Sound output device

Abstract

One or more embodiments of the present specification relate to an acoustic output device, the acoustic output device including a housing, installed within the housing and including a first diaphragm, and the housing having a first front cavity and a first rear cavity respectively corresponding to the front side and the rear side of the first diaphragm installed thereon, the first front cavity and the first rear cavity being acoustically coupled to two holes installed in the housing respectively to output a first sound wave and a second sound wave having a phase difference, respectively, a first speaker; installed within the housing and including a second diaphragm, and the housing having a second front cavity and a second rear cavity installed on the front side and the rear side of the second diaphragm respectively, only one of the second front cavity and the second rear cavity being acoustically coupled to one hole installed in the housing to output a third sound wave, a second speaker.

Description

[Technical Field]

[0001] TECHNICAL FIELD This disclosure relates to the field of audio, and in particular to audio output devices.

[0002] [Incorporated by reference] This application claims priority to a Chinese patent application filed on November 21, 2022, bearing application number 202211455122.0, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] To solve the sound leakage problem of an audio output device, two or more sound sources are typically used to generate two out-of-phase sound signals. Under far-field conditions, the difference in acoustic distance between the two out-of-phase sound sources and a specific point in the far field is essentially negligible, so the two sound signals cancel each other out, reducing far-field sound leakage. While this method can achieve a certain level of sound leakage reduction, it still has certain limitations. For example, the wavelength of high-frequency sound leakage is shorter, and under far-field conditions, the distance between the two sound sources is not negligible relative to the wavelength, so the sound signals emitted from the two sound sources cannot be canceled out. Furthermore, for example, when the acoustic transmission structure of the audio output device resonates, there is a certain phase difference between the phase of the acoustic signal actually emitted from the sound output port of the audio output device and the original phase of the sound wave generation position, which adds an additional resonance peak to the transmitted sound wave, causing a disturbance in the sound field distribution, making it difficult to ensure the effect of reducing high-frequency far-field sound leakage and potentially increasing sound leakage. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, it is desirable to provide a sound output device that has excellent sound field directionality. [Means for solving the problem]

[0005] An acoustic output device according to an embodiment of the present specification includes a housing; a first speaker installed within the housing and including a first vibrating membrane, wherein a first front cavity and a first rear cavity are installed in the housing corresponding to the front and rear sides of the first vibrating membrane, respectively, and the first front cavity and the first rear cavity are acoustically coupled to two holes installed in the housing, respectively, to output a first sound wave and a second sound wave having a phase difference; and a second speaker installed within the housing and including a second vibrating membrane, wherein a second front cavity and a second rear cavity are installed in the housing corresponding to the front and rear sides of the second vibrating membrane, respectively, and only one of the second front cavity and the second rear cavity is acoustically coupled to one hole installed in the housing, to output a third sound wave.

[0006] In some embodiments, the first speaker is driven by a first electrical signal and the second speaker is driven by a second electrical signal, and within a target frequency range, the first electrical signal and the second electrical signal have an amplitude and / or phase difference such that the first sound wave, the second sound wave, and the third sound wave superimpose on each other, resulting in directional far-field radiated sound from the acoustic output device.

[0007] In some embodiments, the first vibrating membrane and the second vibrating membrane have the same vibration direction and are spaced apart along the vibration direction or a direction perpendicular to the vibration direction.

[0008] In some embodiments, the first front cavity and the first rear cavity are acoustically coupled to a first hole and a second hole, respectively, installed in the housing, one of the second front cavity and the second rear cavity is the same cavity as the first rear cavity, and the second front cavity or the second rear cavity, which together with the first rear cavity constitutes the same cavity, outputs the third acoustic wave from the second hole.

[0009] In some embodiments, the resonant frequency of the same cavity is 4 kHz or higher.

[0010] In some embodiments, the volume of the same cavity is 0.28 cm 3 The area of the second hole is 20 mm or less. 2 That's all.

[0011] In some embodiments, the resonant frequency of the second rear cavity or the second front cavity that is not acoustically coupled to the second hole is 1 kHz or less.

[0012] In some embodiments, when driven by the same electrical signal within a target frequency range, the difference in sound pressure level between the superimposed sound wave of the first sound wave and the second sound wave output by the first speaker and the third sound wave output by the second speaker at a far-field position in a specific direction of the acoustic output device is less than 14 dB.

[0013] In some embodiments, the target frequency range includes 1 kHz to 4 kHz.

[0014] In some embodiments, the direction of an extension of a line connecting the first hole and the second hole is the specific direction.

[0015] In some embodiments, the first front cavity and the first rear cavity are acoustically coupled to a first hole and a second hole, respectively, located in the housing, and one of the second front cavity and the second rear cavity is acoustically coupled to a third hole in the housing, the third hole being a different hole than the first hole and the second hole.

[0016] In some embodiments, the second front cavity or the second rear cavity acoustically coupled to the third aperture has a resonant frequency, and the first rear cavity acoustically coupled to the second aperture has another resonant frequency, and the difference between the resonant frequency and the another resonant frequency is 3000 Hz or less.

[0017] In some embodiments, the resonant frequency of the second front cavity or the second rear cavity acoustically coupled to the third hole is 4 kHz or higher.

[0018] In some embodiments, the second rear cavity or the second front cavity that is not acoustically coupled to the third hole has a resonant frequency of 1 kHz or less.

[0019] In some embodiments, when driven by the same electrical signal within a target frequency range, at a far-field position in a specific direction of the acoustic output device, the difference in sound pressure level between the sound wave formed by superimposing the first sound wave and the second sound wave output by the first speaker and the third sound wave output by the second speaker is less than 14 dB, and the target frequency range includes 1 kHz to 4 kHz.

[0020] In some embodiments, the second hole portion and the third hole portion have equivalent holes, and the direction of an extension of a line connecting the first hole portion and the equivalent hole portion is the specific direction.

[0021] In some embodiments, within a range of 100 Hz to 800 Hz, the difference in sound pressure level between the sound waves output by the first speaker from an aperture acoustically coupled to the first rear cavity and the sound pressure level of the third sound waves output by the second speaker from an aperture acoustically coupled to the second speaker is 6 dB or more.

[0022] In some embodiments, in a worn state, the hole acoustically coupled to the first front cavity of the first speaker is positioned close to the user's ear, the hole acoustically coupled to the first rear cavity and the hole for outputting the third sound waves of the second speaker are positioned away from the user's ear, the hole acoustically coupled to the first rear cavity and the hole for outputting the third sound waves of the second speaker have equivalent holes, and the direction from the equivalent hole to the hole acoustically coupled to the first front cavity faces the user's ear.

[0023] In some embodiments, in a worn state, the aperture acoustically coupled to the first front cavity of the first speaker is positioned proximate to a user's ear, the aperture acoustically coupled to the first rear cavity is positioned away from the user's ear, and the direction from the aperture acoustically coupled to the first rear cavity to the aperture acoustically coupled to the first front cavity faces towards the user's ear.

[0024] In some embodiments, the acoustic output device includes at least one of a neckband-type earphone, an ear-hook-type earphone, an in-ear earphone, and a pair of glasses, and when worn, the opposite direction to the specific direction faces the opening of the user's ear canal.

[0025] In some embodiments, an acoustic particulate material is filled into the second front cavity or the second rear cavity that is not acoustically coupled to the aperture.

[0026] The present specification is further illustrated by exemplary embodiments, which are not limiting and will be described in detail with reference to the drawings, in which like numbers refer to like structures. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic diagram of the relative positions of an acoustic output device and a user's ear according to some embodiments of the present disclosure. [Figure 2A] 2 is a schematic diagram of a sound field distribution of sound pressure levels at low and medium frequencies of the sound output device shown in FIG. 1. FIG. [Figure 2B] 2 is a schematic diagram of a sound field distribution of high-frequency sound pressure levels of the sound output device shown in FIG. 1. FIG. [Figure 3] 2 is a frequency response curve diagram of the acoustic output device shown in FIG. 1. [Figure 4] FIG. 1 is a schematic diagram of directionality according to some embodiments of the present disclosure. [Figure 5A] 1A-1C are schematic diagrams of sound output devices including a first speaker and a second speaker arranged in different ways, according to some embodiments of the present disclosure. [Figure 5B] 1A-1C are schematic diagrams of sound output devices including a first speaker and a second speaker arranged in different ways, according to some embodiments of the present disclosure. [Figure 5C] 1A-1C are schematic diagrams of sound output devices including a first speaker and a second speaker arranged in different ways, according to some embodiments of the present disclosure. [Figure 5D] 1A-1C are schematic diagrams of sound output devices including a first speaker and a second speaker arranged in different ways, according to some embodiments of the present disclosure. [Figure 6] 1A-1C are schematic diagrams illustrating the relationship between the resonant frequency of the same cavity and its volume, according to some embodiments herein. [Figure 7] FIG. 10 is a schematic diagram illustrating the relationship between the resonant frequency of the same cavity and the area of the hole acoustically coupled thereto, according to some embodiments herein. [Figure 8] FIG. 1 is a schematic diagram illustrating the relationship between the resonant frequency of a sealed cavity and its volume, according to some embodiments herein. [Figure 9] FIG. 10 is a schematic diagram illustrating the configuration of a sound output device according to some other embodiments of the present specification. [Figure 10A] 1A to 1C are schematic diagrams of acoustic output devices with sound output holes arranged in different ways, according to some embodiments of the present disclosure. [Figure 10B]1A to 1C are schematic diagrams of acoustic output devices with sound output holes arranged in different ways, according to some embodiments of the present disclosure. [Figure 10C] 1A to 1C are schematic diagrams of acoustic output devices with sound output holes arranged in different ways, according to some embodiments of the present disclosure. [Figure 10D] 1A to 1C are schematic diagrams of acoustic output devices with sound output holes arranged in different ways, according to some embodiments of the present disclosure. [Figure 11A] 10B is a schematic diagram showing the directionality of far-field radiation of the acoustic output device shown in FIG. 10A. FIG. [Figure 11B] 10C is a schematic diagram showing the directionality of far-field radiation of the acoustic output device shown in FIG. 10B. [Figure 11C] 10D is a schematic diagram showing the directionality of far-field radiation of the acoustic output device shown in FIG. 10C. [Figure 11D] FIG. 10E is a schematic diagram showing the directionality of far-field radiation of the acoustic output device shown in FIG. 10D. [Figure 12A] FIG. 10 is a schematic diagram illustrating the directionality of far-field radiation of an acoustic output device with exemplary hole placement locations, in accordance with some embodiments herein. [Figure 12B] FIG. 10 is a schematic diagram illustrating the directionality of far-field radiation of an acoustic output device with exemplary hole placement locations, in accordance with some embodiments herein. [Figure 13] FIG. 1 is a schematic diagram of another acoustic output device in accordance with some embodiments of the present disclosure. [Figure 14] 1 is a schematic diagram of sound transmission in an audio output device with a second speaker installed, according to some embodiments of the present disclosure. [Figure 15] 10 is a schematic diagram illustrating an exemplary process of a method for conditioning a second electrical signal, according to some embodiments herein. [Figure 16] 10A-10C are schematic diagrams of frequency response curves of a single sound source and a dual sound source when each is excited independently, in accordance with some embodiments herein; [Figure 17] FIG. 10 is a schematic diagram illustrating the directionality of far-field radiation of an acoustic output device after the second electrical signal is adjusted, according to some embodiments herein. [Figure 18A]FIG. 10 is a diagram illustrating a directivity test curve of an acoustic output device according to some embodiments of the present disclosure. [Figure 18B] FIG. 10 is a diagram illustrating a directivity test curve of an acoustic output device according to some embodiments of the present disclosure. [Figure 19] FIG. 1 is a schematic diagram of an equivalent model of an acoustic output device according to some embodiments of the present disclosure, adjusted according to a preset algorithm. [Figure 20] FIG. 1 is a schematic diagram of an equivalent model of an acoustic output device tuned according to an active algorithm, in accordance with some embodiments of the present disclosure. [Figure 21] FIG. 1 is a schematic block diagram of an amplitude and phase adjustment algorithm according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0028] In order to more clearly explain the technical means of the embodiments of the present specification, the drawings necessary for the description of the embodiments will be briefly described below. Obviously, the drawings described below are only a part of the examples or embodiments of the present specification, and those skilled in the art can apply the present specification to other similar scenarios based on these drawings without any creative effort. Unless otherwise clear from the context or described otherwise, the same symbols in the drawings represent the same structures or operations.

[0029] It should be understood that the terms "system," "device," "unit," and / or "module" used herein are ways of distinguishing between various assemblies, elements, components, parts, or structures at different levels. However, other terms can be used in place of the above terms if they achieve the same purpose.

[0030] As used in this specification and claims, unless the context clearly dictates otherwise, terms such as "a," "one," "one kind," and / or "the" do not specifically refer to the singular but may include the plural. In general, the terms "comprise" and "containing" are intended to indicate only the inclusion of explicitly identified steps and elements; these steps and elements are not an exclusive list, and a method or apparatus may include other steps or elements.

[0031] Flowcharts are used herein to describe operations performed by systems according to embodiments of the present invention. It should be understood that the preceding and following operations are not necessarily performed in exact order. Instead, steps may be processed in reverse order or simultaneously. Also, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0032] In some embodiments, to solve the sound leakage problem of an audio output device, two sound sources with opposite phases can be used to generate two sets of sounds with opposite phases. Under far-field conditions, the difference in acoustic distances of the two sound sources with opposite phases to a specific point in the far field is essentially negligible, so the two sets of sounds can cancel each other out, reducing sound leakage in the far field.

[0033] FIG. 1 is a schematic diagram of the relative positions of an audio output device and a user's ear according to some embodiments of the present disclosure. As shown in FIG. 1 , the audio output device 100 may include a housing 110 and a speaker 120. The speaker 120 may be installed in a cavity defined by the housing 110, and the speaker 120 may include a diaphragm (not shown). The cavity of the housing 110 may include a front cavity 130 and a rear cavity 140, which radiate sound, on the front and rear sides of the diaphragm, respectively. The housing 110 may include a first hole 111 and a second hole 112, and the front cavity 130 may be acoustically coupled to the first hole 111, and the rear cavity 140 may be acoustically coupled to the second hole 112. When the speaker 120 outputs sound waves, sound waves on the front side of the diaphragm (also referred to as first sound waves) may pass through the front cavity 130 and emerge from the first hole 111, and sound waves on the rear side of the diaphragm (also referred to as second sound waves) may pass through the rear cavity 140 and emerge from the second hole 112. In this case, the first hole 111 and the second hole 112 can be regarded as a pair of dual sound sources, which can emit two sets of sounds with the same amplitude but opposite phases. For ease of understanding, in some embodiments herein, the front side of the diaphragm refers to the side of the diaphragm away from a magnetic circuit assembly (not shown), and the rear side of the diaphragm refers to the side of the diaphragm facing the magnetic circuit assembly. Of course, in certain scenarios, the front side and the rear side of the diaphragm may be interchangeable, i.e., the side of the diaphragm away from the magnetic circuit assembly may be referred to as the rear side, and the side of the diaphragm facing the magnetic circuit assembly may be referred to as the front side.

[0034] 1 , when a user wears or uses the audio output device 100, the audio output device 100 may be positioned near the user's pinna, and the first hole 111 may face the user's ear canal opening 201, so that sound emitted from the first hole 111 can be transmitted to the user's ear canal. The second hole 112 may be farther away from the ear canal opening 201 than the first hole 111, and the distance between the first hole 111 and the ear canal opening is smaller than the distance between the second hole 112 and the ear canal opening.

