between the first sound and the second sound, thereby making the volume in the direction of the listener's ear canal opening higher, and the sound leakage in the opposite direction of the listener's ear canal opening and the sound leakage in other directions smaller, thereby better balancing the openness of the ear canal and the privacy of listening. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] This specification 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:

[0056] FIG1 is a schematic diagram of an exemplary directional radiation sound field of an acoustic output device according to some embodiments of this specification;

[0057] FIG2 is a structural block diagram of an exemplary acoustic output device according to some embodiments of this specification;

[0058] FIG3A is a schematic diagram of a directional radiation sound field of an exemplary acoustic output device according to some embodiments of this specification;

[0059] FIG3B is a schematic diagram of a directional radiation sound field of an exemplary acoustic output device according to some embodiments of this specification;

[0060] FIG3C is a schematic diagram of a method for calculating the distance between acoustic centers according to some embodiments of this specification;

[0061] FIG4 is a schematic diagram of exemplary dual-sound source radiation according to some embodiments of this specification;

[0062] 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;

[0063] FIG6 is a schematic diagram of directional radiation sound fields at different frequencies according to some embodiments of this specification;

[0064] FIG7A is a schematic diagram of an exemplary sound-producing part according to some embodiments of the present specification;

[0065] FIG7B is a schematic diagram of an exemplary sound-producing part according to other embodiments of the present specification;

[0066] FIG7C is a schematic diagram of an exemplary sound-producing part according to other embodiments of this specification;

[0067] FIG8 is a schematic diagram of another exemplary sound-producing part according to some embodiments of this specification;

[0068] FIG9 is a schematic diagram of another exemplary sound-producing part according to some embodiments of this specification;

[0069] FIG10A is a schematic diagram of another exemplary sound-producing part according to some embodiments of the present specification;

[0070] FIG10B is a schematic diagram of the frequency response of the Helmholtz resonant cavity;

[0071] FIG11 is an exemplary structural diagram of a sound-emitting portion having two acoustic drivers according to some embodiments of the present specification;

[0072] 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

[0073] To more clearly illustrate the technical solutions of the embodiments of this specification, the following briefly describes the drawings required for describing the embodiments. Obviously, the drawings described below are merely examples or embodiments of this specification. Those skilled in the art can apply this specification 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.

[0074] 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.

[0075] As used in this specification and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not refer to the singular but also 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.

[0076] Flowcharts are used throughout this specification to illustrate the operations performed by systems according to embodiments of this specification. It should be understood that preceding or following operations do not necessarily need to be 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.

[0077] 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.

[0078] 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 (the first sound source and the second sound source as shown in Figure 1) with equal amplitude and opposite phase to form a dipole, which 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, the dipole's directional radiation sound field diagram in Figure 1 also shows that when one main lobe points toward the listener's ear canal opening, 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.

[0079] In order to further reduce the sound leakage of the acoustic output device, an embodiment of the present specification provides an acoustic output device. The acoustic output device may include a sound-emitting portion and a support structure for supporting the sound-emitting portion. When the user wears the acoustic output device, the support structure can be used to be mounted on the user's head or upper torso, and the acoustic output device fixes the sound-emitting portion near the user's ear but does not block the user's ear canal through the support structure. In some embodiments, the sound-emitting portion can be used to radiate sound to the outside. The sound-emitting portion may include at least one acoustic driver, and a first cavity and a second cavity acoustically coupled to the at least one acoustic driver. At least one first sound outlet is provided in the first cavity, and at least one second sound outlet is provided in the second cavity. At least one acoustic driver can radiate sound (also referred to as first sound) from at least one first sound outlet to the outside through the first cavity, and radiate sound (also referred to as second sound) from at least one second sound outlet to the outside through the second cavity. The first sound and the second sound have a certain phase difference. When this 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 in the opposite direction. In some embodiments, the phase difference between the first sound and the second sound can be between 120° and 179°.

[0080] In some embodiments, by adjusting the phase difference between the two sounds produced by the sound-emitting part, the sound radiated to the far field by the sound-emitting part can be made directional in the low-frequency range (the directionality can be manifested as the two sounds having a sound pressure difference of not less than 6dB in at least one pair of opposite directions), so that the volume in the direction of the listener's ear canal opening can be higher, and the sound leakage in the opposite direction of the listener's ear canal opening and the sound leakage in other directions can be smaller, thereby better balancing the openness of the ear canal and the privacy of listening.

[0081] FIG2 is a block diagram of an exemplary acoustic output device according to some embodiments of the present disclosure. As shown in FIG2 , the acoustic output device 100 may include a supporting structure 110 and a sound-emitting portion 120 .

[0082] 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 head or upper torso. In some embodiments, the support structure 110 can include an arc structure that adapts to the user's auricle. 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, 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 via the user's head or neck, thereby enabling the acoustic output device 100 to be worn.

[0083] 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.

[0084] The sound-emitting unit 120 can be used to generate and radiate sound. In some embodiments, the acoustic output device 100 can secure the sound-emitting unit 120 near the user's ear without blocking the user's ear canal via the support structure 110, thereby allowing the user's ear to remain open. With the ear open, the user can hear the sound output by the sound-emitting unit 120 while also receiving sounds from the external environment.

[0085] In some embodiments, the sound-emitting portion 120 may include at least one 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, at least one first sound outlet hole may be provided on the first cavity 122, and the at least one acoustic driver 121 may radiate sound (also called first sound) from the at least one first sound outlet hole through the first cavity 122; at least one second sound outlet hole may be provided on the second cavity 123, and the at least one acoustic driver 121 may radiate sound (also called second sound) from the at least one second sound outlet hole through the second cavity 123.

[0086] The acoustic driver 121 may be a device that can convert an electrical signal into a sound signal and output it. Exemplarily, the acoustic driver 121 may have a diaphragm and 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, the front side of the acoustic driver 121 may be the side of the diaphragm facing away from the magnetic circuit assembly, and the rear side of the acoustic driver 121 may be the side of the diaphragm facing the magnetic circuit assembly or the side of the magnetic circuit assembly facing away from the diaphragm. When vibrating, the side of the diaphragm facing away from the magnetic circuit assembly and the side facing the magnetic circuit assembly will produce sounds with the same amplitude and opposite phases. By setting the sound transmission path of the sound in the sound-emitting part 120, a specific phase difference can be achieved between the first sound radiated from the first sound outlet after passing through the first cavity 122 and the second sound radiated from the second sound outlet after passing through the second cavity 123 (for example, the phase difference is between 120° and 179°). In some embodiments, the first cavity 122 and the second cavity 123 are respectively located on both sides of the diaphragm, and when the diaphragm vibrates, it can radiate sound to the first cavity 122 and the second cavity 123 respectively. The sound radiated by the diaphragm to the first cavity 122 can be transmitted to the first sound outlet according to the first sound transmission path and radiated outward from the first sound outlet (the sound radiated from the first sound outlet is the first sound); the sound radiated by the diaphragm to the second cavity 123 can be transmitted to the second sound outlet according to the second sound transmission path and radiated outward from the second sound outlet (the sound radiated from the second sound outlet is the second sound). 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.

