Audio output device

Abstract

One or more embodiments of this specification relate to an acoustic output device, the acoustic output device including a housing, a first speaker installed in the housing and acoustically coupled to a first hole and a second hole of the housing respectively, 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 and the second hole respectively, a second speaker installed in the housing, driven by a second electrical signal to output a third sound wave, within a target frequency range, the first sound wave, the second sound wave and the third sound wave overlap with each other, so that the far-field radiation of the acoustic output device exhibits directivity.

Description

Technical Field

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

[0002] [Incorporation by Reference] This application claims the priority of a Chinese patent application with an application number of 202211455122.0 filed on November 21, 2022, and all of its contents are incorporated herein by reference.

Background Art

[0003] In order to solve the problem of sound leakage in an acoustic output device, usually, two or more sound sources are used to generate two acoustic signals with opposite phases. Under the conditions of the far-field, the difference in acoustic distance from two sound sources with opposite phases to a specific point in the far-field can basically be ignored. Therefore, the two acoustic signals can cancel each other out to reduce sound leakage in the far-field. Although this method can achieve a certain sound leakage reduction effect, there are still certain limitations. For example, the wavelength of high-frequency sound leakage is shorter. Under the conditions of the far-field, the distance between the two sound sources cannot be ignored relative to the wavelength, so the sound signals emitted from the two sound sources cannot be cancelled out. Also, for example, when the acoustic transmission structure of the acoustic output device resonates, there is a certain phase difference between the phase of the acoustic signal actually radiated from the sound emission port of the acoustic output device and the original phase of the sound wave generation position. Since additional resonance peaks increase in the transmitted sound wave, it causes disturbance in the sound field distribution, making it difficult to guarantee the high-frequency far-field sound leakage reduction effect, and thus may increase the sound leakage.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, it is desirable to provide an acoustic output device with excellent directivity in the sound field.

Means for Solving the Problems

[0005] The acoustic output device according to the embodiment of this specification includes a housing, and is installed in the housing, acoustically coupled to the first hole portion and the second hole portion of the housing respectively, and 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 portion and the second hole portion respectively. It also includes a first speaker, and a second speaker installed in the housing and driven by a second electrical signal to output a third sound wave. Within the target frequency range, the first sound wave, the second sound wave, and the third sound wave overlap with each other, so that the far-field radiation of the acoustic output device exhibits directivity.

[0006] In some embodiments, the first speaker includes a first diaphragm, and in the housing, a front cavity and a rear cavity are correspondingly installed on the front side and the rear side of the first diaphragm respectively. The front cavity and the rear cavity are acoustically coupled to the first hole portion and the second hole portion respectively. The second speaker is installed in the rear cavity and outputs the third sound wave from the second hole portion acoustically coupled to the rear cavity.

[0007] In some embodiments, the first speaker includes a first diaphragm, and in the housing, a front cavity and a rear cavity are correspondingly installed on the front side and the rear side of the first diaphragm respectively. The front cavity and the rear cavity are acoustically coupled to the first hole portion and the second hole portion respectively. A third hole portion is installed in the housing. The second speaker outputs the third sound wave from the third hole portion, and the distance from the third hole portion to the second hole portion acoustically coupled to the rear cavity is greater than 0 mm and less than or equal to 10 mm.

[0008] In some embodiments, the acoustic output device further includes a modulator, and the modulator modulates the second electrical signal for driving the second speaker according to a preset amplitude-frequency adjustment method.

[0009] In some embodiments, a microphone array for estimating an audio signal at a preset position is installed in the housing, the acoustic output device further includes a modulator, and the modulator modulates the second electrical signal for driving the second speaker based on the audio signal collected by the microphone array.

[0010] In some embodiments, within the range of 100 Hz to 800 Hz, the difference between the sound pressure level of the second sound wave output by the first speaker from the second hole and the sound pressure level of the third sound wave output by the second speaker from the second hole or the third hole is 6 dB or more.

[0011] In some embodiments, the second speaker has a first resonance frequency, the rear cavity has a second resonance frequency, and between the first resonance frequency and the second resonance frequency, the phase difference between the second electrical signal and the first electrical signal is 150° or more.

[0012] In some embodiments, the frequency band between the first resonance frequency and the second resonance frequency includes the range of 1 kHz to 4 kHz.

[0013] In some embodiments, at a frequency of 1 kHz, the phase difference between the second electrical signal and the first electrical signal is 200° or more, and at a frequency of 4 kHz, the phase difference between the second electrical signal and the first electrical signal is 150° or more.

[0014] In some embodiments, the second speaker outputs the third sound wave from the second hole or the third hole, the rear cavity has a second resonance frequency, and at two frequencies before and after the second resonance frequency, the phase difference of the second electrical signal is 100° or more.

[0015] In some embodiments, the second resonance frequency is between 3 kHz and 5 kHz, and at the frequencies of 3 kHz and 5 kHz, the phase difference of the second electrical signal is within the range of 100° to 240°.