[0035] In some embodiments, when the speaker 120 vibrates, the front and rear sides of the speaker 120 can serve as sound wave generating structures, respectively generating sound waves with equal amplitudes and opposite phases. In some embodiments, the sound waves with equal amplitudes and opposite phases can be radiated to the outside from the first hole 111 and the second hole 112, respectively, to form dual sound sources, which can interfere and cancel each other out at a spatial point (e.g., in the far field), thereby effectively alleviating the sound leakage problem in the far field of the audio output device 100.

[0036] FIG. 2A is a schematic diagram of a sound field distribution of sound pressure levels at mid-low frequencies of the audio output device shown in FIG. 1. As shown in FIG. 2A, within the mid-low frequency range (e.g., 50 Hz to 1 kHz), the sound field distribution of the audio output device 100 exhibits good dual sound source directivity and a significant sound leakage reduction effect. That is, within the mid-low frequency range, the dual sound sources formed by the first hole 111 and the second hole 112 of the audio output device 100 output sound waves with opposite phases (i.e., a first sound wave and a second sound wave). The sound field is distributed in a spatial form with two lobe-like structures, with high sound pressure levels in the two opposite directions of the line connecting the dual sound sources and low sound pressure levels in the direction perpendicular to the line connecting the dual sound sources. However, one of the two lobe-like structures formed in the sound field is far from the user's ear, causing significant sound leakage and affecting the sound leakage reduction effect of the audio output device.

[0037] In some embodiments, in the high-frequency range, the first and second sound waves have short wavelengths. Therefore, the distance between the dual sound sources formed by the first hole 111 and the second hole 112 cannot be ignored relative to the wavelength. For example, the acoustic distance to a spatial point (e.g., the far field) of the first sound wave differs from the acoustic distance to a spatial point of the second sound wave due to the distance between the first hole 111 and the second hole 112. Therefore, the phase difference between the first and second sound waves at the spatial point is small (e.g., the phases are the same or close). Therefore, the first and second sound waves not only cannot interfere and cancel each other out at the spatial point, but may also overlap at the spatial point, increasing the amplitude of the sound waves at the spatial point. In some embodiments, the shielding of high-frequency sound waves by structures such as the pinna 210 and / or their influence on the reflection of sound waves may cause a disturbance in the sound field distribution of the acoustic output device 100.

[0038] In some embodiments, the front cavity 130 and the rear cavity 140 have different structures and parameters (e.g., volume, etc.) and therefore have different resonant frequencies. In some embodiments, special acoustic structures (e.g., sound conduits, etc.) may be additionally installed in the front cavity 130 and / or the rear cavity 140 to adjust the resonant frequency. When sound waves in the front cavity 130 and / or the rear cavity 140 resonate, this may change the frequency content of the sound waves transmitted within the front cavity 130 and / or the rear cavity 140 (e.g., add additional resonant peaks to the transmitted sound waves) or may change the phase of the transmitted sound waves. Compared with the case where there is no resonance, the sound waves emitted from the first hole portion 111 and / or the second hole portion 112 will have a change in phase and / or amplitude, and the change in phase and / or amplitude may cause disturbance in the sound field in the high frequency range of the dual sound source, and may affect the interference cancellation effect at the spatial point of the sound waves emitted from the first hole portion 111 and the second hole portion 112. For example, when resonance occurs, the phase difference between the sound waves emitted from the first hole 111 and the second hole 112 changes. For example, if the phase difference between the sound waves emitted from the first hole 111 and the second hole 112 is small (e.g., less than 120°, less than 90°, or 0), the interference cancellation effect of the sound waves at the spatial point decreases, making it difficult to achieve the sound leakage reduction effect. Alternatively, sound waves with small phase differences may overlap each other at the spatial point, increasing the amplitude of sound waves near the resonance frequency at the spatial point (e.g., in the far field), and increasing sound leakage in the far field of the acoustic output device 100. Furthermore, for example, the above-mentioned resonance may increase the amplitude of the transmitted sound waves near the resonance frequency of the acoustic transmission structure (for example, expressed as a resonance peak near the resonance frequency), causing disturbance in the sound field near the resonance frequency of the dual sound source. At this time, the amplitude difference between the sound waves radiated from the first hole 111 and the second hole 112 is large, reducing the effect of canceling out interference at the spatial point of the sound waves, making it difficult to achieve the effect of reducing sound leakage. 2B is a schematic diagram of the sound field distribution of high-frequency sound pressure levels of the audio output device shown in FIG. 1 , and FIG. 3 is a frequency response curve diagram of the audio output device shown in FIG. 2B . As shown in FIG. 2B , within the high-frequency range, the audio signal radiated to the outside through the second hole 112 of the audio output device 100 dominates the overall sound field distribution, resulting in a distorted sound field distribution. Because there is a certain difference between the amplitude / phase of the sound waves actually radiated through the second hole 112 of the audio output device 100 and the original amplitude / phase of the sound waves emitted from the speaker 120, the two audio waves radiated through the first hole 111 and the second hole 112 not only fail to reduce sound leakage from a specific location in the far field but also increase sound leakage from that location.

[0039] 3, curve L3 indicates the frequency response curve of the front cavity 130 (e.g., the first hole 111) of the acoustic output device 100, and curve L3' indicates the frequency response curve of the rear cavity 140 (e.g., the second hole 112) of the acoustic output device 100. As can be seen from Fig. 3, within the high frequency range, the front cavity 130 (having a resonance peak at a frequency of about 6 kHz) and the rear cavity 140 (having a resonance peak at a frequency of about 4 kHz) of the acoustic output device 100 have clearly different resonance peaks. As can be seen by comparing curves L3 and L3', the sound output device 100 exhibits good sound leakage reduction effects, with the volume levels of the front and rear cavities being nearly equal in the mid-low frequency range (e.g., 50 Hz to 1500 Hz). However, in the high frequency range (e.g., 1500 Hz to 20 kHz), the volume levels of the front and rear cavities differ significantly, significantly reducing the sound leakage reduction effect. As can be seen from FIGS. 2B and 3, in the high frequency range, the sound field distribution of the dual sound sources becomes distorted, which may result in failure to reduce far-field sound leakage and, ultimately, increase far-field sound leakage. In some embodiments, the structure of the sound output device 100 can be adjusted to adjust the sound field distribution of the dual sound sources, resulting in a more directional sound field, thereby alleviating the problem of increased far-field sound leakage.

[0040] In some embodiments, a second speaker may be installed in the audio output device to cancel out sound waves from the second speaker and sound waves generated by speaker 120 (also referred to as the first speaker), thereby suppressing disturbances in the sound field in a dual sound source structure (e.g., in a high frequency range) and reducing or eliminating sound leakage from the far field of the audio output device. In some embodiments, the audio output device may include a housing, a first speaker, and a second speaker. The first speaker is installed in the housing and acoustically coupled to two holes (e.g., a first hole and a second hole) of the housing, respectively, to output a first sound wave and a second sound wave having a phase difference, respectively. In some embodiments, the first speaker includes a first diaphragm, and a first front cavity and a first rear cavity are respectively disposed in front and rear of the first diaphragm in the housing, and the first front cavity and the first rear cavity are acoustically coupled to the two holes (e.g., the first hole and the second hole), respectively, to output a first sound wave and a second sound wave having a phase difference. In some embodiments, the first speaker may be driven by a first electric signal to output the first sound wave and the second sound wave having a phase difference from the two holes (e.g., the first hole and the second hole). The second speaker is disposed within the housing and acoustically coupled to one hole (e.g., a third hole, which may be either the first hole or the second hole or may be another hole different from the first hole and the second hole) disposed in the housing. In some embodiments, the second speaker includes a second diaphragm, and the housing has a second front cavity and a second rear cavity disposed in front of and behind the second diaphragm, respectively, and only one of the second front cavity and the second rear cavity is acoustically coupled to one of the holes (e.g., the third hole) to output the third sound wave. In some embodiments, the second speaker may be driven by a second electrical signal to output the third sound wave from one of the holes (e.g., the third hole).In this case, the first sound wave and the second sound wave of the first speaker are output from two holes (e.g., the first hole and the second hole), respectively, forming a dual sound source, and the third sound wave of the second speaker is output from only one hole (e.g., the third hole), forming a single sound source. In some embodiments, within a target frequency range, the third sound wave output by the second speaker and the first and second sound waves output by the first speaker can be superimposed and canceled at a far-field position in a specific direction of the acoustic output device. The superimposed and canceled sound pressure at the position is small (e.g., close to zero) and the sound pressure at a corresponding far-field position in the opposite direction of the specific direction is large so that the absolute value of the sound pressure level difference between the two positions is equal to or greater than a predetermined sound pressure level threshold, thereby making the far-field radiation of the acoustic output device directional. Here, the two corresponding far-field positions in the specific direction and the opposite direction are at equal distances from the acoustic output device. In some embodiments, for the sound pressure levels at two far-field positions in the specific direction and the corresponding opposite direction, test microphones installed at the two far-field positions can measure the sound pressures at the corresponding far-field positions, and then obtain the corresponding sound pressure levels using the sound pressures, and finally obtain the sound pressure level difference between the two far-field positions in the specific direction and the corresponding opposite direction.

[0041] To ensure that the sound waves output by the first speaker (e.g., the superposition of the first and second sound waves) and the sound waves output by the second speaker (e.g., a third sound wave) can be effectively canceled out at the far-field position, the sound waves output by the first speaker and the second speaker should have equal or similar amplitudes and opposite or nearly opposite phases at the far-field position. Considering that the frequency responses of the first and second speakers may differ due to their different structures when driven by the same electrical signal, providing electrical signals of different intensities to the first and second speakers to compensate for the difference in frequency response ultimately results in the sound waves output by the first speaker and the second speaker having the same or similar amplitudes at the far-field position. For example, a processing circuit can provide different levels of gain to the two electrical signals driving the first and second speakers to achieve compensation for the difference in frequency response. To reduce the difficulty of adjusting the electrical signal and improve the stability of the electrical signal, the difference in frequency response between the first speaker and the second speaker at the far-field position can be reduced. For example, the difference in frequency response between the first speaker and the second speaker at the far-field position can be reduced by adjusting the structures of the first speaker and the second speaker, such as the volume of the cavity, the dimensions and positions of the holes, etc. For details on adjusting the parameters related to the structures of the first speaker and the second speaker, please refer to the descriptions elsewhere in this specification.The phrase "reducing the difference in frequency response between the first speaker and the second speaker at a far-field position" described here may be understood to mean that, within a target frequency range, the difference in sound pressure level between the superimposed sound wave of the first sound wave and the second sound wave output by the first speaker and the third sound wave output by the second speaker is less than 14 dB at a far-field position in a specific direction of the audio output device, driven by the same electrical signal (i.e., the first electrical signal and the second electrical signal are the same), and thereby, after appropriate amplitude and frequency adjustment is made to the first electrical signal or the second electrical signal, the first sound wave and the second sound wave output by the first speaker and the third sound wave output by the second speaker superimpose and cancel each other out at a far-field position in a specific direction of the audio output device, resulting in a low sound pressure at the far-field position, for example, close to zero. In some embodiments, in order to reduce the sound pressure at a far-field position in a specific direction of the acoustic output device and improve the sound leakage reduction effect of the acoustic output device, the acoustic output device is driven by the same electrical signal (i.e., the first electrical signal and the second electrical signal are the same) within a target frequency range, and the sound pressure level difference between the superimposed sound wave of the first sound wave and the second sound wave output by the first speaker and the third sound wave output by the second speaker at a far-field position in a specific direction of the acoustic output device is less than 10 dB. In some embodiments, to further reduce the sound pressure at a far-field position in a specific direction of the acoustic output device and improve the sound leakage reduction effect of the acoustic output device, within a target frequency range, the difference in sound pressure level between the superimposed sound wave of the first sound wave and the second sound wave output by the first speaker and the third sound wave output by the second speaker, driven by the same electrical signal (i.e., the first electrical signal and the second electrical signal are the same), at the far-field position in the specific direction of the acoustic output device, is less than 6 dB. In some embodiments, the target frequency range may include a first frequency range, and the mutual superimposition of the first sound wave, the second sound wave, and the third sound wave within the first frequency range causes the far-field radiation of the acoustic output device to exhibit a heart-shaped directivity.In some embodiments, the target frequency range may include a second frequency range, where the sound pressure level of the third sound wave is much smaller than the sound pressure level of the second sound wave. When the first sound wave, the second sound wave, and the third sound wave overlap each other, the influence of the third sound wave can be ignored. The first sound wave and the second sound wave are considered to be dual sound sources and overlap each other, so that the far-field radiation of the acoustic output device exhibits dual-source directivity. In some embodiments, the first frequency range may include a mid-high frequency band (e.g., 800 Hz to 10 kHz, etc.), and the second frequency range may include a mid-low frequency band (e.g., 100 Hz to 800 Hz, etc.). For more information regarding the directionality and heart-shaped directivity of the acoustic output device, see FIG. 4 and its related description. For more information regarding dual-source directivity, see FIG. 2A above and its related description.

[0042] In some embodiments, the audio output device may include at least one of neckband-type earphones, ear-hook-type earphones, in-ear earphones, and glasses. In a worn state, the opposite direction of the specific direction may face the user's ear canal. FIG. 4 is a schematic diagram of directionality according to some embodiments of the present disclosure. As shown in FIG. 4, the audio output device shown in FIG. 4 is in a worn state, with AS1 indicating a sound output hole portion of a front cavity of the audio output device and AS2 indicating a sound output hole portion of a rear cavity of the audio output device. In some embodiments, the far-field radiation of the audio output device exhibits directionality when the sound output direction of the audio output device is within a specified direction range, i.e., the far-field radiation of the audio output device within the specified direction range is significantly greater than the far-field radiation outside the specified direction range. In some embodiments, when the sound output device is in a worn state, the direction X1 from the sound output hole portion AS2 corresponding to the rear cavity of the sound output device to the sound output hole portion AS1 corresponding to the front cavity (i.e., the direction X1 from the sound output hole portion AS2 of the rear cavity to the sound output hole portion AS1 of the front cavity) and nearby directions (e.g., direction X2, direction X3) point toward the opening of the user's ear canal. That is, in a worn state, the sound output hole portion AS1 corresponding to the front cavity of the sound output device is closer to the opening of the user's ear canal. The direction X1' from the sound output hole portion AS1 of the front cavity to the sound output hole portion AS2 of the rear cavity and nearby directions (e.g., direction X2', direction X3') point toward the opening of the sound output device from the opening of the user's ear canal. In some embodiments, in the worn and / or unworn state, the direction X1 from the sound output hole portion AS2 of the rear cavity to the sound output hole portion AS1 of the front cavity of the audio output device and its vicinity may constitute the specified directional range described above. The far-field radiation of the audio output device in the direction X1 and its vicinity is clearly greater than the far-field radiation in other directional ranges (e.g., a range of directions perpendicular to the direction X1 and its vicinity, a range of directions opposite to the direction X1 and its vicinity, etc.). In some embodiments, the directivity of the audio output device may be expressed such that the absolute value of the sound pressure level difference between two corresponding far-field positions in a specific direction of the audio output device and the opposite direction is equal to or greater than a predetermined sound pressure level threshold.When the device is worn, the specific direction may refer to a direction away from the user's ear canal, and the opposite direction may refer to a direction from the audio output device toward the user's ear canal. In some embodiments, the specific direction may refer to the direction X1' from the sound output hole AS1 of the front cavity to the sound output hole AS2 of the rear cavity and a direction near that direction. The opposite direction to the specific direction may refer to the direction X1 from the sound output hole AS2 of the rear cavity to the sound output hole AS1 of the front cavity and a direction near that direction. In some embodiments, the direction near the direction X1' may be understood to be a direction that forms an angle with the direction X1' of less than 60°. Note that, for ease of understanding the directivity, only two holes, AS1 and AS2, will be used as an example. If the audio output device has more different holes, AS1 may be understood to be an equivalent hole formed by some of the holes, and AS2 may be understood to be an equivalent hole formed by other holes. In this case, the direction of the directivity may be determined by the position of the equivalent hole. In some embodiments, the position of an equivalent hole formed by multiple holes can be determined in the following manner: the center points of adjacent holes are connected in order to form a polygon or polyhedron, and the centroid of the polygon or polyhedron is the center point of the equivalent hole, which can represent the position of the equivalent hole.