[0087] 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 sound outlet through the first cavity 122, and the amplitude and phase of the second sound radiated from the second sound outlet 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.

[0088] 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 in the first cavity 122 can be radiated outward through the first sound outlet, and the sound in the second cavity 123 can be radiated outward through the second sound outlet. In some embodiments, the number of the first sound outlet and / or the second sound outlet can be one or more. The number of sound outlets can be reasonably set according to actual needs and is not specifically limited in this specification.

[0089] 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 sound outlet of the cavity. In some embodiments, the phase of the first sound radiated from the first sound outlet and / or the phase of the second sound radiated from the second sound outlet by the acoustic driver 121 can be regulated 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 sound outlet and the phase of the second sound at the second sound outlet). 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 places in this specification, for example, FIG. 7A to FIG. 10B .

[0090] 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 .

[0091] In some embodiments, when the phase difference between the first sound and the second sound is within a specific range (e.g., 120° to 179°), the sound radiated from the sound-emitting portion 120 to the far field can exhibit directionality within at least a portion of the low-frequency range, such that the radiation field of the sound in the far field has only one strong direction (the sound pressure in the strong direction and the directions adjacent thereto is sufficiently high), while the radiation intensity in other directions is relatively low. In some embodiments, the sound radiated from the first cavity 122 and the second cavity 123 can have a sound pressure difference of not less than 15 dB in at least one pair of opposite directions (e.g., the direction toward the ear canal opening and the direction away from the ear canal opening when the user wears the acoustic output device 100). In some embodiments, the sound radiated from the first cavity 122 and the second cavity 123 can have a sound pressure difference of not less than 13 dB in at least one pair of opposite directions (e.g., the direction toward the ear canal opening and the direction away from the ear canal opening when the user wears the acoustic output device 100). In some embodiments, the sound radiated from the first cavity 122 and the second cavity 123 may have a sound pressure difference of no less than 10 dB in at least one pair of opposite directions (for example, the direction toward the ear canal opening and the direction away from the ear canal opening when the user is wearing the acoustic output device 100). In some embodiments, the sound radiated from the first cavity 122 and the second cavity 123 may have a sound pressure difference of no less than 8 dB in at least one pair of opposite directions (for example, the direction toward the ear canal opening and the direction away from the ear canal opening when the user is wearing the acoustic output device 100). In some embodiments, the sound radiated from the first cavity 122 and the second cavity 123 may have a sound pressure difference of no less than 6 dB in at least one pair of opposite directions (for example, the direction toward the ear canal opening and the direction away from the ear canal opening when the user is wearing the acoustic output device 100). In some embodiments, the sound radiated from the first cavity 122 and the second cavity 123 can have a sound pressure difference of no less than 5 dB in at least one pair of opposite directions (for example, the direction toward the ear canal opening and the direction away from the ear canal opening when the user is wearing the acoustic output device 100). In some embodiments, the sound radiated from the first cavity 122 and the second cavity 123 can have a sound pressure difference of no less than 3 dB in at least one pair of opposite directions (for example, the direction toward the ear canal opening and the direction away from the ear canal opening when the user is wearing the acoustic output device 100). In some embodiments, when the user is wearing the acoustic output device 100, the direction of strong directivity can be oriented toward the user's ear canal opening. In this way, when the user is wearing the acoustic output device 100, the sound transmitted to the user's ear canal opening can be sufficiently loud while also reducing sound leakage in other directions (for example, away from the ear canal opening), thereby improving the user's listening experience and privacy.In some embodiments, the sound pressure difference can be measured by setting up a collection position in a pair of opposite directions of the acoustic output device 100 (for example, the direction toward which the first sound outlet is directed and the direction away from which the first sound outlet is directed). The collection distance from the midpoint of the line connecting the acoustic center of the first sound outlet and the acoustic center of the second sound outlet to each collection position is the same and is no less than 20 cm. Sound collection devices are placed at the two collection positions to collect the sound pressure of the acoustic output device 100, and the difference between the two sound pressures is calculated, which is the sound pressure difference between the sound radiated from the first cavity 122 and the second cavity 123 in at least one pair of opposite directions.

[0092] It should be noted that the acoustic center of the sound hole (for example, the first sound hole or the second sound hole) can indicate the equivalent sound position of the sound hole, and the equivalent sound position can be determined based on the shape, size and number of the sound holes. When the number of the sound hole is one, the acoustic center can be the geometric center of the sound hole (for example, the sound hole has an outer opening and an inner opening in the depth direction, and the geometric center of the sound hole refers to the centroid of the outer opening). When the number of the sound holes is two, the acoustic center can be the midpoint of the line connecting the geometric centers of the two sound holes. For example, when the number of the first sound holes is two, the acoustic center of the first sound hole can be the midpoint of the line connecting the geometric centers of the two first sound holes. When the number of the sound holes is three, the acoustic center can be the center of the circumscribed circle of the geometric centers of the three sound holes, or the acoustic center can also be the centroid of the triangle surrounded by the line connecting the geometric centers of the three sound holes. When the number of the sound outlet holes is four (or more), the acoustic center may be the centroid of a quadrilateral (or polygon) formed by connecting lines of the geometric centers of the four (or more) sound outlet holes.

[0093] In some embodiments, the spacing between the first sound hole and the second sound hole can be 2mm-60mm. The spacing between the first sound hole and the second sound hole can refer to the spacing between the acoustic center of the first sound hole and the acoustic center of the second sound hole. Taking the example that the number of first sound holes is one and the number of second sound holes is two, one first sound hole and two second sound holes can form a triangle determined by three sides. The lengths of the three sides of the triangle can be obtained by measurement, and then the distance from the acoustic center of the first sound hole to the acoustic center of the second sound hole can be calculated (when the number of second sound holes is two, the acoustic center can be the midpoint of the line connecting the geometric centers of the two sound holes). For example, referring to Figure 3C, the geometric center A of the first sound hole, the geometric center B1 of one second sound hole and the geometric center B2 of another second sound hole can form a triangle 300. The lengths of the three sides of the triangle 300 can be obtained by measurement, which are a, b and c respectively. The acoustic center of the first sound hole is the geometric center A of the first sound hole. The acoustic centers of the two second sound holes are the midpoint B3 of the line connecting the geometric centers of the two sound holes (i.e., geometric center B1 and geometric center B2). The distance from the acoustic center of the first sound hole to the acoustic center of the second sound hole is the length of line segment AB3 (denoted as x). The value of x can be calculated according to the following formula: cosθ=-cos(180°-θ).(13)

[0094] Here, θ represents the angle formed by line segment AB3 and line segment B1B3.