[0016] In some embodiments, at frequencies of 3 kHz and 5 kHz, the phase difference of the second electrical signal is in the range of 138° to 160°.

[0017] In some embodiments, the front cavity has a third resonance frequency, and at two frequencies before and after the third resonance frequency, the phase difference of the second electrical signal is 100° or more.

[0018] In some embodiments, the third resonance frequency is in the range of 5 kHz to 8 kHz, and at frequencies of 5 kHz and 8 kHz, the phase difference of the second electrical signal is in the range of 100° to 200°.

[0019] In some embodiments, at frequencies of 5 kHz and 8 kHz, the phase difference of the second electrical signal is in the range of 115° to 160°.

[0020] In some embodiments, the directivity is expressed such that the absolute value of the difference in sound pressure levels in at least one pair of opposite directions of the far-field radiated sound of the acoustic output device is equal to or greater than a preset sound pressure level threshold.

[0021] In some embodiments, the directivity is expressed such that the absolute value of the difference in sound pressure levels in at least one pair of opposite directions of the far-field radiated sound of the acoustic output device is 6 dB or more.

[0022] In some embodiments, the at least one pair of opposite directions includes a pair of opposite directions corresponding to a line connecting the first hole and the second hole.

[0023] The present specification will be further described by exemplary embodiments, and these exemplary embodiments will be described in detail with reference to the drawings. These embodiments are not limiting, and in these embodiments, the same numbers indicate the same structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0024]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 5C

Figure 5D

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10A

Figure 10B

Figure 10C

Figure 10D

Figure 11A

Figure 11B

Figure 11C

Figure 11D

Figure 12A

Figure 12B

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18A

Figure 18B

Figure 19

Figure 20

Figure 21

Embodiments for Carrying Out the Invention

[0025] To more clearly explain the technical means of the embodiments of this 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 this specification, and those skilled in the art can apply this specification to other similar scenarios based on these drawings without creative effort. Unless otherwise apparent from the context or stated otherwise, the same reference numerals in the figures represent the same structure or operation.

[0026] It should be understood that the "system", "device", "unit" and / or "module" used in this specification is a way to distinguish various assemblies, elements, members, parts or assemblies at different levels. However, other expressions can be used instead of the above terms if other terms can achieve the same purpose.

[0027] As used in this specification and the claims, unless the context clearly dictates otherwise, terms such as "one," "a," "an," and / or "the" are not specifically intended to refer to the singular but may include the plural. In general, the terms "comprising" and "including" merely indicate that the steps and elements specifically identified are included, and these steps and elements are not an exclusive listing, and the method or apparatus may include other steps or elements.

[0028] In this specification, flowcharts are used to describe the operations performed by the systems according to the examples of this specification. It should be understood that the preceding and subsequent operations are not necessarily executed exactly in order. Instead, each step may be processed in reverse order or simultaneously. Also, other operations may be added to these processes, and one or more operations may be removed from these processes.

[0029] In some embodiments, in order to solve the sound leakage problem of the acoustic output device, two sound sources with opposite phases can be utilized to emit two sets of sounds with opposite phases. Under far-field conditions, since the difference in acoustic distance from two sound sources with opposite phases to a specific point in the far field can be basically ignored, the two sets of sounds can cancel each other out to reduce sound leakage in the far field.

[0030] FIG. 1 is a schematic diagram of the relative positions of an acoustic output device according to some embodiments of the present specification and a user's ear. As shown in FIG. 1, the acoustic output device 100 may include a housing 110 and a speaker 120. The speaker 120 may be installed in a cavity formed by the housing 110. The speaker 120 includes a diaphragm (not shown). In the cavity of the housing 110, a front cavity 130 and a rear cavity 140 for radiating sound are installed on the front side and the rear side of the diaphragm, respectively. A first hole 111 and a second hole 112 are installed in the housing 110. 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, the sound waves on the front side of the diaphragm (or called the first sound waves) may pass through the front cavity 130 and be emitted from the first hole 111, and the sound waves on the rear side of the diaphragm (or called the second sound waves) may pass through the rear cavity 140 and be emitted from the second hole 112. At this time, the first hole 111 and the second hole 112 can be regarded as a set of dual sound sources, and can emit two sets of sounds with the same amplitude but opposite phases. For ease of understanding, in some embodiments of the present specification, the front side of the diaphragm refers to the side away from the magnetic circuit assembly (not shown) of the diaphragm, and the rear side of the diaphragm refers to the side facing the magnetic circuit assembly of the diaphragm. Naturally, in a specific scenario, the front side and the rear side of the diaphragm may be replaced with each other, that is, the side away from the magnetic circuit assembly of the diaphragm may be regarded as the rear side, and the side facing the magnetic circuit assembly of the diaphragm may be regarded as the front side.

[0031] In some embodiments, as shown in FIG. 1, when the user wears or uses the acoustic output device 100, the acoustic output device 100 may be located near the user's auricle, and the first hole 111 may face the user's ear canal opening 201, so that the sound emitted from the first hole 111 can be transmitted to the user's external auditory canal. The second hole 112 may be farther 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.