[0043] In some embodiments, the far-field radiation of the acoustic output device may exhibit a heart-shaped directivity, which is expressed by the absolute value of the difference in sound pressure levels of the far-field radiation sound of the acoustic output device in at least one pair of opposite directions within a specified directional range being equal to or greater than a predetermined sound pressure level threshold. The at least one pair of opposite directions may be within the specified directional range and its opposite direction, respectively. In some embodiments, the at least one pair of opposite directions may include the specific direction and its opposite direction. That is, the specific direction and its opposite direction may be included within the specified directional range and its opposite direction, respectively. In some embodiments, the at least one pair of opposite directions may include a pair of opposite directions corresponding to a line connecting the sound output hole portion AS1 (e.g., the first hole) of the front cavity and the sound output hole portion AS2 (e.g., the second hole) of the rear cavity. The heart-shaped directivity of the acoustic output device may be expressed by the sound field intensities of a pair of opposite or nearly opposite directions within the specified directional range and its opposite direction being significantly different from each other. For example, of the pair of opposite or substantially opposite directions described above, one direction may be near the direction X1' from the sound emitting holes of the front cavity to the sound emitting holes of the rear cavity, and the other direction may be near the direction X1 from the sound emitting holes of the rear cavity to the sound emitting holes of the front cavity. For example, the direction X1' may be opposite or substantially opposite to the direction X1, the direction X2, and the direction X3.

[0044] By installing the audio output device so that its far-field radiation exhibits a heart-shaped directivity, the sound output from the audio output device can be transmitted in a concentrated manner in the direction of the user's ear canal opening, reducing the transmission of sound in other directions, improving the problem of sound leakage from the audio output device, and improving the user's listening experience.

[0045] In some embodiments, the preset sound pressure level threshold may be 6 dB. For example, the far-field radiation of the acoustic output device exhibiting a heart-shaped directivity may be expressed as an absolute value of the difference in sound pressure levels of the far-field radiation sound of the acoustic output device in at least one pair of opposite directions (e.g., direction X1 and direction X1') being 6 dB or more, thereby allowing the user to receive a high volume at the opening of the ear canal and achieving a clear listening experience.

[0046] In some embodiments, the first electrical signal driving the first speaker and the second electrical signal driving the second speaker have an amplitude and / or phase difference within a target frequency range, and the first, second, and third sound waves are mutually overlapped and canceled out at a far-field position in a specific direction of the acoustic output device within the target frequency range, so that the sound pressure of the overlapped and canceled sound waves is small, for example, close to zero, thereby making the far-field radiation of the acoustic output device directional and improving the problem of sound leakage in the far field of the acoustic output device. In some embodiments, the first electrical signal may be measured by a measuring device (e.g., an oscilloscope) installed between the first speaker and a corresponding signal generator, and the second electrical signal may be measured by a measuring device (e.g., an oscilloscope) installed between the second speaker and a corresponding signal generator. In some embodiments, the adjusted first electrical signal and / or the adjusted second electrical signal may be measured by a measuring device installed between the corresponding speaker and a corresponding signal modulator.

[0047] To achieve directionality of far-field radiation of the audio output device, the first speaker and the second speaker may be arranged in a variety of ways. Figures 5A to 5D are schematic configuration diagrams of audio output devices including the first speaker and the second speaker arranged in different ways according to some embodiments of the present disclosure. As shown in Figures 5A to 5D , in some embodiments, the first diaphragm 521 and the second diaphragm 551 have the same vibration direction (e.g., the up-down direction in Figures 5A to 5D ) and are spaced apart along the vibration direction, i.e., the first speaker 520 and the second speaker 550 are spaced apart along the vibration direction (as shown in Figures 5A and 5B ). In some embodiments, the first diaphragm 521 and the second diaphragm 551 are spaced apart along a direction perpendicular to the vibration direction, i.e., the first speaker 520 and the second speaker 550 are spaced apart along a direction perpendicular to the vibration direction (as shown in FIGS. 5C and 5D ). Ideally, the first diaphragm 521 and the second diaphragm 551 have the same vibration direction. In an actual product, considering factors such as structural design and installation error, the first diaphragm 521 and the second diaphragm 551 may not have exactly the same vibration direction, but may have a slight difference (for example, the included angle between the vibration directions of the first diaphragm 521 and the second diaphragm 551 is less than 10°). In this case, the direction in which the first speaker 520 and the second speaker 550 are arranged or the direction perpendicular to the direction in which they are arranged may be the vibration direction of the first diaphragm 521, the vibration direction of the second diaphragm 551, or a direction between the included angle formed by the vibration directions of the two diaphragms. In some embodiments, the orientation of the first diaphragm 521 arranged with respect to the first speaker 520 may be the same as or opposite to the orientation of the second diaphragm 551 arranged with respect to the second speaker 550. In some embodiments, the first rear cavity 540 of the first speaker 520 and the second rear cavity 570 of the second speaker 550 may be adjacent to or communicate with each other, and in this case, the second front cavity 560 of the second speaker 550 is sealed, as shown in FIGS. 5A and 5C .In some embodiments, the first rear cavity 540 of the first speaker 520 and the second front cavity 560 of the second speaker 550 may be adjacent to or in communication with each other, with the second rear cavity 570 of the second speaker 550 being sealed, as shown in Figures 5B and 5D. In some embodiments, when the volumes of each cavity (e.g., the first front cavity 530, the first rear cavity 540, the second front cavity 560, the second rear cavity 570, etc.) are the same, the acoustic output device 500 shown in Figure 5A may be equivalent to the acoustic output device 500 shown in Figure 5C, and the acoustic output device 500 shown in Figure 5B may be equivalent to the acoustic output device 500 shown in Figure 5D.

[0048] Hereinafter, an example of a sound output device will be described in which a first speaker and a second speaker are arranged at an interval along the vibration direction.

[0049] 5A and 5B , in some embodiments, an acoustic output device 500 includes a housing 510, a first speaker 520, and a second speaker 550. The first speaker 520 is disposed within the housing 510 and includes a first vibrating membrane 521. A first front cavity 530 and a first rear cavity 540 are disposed on the front and rear sides of the first vibrating membrane 521, respectively. The first front cavity 530 and the first rear cavity 540 are acoustically coupled to a first hole 511 and a second hole 512 of the housing 510, respectively. The first speaker 520 is driven by a first electrical signal to output a first sound wave and a second sound wave having a phase difference from the first hole 511 and the second hole 512, respectively. The second speaker 550 is installed in the housing 510 and includes a second vibrating membrane 551, with a second front cavity 560 and a second rear cavity 570 installed on the front and rear sides of the second vibrating membrane 551, respectively, and one of the second front cavity 560 and the second rear cavity 570 is the same cavity as the first rear cavity 540, i.e., the second front cavity 560 or the second rear cavity 570 constituting the same cavity is acoustically coupled to the second hole 512 of the housing 510, and the second speaker 550 is driven by a second electrical signal to output a third sound wave from the second hole 512. In some embodiments, the second front cavity 560 and the first rear cavity 540 may be the same cavity, and in this case, the first diaphragm 521 and the second diaphragm 551 have the same orientation, as shown in FIG. 5B . In some embodiments, the second rear cavity 570 and the first rear cavity 540 may be the same cavity, and in this case, the first diaphragm 521 and the second diaphragm 551 have opposite orientations, as shown in FIG. 5A . Comparing the audio output device 500 shown in FIG. 5A with the audio output device 500 shown in FIG. 5B , the audio output device 500 shown in FIG. 5A and the audio output device 500 shown in FIG. 5B have different frequency response curves because the first diaphragm 521 and the second diaphragm 551 are installed in different orientations. However, the far-field sound emitted by both audio output devices can achieve directionality.Hereinafter, the acoustic output device 500 will be described using an example in which the first speaker 520 and the second speaker 550 shown in FIG. 5A are arranged at an interval along the vibration direction, and the first vibrating membrane 521 and the second vibrating membrane 551 are oriented in opposite directions (i.e., the second rear cavity 570 and the first rear cavity 540 are the same cavity).

[0050] 4, 5A, and 5B, the first front cavity 530 may be the front cavity of the sound output device 500, and the same cavity may be the rear cavity of the sound output device 500. In this case, the first hole 511 is the sound output hole AS1 of the front cavity of the sound output device 500, and the second hole 512 is the sound output hole AS2 of the rear cavity of the sound output device 500, and the direction of the extension line of the line connecting the first hole 511 and the second hole 512 is a specific direction.

[0051] In some embodiments, the first and second electrical signals are configured to have a difference in amplitude and / or phase within a target frequency range, such that the first sound wave generated by the first speaker 520 in the first front cavity 530, the second sound wave generated by the first speaker 520 in the first rear cavity 540, and the third sound wave generated by the second speaker 550 in the second rear cavity 570 all meet certain phase and amplitude requirements at a far-field position in a specific direction of the audio output device 500. For example, the superimposed sound wave formed by the first and second sound waves at a far-field position in a specific direction and the third sound wave have a phase difference, and after superposition and cancellation, the sound pressure at the far-field position is small, for example, close to zero, so that the absolute value of the sound pressure level difference between the far-field position in the specific direction and the corresponding far-field position in the opposite direction to the specific direction is equal to or greater than a predetermined sound pressure level threshold, thereby realizing the directionality of the sound output device 500. At the same time, this installation can suppress sound field disturbance in the high-frequency range of the dual sound sources, thereby reducing or eliminating far-field sound wave radiation from the sound output device 500.

[0052] To prevent the resonant frequency of each cavity from interfering with the realization of the heart-shaped directivity of the audio output device and improve the user's listening experience, the structural parameters of each cavity are adjusted so that the resonant frequency of each cavity is outside the frequency range in which the heart-shaped directivity is realized. In some embodiments, the target frequency range in which the audio output device achieves the heart-shaped directivity may be within the flat frequency response range of the first speaker 520 and the second speaker 550. That is, the resonant frequency of the same cavity of the first speaker 520 and the second speaker 550 (e.g., the same cavity formed by the first rear cavity 540 and the second rear cavity 570 in FIG. 5A , or the same cavity formed by the first rear cavity 540 and the second front cavity 560 in FIG. 5B ) determines the upper frequency limit in which the heart-shaped directivity can be easily realized. In some embodiments, to improve the user's listening experience, the audio output device may have heart-shaped directivity within a frequency range to which the human ear is sensitive, for example, around 3 kHz or 3.5 kHz. In this case, the upper limit of the frequency range in which the far-field radiation of the audio output device achieves heart-shaped directivity may be 4 kHz or higher (e.g., the frequency range in which the heart-shaped directivity is achieved may be 1 kHz to 4 kHz). In this case, the resonant frequency of the same cavity is 4 kHz or higher. In some embodiments, the frequency range in which the heart-shaped directivity is achieved may vary depending on the application scenario of the audio output device. For example, for an audio output device that operates primarily in mid-low frequency conditions, the frequency range in which the heart-shaped directivity is achieved may be 800 Hz to 2 kHz, and the resonant frequency of the same cavity may be 2 kHz or higher. In other embodiments, for an audio output device that operates primarily in mid-high frequency conditions, the upper limit of the frequency range in which the heart-shaped directivity is achieved may be higher, and the resonant frequency of the same cavity may also be higher accordingly. In order to improve the output quality of the acoustic output device within the frequency range sensitive to the human ear, the resonant frequency of the same cavity may be outside the frequency range sensitive to the human ear, for example, greater than 4 kHz, greater than 4.5 kHz, or greater than 5 kHz.In this case, the upper limit of the frequency range that realizes the heart-shaped directivity may be 4 kHz, 4.5 kHz, 5 kHz, or the like.

[0053] 6 is a schematic diagram illustrating the relationship between the resonant frequency of the same cavity and its volume, according to some embodiments herein, and FIG. 7 is a schematic diagram illustrating the relationship between the resonant frequency of the same cavity and the area of the hole acoustically coupled thereto, according to some embodiments herein. As shown in FIGS. 6 and 7, in some embodiments, when the resonant frequency of the same cavity is adjusted to 3.8 kHz or higher, the volume of the same cavity is correspondingly increased to 0.38 cm. 3 and a second hole 512 acoustically coupled to the same cavity has an area of 17 mm 2 In some embodiments, if the resonant frequency of the same cavity is adjusted to 4 kHz or higher, the volume of the same cavity is correspondingly increased to 0.28 cm 3 and the area of the second hole 512 acoustically coupled to the same cavity is 20 mm 2 In some embodiments, if the resonant frequency of the same cavity is adjusted to 4.2 kHz or higher, the volume of the same cavity is adjusted accordingly to 0.2 cm 3 or less, and the area of a second hole 512 acoustically coupled to the same cavity is 22 mm 2 In some embodiments, if the resonant frequency of the same cavity is adjusted to 4.3 kHz or higher, the volume of the same cavity is correspondingly increased to 0.18 cm 3 or less, and a second hole 512 acoustically coupled to the same cavity has an area of 23 mm 2 By adjusting the volume of the identical cavity and the area of the hole acoustically coupled to the identical cavity, the resonant frequency of the identical cavity can be further adjusted to be outside the frequency range in which the audio output device achieves heart-shaped directivity, thereby avoiding interfering with the realization of the heart-shaped directivity of the audio output device and improving the listening experience for the user.

[0054] In some embodiments, one of the second front cavity 560 and the second rear cavity 570 of the second speaker 550 that does not constitute the same cavity is a sealed cavity and is not acoustically coupled to the second aperture 512. For example, the second front cavity 560 in FIG. 5A is a sealed cavity and is not acoustically coupled to the second aperture 512. Also, for example, the second rear cavity 570 in FIG. 5B is a sealed cavity and is not acoustically coupled to the second aperture 512. In some embodiments, the resonant frequency of the sealed cavity is adjusted to be equal to or lower than the lower frequency limit of the target frequency range for achieving heart-shaped directivity, so that the resonant frequency of the sealed cavity is not within the frequency band in which the audio output device achieves heart-shaped directivity. In some embodiments, the resonant frequency of the sealed cavity may be set to 1 kHz or less, and the lower frequency limit at which the audio output device achieves heart-shaped directivity may be set to 1 kHz or more (e.g., the frequency range at which the heart-shaped directivity is achieved may include 1 kHz to 4 kHz), thereby improving the output performance of the audio output device within a frequency range to which the human ear is sensitive. In some embodiments, the resonant frequency of the sealed cavity may be lower than the lower frequency limit of the frequency range at which the audio output device achieves heart-shaped directivity. For example, the resonant frequency of the sealed cavity may be 800 Hz or less. In some embodiments, taking into account factors such as structural design and ease of processing and installation, the resonant frequency of the sealed cavity may be 600 Hz or less.