[0095] According to formula (13)-formula (15), we can calculate:

[0096] In some embodiments, within the low frequency range, the phase difference between the first sound and the second sound may be between 120° and 179°. In some embodiments, within the low frequency range, the phase difference between the first sound and the second sound may be between 125° and 170°. In some embodiments, within the low frequency range, the phase difference between the first sound and the second sound may be between 130° and 165°. In some embodiments, within the low frequency range, the phase difference between the first sound and the second sound may be between 135° and 160°. In some embodiments, within the low frequency range, the phase difference between the first sound and the second sound may be between 140° and 155°. In some embodiments, within the low frequency range, the phase difference between the first sound and the second sound may be between 170° and 179°. In some embodiments, within the low frequency range, the phase difference between the first sound and the second sound may be between 176° and 179°.

[0097] In some embodiments, when the frequency is 1000 Hz, the phase difference between the first sound and the second sound may be between 125° and 178°. In some embodiments, when the frequency is 1000 Hz, the phase difference between the first sound and the second sound may be between 140° and 178°. In some embodiments, when the frequency is 1000 Hz, the phase difference between the first sound and the second sound may be between 160° and 178°. In some embodiments, when the frequency is 1000 Hz, the phase difference between the first sound and the second sound may be between 165° and 178°. In some embodiments, when the frequency is 1000 Hz, the phase difference between the first sound and the second sound may be between 170° and 178°. In some embodiments, when the frequency is 1000 Hz, the phase difference between the first sound and the second sound may be between 175° and 178°.

[0098] When the distance between the first sound outlet and the second sound outlet is different, the phase difference between the first sound and the second sound may be different. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet is 2mm-4mm, and when the frequency is 1000Hz, the phase difference between the first sound and the second sound is between 174° and 178°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet is 2mm-4mm, and when the frequency is 1000Hz, the phase difference between the first sound and the second sound is between 175° and 178°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet is 4mm-8mm, and when the frequency is 1000Hz, the phase difference between the first sound and the second sound is between 170° and 177°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet is 4mm-8mm, and when the frequency is 1000Hz, the phase difference between the first sound and the second sound is between 169° and 176°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet is 8mm-16mm, and when the frequency is 1000Hz, the phase difference between the first sound and the second sound is between 162° and 173°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet is 8mm-16mm, and when the frequency is 1000Hz, the phase difference between the first sound and the second sound is between 163° and 172°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet is 16mm-20mm, and when the frequency is 1000Hz, the phase difference between the first sound and the second sound is between 158° and 165°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet is 16mm-20mm, and when the frequency is 1000Hz, the phase difference between the first sound and the second sound is between 159° and 164°.

[0099] In some embodiments, when the frequency is 200 Hz, the phase difference between the first sound and the second sound may be greater than 175° and less than 179.8°. In some embodiments, when the frequency is 200 Hz, the phase difference between the first sound and the second sound may be greater than 177° and less than 179.8°. In some embodiments, when the frequency is 200 Hz, the phase difference between the first sound and the second sound may be greater than 179° and less than 179.8°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be 2 mm-20 mm, and when the frequency is 200 Hz, the phase difference between the first sound and the second sound may be greater than 175° and less than 179.8°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be 2 mm-20 mm, and when the frequency is 200 Hz, the phase difference between the first sound and the second sound may be greater than 174° and less than 179.8°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is 200Hz, the phase difference between the first sound and the second sound can be greater than 176° and less than 179.8°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is 200Hz, the phase difference between the first sound and the second sound can be greater than 177.8° and less than 179.8°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is 200Hz, the phase difference between the first sound and the second sound can be greater than 177° and less than 179.8°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is 200Hz, the phase difference between the first sound and the second sound can be greater than 176° and less than 179.8°.

[0100] In some embodiments, when the frequency is 500 Hz, the phase difference between the first sound and the second sound may be between 169° and 179°. In some embodiments, when the frequency is 500 Hz, the phase difference between the first sound and the second sound may be between 174° and 179°. In some embodiments, when the frequency is 500 Hz, the phase difference between the first sound and the second sound may be between 177° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be between 2 mm and 20 mm, and when the frequency is 500 Hz, the phase difference between the first sound and the second sound may be between 169° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be between 2 mm and 20 mm, and when the frequency is 500 Hz, the phase difference between the first sound and the second sound may be between 168° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is 500Hz, the phase difference between the first sound and the second sound can be between 175° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is 500Hz, the phase difference between the first sound and the second sound can be between 174° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is 500Hz, the phase difference between the first sound and the second sound can be between 177° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is 500Hz, the phase difference between the first sound and the second sound can be between 176° and 179°.

[0101] In some embodiments, when the frequency is 1500 Hz, the phase difference between the first sound and the second sound may be between 149° and 177°. In some embodiments, when the frequency is 1500 Hz, the phase difference between the first sound and the second sound may be between 164° and 177°. In some embodiments, when the frequency is 1500 Hz, the phase difference between the first sound and the second sound may be between 173° and 177°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be between 2 mm and 20 mm, and when the frequency is 1500 Hz, the phase difference between the first sound and the second sound may be between 149° and 177°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be between 2 mm and 20 mm, and when the frequency is 1500 Hz, the phase difference between the first sound and the second sound may be between 148° and 178°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is 1500Hz, the phase difference between the first sound and the second sound can be between 164° and 177°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is 1500Hz, the phase difference between the first sound and the second sound can be between 163° and 178°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is 1500Hz, the phase difference between the first sound and the second sound can be between 173° and 177°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is 1500Hz, the phase difference between the first sound and the second sound can be between 172° and 178°.

[0102] In some embodiments, when the frequency is 2000 Hz, the phase difference between the first sound and the second sound may be between 139° and 176°. In some embodiments, when the frequency is 2000 Hz, the phase difference between the first sound and the second sound may be between 159° and 176°. In some embodiments, when the frequency is 2000 Hz, the phase difference between the first sound and the second sound may be between 171° and 176°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be between 2 mm and 20 mm, and when the frequency is 2000 Hz, the phase difference between the first sound and the second sound may be between 139° and 176°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be between 2 mm and 20 mm, and when the frequency is 2000 Hz, the phase difference between the first sound and the second sound may be between 138° and 177°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is 2000Hz, the phase difference between the first sound and the second sound can be between 159° and 176°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is 2000Hz, the phase difference between the first sound and the second sound can be between 158° and 177°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is 2000Hz, the phase difference between the first sound and the second sound can be between 169° and 176°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is 2000Hz, the phase difference between the first sound and the second sound can be between 170° and 175°.