[0055] 8 is a schematic diagram illustrating the relationship between the resonant frequency of a sealed cavity and its volume, according to some embodiments of the present disclosure. As shown in FIG. 8, in some embodiments, if the resonant frequency of the sealed cavity of the second speaker 550 is 1 kHz or less, the volume of the sealed cavity is accordingly 0.8 cm. 3 In some embodiments, if the resonant frequency of the sealed cavity of the second speaker 550 is 1.2 kHz or less, the volume of the sealed cavity may be set to 0.6 cm or less accordingly. 3In some embodiments, if the resonant frequency of the sealed cavity of the second speaker 550 is 1.4 kHz or less, the volume of the sealed cavity is accordingly 0.5 cm 3 In some embodiments, if the resonant frequency of the sealed cavity of the second speaker 550 is 1.6 kHz or less, the volume of the sealed cavity may be set to 0.45 cm 3 In some embodiments, if the resonant frequency of the sealed cavity of the second speaker 550 is 0.8 kHz or less, the volume of the sealed cavity is accordingly 1.1 cm 3 By adjusting the volume of the sealed cavity, the resonant frequency of the sealed cavity can be further controlled to be equal to or lower than the lower limit of the target frequency range in which the audio output device achieves heart-shaped directivity, thereby avoiding interference and improving the user's listening quality and the sound leakage reduction effect of the audio output device.

[0056] In some embodiments, because the second speaker has a sealed cavity, the second speaker is less likely to output low-frequency sound waves from the hole (e.g., second hole 512) acoustically coupled thereto. Therefore, in the low-frequency range, the sound pressure of the sound waves output by the second speaker is much smaller than the sound pressure of the sound waves output by the first speaker. At this time, the sound waves output by the second speaker can be ignored, and the sound waves of the audio output device are mainly output by the first speaker, thereby achieving dual sound source directivity. In the mid- to high-frequency range, the first speaker and the second speaker cooperate to output the sound waves of the audio output device, thereby achieving heart-shaped directivity. In some embodiments, the audio output device can achieve dual sound source directivity in a frequency range of 100 Hz to 800 Hz and can achieve heart-shaped directivity in a frequency range of 1 kHz to 4 kHz. In some embodiments, the frequency range in which the audio output device achieves dual sound source directivity can be designed and adjusted according to actual conditions. For example, the target frequency range in which the audio output device achieves dual-source directivity may be 100 Hz to 1.2 kHz, 100 Hz to 1.5 kHz, 200 Hz to 2 kHz, etc. In some embodiments, to achieve dual-source directivity within the target frequency range, the amplitude of the second electrical signal driving the second speaker may be reduced within the target frequency range, e.g., the amplitude of the second electrical signal within the target frequency range may be adjusted to 0, i.e., the second electrical signal is not provided within the target frequency range. In some embodiments, to avoid disturbance of the sound field of the audio output device, the lower frequency limit of the frequency range in which the audio output device achieves heart-shaped directivity may be greater than the upper frequency limit of the frequency range in which the audio output device achieves dual-source directivity. If the target frequency range in which the acoustic output device achieves dual sound source directivity is different, the mid-to-high frequency range in which the acoustic output device achieves heart-shaped directivity may also change accordingly. Since the resonant frequency of the sealed cavity of the second speaker affects the lower frequency limit of the frequency range in which heart-shaped directivity is achieved, the resonant frequency of the sealed cavity of the second speaker must also change accordingly.For example, if the audio output device achieves dual sound-source directivity between 100 Hz and 800 Hz and heart-shaped directivity between 1 kHz and 4 kHz, the resonant frequency of the sealed cavity of the second speaker may be 1 kHz or less. Also, for example, if the audio output device achieves dual sound-source directivity between 100 Hz and 1.2 kHz and heart-shaped directivity between 1.5 kHz and 4 kHz, the resonant frequency of the sealed cavity of the second speaker may be 1.5 kHz or less. In some embodiments, in a worn state, the hole acoustically coupled to the first front cavity of the first speaker may be located close to the user's ear, and the hole acoustically coupled to the first rear cavity may be located away from the user's ear, such that the direction from the hole acoustically coupled to the first rear cavity to the hole acoustically coupled to the first front cavity faces the user's ear, i.e., the dual sound-source directivity formed in the low frequency range faces the user's ear. In some embodiments, in a worn state, the hole acoustically coupled to the first front cavity of the first speaker may be located close to the user's ear, the hole acoustically coupled to the first rear cavity and the hole for outputting the third sound wave of the second speaker are located away from the user's ear, the hole acoustically coupled to the first rear cavity and the hole for outputting the third sound wave of the second speaker have equivalent holes, and the direction from the equivalent hole to the hole acoustically coupled to the first front cavity is directed toward the user's ear, i.e., the directionality formed in the mid-to-high frequency range can be directed toward the user's ear.

[0057] FIG. 9 is a schematic diagram of an audio output device according to some other embodiments of the present specification. To prevent sound waves radiated by the first speaker and the second speaker from interfering with each other and reducing the mutual radiation impedance, the audio output device may be configured so that the first speaker 620 and the second speaker 650 do not share the same cavity, as shown in FIG. 9 . For example, the housing of the audio output device may have two storage spaces, and the first speaker 620 and the second speaker 650 may be installed in two storage spaces, respectively. Alternatively, the first speaker 620 and the second speaker 650 may be installed in the same storage space of the housing, but a partition plate may be installed between them to prevent the two cavities corresponding to the two speakers from communicating with each other. Hereinafter, an audio output device 600 according to some other embodiments will be described, taking as an example a device in which the first speaker and the second speaker are spaced apart along the vibration direction and the first diaphragm and the second diaphragm are oriented in opposite directions.

[0058] As shown in FIG. 9 , an audio output device 600 may include a housing 610, a first speaker 620, and a second speaker 650. The first speaker 620 includes a first diaphragm 621. A first front cavity 630 and a first rear cavity 640 are respectively provided on the front and rear sides of the first diaphragm 621. The housing 610 includes a first hole 611 acoustically coupled to the first front cavity 630 and a second hole 612 acoustically coupled to the first rear cavity 640. The first hole 611 and the second hole 612 serve as sound emission holes for the first speaker 620, forming dual sound sources. The second speaker 650 includes a second diaphragm 651. A second front cavity 660 and a second rear cavity 670 are respectively provided on the front and rear sides of the second diaphragm 651. One of the second front cavity 660 and the second rear cavity 670 is acoustically coupled to a third hole 613 in the housing 610, and the other is a sealed cavity. The third hole 613 is a hole different from the first hole 611 and the second hole 612. In some embodiments, a partition plate 614 is installed in the housing 610, and the cavity acoustically coupled to the third hole 613 (e.g., the second rear cavity 570 in FIG. 9 ) and the first rear cavity 640 are separated by the partition plate 614, and the second hole 612 and the third hole 613 are located on either side of the partition plate 614.

[0059] In some embodiments, within the target frequency range, the sound pressure of the superimposed sound waves of the first and second sound waves output by the first speaker 620 and the third sound wave output by the second speaker 650 at a far-field position in a specific direction of the acoustic output device 600 is small, for example, close to zero, so that the far-field radiation of the acoustic output device 600 exhibits directionality and alleviates the problem of sound leakage in the far field of the acoustic output device 600. In some embodiments, the target frequency range may include 1 kHz to 4 kHz so that the acoustic output device 600 has a flat frequency response curve within a wide frequency range and excellent heart-shaped directivity.

[0060] When showing the directivity of the sound output device 600, the second hole 612 acoustically coupled to the first rear cavity 640 of the first speaker 620 and the third hole 613 acoustically coupled to the second rear cavity 670 of the second speaker 650 may be equivalent to one hole. Specifically, a center position point M between the second hole 612 and the third hole 613 is determined, and the center position point M can represent the position of the equivalent hole. In this case, the first front cavity 630 can be the front cavity of the sound output device 600, and the cavity acoustically coupled to the first rear cavity 640 and the third hole 613 (for example, the second rear cavity 670 shown in FIG. 9 ) can be the rear cavity of the sound output device 600. The first hole 611 can be the sound emitting hole AS1 of the front cavity of the sound output device 600, and the equivalent holes of the second hole 612 and the third hole 613 can be the sound emitting hole AS2 of the rear cavity of the sound output device 600. The direction of the extension line of the line connecting the first hole 611 and the equivalent hole (point M) is a specific direction.

[0061] In some embodiments, the upper frequency limit at which the acoustic output device 600 achieves heart-shaped directivity is determined by the resonant frequency of the cavity (the second front cavity 660 or the second rear cavity 670) acoustically coupled to the third hole 613 and the resonant frequency of the first rear cavity 640. If the difference between the two resonant frequencies is too large, one of the resonant frequencies will be too small, which will result in the upper frequency limit at which the acoustic output device 600 achieves heart-shaped directivity being too small, and the frequency band range at which the acoustic output device 600 achieves heart-shaped directivity being too small, ultimately affecting the output performance of the acoustic output device 600. In some embodiments, the difference between the two resonant frequencies is 3000 Hz or less. Furthermore, to increase the upper frequency limit of the heart-shaped directivity, in some embodiments, the difference between the two resonant frequencies is 2500 Hz or less. Furthermore, to increase the upper frequency limit of the heart-shaped directivity even further, in some embodiments, the difference between the two resonant frequencies is 2000 Hz or less. Preferably, the difference between the two resonant frequencies is 1500 Hz or less, and more preferably, the difference between the two resonant frequencies is 1000 Hz or less.

[0062] In some embodiments, the upper frequency limit of the heart-shaped directivity may be 4 kHz or greater so that the acoustic output device can achieve a heart-shaped directivity within the audio frequency range to which the human ear is sensitive. In some embodiments, the resonant frequency of the cavity (the second front cavity 660 or the second rear cavity 670) acoustically coupled to the third hole 613 can be outside the frequency range that achieves the heart-shaped directivity to avoid the resonant frequency of the cavity interfering with the heart-shaped directivity. For example, the resonant frequency of the cavity (the second front cavity 660 or the second rear cavity 670) acoustically coupled to the third hole 613 is 4 kHz or greater. In some embodiments, the resonant frequency of the cavity (the second front cavity 660 or the second rear cavity 670) acoustically coupled to the third hole 613 is 5 kHz or greater to increase the upper frequency limit of the heart-shaped directivity.

[0063] In some embodiments, the structure of the first rear cavity 640 and the second hole 612 and the structure of the cavity acoustically coupled to the third hole 613 (the second front cavity 660 or the second rear cavity 670) and the third hole 613 are the same or similar, and the resonant frequencies of the two are close (e.g., the difference between the resonant frequencies of the two is less than 3000 Hz). When the resonant frequency of the cavity acoustically coupled to the third hole 613 (the second front cavity 660 or the second rear cavity 670) is 4 kHz or higher, the volume of the cavity acoustically coupled to the third hole 613 (e.g., the second rear cavity 570 shown in FIG. 9) is less than 0.3 cm. 3 Accordingly, the area of the third hole 613 is 12 mm 2 At this time, the volume of the first rear cavity 640 is also 0.3 cm 3 The area of the second hole 612 may be 12 mm or less. 2 It may be more than that.

[0064] In some embodiments, one of the second front cavity 660 and the second rear cavity 670 of the second speaker 650 that is not acoustically coupled to the second hole 612 is a sealed cavity, e.g., the second front cavity 660 in FIG. 9 is a sealed cavity. The resonant frequency of the sealed cavity can determine the lower frequency limit of the frequency range that achieves the heart-shaped directivity. In some embodiments, to avoid the resonant frequency of the sealed cavity interfering with the heart-shaped directivity, the resonant frequency of the sealed cavity can be outside the frequency range that achieves the heart-shaped directivity. For example, the resonant frequency of the sealed cavity (e.g., the second front cavity 660 in FIG. 9) can be 1 kHz or less. In some embodiments, the resonant frequency of the sealed cavity can be lower than the lower frequency limit of the frequency range that achieves the heart-shaped directivity of the audio output device. For example, the resonant frequency of the sealed cavity can be 900 Hz or less. In some embodiments, taking into consideration factors such as structural design and the difficulty of processing and installation, the resonant frequency of the sealed cavity may be 1.1 kHz or less. In this case, the frequency range at which the acoustic output device achieves heart-shaped directivity may be reduced accordingly, and the lower limit of the frequency at which heart-shaped directivity is achieved may be 1.1 kHz.

[0065] In some embodiments, when the first hole 611 acoustically coupled to the first front cavity 630 is arranged in a corresponding region of the housing 610 along the vibration direction of the first speaker 620 (i.e., the direction of the line connecting the geometric center of the first hole 611 and the geometric center of gravity of the first diaphragm 621 of the first speaker 620 is parallel to the vibration direction), the holes corresponding to the first rear cavity 640 and its adjacent cavity (the second front cavity 660 or the second rear cavity 670) may be arranged in multiple ways. Hereinafter, different hole arrangements of the audio output device 600 will be described using an example in which the first speaker and the second speaker do not have the same cavity, are spaced apart along the vibration direction, and the first diaphragm and the second diaphragm are oriented in opposite directions.

[0066] 10A to 10D are schematic diagrams of acoustic output devices according to some embodiments of the present specification, in which sound output holes are arranged in different ways, and FIGS. 11A to 11D are schematic diagrams showing the directivity of far-field radiation of the acoustic output devices shown in FIGS. 10A to 10D, respectively. 10A and 11A, when the first hole 611 is installed directly above the vibration direction of the first speaker 620 (i.e., the first hole 611 is located on the side wall of the housing directly opposite the first diaphragm 621, and the line connecting the geometric center of the first hole 611 and the geometric center of gravity of the first diaphragm 621 is parallel to the vibration direction of the first speaker 620), and the second hole 612 and the third hole 613 are installed on the same side wall of the housing in a direction parallel to the vibration direction of the first hole 611, the maximum and minimum directions of the output sound pressure of the sound output device are the directional directions of the sound output device, and the maximum and minimum directions are opposite. The minimum direction is the specific direction described above, and the sound pressure at a far-field position in the specific direction (minimum direction) of the sound output device is small (e.g., close to zero). The specific direction is a direction from the sound emission hole portion of the front cavity of the sound output device 600 (e.g., the first hole portion 611 in FIG. 10A) to the sound emission hole portion of the rear cavity (e.g., point M of the equivalent hole portion of the second hole portion 612 and the third hole portion 613 in FIG. 10A).

[0067] As shown in FIGS. 10B and 11B, the first hole 611 is installed directly above the vibration direction of the first speaker 620, that is, the first hole 611 is located on the side wall of the housing directly opposite the first vibrating membrane, the first rear cavity 640 is acoustically coupled to both of the two acoustic holes (the second hole 612 and the other second hole 612′), and the second hole 612 and the other second hole 612′ are acoustically coupled to the first hole 611. The second rear cavity 670 is adjacent to the first rear cavity 640, and the second rear cavity 670 is acoustically coupled to both the third hole 613 and the other third hole 613'. The third hole 613 and the other third hole 613' are respectively installed on the two side walls of the housing parallel to the vibration direction relative to the first hole 611. At this time, the second hole 612 and the other second hole 612' are symmetrical with respect to the first hole 611, and the third hole 613 and the other third hole 613' are symmetrical with respect to the first hole 611 along the vibration direction. In this case, the direction of the line connecting the equivalent holes of the second hole 612, the other second hole 612', the third hole 613, and the other third hole 613' to the first hole 611 substantially coincides with the vibration direction. As shown in FIG. 10B , point M indicates the position of the equivalent hole. In this case, the line connecting point M to the geometric center of the first hole 611 is parallel to the vibration direction of the first speaker 620, and point M is located on the midline of the line connecting the geometric center of the second hole 612 to the geometric center of the third hole 613. For example, if the second hole 612 and the third hole 613 are arranged symmetrically with respect to the partition plate 614, point M may be located at the geometric center of the partition plate 614. The sound pressure maximum and minimum directions of the far-field radiation of the acoustic output device 600 are the directivity directions of the acoustic output device, and the maximum and minimum directions are opposite to each other. The minimum direction is a specific direction, namely, the direction from the sound output hole portion of the front cavity of the acoustic output device 600 (for example, the first hole portion 611 in FIG. 10B ) to the sound output hole portion of the rear cavity (for example, point M representing the equivalent hole portions of the second hole portion 612, the other second hole portion 612′, the third hole portion 613, and the other third hole portion 613′ in FIG. 10B ).

[0068] As shown in FIGS. 10C and 11C, the first hole 611 is disposed directly above the vibration direction of the first speaker 620, that is, the first hole 611 is located on the side wall of the housing directly opposite the first vibrating membrane, the first rear cavity 640 is acoustically coupled to both the second hole 612 and the other second hole 612′, and the second hole 612 and the other second hole 612′ are respectively disposed on two side walls of the housing parallel to the vibration direction relative to the first hole 611, and the second rear cavity 670 is , adjacent to the first rear cavity 640, where the second rear cavity 670 is a sealed cavity, and the second front cavity 660 is acoustically coupled to the third hole 613. Along the vibration direction, the third hole 613 is located on the housing opposite the first hole 611, i.e., directly below the geometric center of gravity of the second diaphragm 651 of the second speaker 650, i.e., the third hole 613 is located on the side wall of the housing directly opposite the geometric center of gravity of the second diaphragm 651. At this time, the direction of the line connecting the equivalent holes of the second hole 612 and the other second hole 612' to the first hole 611 is approximately aligned with the vibration direction. As shown in FIG. 10C , point M indicates the position of the equivalent hole. At this time, the far-field radiation of the acoustic output device 600 has a main lobe (corresponding to the direction of the sound pressure maximum) and side lobes. The direction of the main lobe (i.e., the direction of the maximum) is the direction from point M, which represents the equivalent hole of the second hole 612 and the other second hole 612', to the first hole 611. The direction of the side lobe is the direction from point M, which represents the equivalent hole of the second hole 612 and the other second hole 612', to the third hole 613. As can be seen from FIGS. 10C and 11C, the directions of the minimum are the direction from the second hole 612 to the third hole 613 and the direction from the other second hole 612' to the third hole 613.

[0069] As shown in FIGS. 10D and 11D, the first hole 611 is located directly above the vibration direction of the first speaker 620, that is, the first hole 611 is located on the side wall of the housing directly opposite the first vibrating membrane, the first rear cavity 640 is acoustically coupled to both the second hole 612 and the other second hole 612′, and the second hole 612 and the other second hole 612′ are respectively located on two side walls of the housing parallel to the vibration direction relative to the first hole 611, and the second rear cavity 670 is adjacent to the first rear cavity 640 and is located between the first rear cavity 640 and the second rear cavity 670. The cavity 670 is acoustically coupled to both the third hole 613 and the other third hole 613', which are respectively located on two side walls of the housing parallel to the vibration direction relative to the first hole 611, and the second front cavity 660 is acoustically coupled to the fourth hole 615, which is located directly below the housing corresponding to the position of the first hole 611 along the vibration direction, i.e., the fourth hole 615 is located on the side wall of the housing directly opposite the geometric center of gravity of the second vibrating membrane. In this case, the first hole 611 of the first speaker 620 and the equivalent hole of the second hole 612 and the other second hole 612' are considered to be a pair of dual sound sources, and the equivalent hole of the third hole 613 and the other third hole 613' of the second speaker 650 and the fourth hole 615 are considered to be a pair of dual sound sources. In this case, the second hole 612 and the third hole 613 have a point M1 representing the equivalent hole, the other second hole 612' and the other third hole 613' have a point M2 representing the equivalent hole, and the second hole 612, the other second hole 612', the third hole 613 and the other third hole 613' all have a point M3 representing the equivalent hole. The position of point M3 can be determined by referring to the position of point M in FIG. 10B, and will not be described here. The direction of the line connecting point M3 representing the equivalent hole and first hole 611 is approximately the same as the vibration direction. The far-field radiation of the acoustic output device 600 has a main lobe (corresponding to the direction of the sound pressure maximum) and side lobes. The direction of the main lobe (i.e., the direction of the maximum) is from point M3 representing the equivalent hole to the first hole 611. The direction of the side lobe is from point M3 representing the equivalent hole to the fourth hole 615.As can be seen from FIGS. 10D and 11D , the minimum direction is the direction from point M1, which represents the equivalent hole, to the fourth hole 615, and the direction from point M2, which represents the equivalent hole, to the fourth hole 615. In this case, the far-field radiation of the acoustic output device 600 may achieve a weak heart-shaped directivity, as shown in FIG. 11D . Comparing the heart-shaped directivity shown in FIG. 11A with the heart-shaped directivity shown in FIG. 11D , the acoustic output device 600 shown in FIG. 11D has a narrower minimum region in the far-field radiation, a higher sound pressure level in the minimum direction and in directions on both sides of the minimum direction, and a uniform sound pressure level in directions near the maximum direction (directions between 0° and 180°). In some embodiments, the acoustic output device 600 shown in FIG. 10D is applied to scenarios where uniform radiation is required in a half-space.

[0070] In some embodiments, the arrangement of the sound output holes of the sound output device is not limited to the above-described arrangement, and the sound output holes may be arranged according to actual needs. In some embodiments, the first hole corresponding to the first front cavity of the first speaker may be arranged to correspond to the listening position of the user's ear in a worn state (e.g., arranged toward or close to the ear canal of the user's ear), and the sound output holes corresponding to the first rear cavity of the first speaker and the sound output holes of the second speaker should be as far away from the first hole as possible to reduce interference of other sound output holes with the first sound waves radiated from the first hole. In some embodiments, depending on the actual application scenario, the listening quality of the audio output device, or the need for sound leakage reduction, it is possible to determine the area where sound leakage from the audio output device needs to be reduced (e.g., a 30° sector area 10 cm away from the user's ear), thereby determining the direction of maximum sound pressure and the direction of minimum sound pressure in the direction of directional far-field radiation from the audio output device, and further determining the installation position of the corresponding sound emission hole section.

[0071] To reduce the overall size of the audio output device, the size of the single-source speaker should not be too large. Otherwise, the fundamental resonant frequency of the single-source speaker (i.e., the resonant frequency of the sealed cavity of the single-source speaker) will be high, and the lower frequency limit of the frequency range in which the audio output device achieves heart-shaped directivity will not reach the frequency band of the human voice. FIGS. 12A and 12B are schematic diagrams illustrating the far-field radiation directivity of an audio output device with exemplary hole placement locations, according to some embodiments of the present disclosure. As shown in FIGS. 12A and 12B , the audio output device 700 includes a first speaker 710 and a second speaker 720. The front and rear cavities of the first speaker 710 are acoustically coupled to a first hole 711 and a second hole 712, respectively, to form a dual audio source. The second speaker 720 has one cavity sealed and the other cavity acoustically coupled to a third hole 713, to form a single audio source. 12A and 12B , in order to constantly reduce sound leakage to the sides of the user's head from the sound output device 700 across the entire frequency band, the second speaker 720, which is a single sound source, is smaller in size than the first speaker 710, which is a dual sound source, and its length is closer to the thickness of the first speaker 710. The first hole 711 is disposed toward the user's ear canal, and the second hole 712 and the third hole 713 are both disposed away from the first hole 711. In this case, since the output sound pressure level of the single sound source is smaller than that of the dual sound source within the mid-low frequency range (e.g., 1 kHz or less), the output of the single sound source can be ignored, and the sound output device 700 operates independently as an approximately dual sound source, achieving an "8"-shaped dual sound source directivity as shown in FIG. 12A , thereby reducing sound leakage. Within the frequency range of mid-high frequencies (for example, 1 kHz to 4 kHz), the single sound source and the dual sound sources work together to achieve a heart-shaped directivity, as shown in FIG. 12B.

[0072] In some embodiments, filling a sealed cavity that is not acoustically coupled to the aperture of the second speaker of the audio output device (e.g., the second front cavity 560 shown in FIG. 5A or the second rear cavity 570 shown in FIG. 5B ) with acoustic particle material can increase the virtual volume of the sealed cavity, lower the resonant frequency of the sealed cavity, lower the lower frequency limit of the heart-shaped directivity of the audio output device, and increase the frequency range of the heart-shaped directivity.

[0073] 13 is a schematic diagram of another audio output device according to some embodiments herein. As shown in FIG. 13, in some embodiments, audio output device 800 may include a first speaker 810, a second speaker 820, and a third speaker 830 that are individually positioned. The first speaker 810 can emit a first sound wave, and the second speaker 820 can emit a second sound wave. The first and second sound waves emitted by the two speakers can satisfy certain phase and amplitude conditions (e.g., the same amplitude and opposite phase), thereby forming a dual sound source structure. The third speaker 830 can emit a third sound wave. The third sound wave emitted by the third speaker 830 can satisfy certain phase and amplitude conditions with the second sound wave emitted by the second speaker 820 and the first sound wave emitted by the first speaker 810 at a far-field position in a specific direction of the audio output device 800. As a result, the third sound wave, the first sound wave, and the second sound wave overlap and cancel each other out at the far-field position, thereby realizing the far-field directivity of the audio output device 800. In some embodiments, first speaker 810, second speaker 820, and third speaker 830 may be speakers that have a sealed front or rear cavity and derive sound only from the unsealed cavity. In some embodiments, audio output device 800 may include an audio box.

[0074] In some embodiments, a test microphone may be used to measure the output of the acoustic output device. In some embodiments, a test microphone may be installed at a far-field position in a specific direction of the acoustic output device and a corresponding far-field position in the opposite direction, respectively, to measure the sound pressure levels at the two far-field positions, obtain a sound pressure level difference between the two corresponding far-field positions, and compare the absolute value of the sound pressure level difference with a preset sound pressure level threshold to determine whether the acoustic output device has directionality in the specific direction and the opposite direction.

[0075] FIG. 14 is a schematic diagram of acoustic transmission of an audio output device having a second speaker installed therein, according to some embodiments of the present disclosure. As shown in FIG. 14 , in some embodiments, one test microphone may be installed at a far-field position in a specific direction of the audio output device. In some embodiments, the far-field position of the audio output device may be a position where the distance from the audio output device is greater than a preset distance threshold, for example, greater than 25 cm. In some embodiments, when the frequency range is 1 kHz to 4 kHz, the far-field position of the audio output device may be a position where the distance from the audio output device is greater than 5.5 cm. In some embodiments, the test microphone may be installed at a position 30 cm away from the audio output device in the specific direction. The specific direction is a direction from a sound output hole (e.g., a first hole) in the front cavity of the audio output device to a sound output hole (e.g., a second hole) in the rear cavity of the audio output device and a direction in the vicinity thereof. In some embodiments, the front cavity of the acoustic output device may be the first front cavity of the first speaker, and the rear cavity of the acoustic output device may be an equivalent or identical cavity to the first rear cavity of the first speaker and the output cavity of the second speaker. When the acoustic output device is in a worn state, the specific direction may be a direction away from the ears of a user of the acoustic output device. In some embodiments, to achieve directionality, the absolute value of the difference in sound pressure levels measured by a test microphone at two corresponding far-field positions in a specific direction of the acoustic output device and the opposite direction is set to be equal to or greater than a predetermined sound pressure level threshold. The sound pressure measured by the test microphone at the far-field position in the specific direction may be small, for example, close to zero.

[0076] In some embodiments, the sound pressure received by the test microphone includes two sets of sound waves: one set of sound waves (e.g., a first sound wave) radiated from a hole acoustically coupled to the front cavity, with a transfer function z(1), and the other set of sound waves (e.g., a second sound wave and a third sound wave) radiated from a hole acoustically coupled to the rear cavity, with a transfer function z(2). To ensure that the far-field radiation of the acoustic output device exhibits directionality, the two sets of sound waves received by the test microphone should cancel each other, i.e., the two sets of sound waves should have equal sound pressure amplitudes and opposite phases at the test microphone, and the received signal p of the test microphone should be mic is as follows:

[0077] p mic =p(1)*z(1)+[p(2)+p(3)]*z(2)=0 (1) In the formula, p(1) is the sound pressure radiated from the front cavity by the dual sound source (i.e., the first speaker, for example, SPK1 in FIG. 14), p(2) is the sound pressure radiated from the rear cavity by the dual sound source (i.e., the first speaker, for example, SPK1 in FIG. 14), and p(3) is the sound pressure radiated from the rear cavity by the single sound source (i.e., the second speaker, for example, SPK2 in FIG. 14).

[0078] In some embodiments, it is necessary to avoid mutual interference between p(1), p(2), and p(3) when measuring them. Therefore, when measuring p(1), the first speaker is turned on, the second speaker is turned off, and the hole (e.g., the second hole) communicating with the rear cavity is temporarily blocked with cotton, rubber, or the like, and measurement can be performed using another test microphone installed in or near the hole (e.g., the first hole) communicating with the front cavity. When measuring p(2), the first speaker is turned on, the second speaker is turned off, and the hole (e.g., the first hole) communicating with the front cavity is temporarily blocked with cotton, rubber, or the like, and measurement can be performed using another test microphone installed in or near the hole (e.g., the second hole) communicating with the rear cavity of the first speaker. When measuring p(3), the second speaker is operated, the first speaker is turned off, and the measurement can be performed using the other test microphone installed in or near a hole communicating with the rear cavity of the second speaker (e.g., the second hole or the third hole described below).

[0079] In some embodiments, a large baffle (e.g., 1 m in diameter) may also be installed around the acoustic output device. The baffle is installed around the acoustic output device and tightly connected to the acoustic output device. The sound emission holes of the front cavity (i.e., the holes communicating with the front cavity) and the sound emission holes of the rear cavity (i.e., the holes communicating with the rear cavity) are located on either side of the baffle. By installing the baffle, mutual interference between the first sound wave radiated from the sound emission holes of the front cavity and the second and third sound waves radiated from the sound emission holes of the rear cavity is significantly reduced, and therefore they are separated from each other, improving the measurement accuracy of p(1), p(2), and p(3). In some embodiments, when a baffle is installed, p(1) and p(2) can be measured simultaneously with the first speaker operating and the second speaker off, and test microphones placed in the holes leading to the front cavity and the holes leading to the rear cavity.