[0103] In some embodiments, when the frequency is 3000 Hz, the phase difference between the first sound and the second sound may be between 121° and 174°. In some embodiments, when the frequency is 3000 Hz, the phase difference between the first sound and the second sound may be between 149° and 174°. In some embodiments, when the frequency is 3000 Hz, the phase difference between the first sound and the second sound may be between 167° and 174°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be between 2 mm and 20 mm, and when the frequency is 3000 Hz, the phase difference between the first sound and the second sound may be between 121° and 174°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be between 2 mm and 20 mm, and when the frequency is 3000 Hz, the phase difference between the first sound and the second sound may be between 120° and 175°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is 3000Hz, the phase difference between the first sound and the second sound can be between 149° and 174°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is 3000Hz, the phase difference between the first sound and the second sound can be between 148° and 175°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is 3000Hz, the phase difference between the first sound and the second sound can be between 167° and 174°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is 3000Hz, the phase difference between the first sound and the second sound can be between 166° and 175°.

[0104] In some embodiments, when the distance between the first sound outlet hole and the second sound outlet hole is determined, the phase difference between the first sound and the second sound may be within a specific range at certain frequency bands or frequency values.

[0105] In some embodiments, there may be multiple frequency values ​​within the frequency band of 500Hz-3000Hz. When the frequency is any one of these frequency values, the phase difference between the first sound and the second sound may be between 121° and 179°. In some embodiments, the frequency value that makes the phase difference between the first sound and the second sound between 121° and 179° may include but is not limited to one or more of 500Hz, 800Hz, 1000Hz, 1200Hz, and 1500Hz. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet may be between 2mm and 20mm. When the frequency is one or more of 500Hz, 800Hz, 1000Hz, 1200Hz, and 1500Hz, the phase difference between the first sound and the second sound may be between 121° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-20mm, and when the frequency is one or more of 500Hz, 800Hz, 1000Hz, 1200Hz, and 1500Hz, the phase difference between the first sound and the second sound can be between 120° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is one or more of 500Hz, 800Hz, 1000Hz, 1200Hz, and 1500Hz, the phase difference between the first sound and the second sound can be between 164° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and when the frequency is one or more of 500Hz, 800Hz, 1000Hz, 1200Hz, and 1500Hz, the phase difference between the first sound and the second sound can be between 163° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is one or more of 500Hz, 800Hz, 1000Hz, 1200Hz, and 1500Hz, the phase difference between the first sound and the second sound can be between 175° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and when the frequency is one or more of 500Hz, 800Hz, 1000Hz, 1200Hz, and 1500Hz, the phase difference between the first sound and the second sound can be between 174° and 179°.

[0106] In some embodiments, by setting the distance between the first sound outlet and the second sound outlet, the phase difference between the first sound and the second sound can be between 121° and 179° within the frequency band of 500Hz-3000Hz. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be between 2mm-20mm, and the phase difference between the first sound and the second sound can be between 121° and 179° within the frequency band of 500Hz-3000Hz. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be between 2mm-20mm, and the phase difference between the first sound and the second sound can be between 120° and 179° within the frequency band of 500Hz-3000Hz. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be between 2mm-10mm, and the phase difference between the first sound and the second sound can be between 164° and 179° within the frequency band of 500Hz-3000Hz. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-10mm, and in the frequency band of 500Hz-3000Hz, the phase difference between the first sound and the second sound can be between 163° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and in the frequency band of 500Hz-1500Hz, the phase difference between the first sound and the second sound can be between 175° and 179°. In some embodiments, the distance between the acoustic center of the first sound outlet and the acoustic center of the second sound outlet can be 2mm-4mm, and in the frequency band of 500Hz-1500Hz, the phase difference between the first sound and the second sound can be between 174° and 179°. It should be noted that the endpoints of the various spacing ranges in the embodiments of this specification may overlap, but the endpoints of the phase difference ranges corresponding to the various spacing ranges do not overlap. This is mainly to take into account the measurement error in actual measurement.

[0107] It should be noted that the phase of the sound radiated from the sound outlet described in the embodiments of this specification can be measured at a spatial position at a specific distance from the sound outlet (or the geometric center of the sound outlet). In some embodiments, the specific distance can be 1mm-10mm. Preferably, the phase of the sound radiated from the sound outlet can be measured at the geometric center of the sound outlet. In some embodiments, the phase difference test method can be to measure the phase of the sounds radiated from the first sound outlet and the second sound outlet (the first sound and the second sound, respectively), and then calculate the phase difference between the first sound and the second sound. When testing the sound of the first sound outlet (or the second sound outlet), a baffle can be used to separate the first sound outlet and the second sound outlet to prevent the second sound outlet (or the first sound outlet) from interfering with the test. Furthermore, the sound collection device can be placed no more than 10mm away from the first sound outlet (or the second sound outlet) to collect the first sound, further preventing the second sound outlet (or the first sound outlet) from interfering with the test. When using a baffle to separate the first and second sound outlets to test the sound of the first sound outlet (or the second sound outlet), the distance between the measurement position and the geometric center of the corresponding sound outlet must be kept within the above-mentioned specific distance (1mm-10mm). As an example only, the size of the baffle can be a standard size. For example, the length, width and height of the baffle can be 1650mm, 1350mm and 30mm respectively. It should be further explained that when the number of first sound outlets (or second sound outlets) is two or more, any one of them can be selected for testing. For example, a first sound outlet and a second sound outlet located at a specific relative position (such as the minimum or maximum relative distance) can be selected, and the phase of the sound emitted by each of them can be tested separately, and the phase difference can be calculated. In addition, the sound measurement within a specific frequency band (for example, 500Hz-3000Hz) does not have to be achieved by exhaustive enumeration, but can be achieved by setting multiple (for example, 20-30) frequency sampling points with equal step sizes and endpoints at the frequency band endpoints, and measuring the sound at each sampling point separately.

[0108] It should be noted that the low-frequency range described in the embodiments of this specification may refer to a frequency range less than 1000 Hz. The far field may refer to a spatial range whose distance from the sound-emitting unit 120 is greater than or equal to twice the wavelength corresponding to a specified frequency (e.g., a specific frequency within the low-frequency range).

[0109] Figures 3A and 3B are schematic diagrams of the directional radiation sound field of an exemplary acoustic output device according to some embodiments of the present specification. As shown in Figures 3A and 3B, AS1 and AS2 respectively represent the first sound source and the second sound source formed by the sound-emitting portion 120 of the acoustic output device 100. When the first sound generated by the first sound source and the second sound generated by the second sound source have a specific phase difference (for example, 120° to 179°), the first sound source AS1 and the second sound source AS2 can form a highly directional radiation sound field, for example, a cardioid directional radiation sound field (as shown in Figure 3A) or a supercardioid directional radiation sound field (as shown in Figure 3B). It should be noted that the first sound outlet can constitute the first sound source, and the position of the first sound source can be regarded as being located at the acoustic center of the first sound outlet. The second sound outlet can constitute the second sound source, and the position of the second sound source can be regarded as being located at the acoustic center of the second sound outlet.