[0080] Based on the distributive law of convolution, equation (1) may be expressed as:

[0081] p mic =[p(1)*z(1)+p(2)*z(2)]+p(3)*z(2)=0 (2) In the equation, [p(1)*z(1)+p(2)*z(2)] represents the sound pressure at the test microphone of the sound waves (e.g., the first sound wave and the second sound wave) radiated from the dual sound source (i.e., the first speaker, e.g., SPK1 in FIG. 14), and p(3)*z(2) represents the sound pressure at the test microphone of the sound wave (e.g., the third sound wave) radiated from the single sound source (i.e., the second speaker, e.g., SPK2 in FIG. 14). Therefore, by adjusting the first electrical signal and the second electrical signal, the dual sound source (i.e., the first speaker) and the single sound source (i.e., the second speaker) can be excited, respectively, and the amplitude and phase of the sound pressure of the sound waves radiated from the two sound sources reaching the test microphone can be recorded. By adjusting the amplitude and phase of the second electrical signal driving the single sound source (i.e., SPK2 of the second speaker) and / or the amplitude and phase of the first electrical signal driving the dual sound source (i.e., SPK1 of the first speaker), the sound wave (i.e., the third sound wave) radiated from the single sound source (i.e., the second speaker) and the sound wave (i.e., the superimposed sound wave of the first sound wave and the second sound wave) radiated from the dual sound source (i.e., the first speaker) have the same sound pressure amplitude (i.e., the same sound pressure level amplitude) but opposite phase at the test microphone, i.e., the sound pressure at the far-field position in a specific direction of the acoustic output device is zero, thereby causing the sound pressure level at the far-field position in a specific direction of the acoustic output device to be zero, and the absolute value of the sound pressure level difference between the far-field positions in at least one pair of opposite directions of the acoustic output device is equal to or greater than a predetermined sound pressure level threshold, thereby achieving directionality of the far-field radiation of the acoustic output device.

[0082] 15 is a schematic diagram illustrating an exemplary process of a method for adjusting a second electrical signal according to some embodiments of the present disclosure. As shown in FIG. 15, a process 900 may include the following steps 910 to 940.

[0083] In step 910, the dual sound sources are excited independently to record a first sound pressure level amplitude and a first phase of the test microphone.

[0084] In some embodiments, the dual sound sources may be a first speaker. The installation position of the test microphone may be a far-field position in a specific direction of the sound output device. In some embodiments, the specific direction may be a direction from the sound output hole of the front cavity to the sound output hole of the rear cavity and a direction nearby the direction within a specified direction range. In this case, the first sound pressure level amplitude and the first phase measured by the test microphone may be the first sound pressure level amplitude and the first phase after the first sound wave and the second sound wave generated from the first speaker are superimposed by the test microphone.

[0085] In some embodiments, the independent excitation of the dual sound sources can be achieved by providing a first electrical signal only to the first speaker and not providing a second electrical signal to the second speaker, such that the first speaker is activated and the second speaker is not activated.

[0086] In step 920, the single sound source is excited independently and a second sound pressure level amplitude and a second phase of the test microphone are recorded.

[0087] In some embodiments, the single sound source may be a second speaker. The test microphone may be installed at a far-field position in a specific direction of the acoustic output device, which may be the same as the test microphone position in step 910. In this case, the sound pressure level amplitude and phase measured by the test microphone may be a second sound pressure level amplitude and a second phase at the test microphone of a third sound wave generated from the second speaker.

[0088] In some embodiments, the sole excitation of a single sound source can be achieved by providing the second electrical signal only to the second speaker and not providing the first electrical signal to the first speaker, such that the second speaker is activated and the first speaker is not activated.

[0089] In step 930, the sound pressure level amplitude difference and phase difference between the single sound source and the dual sound source are calculated.

[0090] The second sound pressure level amplitude of the single sound source measured by the test microphone is compared with the first sound pressure level amplitude of the dual sound sources to obtain a sound pressure level amplitude difference between them.The second phase of the single sound source measured by the test microphone is compared with the first phase of the dual sound sources to obtain a phase difference between them.

[0091] In step 940, the second electrical signal is adjusted so that the sound waves emitted from the single sound source have the same sound pressure level amplitude at the test microphone as those of the dual sound sources and are opposite in phase to those of the dual sound sources.

[0092] By adjusting the second electrical signal driving the single sound source based on the sound pressure level amplitude difference and phase difference between the single sound source and the dual sound sources obtained in step 930, the sound wave radiated from the single sound source has the same sound pressure level amplitude as that of the dual sound source at the test microphone and the opposite phase to that of the dual sound source, thereby causing the third sound wave radiated from the single sound source and the first and second sound waves radiated from the dual sound sources to overlap and cancel each other at the position of the test microphone, causing the far-field radiation of the acoustic output device to exhibit directionality (e.g., heart-shaped directivity) and reducing sound leakage in the far field of the acoustic output device.

[0093] In some embodiments, the first electrical signal driving the dual sound sources is adjusted based on the sound pressure level amplitude difference and phase difference between the single sound source and the dual sound sources obtained in step 930, so that the sound waves radiated from the single sound source and the dual sound sources have the same sound pressure level amplitude and opposite phase at the test microphone, thereby making the far-field radiation of the acoustic output device directional (e.g., heart-shaped directivity) and reducing sound leakage in the far field of the acoustic output device.

[0094] FIG. 16 is a schematic diagram of frequency response curves when a single sound source and dual sound sources are excited independently, according to some embodiments of the present specification. As a mere example, the single sound source (i.e., the second speaker) and dual sound sources (i.e., the first speaker) share a rear cavity of an audio output device (e.g., the structure shown in FIG. 5A ), and the volume of the rear cavity of the audio output device is equal to the volume of the front cavity. At this time, the hole communicating with the front cavity is the first hole, and the hole communicating with the rear cavity is the second hole (e.g., the structure shown in FIG. 5A ). The first hole and the second hole have the same area. The second electric signal exciting the single sound source and the first electric signal exciting the dual sound source both have an amplitude of 1 V and a phase of 0°. As shown in FIG. 16 , under the above-mentioned conditions, the curve L 101 shows the frequency response curve measured by the test microphone when the dual sound source is excited singly, and the curve L 102 shows the frequency response curve measured by the test microphone when excited by a single sound source alone.

[0095] Under the above conditions, the process 900 can measure the sound pressure level amplitude difference and phase difference at the position of the test microphone (i.e., the far field of the sound output device) between the single sound source and the dual sound source at different frequencies. Then, the curve L in FIG. 101 and curve L 102 By comparing the amplitudes of the sound pressure levels at different frequencies between a single sound source and a dual sound source, the sound pressure level amplitude difference at the position of the test microphone (i.e., in the far field of the acoustic output device) can be determined.

[0096] In some embodiments, the amplitude and phase of the first electrical signal and the second electrical signal are adjusted so that there is a certain amplitude and / or phase difference between the first electrical signal and the second electrical signal within a target frequency range. This causes the sound waves (third sound waves) generated from the single sound source (second speaker) and the sound waves (first sound wave, second sound wave) generated from the dual sound sources (first speaker) to overlap with each other, thereby providing directional far-field radiation from the acoustic output device. In some embodiments, the target frequency range may include 100 Hz to 10 kHz. In some embodiments, an acoustic output device configured with a single sound source and dual sound sources can reduce sound leakage over a wide frequency band from 100 Hz to 10 kHz. The target frequency range may include a first frequency range, which may include a portion of a mid-high frequency band, for example, 800 Hz to 10,000 Hz, within which the acoustic output device can reduce sound leakage using the principle of heart-shaped directivity, i.e., the far-field radiation of the acoustic output device exhibits heart-shaped directivity. The target frequency range may include a second frequency range, which may include a portion of a mid-low frequency band, within which the acoustic output device can reduce sound leakage using the principle of dual sound source directivity, for example, 100 Hz to 800 Hz. See FIG. 1 and related descriptions for details.

[0097] In some embodiments, the acoustic output device can have dual-source directivity within the range of 100 Hz to 800 Hz. That is, within the range of 100 Hz to 800 Hz, the sound pressure level of the sound wave (for example, the superimposed sound wave of the first sound wave and the second sound wave) output by the first speaker from the hole (for example, the second hole) acoustically coupled to the first rear cavity, and the sound pressure level of the third sound wave output by the second speaker from the hole (for example, the third hole) acoustically coupled to the second speaker, the difference is 6 dB or more. In some embodiments, when the sound pressure radiated from the rear cavity by a single source is much smaller than the sound pressure radiated from the rear cavity by a dual source, that is, when p(3) << p(2), compared with the sound pressure level radiated by the dual source, the sound pressure level radiated by the single source is extremely small, and the acoustic output device can achieve dual-source directivity. For example, when p(2) / p(3) ≧ 2, it can be considered that p(3) << p(2). At this time, the difference in the sound pressure level radiated from the rear cavity between the dual source and the single source is 6 dB or more. That is, the difference between the sound pressure level corresponding to p(2) and the sound pressure level corresponding to p(3) is 6 dB or more, and the acoustic output device can achieve dual-source directivity.

[0098] From the above, when the same electrical signal (i.e., the first electrical signal and the second electrical signal have the same amplitude and phase) is provided to the single sound source and the dual sound sources within the frequency band of 100 Hz to 800 Hz, the front cavity of the single sound source (second speaker) is sealed, and only the rear cavity is connected to the outside air, preventing free air flow. Therefore, the single sound source has difficulty outputting low-frequency sound waves from the hole acoustically coupled to the rear cavity. As a result, within the frequency band, the difference in sound pressure level between the sound waves output by the dual sound source (first speaker) from the hole acoustically coupled to the rear cavity and the sound waves output by the single sound source (second speaker) from the hole acoustically coupled to the rear cavity can be 6 dB or more. In this case, the sound output device can exhibit excellent dual sound source directivity, thereby realizing a design that reduces sound leakage at mid- to low-frequency frequencies. In some embodiments, to achieve a difference of 6 dB or more between the sound pressure levels of the sound waves output by the dual sound sources (first speaker) from the aperture acoustically coupled to the rear cavity and the sound pressure level of the sound waves output by the single sound source (second speaker) from the aperture acoustically coupled to the rear cavity in the range of 100 Hz to 800 Hz, a method may be used in which the amplitude of the second electrical signal driving the single sound source (second speaker) is reduced in the range of 100 Hz to 800 Hz. For example, the amplitude of the second electrical signal may be zero in the range of 100 Hz to 800 Hz, i.e., no second electrical signal may be provided to the single sound source in the range of 100 Hz to 800 Hz. In some embodiments, in a worn state, the hole acoustically coupled to the first front cavity of the first speaker is located close to the user's ear, and the hole acoustically coupled to the first rear cavity is located away from the user's ear, and the direction from the hole acoustically coupled to the first rear cavity to the hole acoustically coupled to the first front cavity is directed toward the user's ear, i.e., the dual sound source directivity formed in the low frequency range can be directed toward the user's ear.

[0099] In some embodiments, the first, second, and third sound waves may be superimposed on each other at a far-field position in a specific direction of the acoustic output device within a frequency range of 1 kHz to 10 kHz by setting the sound pressure level at the far-field position to zero and setting the absolute value of the sound pressure level difference between at least one pair of far-field positions in opposite directions of the acoustic output device to equal to or greater than a predetermined sound pressure level threshold, thereby making the far-field radiation of the acoustic output device directional. The amplitudes and phases of the first and second electrical signals may be adjusted. In some embodiments, as shown in FIG. 16 , the resonant frequency corresponding to the resonant peak E of the dual sound source is close to the resonant frequency corresponding to the resonant peak D of the single sound source, so that the dual sound source and the single sound source have a first resonant frequency (i.e., the frequency corresponding to the resonant peak D). The rear cavity shared by the single sound source and the dual sound source has a second resonant frequency (i.e., the frequency corresponding to the resonant peak F). As can be seen from FIG. 16 , the frequency response curves of the single sound source and the dual sound source have flat regions between the first resonant frequency and the second resonant frequency. In some embodiments, the frequency band between the first resonant frequency and the second resonant frequency may include a range of 1 kHz to 4 kHz. In some embodiments, the first resonant frequency may be near 1 kHz and the second resonant frequency may be near 4 kHz, thereby improving the acoustic output performance of the acoustic output device. In some embodiments, by adjusting the second electrical signal and / or the first electrical signal, the far-field radiation of the acoustic output device can have a heart-shaped directivity between the first resonant frequency and the second resonant frequency (e.g., 1 kHz to 4 kHz). In some embodiments, by adjusting the second electrical signal and / or the first electrical signal in a frequency band higher than the second resonant frequency (e.g., 4 kHz to 10 kHz), the far-field radiation of the acoustic output device can exhibit a heart-shaped directivity.In some embodiments, in a worn state, the hole acoustically coupled to the first front cavity of the first speaker is located close to the user's ear, the hole acoustically coupled to the first rear cavity and the hole for outputting the third sound wave of the second speaker are located away from the user's ear, the hole acoustically coupled to the first rear cavity and the hole for outputting the third sound wave of the second speaker have equivalent holes, and the direction from the equivalent hole to the hole acoustically coupled to the first front cavity is directed toward the user's ear, i.e., the directionality formed in the mid-to-high frequency range can be directed toward the user's ear.

[0100] In some embodiments, the phase difference between the second electrical signal and the first electrical signal is 150° or more between the first resonant frequency and the second resonant frequency. In some embodiments, the phase difference between the second electrical signal and the first electrical signal is 150° or more within a frequency range of 1 kHz to 4 kHz. For example, in the case shown in FIG. 16 , when the amplitude of the first electrical signal is maintained at 1 V (i.e., 1000 mV) and the phase is maintained at 0°, the second electrical signal can be modulated to zero the sound pressure level at a far-field position in a specific direction of the acoustic output device and to make the absolute value of the sound pressure level difference between at least one pair of far-field positions in opposite directions of the acoustic output device equal to or greater than a predetermined sound pressure level threshold. Within a frequency range of 1 kHz to 4 kHz, the phase and amplitude of the modulated second electrical signal at each frequency are as follows: At 1 kHz, the second electrical signal has an amplitude of 27.5 mV and a phase of 250°. At 1.5 kHz, the second electrical signal has an amplitude of 344.3 mV and a phase of 225°. At 2 kHz, the second electrical signal has an amplitude of 472 mV and a phase of 229°. At 3 kHz, the second electrical signal has an amplitude of 738.7 mV and a phase of 202°. At 4 kHz, the second electrical signal has an amplitude of 708.76 mV and a phase of 179°. Note that in some embodiments, the sound pressure at a far-field position in a particular direction of the acoustic output device may be small but not zero. Therefore, the amplitude and phase of the corresponding second electrical signal may have a deviation of 10%. For example, at 1 kHz, the second electrical signal may have an amplitude of 27.5*(1±0.1) mV and a phase of 250*(1±0.1)°, i.e., the second electrical signal may have an amplitude of 24.75 mV to 30.25 mV and a phase of 225° to 247.5°.

[0101] As can be seen from FIG. 16 , the single sound source (i.e., the second speaker) has a first resonant frequency, i.e., a frequency corresponding to resonant peak D. When passing through the first resonant frequency, the sound waves radiated from the single sound source are inverted in phase. Correspondingly, the resonant peak E of the dual sound source near the first resonant frequency is generated because the diaphragm of the inactive single sound source acts as a passive diaphragm when the dual sound source is in operation. Therefore, the sound waves radiated from the dual sound source are not inverted at the resonant frequency of resonant peak E. Therefore, it is necessary to compensate the phase of the sound waves radiated from the single sound source to ensure that the sound waves radiated from the single sound source and the dual sound source maintain opposite phases in the far field around the first resonant frequency. In some embodiments, the phase difference of the second electrical signal is 100° or more at two frequencies around the first resonant frequency. At frequencies before the first resonant frequency, the phase of the second electrical signal is the pre-compensation phase, and at frequencies after the first resonant frequency, the phase of the second electrical signal is the compensated phase. In some embodiments, the phase difference of the second electrical signal at two frequencies before and after the first resonant frequency may be 100° to 240°. In some embodiments, the phase difference of the second electrical signal at two frequencies before and after the first resonant frequency may be 120° to 220°. In some embodiments, the phase difference of the second electrical signal at two frequencies before and after the first resonant frequency may be 140° to 180°. In some embodiments, the phase difference of the second electrical signal at two frequencies before and after the first resonant frequency may be 150° to 160°.

[0102] In addition, when the phase of the sound waves emitted from only one of the dual sound source and the single sound source changes by 180° around a certain resonant frequency, in order to avoid such a change causing the sound waves in the far field to be cancelled out, it is necessary to change the electric signal of one of the dual sound source or the single sound source around the resonant frequency (for example, to be inverted by 180° or nearly 180°). However, since the phase difference between the first electric signal and the second electric signal at each frequency may be different, after compensating the phase of one of the electric signals based on this, the final phase difference between the two may not be exactly 180°, but may be close to or almost 180°.

[0103] In some embodiments, in actual products, the specifications of the speakers of the sound output device may differ, the dimensions of the front cavity and the rear cavity may differ, the area size and depth of the corresponding sound emitting hole portion may differ, and the structural shapes of the front cavity and the rear cavity may differ, which may cause the positions of the resonance peaks (e.g., resonance peaks D and F of a single sound source, resonance peak G of a dual sound source, etc.) to be shifted. Therefore, the ranges of the phase difference values of the second electrical signal may be different at two frequencies in different frequency ranges before and after the resonance peaks.

[0104] In some embodiments, the phase difference of the second electrical signal at two frequencies of 100 Hz around the first resonant frequency may be 100° to 240°. In some embodiments, because the dimensions of the single sound source may vary, the phase difference of the second electrical signal at two frequencies of 500 Hz around the first resonant frequency may be 120° to 220°. In some embodiments, because the structure of the single sound source may vary, the phase difference of the second electrical signal at two frequencies of 1000 Hz around the first resonant frequency may be 140° to 180°.

[0105] In some embodiments, as can be seen from FIG. 16 , the first resonant frequency (the frequency corresponding to resonant peak D) is between 800 Hz and 1.2 kHz, and is around 1 kHz. In some embodiments, the phase difference of the second electrical signal between 800 Hz and 1.2 kHz is between 100° and 220°, for example, between 130° and 180°. In some embodiments, because the dimensions of the single sound source may vary, the phase difference of the second electrical signal between 900 Hz and 1.1 kHz may be between 120° and 150°, for example, between 130° and 150°. In some embodiments, because the dimensions of the single sound source may vary, the phase difference of the second electrical signal between 950 Hz and 1 kHz may be between 140° and 170°, for example, between 145° and 155°.

[0106] As can be seen from FIG. 16 , in some embodiments, the rear cavity shared by the single sound source and the dual sound sources has a second resonant frequency (i.e., a frequency corresponding to the resonant peak F). Across the second resonant frequency, the sound waves radiated from the single sound source and the dual sound source are not 180° out of phase with each other. Observing the vibration pattern, the sound waves change from opposing motion to relative motion. Therefore, it is still necessary to compensate the phase of the sound waves radiated from one of the single sound source or the dual sound source across the second resonant frequency. In some embodiments, within a frequency band between two frequencies across the second resonant frequency, the phase difference of the second electric signal is 100° or more. In some embodiments, the phase difference of the second electric signal between the two frequencies across the second resonant frequency may be 100° to 260°. In some embodiments, the phase difference of the second electric signal between the two frequencies across the second resonant frequency may be 120° to 170°. In some embodiments, the phase difference of the second electrical signal between two frequencies before and after the second resonant frequency may be between 140° and 160°.

[0107] In some embodiments, the phase difference of the second electric signal may be 100° to 260° at two frequencies, 100 Hz before and after the second resonant frequency. In some embodiments, because the dimensions of the rear cavity may be different, the phase difference of the second electric signal may be 130° to 180° at two frequencies, 300 Hz before and after the second resonant frequency. In some embodiments, because the area size of the sound emitting hole portion of the rear cavity may be different, the phase difference of the second electric signal may be 160° to 170° at two frequencies, 500 Hz before and after the second resonant frequency. In some embodiments, because the depth of the sound emitting hole portion of the rear cavity may be different, the phase difference of the second electric signal may be 140° to 180° at two frequencies, 700 Hz before and after the second resonant frequency. In some embodiments, the rear cavity may have a different structure, resulting in different volumes, and the phase difference of the second electrical signal may be 170° to 240° at two frequencies 700 Hz before and after the second resonant frequency.

[0108] In some embodiments, as can be seen from FIG. 16 , the second resonant frequency (the frequency corresponding to the resonant peak F) is between 3 kHz and 5 kHz, and is around 4 kHz. In some embodiments, the phase difference of the second electrical signal between 3 kHz and 5 kHz may be within a range of 100° to 240°, for example, 138° to 160°. In some embodiments, since the volume of the rear cavity may be different, the phase difference of the second electrical signal between 3.1 kHz and 4.8 kHz may be within a range of 120° to 140°, for example, 130° to 140°. In some embodiments, since the area of the sound emission hole portion of the rear cavity may be different, the phase difference of the second electrical signal between 3.5 kHz and 4.5 kHz may be within a range of 160° to 170°, for example, 162° to 168°. In some embodiments, because the depth of the sound emission hole portion of the rear cavity may be different, the phase difference of the second electrical signal at 3.8 kHz and 4.2 kHz may be in the range of 155° to 180°, for example, 160° to 170°.

[0109] As can be seen from FIG. 16 , in some embodiments, the front cavity of the dual sound source (first speaker) has a third resonant frequency (i.e., a frequency corresponding to the resonant peak G). Passing through the third resonant frequency, the sound waves radiated from the dual sound source are phase-inverted. Accordingly, when the single sound source is excited alone, a resonant peak (not shown) of the single sound source near the third resonant frequency occurs due to the passive diaphragm of the inactive dual sound source. However, the sound waves radiated from the single sound source near the third resonant frequency are not phase-inverted. Therefore, to ensure that the sound waves radiated from the single sound source and the dual sound source maintain opposite phases in the far field, the phase of the sound waves radiated from the single sound source must be compensated. The second electrical signal must be compensated within a frequency band between two frequencies before and after the third resonant frequency. In some embodiments, the phase difference of the second electrical signal is 100° or more at the two frequencies before and after the third resonant frequency. In some embodiments, the phase difference of the second electrical signal between two frequencies around the third resonant frequency may be between 100° and 240°. In some embodiments, the phase difference of the second electrical signal between two frequencies around the third resonant frequency may be between 170° and 200°.

[0110] In some embodiments, the phase difference of the second electric signal may be 175° to 185° at two frequencies, 100 Hz before and after the third resonant frequency. In some embodiments, because the dimensions of the front cavity may be different, the phase difference of the second electric signal may be 170° to 200° at two frequencies, 200 Hz before and after the third resonant frequency. In some embodiments, because the volumes of the front cavities may be different, the phase difference of the second electric signal may be 150° to 180° at two frequencies, 600 Hz before and after the third resonant frequency. In some embodiments, because the areas and / or depths of the sound emission holes in the front cavities may be different, the phase difference of the second electric signal may be 120° to 200° at two frequencies, 1000 Hz before and after the third resonant frequency.

[0111] In some embodiments, as can be seen from FIG. 16 , the third resonant frequency (the frequency corresponding to the resonant peak G) is 5 kHz to 8 kHz. In some embodiments, the phase difference of the second electrical signal at 5 kHz and 8 kHz may be in the range of 100° to 200°, for example, 115° to 160°. In some embodiments, since the volume of the front cavity may be different, the phase difference of the second electrical signal at 5.1 kHz and 7.5 kHz may be in the range of 110° to 150°, for example, 130° to 140°. In some embodiments, since the area of the sound emission hole portion of the front cavity may be different, the phase difference of the second electrical signal at 5.4 kHz and 7 kHz may be in the range of 140° to 170°, for example, 150° to 159°. In some embodiments, since the depth of the sound emission hole portion of the front cavity may be different, the phase difference of the second electrical signal at 5.8 kHz and 6 kHz may be in the range of 170° to 180°, for example, 170° to 176°.

[0112] By adjusting the amplitudes and phases at multiple frequencies of the second electrical signal driving the single sound source and / or the first electrical signal driving the dual sound sources so that the second electrical signal and the first electrical signal have corresponding amplitude and phase differences, the sound pressures at the test microphone of the sound waves radiated from both the single sound source and the dual sound sources are small, e.g., close to zero, and equation (1) holds.

[0113] 17 is a schematic diagram illustrating the directionality of far-field radiation of an acoustic output device after the second electrical signal is adjusted, according to some embodiments of the present disclosure. As shown in FIG. 17, by setting the second electrical signal at frequencies of 1 kHz, 2 kHz, 3 kHz, 5 kHz, 8 kHz, and 10 kHz, the output (e.g., the phase and / or amplitude of the output) of the single sound source (the second speaker) can be adjusted to have almost no output at a far-field position in a specific direction of the acoustic output device, and the far-field radiation of the acoustic output device then exhibits directionality. The 0° direction indicates a direction toward the opening of the ear canal of the user of the audio output device, for example, the direction from the sound output hole AS2 (e.g., the second hole) of the rear cavity of the audio output device to the sound output hole AS1 (e.g., the first hole) of the front cavity of the audio output device (direction X1 in FIG. 4 ). The 180° direction indicates a direction away from the opening of the ear canal of the user of the audio output device, for example, the direction from the sound output hole AS1 (e.g., the first hole) of the front cavity of the audio output device to the sound output hole AS2 (e.g., the second hole) of the rear cavity of the audio output device (direction X1′ in FIG. 4 ). At a frequency of 1 kHz, the far-field radiation of the audio output device exhibits a heart-shaped directivity, with the sound field maximum point near 15° and the sound field minimum point near 180°, and the absolute value of the sound pressure level difference between the two directions is approximately 22.5 dB. At a frequency of 2 kHz, the far-field radiation of the acoustic output device exhibits a heart-shaped directivity, with the sound field maximum point near 15° and the sound field minimum point near 200°, and the absolute value of the difference in sound pressure level between the two directions is approximately 20.8 dB. At a frequency of 3 kHz, the far-field radiation of the acoustic output device exhibits a heart-shaped directivity, with the sound field maximum point near 15° and the sound field minimum point near 190°, and the absolute value of the difference in sound pressure level between the two directions is approximately 19.9 dB. At a frequency of 5 kHz, the far-field radiation of the acoustic output device exhibits a heart-shaped directivity, with the sound field maximum point near 30° and the sound field minimum point near 200°, and the absolute value of the difference in sound pressure level between the two directions is approximately 19.6 dB.At a frequency of 8 kHz, the far-field radiation of the acoustic output device exhibits a heart-shaped directivity, including a main lobe and a side lobe, the direction of the main lobe (i.e., the direction of the maximum value of the sound field) being around 40°, the direction of the side lobe being around 200°, and there being minima between the side lobe and the main lobe, the directions of the minima being around 150° and 250°, respectively, and the absolute values of the sound pressure level differences between the two minima and the maximum value being approximately 16.6 dB and 12.9 dB, respectively. At a frequency of 10 kHz, the far-field radiation of the acoustic output device exhibits a heart-shaped directivity, including a main lobe and a side lobe, the direction of the main lobe (i.e., the direction of the maximum value of the sound field) being around 10°, the direction of the side lobe being around 200°, and there being minima between the side lobe and the main lobe, the directions of the minima being around 160° and 240°, respectively, and the absolute values of the sound pressure level differences between the two minima and the maximum value being approximately 32.4 dB and 19.93 dB, respectively. Therefore, at frequencies of 1 kHz, 2 kHz, 3 kHz, 5 kHz, 8 kHz, and 10 kHz, the directional direction of far-field radiation of the acoustic output device is from 180° and its vicinity to 0° and its vicinity, i.e., the direction from the sound output hole portion AS2 (e.g., the second hole portion) of the rear cavity of the acoustic output device to the sound output hole portion AS1 (e.g., the first hole portion) of the front cavity (direction X1 shown in Figure 4) and its vicinity.

[0114] 18A and 18B are diagrams of directivity test curves for an audio output device according to some embodiments of the present disclosure. The test signal used in FIG. 18A is a white noise signal, and the test signal used in FIG. 18B is a sweep signal. The frequency range of the white noise signal and the sweep signal is set to 1 kHz to 4 kHz, and the directivity of the audio output device within the 1 kHz to 4 kHz frequency range is measured. In some embodiments, the white noise signal may be a signal that includes all frequencies within the 1 kHz to 4 kHz frequency range at any given time, and the white noise signal can simulate a complex signal output. The sweep signal may be a signal that gradually changes from 1 kHz to 4 kHz, and the sweep signal is a signal that includes only a single frequency at any given time, and the sweep signal can simulate a simple signal input. As shown in FIGS. 18A and 18B, the dotted line indicates the frequency response curve of the audio output device in the 0° direction, and the solid line indicates the frequency response curve of the audio output device in the 180° direction. In some embodiments, the output sound pressure level in the 0° direction of the acoustic output device may be measured by a test microphone installed near the sound output hole (e.g., the first hole) of the front cavity (e.g., at a point 10 cm away from the sound output hole of the front cavity), and the output sound pressure level in the 180° direction of the acoustic output device may be measured by a test microphone installed near the sound output hole (e.g., the second hole and / or the third hole) of the rear cavity (e.g., at a point 10 cm away from the sound output hole of the rear cavity). In some embodiments, the test microphone, the sound output hole of the front cavity, and the sound output hole of the rear cavity are on the same straight line, which is the straight line between the 0° direction and the 180° direction. As shown in Figure 18A, when the test signal is a white noise signal, the absolute value of the difference in sound pressure level between the 0° direction and the 180° direction of the audio output device is 8dB to 18dB, and the audio output device has excellent heart-shaped directivity.As shown in Figure 18B, when the test signal is a sweep signal, the absolute value of the difference in sound pressure level between the 0° direction and the 180° direction of the audio output device is 15dB to 25dB, and the audio output device has even better heart-shaped directivity. Note that the above description applies to cases where adjustments are made to only the second electrical signal. In some embodiments, corresponding adjustments may be made to only the first electrical signal. In some embodiments, corresponding adjustments may be made to both the first electrical signal and the second electrical signal. Specific methods for adjusting electrical signals will be described below using adjustment of the second electrical signal as an example.

[0115] FIG. 19 is a schematic diagram of an equivalent model of an audio output device according to some embodiments of the present disclosure, adjusted according to a preset algorithm. As shown in FIG. 19 , in some embodiments, the audio output device may further include a modulator, which may modulate a second electrical signal driving a second speaker according to a preset algorithm, such that within a target frequency range, a third sound wave output by the second speaker and the first and second sound waves output by the first speaker are superimposed and canceled at a far-field position in a specific direction of the audio output device, and the absolute value of the sound pressure level difference between at least one pair of far-field positions in opposite directions of the audio output device is equal to or greater than a preset sound pressure level threshold (e.g., the sound pressure at the far-field position in a specific direction of the audio output device is small, e.g., close to zero). In some embodiments, the preset algorithm may include a preset amplitude / frequency adjustment method, such as a preset amplitude modulation scheme or a preset frequency (phase) modulation scheme. For more details regarding amplitude modulation and phase modulation, please refer to the related description of FIG. 21 , and further description will be omitted here.