[0110] 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 extremely strong, while the sound field radiation in other directions is relatively 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. At this time, only the radiation directed to the ear canal opening and its vicinity is strong, while the other directions are all weakly directional directions, thereby reducing the sound leakage of the acoustic output device. 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.

[0111] Figure 4 is a schematic diagram of an exemplary dual-source radiation system according to some embodiments of this specification. As shown in Figure 4, the first sound source AS1 and the second sound source AS2 can each represent two sound sources formed by the sound-emitting portion 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 point P, r2 represents the distance from the second sound source AS2 to point P, r represents the distance from the midpoint O of the line connecting the first sound source AS1 and the second sound source AS2 to point P, and θ represents the angle between the line connecting the first sound source AS1 and the second sound source AS2 and the line connecting the midpoint O and point P.

[0112] The sound pressures at the first sound source AS1 and the second sound source AS2 can be respectively:

[0113] in, 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:

[0114] 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:

[0115] 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:

[0116] Solving the above equation (4), we can get the phase difference between the first sound source AS1 and the second sound source AS2 Relationships that need to be satisfied:

[0117] From formula (5), 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.

[0118] 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. As shown in Figure 5, the horizontal axis represents frequency f in Hz; the vertical axis represents the spacing l between the two sound sources in mm. Each curve represents the required phase difference under different conditions (i.e., different frequencies f and different spacing l). Comparing the various curves in Figure 5, we can see that to achieve a cardioid-shaped directional sound field, when the spacing l remains 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 remains constant, 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.

[0119] 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:

[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° to 179°), in a wide frequency band (e.g., 200Hz to 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 supercardioid 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° to 179°, both sound sources can also form a strong directional radiation sound field within the frequency range of 200Hz to 2000Hz.

[0122] In some embodiments, since the far-field condition can be limited to kl<<1 (and r>>l), and the size of the wave vector is negatively correlated with the wavelength, in order to meet the far-field condition, the wave vector cannot be too large, that is, the wavelength cannot be too small, that is, the frequency cannot be too high. Based on this, the frequency range in which the two sound sources described in the embodiments of this specification can form a highly directional radiation sound field is mostly in the low-frequency range (for example, less than 1000Hz).

[0123] Figure 7A is a schematic diagram of an exemplary sound-emitting portion according to some embodiments of the present specification. As shown in Figure 7A, the sound-emitting portion 700 may include at least one acoustic driver 721, a first cavity 722, and a second cavity 723. The first cavity 722 and the second cavity 723 are located on the front and rear sides of the acoustic driver 721, respectively. The first cavity 722 may have at least one first sound outlet 724, and the second cavity 723 may have at least one second sound outlet 725. The number of first sound outlets 724 and second sound outlets 725 may be one or more, and the number of sound outlets may be reasonably set according to needs. The acoustic driver 721 may radiate a first sound to the outside world through the first cavity 722 and the first sound outlet 724, and may radiate a second sound to the outside world through the second cavity 723 and the second sound outlet 725. In some embodiments, the at least one acoustic driver 721 may be a single acoustic driver. For example, the acoustic driver 721 shown in FIG7A may include a diaphragm, which can radiate sound to both sides of the diaphragm, that is, to the first cavity 722 and the second cavity 723 when the diaphragm vibrates. In some embodiments, at least one acoustic driver 721 may also include two acoustic drivers (that is, the diaphragm in FIG7A can be replaced with two acoustic drivers), and the two acoustic drivers are driven by two sets of electrical signals to radiate sound to the first cavity 722 and the second cavity 723. The sound in the first cavity 722 can be radiated to the outside through the first sound outlet 724, that is, the first sound outlet 724 radiates the first sound to the outside. The sound in the second cavity 723 can be radiated to the outside through the second sound outlet 725, that is, the second sound outlet 725 radiates the second sound to the outside.

[0124] In some embodiments, in order to make the sound radiated from the sound-emitting part 700 to the far field in the low frequency range (for example, less than 1000 Hz) exhibit strong directivity (for example, cardioid or supercardioid), it is necessary to make the phase difference between the first sound radiated from the first sound outlet 724 and the second sound radiated from the second sound outlet 725 be within a specific range (for example, 120° to 179°). Since the initial value of the phase difference between the two sound waves radiated from the acoustic driver 721 to the first cavity 722 and the second cavity 723 respectively is 180°, it is necessary to set an acoustic structure in the first cavity 722 and / or the second cavity 723 so that the phase difference between the first sound and the second sound meets the conditions. In some embodiments, the sound-emitting part 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 regulate the actual output phase of the first sound and / or the second sound, thereby adjusting the phase difference between the first sound and the second sound. In some embodiments, the acoustic structure 726 can create an acoustic path difference between a first acoustic path of the first sound propagating in the first cavity 722 and a second acoustic path of the second sound propagating in the second cavity 723, thereby changing the phase difference between the first sound radiated from the first sound outlet 724 and the second sound radiated from the second sound outlet 725. This embodiment is described using the acoustic structure 726 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. In some embodiments, the acoustic structure 726 can 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 FIG7A , four baffles can be provided in the second cavity 723, two of which are provided on the first inner wall 7231 of the second cavity 723, and the remaining two baffles are provided on the second inner wall 7232 (the second inner wall 7232 is provided opposite the first inner wall 7231), with the free ends of the baffles on the two inner walls facing each other. In this case, a gap exists between the free ends of the two opposing baffles, allowing sound to bypass the baffles and pass through the gap to the second sound outlet 725. In some embodiments, the number and / or position of the baffles in the second cavity 723 can also be arranged in other ways. For example, as shown in Figure 7B, a baffle can be set on only one inner wall of the second cavity 723 (for example, the second inner wall 7232), one end of the baffle is connected to the second inner wall 7232, and the free end of the baffle extends to the vicinity of the first inner wall 7231 (a gap is formed between the free end of the baffle and the first inner wall 7231). Sound can bypass the baffle and be transmitted to the second sound outlet 725 from 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 can be connected to the first inner wall 7231 and the second inner wall 7232 respectively. In this case, a hole can be opened on the baffle so that the sound can bypass the baffle and be transmitted to the second sound outlet 725 through the hole. In the process of the sound bypassing the baffle and transmitting to the second sound outlet 725, the distance traveled by the sound (that is, the sound path) is changed compared to when no baffle is provided. The sound wave radiated from the front side of the acoustic driver 721 is radiated from the first sound outlet 724 to the outside world through the first cavity 722. The distance traveled by the sound wave is the first sound path L1. The sound wave radiated from the rear side of the acoustic driver 721 is radiated from the second sound outlet 725 to the outside world 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.

[0125] The phase delay between the first sound radiated from the first sound outlet 724 and the second sound radiated from the second sound outlet 725 can be:

[0126] Here, c represents the speed of sound. Therefore, the phase difference between the first sound and the second sound is for:

[0127] It can be seen from this that the actual output phase difference between the first sound and the second sound can be controlled by controlling the sound path difference between the first sound path L1 and the second sound path L2 (for example, the sound path difference can be made to be in the range of 1mm to 57mm), so that the phase difference between the first sound and the second sound is in the range of 120° to 179°, thereby making the sound radiated to the far field by the sound-emitting part 700 exhibit strong directivity (for example, cardioid or supercardioid).