[0116] In some embodiments, the principle of Fig. 19 is similar to that shown in Fig. 14, and determines a preset algorithm (e.g., a modulation function H of a modulator) for modulating the second electrical signal based on a sound pressure measured by a test microphone placed at a far-field position in a specific direction of the acoustic output device. When the acoustic output device is operating, the modulator can directly modulate the second electrical signal according to the preset algorithm.

[0117] In some embodiments, the signal Music may include a first electrical signal for driving a first speaker and a second electrical signal for driving a second speaker. The first speaker and the second speaker can receive the first electrical signal and the second electrical signal of the signal Music, respectively, and output sound into a space. The test microphone is installed at a far-field position in a specific direction of the sound output device to measure the sound pressure of the sound at the position. If the sound pressure signal received by the test microphone is zero, it indicates that the sound pressure of the sound (i.e., the sound after the first sound wave, the second sound wave, and the third sound wave are superimposed) radiated by the first speaker and the second speaker to the target position (i.e., the far-field position in the specific direction of the sound output device described above) is zero, i.e., Music H1+Music H0 H2=0 (3) In the equation, H1 and H2 respectively represent the transfer function for transferring the sound waves (first sound wave, second sound wave) generated from the first speaker to the test microphone and the transfer function for transferring the third sound wave generated from the second speaker to the test microphone, and H0 represents the transfer function of the modulator that modulates the second electrical signal that drives the second speaker.

[0118] By turning off the second speaker, the transfer function H1 (first transfer function) of the first speaker can be measured. H1=Mic' / Music' (4) In the formula, Music′ represents the signal (first electrical signal) input when the second speaker is turned off, and Mic′ represents the sound pressure signal received by the test microphone when the second speaker is turned off.

[0119] Similarly, by turning off the first speaker, the transfer function H2 (second transfer function) of the second speaker can be measured, H2=(Mic″) / (Music″) (5) In the formula, Music" indicates the signal (second electrical signal) input when the first speaker is turned off, and Mic" indicates the sound pressure signal received by the test microphone when the first speaker is turned off.

[0120] Based on equations (3) to (5), the transfer function H0 of the modulator can be obtained,

[0121]

number

[0122] Thus, by determining the transfer function H0 of the modulator for different frequencies based on the above-described equation (6) and applying the determined modulator to the audio output device, the audio output device can achieve a sound leakage reduction effect at different frequencies. In some alternative embodiments, when multiple test microphones are used, it is possible to measure or simulate sounds output from the first speaker and the second speaker at any position in space. Therefore, by using at least one pair of test microphones installed in opposite directions, it is possible to measure the difference in sound pressure level of the far-field radiated sound of the audio output device in at least one pair of opposite directions. By adjusting the transfer function of the modulator based on equations (3) to (6) according to different frequencies, the difference in sound pressure level of the far-field radiated sound of the audio output device in at least one pair of opposite directions can be equal to or greater than a predetermined sound pressure level threshold.

[0123] In some embodiments, the test microphone may include a microphone array that measures sound at far-field positions in specific directions of the audio output device, thereby improving the accuracy of the measurement data.

[0124] 20 is a schematic diagram of an equivalent model of an acoustic output device tuned according to an active algorithm, according to some embodiments of the present disclosure. As shown in FIG. 20 , in some embodiments, the acoustic output device may further include a controller, a modulator, and a microphone array. The microphone array may be disposed on a housing of the acoustic output device. The microphone array may estimate audio signals at preset positions. The preset positions may include far-field positions in a specific direction of the acoustic output device. In some embodiments, the preset positions may include far-field positions in at least one pair of opposite directions of the acoustic output device. In some embodiments, the controller may determine an active algorithm (e.g., an amplitude-frequency active adjustment method) based on the audio signal collected by the microphone array, and the modulator may dynamically modulate the second electrical signal driving the second speaker based on the active algorithm (e.g., the amplitude-frequency active adjustment method) determined by the controller, so that, within a target frequency range, the third sound wave output by the second speaker and the first sound wave and the second sound wave output by the first speaker are superimposed and canceled out at a far-field position in a specific direction of the acoustic output device, and the absolute value of the sound pressure level difference between the far-field positions in at least one pair of opposite directions of the acoustic output device is equal to or greater than a predetermined sound pressure level threshold, thereby realizing directionality of the far-field radiation of the acoustic output device.

[0125] In some embodiments, after the audio output device is worn by the user, the transfer function corresponding to the first speaker changes from an initial value H1 to

[0126]

number

[0127] The transfer function corresponding to the second speaker changes from the initial value H2 to

[0128]

number

[0129] to accommodate different users

[0130]

number

[0131] and

[0132]

number

[0133] may be different. Accordingly, the above equation (3) can be expressed as follows:

[0134]

number

[0135] In some embodiments, a variable

[0136]

number

[0137] and

[0138]

number

[0139] The controller can adjust H0 based on the sound waves collected by the microphone array so that Equation (7) holds, thereby achieving a sound leakage reduction effect in a specific direction. The adjusted H0 can be determined based on Equation (6).

[0140]

number

[0141] In the method described in FIG. 20 , H0 can be adjusted in real time based on the collected sound waves to achieve the effect of reducing sound leakage in real time, so that the absolute value of the sound pressure level difference between at least one pair of far-field positions in opposite directions of the acoustic output device is equal to or greater than a predetermined sound pressure level threshold, thereby realizing the directionality of the far-field radiation of the acoustic output device.

[0142] In some embodiments, for sound output devices with different structures, the corresponding transfer function H1 of the first speaker and the transfer function H2 of the second speaker may also be different, and therefore the adjustment method for the corresponding transfer function H0 of the modulator may also be different. For example, the corresponding adjustment method may be different depending on whether the first speaker and the second speaker are installed in the same cavity or not. Also, for example, if the distance between the sound output hole portion (e.g., second hole 912) of the rear cavity of the first speaker and the sound output hole portion (e.g., third hole 913) of the second speaker is different, the corresponding adjustment method may be different. Furthermore, for example, if the acoustic resistance at the sound output hole portions (e.g., first hole 911, second hole 912, third hole 913, etc.) is different, the corresponding adjustment method may be different.

[0143] FIG. 21 is a schematic block diagram of an amplitude and phase adjustment algorithm according to some embodiments of the present disclosure. As shown in FIG. 21 , taking the example of adjusting a second electrical signal for driving a second speaker, an input signal includes an initial first electrical signal and an initial second electrical signal, which are input to the first speaker and the second speaker, respectively, and the first speaker and the second speaker vibrate to generate sound waves that are superimposed on each other. The transfer function H0 of the modulator can be determined according to the principles shown in FIG. 19 and / or FIG. 20 , and the amplitude adjustment value and phase adjustment value of the initial second electrical signal can be determined based on the transfer function H0. In some embodiments, the amplitude of the initial second electrical signal can be adjusted using a filter. In some embodiments, an infinite impulse response (IIR) filter can be selected as the filter. The IIR filter has a small computational complexity and is excellent in real-time performance. In some embodiments, a finite impulse response (FIR) filter can be selected as the filter. The FIR filter has high stability, a controllable phase, and can select amplitudes. Synchronously input signals can be synchronously output, thereby avoiding signal distortion. In some embodiments, a phase shifter can adjust the phase of the initial second electrical signal. In some embodiments, the adjustment of the initial second electrical signal by the filter and the adjustment of the initial second electrical signal by the phase shifter can be performed synchronously, or one can be performed first and the other can be performed later. The adjusted second electrical signal is output as an output signal together with the initial first electrical signal. Sound waves generated from the second speaker driven by the adjusted second electrical signal can be superimposed and canceled with sound waves generated from the first speaker driven by the initial first electrical signal at a target position (e.g., a far-field position in a specific direction of the audio output device), thereby ensuring that the absolute value of the sound pressure level difference between at least one pair of far-field positions in opposite directions of the audio output device is equal to or greater than a predetermined sound pressure level threshold (e.g., 6 dB or more), thereby achieving directivity of the audio output device.

[0144] Having described the basic concepts above, it will be apparent to those skilled in the art that the detailed disclosure above is provided by way of example only and is not intended to limit the scope of the present application. Although not expressly described herein, those skilled in the art may make various changes, improvements, and modifications to the present application. These changes, improvements, and modifications are intended to be suggested by the present application and are therefore within the spirit and scope of the exemplary embodiments of the present application.

[0145] Furthermore, certain terms are used herein to describe embodiments of the present application. For example, "one embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of the present application. Therefore, it is emphasized and understood that two or more references to "one embodiment" or "one embodiment" or "one alternative embodiment" in different parts of this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics of one or more embodiments of the present application may be combined as appropriate.

[0146] Similarly, in the foregoing description of embodiments of the present application, various features may be grouped together in a single embodiment, drawing, or description for the purpose of simplifying the disclosure and facilitating an understanding of one or more embodiments of the present invention. However, this method of disclosure should not be interpreted as reflecting an intention that the present subject matter requires more features than are recited in each claim. Rather, an embodiment may include fewer than all features of a single embodiment disclosed above.

[0147] In some examples, numbers describing the number of components and attributes are used; it should be understood that the numbers describing such examples are, in some instances, modified by the modifiers "about," "approximately," or "generally." Unless otherwise specified, "about," "approximately," or "generally" indicates that the number can vary by ±20%. Thus, in some implementations, all numerical parameters used in the specification and claims are approximations that may vary depending on the characteristics required for a particular implementation. In some embodiments, numerical parameters should be calculated using the specified number of significant digits and ordinary rounding techniques. While in some embodiments, the numerical ranges and parameters used to determine ranges are approximations, in specific embodiments, such numerical values are set as precisely as possible.

[0148] All patents, patent applications, published patent applications, and other materials, such as papers, books, specifications, publications, and documents, referenced in this application are incorporated herein by reference in their entirety, except for prosecution history documents that are inconsistent with or inconsistent with the content of this application and documents that may have a limiting effect on the broadest scope of the claims of this application (now or later related to this application). Furthermore, if the explanations, definitions, and / or term usage in the accompanying materials of this application are inconsistent with or inconsistent with the content set forth in this application, the explanations, definitions, and / or term usage in this application shall control.

[0149] Finally, it should be understood that the embodiments described herein are merely illustrative of the principles of the present embodiments. Other variations may be within the scope of the present application. Thus, by way of example, and not of limitation, alternative configurations of the present embodiments may be considered consistent with the teachings of the present application. Thus, the present embodiments are not limited to the embodiments expressly introduced and described herein. [Explanation of symbols]

[0150] 100 Sound output device 110 Housing 111 First hole 112 Second hole 120 speakers 130 Front Cavity 140 rear cavity 521 First diaphragm 551 Second Vibration Membrane 614 Partition

Claims

1. Housing and a first speaker disposed within the housing, the first speaker including a first diaphragm, the first front cavity and the first rear cavity being disposed in front of and behind the first diaphragm, respectively, the first front cavity and the first rear cavity being acoustically coupled to two holes disposed in the housing, and outputting a first sound wave and a second sound wave having a phase difference; a second speaker that is installed within the housing and includes a second diaphragm, a second front cavity and a second rear cavity are installed in the housing on the front and rear sides of the second diaphragm, respectively, and only one of the second front cavity and the second rear cavity is acoustically coupled to one hole installed in the housing, and outputs a third sound wave; An acoustic output device, wherein within a target frequency range, the third acoustic wave overlaps and cancels the first acoustic wave and the second acoustic wave at a far-field position in a specific direction of the acoustic output device.

2. 2. The acoustic output device of claim 1, wherein the first front cavity and the first rear cavity are acoustically coupled to a first hole and a second hole, respectively, provided in the housing, one of the second front cavity and the second rear cavity is the same cavity as the first rear cavity, and the second front cavity or the second rear cavity, which together with the first rear cavity constitutes the same cavity, outputs the third sound wave from the second hole.

3. The acoustic output device according to claim 2 , wherein the resonant frequency of the same cavity is 4 kHz or higher.

4. The volume of the same cavity is 0.28 cm ３ The area of the second hole is 20 mm or less. ２ The sound output device according to claim 2 .

5. The acoustic output device according to claim 3 , wherein the second rear cavity or the second front cavity that is not acoustically coupled to the second hole has a resonance frequency of 1 kHz or less.

6. When driven by the same electrical signal within a target frequency range, at a far-field position in a specific direction of the acoustic output device, a sound pressure level difference between a sound wave resulting from the superposition of the first sound wave and the second sound wave output by the first speaker and a third sound wave output by the second speaker is less than 14 dB; The direction of an extension line of a line connecting the first hole portion and the second hole portion is the specific direction. The sound output device according to claim 3 .

7. The acoustic output device of claim 6, wherein the target frequency range includes 1 kHz to 4 kHz.

8. 2. The acoustic output device of claim 1, wherein the first front cavity and the first rear cavity are acoustically coupled to a first hole and a second hole, respectively, provided in the housing, and one of the second front cavity and the second rear cavity is acoustically coupled to a third hole in the housing, the third hole being a hole different from the first hole and the second hole.

9. 9. The acoustic output device of claim 8, wherein the second front cavity or the second rear cavity acoustically coupled to the third hole has a resonant frequency, and the first rear cavity acoustically coupled to the second hole has another resonant frequency, and a difference between the resonant frequency and the another resonant frequency is 3000 Hz or less.

10. The acoustic output device according to claim 8 , wherein the second front cavity or the second rear cavity acoustically coupled to the third hole has a resonance frequency of 4 kHz or higher.

11. The acoustic output device according to claim 8 , wherein the second rear cavity or the second front cavity that is not acoustically coupled to the third hole portion has a resonance frequency of 1 kHz or less.

12. When driven by the same electrical signal within a target frequency range, at a far-field position in a specific direction of the acoustic output device, a sound pressure level difference between a sound wave resulting from the superposition of the first sound wave and the second sound wave output by the first speaker and a third sound wave output by the second speaker is less than 14 dB; the target frequency range includes 1 kHz to 4 kHz; the second hole and the third hole have equivalent holes, the direction of an extension line of a line connecting the first hole portion and the equivalent hole portion is the specific direction; The sound output device according to claim 8 .

13. 2. The acoustic output device according to claim 1, wherein a difference in sound pressure level between the sound waves output by the first speaker from the hole acoustically coupled to the first rear cavity and the sound pressure level of the third sound waves output by the second speaker from the hole acoustically coupled to the second speaker is 6 dB or more within a range of 100 Hz to 800 Hz.

14. 2. The acoustic output device of claim 1, wherein, in a worn state, the hole acoustically coupled to the first front cavity of the first speaker is located close to the user's ear, the hole acoustically coupled to the first rear cavity and the hole for outputting the third sound wave of the second speaker are located away from the user's ear, the hole acoustically coupled to the first rear cavity and the hole for outputting the third sound wave of the second speaker have equivalent holes, and the direction from the equivalent hole to the hole acoustically coupled to the first front cavity faces the user's ear.

15. The acoustic output device of claim 1 , wherein an acoustic particulate material is filled into the second front cavity or the second rear cavity that is not acoustically coupled to the aperture.

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