[0128] It can be understood that the number, position, size and setting method of the baffles can affect the second sound path L2 of the sound wave in the second cavity 723, thereby affecting the phase difference between the first sound and the second sound. Therefore, the number, position, size and setting method of the baffles can be reasonably set according to the requirements of the phase difference between the first sound and the second sound.

[0129] Furthermore, this embodiment also shows that, when other parameters (e.g., the first and second sound ranges) remain the same, the phase difference between the first and second sounds is negatively correlated with frequency. The higher the frequency, the smaller the phase difference between the first and second sounds; the lower the frequency, the larger the phase difference between the first and second sounds.

[0130] FIG. 8 is a schematic diagram of another exemplary sound generating portion shown in accordance with some embodiments of the present specification. The structure of the sound generating portion 800 shown in FIG. 8 is similar to the structure of the sound generating portion 700 shown in FIG. 7A. For example, the sound generating portion 800 may include at least one acoustic driver 821, a first cavity 822, and a second cavity 823. At least one first sound outlet hole 824 may be formed on the first cavity 822, and at least one second sound outlet hole 825 may be formed on the second cavity 823. For specific details regarding the acoustic driver 821, the first cavity 822, the second cavity 823, the first sound outlet hole 824, and the second sound outlet hole 825, reference may be made to the relevant description in FIG. 7A. The difference between the sound generating portion 800 and the sound generating portion 700 lies in the different acoustic structures. An acoustic structure for changing the sound propagation speed may be provided in the first cavity 822 and / or the second cavity 823 of the sound generating portion 800. For example, the acoustic structure may be a slow acoustic structure capable of slowing down the speed of sound when propagating in itself. The speed of sound propagating in air is faster than the speed of sound propagating in the slow acoustic structure. In some embodiments, the slow acoustic structure may include at least one of acoustic mesh, acoustic porous material, etc. When sound waves pass through the micropores in the mesh or porous material, due to the viscous effect of the micropores on air, the speed of the sound waves slows down when passing through the micropores, thereby achieving the effect of slowing down. Specifically, the speed of sound propagating in air (also referred to as the normal sound speed) is c, and the speed of sound propagating in the slow acoustic structure (also called the equivalent sound speed) is c'. From the above description, it can be seen that c' < c. Therefore, by providing a slow acoustic structure in the cavity to change the sound propagation speed, the actual output phase of the first sound and / or the second sound can be regulated, thereby adjusting the phase difference between the first sound and the second sound.

[0131] In this embodiment, the case where the slow acoustic structure 826 is provided in the second cavity 823 is taken as an example for illustration. As shown in FIG. 8, a slow acoustic structure 826 may be provided in the second cavity 823. The sound waves radiated from the front side of the acoustic driver 821 are radiated to the outside through the first sound outlet hole 824, and the path traveled by this 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 through the second sound outlet hole 825, and the path traveled by this sound wave may include a second sound path L2 propagated through air and a third sound path L3 propagated through the slow acoustic structure 826.

[0132] The differential time delay between the first sound radiated from the first sound outlet hole 824 and the second sound radiated from the second sound outlet hole 825 may be:

[0133] where c represents the normal sound speed and c' represents the equivalent sound speed in the slow acoustic structure 826. Thus, the phase difference between the first sound and the second sound is:

[0134] It can be seen from this that the actual output phase difference between the first sound and the second sound 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 and the second sound 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).

[0135] 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 and second sounds is negatively correlated with frequency. The higher the frequency, the smaller the phase difference between the first and second sounds; the lower the frequency, the larger the phase difference between the first and second sounds.

[0136] FIG9 is a schematic diagram of another exemplary sound-emitting portion according to some embodiments of the present specification. The structure of the sound-emitting portion 900 shown in FIG9 is similar to that of the sound-emitting portion 700 shown in FIG7A . For example, the sound-emitting portion 900 may include at least one acoustic driver 921, a first cavity 922, and a second cavity 923. The first cavity 922 may be provided with at least one first sound outlet 924, and the second cavity 923 may be provided with at least one second sound outlet 925. For details about the acoustic driver 921, the first cavity 922, the second cavity 923, the first sound outlet 924, and the second sound outlet 925, please refer to the relevant description of FIG7A . The difference between the sound-emitting portion 900 and the sound-emitting portion 700 lies in the difference in the acoustic structure. As shown in FIG9 , an expansion acoustic structure 926 may be provided in the first cavity 922 and / or the second cavity 923 of the sound-emitting portion 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 the sound wave propagates in the waveguide (that is, the 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. Correspondingly, 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 the 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 sound speed can be obtained by simulation or experimental testing.

[0137] 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 and the second sound.

[0138] As shown in Figure 9, the sound waves radiated from the front side of the acoustic driver 921 radiate from the first sound outlet 924 to the outside world, and the distance traveled by the sound waves is the first sound path L1. The sound waves radiated from the rear side of the acoustic driver 921 radiate from the second sound outlet 825 to the outside world through the expanded acoustic structure 926 and the second cavity 923, and the distance traveled by the sound waves is the second sound path L2. Among them, the sound speed in the first sound path L1 is the normal sound speed c, and the sound speed in the second sound path L2 is the equivalent sound speed c'. The phase delay between the first sound radiated from the first sound outlet 924 and the second sound radiated from the second sound outlet 925 is:

[0139] 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 and the second sound is for:

[0140] It can be seen from this that the actual output phase difference between the first sound and the second sound can be controlled by setting an expanded acoustic structure 926 in the cavity to control the equivalent sound speed of the sound wave propagating in the cavity, so that the phase difference between the first sound and the second sound 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).

[0141] 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 and second sounds is negatively correlated with frequency. The higher the frequency, the smaller the phase difference between the first and second sounds; the lower the frequency, the larger the phase difference between the first and second sounds.

[0142] Figure 10A is a schematic diagram of another exemplary sound-emitting portion according to some embodiments of this specification. The structure of the sound-emitting portion 1000 shown in Figure 10A is similar to that of the sound-emitting portion 700 shown in Figure 7A. 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 sound outlet 1024, and the second cavity 1023 may be provided with at least one second sound outlet 1025. For details regarding the acoustic driver 1021, the first cavity 1022, the second cavity 1023, the first sound outlet 1024, and the second sound outlet 1025, please refer to the relevant description of Figure 7A. The difference between the sound-emitting portion 1000 and the sound-emitting portion 700 lies in the difference in acoustic structure. As shown in Figure 10A, 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. Sound modulation (e.g., phase modulation) near the resonant frequency of the sound-absorbing structure 1026 may be used to control the actual output phase difference between the two sound waves. In some embodiments, the sound-absorbing structure 1026 may be a Helmholtz resonator. In some embodiments, the sound-absorbing structure 1026 may be a microperforated plate resonator. In some embodiments, the sound-absorbing structure 1026 may be a quarter-wavelength tube resonator.

[0143] 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:

[0144] 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).

[0145] Figure 10B is a schematic diagram of the frequency response of the Helmholtz resonant cavity. The horizontal axis represents the frequency in Hz, and the vertical axis represents the amplitude response (in dB) or the phase response (in degrees (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 resonant frequency f0 of the Helmholtz resonant cavity 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° to eventually approaching 0°. It can be seen that within the low-frequency range (for example, between 40Hz and 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 sound outlet 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).

[0146] In some embodiments, to ensure that the phase difference between the first sound and the second sound within a certain range before the resonant frequency of the sound absorbing structure 1026 (e.g., a low-frequency range less than 1000 Hz) meets the requirements, the resonant frequency of the sound absorbing structure 1026 can be set between 1000 Hz and 3000 Hz. In some embodiments, to ensure that the phase difference between the first sound and the second sound within a certain range before the resonant frequency of the sound absorbing structure 1026 meets the requirements, the resonant frequency of the sound absorbing structure 1026 can be set between 1000 Hz and 2500 Hz. In some embodiments, to ensure that the phase difference between the first sound and the second sound within a certain range before the resonant frequency of the sound absorbing structure 1026 meets the requirements, the resonant frequency of the sound absorbing structure 1026 can be set between 1000 Hz and 2000 Hz. In some embodiments, to ensure that the phase difference between the first sound and the second sound within a certain range before the resonant frequency of the sound absorbing structure 1026 meets the requirements, the resonant frequency of the sound absorbing structure 1026 can be set between 1100 Hz and 1900 Hz. In some embodiments, in order to ensure that the phase difference between the first sound and the second sound within a certain range before the resonant frequency of the sound absorbing structure 1026 meets the requirements, the resonant frequency of the sound absorbing structure 1026 can be set to be between 1200 Hz and 1800 Hz.

[0147] In some embodiments, when at least one acoustic driver of the sound-emitting part is a single driver or includes two acoustic drivers, the phase difference between the first sound and the second sound 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 is 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 or the second sound is changed, thereby achieving the adjustment of the phase difference between the first sound and the second sound. In some embodiments, when at least one acoustic driver includes two acoustic drivers, the phase difference between the first sound and the second sound 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. For example, Figure 11 is an exemplary structural diagram of a sound-emitting part with two acoustic drivers according to some embodiments of this specification. 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 at least one first sound outlet 1124, through which the first acoustic driver 1121A may radiate a first sound to the outside world. The second cavity 1123 may have at least one second sound outlet 1125, through which the second acoustic driver 1121B may radiate a second sound 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 and the second sound may be set to be 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 can 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 and the second sound.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 is set in the second cavity 1123) so that the phase difference between the first sound and the second sound is between 120° and 179°.

[0148] 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 regulating the phase difference between the two sounds generated by the sound-emitting part, the sound radiated to the far field by the acoustic output device in the low-frequency range can be directional, 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 direction opposite to the ear canal opening and in other directions is small, thereby better balancing the openness of the ear canal and the privacy of listening; (2) by arranging a variety of acoustic structures (for example, baffles, slow acoustic structures, expansion acoustic structures, and sound absorption structures) in the sound-emitting part of the acoustic output device to regulate the phase difference between the two sounds generated by the sound-emitting part, the regulation of the phase difference can be made more flexible and more accurate, 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 phase difference of the two sounds can be regulated by directly regulating the two electrical drive signals, which can make the structure of the acoustic output device simpler and the cost lower.

[0149] 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.

[0150] This specification also uses specific terms to describe the embodiments of this specification. For example, "one embodiment," "an embodiment," and / or "some embodiments" refer to a feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "one embodiment," "an embodiment," or "an alternative embodiment" two or more times in different locations in this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics of one or more embodiments of this specification may be appropriately combined.

[0151] In addition, unless expressly stated in the claims, the order of the processing elements and sequences, the use of alphanumeric characters, or the use of other names described in this specification are not intended to limit the order of the processes and methods of this specification. Although the above disclosure discusses some of the invention embodiments currently considered useful through various examples, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that are consistent with the spirit and scope of the embodiments of this specification. For example, although the system components described above can be implemented by hardware devices, they can also be implemented only by software solutions, such as installing the described system on an existing server or mobile device.

[0152] Similarly, it should be noted that, in order to simplify the presentation of this specification and thus facilitate understanding of one or more embodiments of the invention, the foregoing descriptions of the embodiments of this specification sometimes combine multiple features into a single embodiment, figure, or description thereof. However, this disclosure method does not imply that the subject matter of this specification requires more features than those recited in the claims. In fact, an embodiment may have fewer features than all of the features of a single disclosed embodiment.

[0153] In some embodiments, numbers are used to describe the quantity of components and attributes. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise stated, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the description and claims are approximate values, which may change according to the required characteristics of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of this specification are approximate values, in specific embodiments, the settings of such numerical values ​​are as accurate as possible within the feasible range.

[0154] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. The specific implementation methods recorded in this application are only exemplary, and one or more technical features in the specific implementation methods are optional or additional, and do not constitute necessary technical features of the inventive concept of this application. In other words, the scope of protection of this application covers and is far greater than the specific implementation methods. Therefore, as an example and not a limitation, the alternative configurations of the embodiments of this specification may be considered to be consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. An acoustic output device, include: A sound-producing part, the sound-producing part comprising: at least one acoustic driver; A first cavity and a second cavity acoustically coupled to the at least one acoustic driver, the first cavity has at least one first sound outlet hole, the second cavity has at least one second sound outlet hole, the at least one acoustic driver radiates sound to the outside through the at least one first sound outlet hole and the at least one second sound outlet hole, wherein: In at least part of the low-frequency range, the sound radiated from the sound-emitting portion to the far field exhibits directivity, and the directivity is manifested in that the sound radiated from the first sound outlet hole and the second sound outlet hole has a sound pressure difference of not less than 3dB in at least one pair of opposite directions.

2. The acoustic output device according to claim 1, It is characterized in that The at least one acoustic driver is a single acoustic driver having a front side and a rear side and radiating sound to the first cavity and the second cavity through the front side and the rear side, respectively.

3. The acoustic output device according to claim 1, It is characterized in that 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.

4. The acoustic output device according to claim 2 or 3, It is characterized in that The acoustic driver radiates a first sound outward through the at least one first sound outlet hole, and radiates a second sound outward through the at least one second sound outlet hole; a phase difference between the first sound and the second sound is between 120° and 179°.

5. The acoustic output device according to claim 4, It is characterized in that The phase difference between the first sound and the second sound is between 170° and 179°.

6. The acoustic output device according to claim 4, It is characterized in that In a preset frequency range, the phase difference between the first sound and the second sound is negatively correlated with the magnitude of the frequency.

7. The acoustic output device according to claim 4, It is characterized in that The first sound propagates in the first cavity with a first sound path, and the second sound propagates in the second cavity with a second sound path, and the first sound path and the second sound path have a sound path difference.

8. The acoustic output device according to claim 7, It is characterized in that The first cavity and / or the second cavity is provided with an acoustic structure, and the acoustic structure includes a baffle.

9. The acoustic output device according to claim 4, It is characterized in that The first cavity or the second cavity is provided with at least one of an acoustic gauze and an acoustic porous material.

10. The acoustic output device according to claim 4, It is characterized in that The first cavity or the second cavity is provided with an expansion acoustic structure, and the expansion acoustic structure changes the cross-sectional area of ​​the first cavity or the second cavity at different positions on the sound transmission path.

11. The acoustic output device according to claim 4, It is characterized in that The first cavity or the second cavity is provided with a sound absorbing structure, and the resonance frequency of the sound absorbing structure is between 1000 Hz and 3000 Hz.

12. The acoustic output device according to claim 3, It is characterized in that The electrical driving signals corresponding to the two acoustic drivers have different phases.

13. The acoustic output device according to any one of claims 1 to 3, It is characterized in that 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 support structure is configured to carry the sound-emitting part and wear the sound-emitting part on the user's ear without blocking the ear canal.

14. An acoustic output device, include: A sound-producing part, the sound-producing part comprising: at least one acoustic driver; A first cavity and a second cavity acoustically coupled to the at least one acoustic driver, the first cavity having at least one first sound outlet hole, the second cavity having at least one second sound outlet hole, the at least one acoustic driver radiating a first sound to the outside through the first cavity and the at least one first sound outlet hole, and radiating a second sound to the outside through the second cavity and the at least one second sound outlet hole; wherein at 1000 Hz, the phase difference between the first sound and the second sound is between 125° and 178°.

15. The acoustic output device according to claim 14, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole is 2 mm-60 mm.

16. The acoustic output device according to claim 14, It is characterized in that At 1000 Hz, the phase difference between the first sound and the second sound is between 174° and 178°.

17. The acoustic output device according to claim 16, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole is within 2 mm-4 mm.

18. The acoustic output device according to claim 14, It is characterized in that At 1000 Hz, the phase difference between the first sound and the second sound is between 170° and 177°.

19. The acoustic output device according to claim 18, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole is within 4 mm-8 mm.

20. The acoustic output device according to claim 14, It is characterized in that At 1000 Hz, the phase difference between the first sound and the second sound is between 162° and 173°.

21. The acoustic output device according to claim 20, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole is within 8 mm-16 mm.

22. The acoustic output device according to claim 14, It is characterized in that At 1000 Hz, the phase difference between the first sound and the second sound is between 158° and 165°.

23. The acoustic output device according to claim 22, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole is within 16 mm-20 mm.

24. The acoustic output device according to claim 14, It is characterized in that At 2000 Hz, the phase difference between the first sound and the second sound is between 138° and 177°.

25. The acoustic output device according to claim 24, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole is within 2 mm-20 mm.

26. The acoustic output device according to claim 14, It is characterized in that At 2000 Hz, the phase difference between the first sound and the second sound is between 170° and 175°.

27. The acoustic output device according to claim 26, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole is within 2 mm-4 mm.

28. The acoustic output device according to claim 14, It is characterized in that There are multiple frequency values ​​in the frequency band of 500 Hz-3000 Hz, and at any one of the multiple frequency values, the phase difference between the first sound and the second sound is between 121° and 179°.

29. The acoustic output device according to claim 28, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 20 mm.

30. The acoustic output device according to claim 28, It is characterized in that There are multiple frequency values ​​in the frequency band of 500 Hz-3000 Hz, and at any one of the multiple frequency values, the phase difference between the first sound and the second sound is between 175° and 179°.

31. The acoustic output device according to claim 30, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 4 mm.

32. The acoustic output device according to claim 14 or 28, It is characterized in that In the frequency band of 500 Hz-3000 Hz, the phase difference between the first sound and the second sound is between 145° and 179°.

33. The acoustic output device according to claim 32, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 10 mm.

34. The acoustic output device according to claim 33, It is characterized in that In the frequency band of 500 Hz-3000 Hz, the phase difference between the first sound and the second sound is between 175° and 179°.

35. The acoustic output device according to claim 34, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 4 mm.

36. The acoustic output device according to claim 14, It is characterized in that At 200 Hz, a phase difference between the first sound and the second sound is greater than 175° and less than 179.8°.

37. The acoustic output device according to claim 36, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 20 mm.

38. The acoustic output device according to claim 36, It is characterized in that At 200 Hz, the phase difference between the first sound and the second sound is between 177° and 179.8°.

39. The acoustic output device according to claim 38, It is characterized in that The distance between the acoustic center of the first sound outlet hole and the acoustic center of the second sound outlet hole ranges from 2 mm to 4 mm.

40. The acoustic output device according to claim 14, It is characterized in that In a preset frequency range, the phase difference between the first sound and the second sound is negatively correlated with the magnitude of the frequency.

41. The acoustic output device according to claim 14, It is characterized in that The at least one acoustic driver is a single acoustic driver having a front side and a rear side and radiating sound to the first cavity and the second cavity through the front side and the rear side, respectively.

42. The acoustic output device according to claim 14, It is characterized in that 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.

43. The acoustic output device according to claim 42, It is characterized in that The electrical driving signals corresponding to the two acoustic drivers have different phases.

44. The acoustic output device according to claim 14, It is characterized in that The first sound propagates in the first cavity with a first sound path, and the second sound propagates in the second cavity with a second sound path, and the first sound path and the second sound path have a sound path difference.

45. The acoustic output device according to claim 44, It is characterized in that The first cavity and / or the second cavity is provided with an acoustic structure, and the acoustic structure includes a baffle.

46. ​​The acoustic output device according to claim 14, It is characterized in that The first cavity or the second cavity is provided with at least one of an acoustic gauze and an acoustic porous material.

47. The acoustic output device according to claim 14, It is characterized in that The first cavity or the second cavity is provided with an expansion acoustic structure, and the expansion acoustic structure changes the cross-sectional area of ​​the first cavity or the second cavity at different positions on the sound transmission path.

48. The acoustic output device according to claim 14, It is characterized in that The first cavity or the second cavity is provided with a sound absorbing structure, and the resonance frequency of the sound absorbing structure is between 1000 Hz and 3000 Hz.

49. The acoustic output device according to claim 14, It is characterized in that 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 support structure is configured to carry the sound-emitting part and wear the sound-emitting part on the user's ear without blocking the ear canal.

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