[0032] In some embodiments, when the speaker 120 vibrates, the front side and the rear side of the speaker 120 can generate sound waves with equal amplitudes and opposite phases as sound wave generating structures, respectively. 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 a dual sound source, and the dual sound source can interfere and cancel each other at a spatial point (for example, the far field), thereby effectively improving the sound leakage problem in the far field of the acoustic output device 100.

[0033] FIG. 2A is a schematic diagram of the sound field distribution of the mid-low frequency sound pressure level of the acoustic output device shown in FIG. 1. As shown in FIG. 2A, within the mid-low frequency range (for example, 50 Hz to 1 kHz), the sound field distribution of the acoustic output device 100 exhibits good dual sound source directivity, and the sound leakage reduction effect is remarkable. That is, within the mid-low frequency range, the dual sound source composed of the first hole 111 and the second hole 112 of the acoustic output device 100 outputs sound waves with opposite phases (that is, the first sound wave and the second sound wave), and the sound field has a distribution form of two lobe-shaped structures in space. In two opposite directions of the line connecting the dual sound sources, the sound pressure level is large, and in the direction perpendicular to the line connecting the dual sound sources, the sound pressure level is small. However, for the two lobe-shaped structures formed in the sound field, one lobe-shaped structure is far from the user's ear and forms a large sound leakage, which affects the sound leakage reduction effect of the acoustic output device.

[0034] In some embodiments, within the high - frequency range, the first sound wave and the second sound wave have short wavelengths. At this time, the distance between the dual sound sources composed of the first hole 111 and the second hole 112 cannot be ignored with respect to the wavelength. For example, due to the distance between the first hole 111 and the second hole 112, the acoustic distance from the first sound wave to a spatial point (e.g., far - field) is different from the acoustic distance from the second sound wave to the spatial point. Thereby, the phase difference between the first sound wave and the second sound wave at the spatial point is small (e.g., the phases are the same or close), and not only can the first sound wave and the second sound wave not interfere and cancel each other out at the spatial point, but they can also overlap at the spatial point, potentially increasing the amplitude of the sound wave at the spatial point. In some embodiments, the shielding of the high - frequency sound wave by a structure such as the auricle 210 and / or the influence on the reflection of the sound wave may cause disturbances in the sound field distribution of the sound output device 100.

[0035] In some embodiments, since the front cavity 130 and the rear cavity 140 have different structures and parameters (such as volume, etc.), the front cavity 130 and the rear cavity 140 have different resonance frequencies. In some embodiments, in order to adjust the resonance frequency, a special acoustic structure (such as a sound guide tube, etc.) may be additionally installed in the front cavity 130 and / or the rear cavity 140. When the sound waves in the front cavity 130 and / or the rear cavity 14 resonate, it may change the frequency components of the sound waves transmitted in the front cavity 130 and / or the rear cavity 140 (for example, increase additional resonance peaks in the transmitted sound waves), or change the phase of the transmitted sound waves. Compared with the case where there is no resonance, the sound waves radiated from the first hole 111 and / or the second hole 112 change in phase and / or amplitude, and due to the above changes in phase and / or amplitude, it causes disturbances in the sound field within the high-frequency range of the dual sound sources, and may affect the interference cancellation effect at the spatial points of the sound waves radiated from the first hole 111 and the second hole 112. For example, when resonating, the phase difference between the sound waves radiated from the first hole 111 and the second hole 112 changes. Exemplarily, when the phase difference between the sound waves radiated from the first hole 111 and the second hole 112 is small (for example, less than 120°, less than 90°, or 0), the interference cancellation effect at the spatial points of the sound waves decreases, making it difficult to achieve the sound leakage reduction effect. Or, the sound waves with a small phase difference may overlap with each other at the spatial points, increasing the amplitude of the sound waves near the resonance frequency at the spatial points (such as the far-field), and increasing the sound leakage in the far-field of the acoustic output device 100. Also, for example, due to the above resonance, it may increase the amplitude near the resonance frequency of the acoustic transmission structure of the transmitted sound waves (for example, expressed as a resonance peak near the resonance frequency), causing disturbances in the sound field near the resonance frequency of the dual sound sources. At this time, the amplitude difference between the sound waves radiated from the first hole 111 and the second hole 112 is large, the interference cancellation effect at the spatial points of the sound waves decreases, and it is difficult to achieve the sound leakage reduction effect. FIG. 2B is a schematic diagram of the sound field distribution of the sound pressure level of the acoustic output device shown in FIG. 1, and FIG. 3 is a frequency response curve diagram of the acoustic output device shown in FIG. 1. As shown in FIG. 2B, within the high-frequency range, the acoustic signal radiated from the second hole 112 of the acoustic output device 100 to the outside is dominant in the overall sound field distribution, and the sound field distribution is disturbed. Since there is a certain difference between the amplitude / phase of the sound wave actually radiated from the second hole 112 of the acoustic output device 100 and the original amplitude / phase of the sound wave emitted from the speaker 120, the two sound waves radiated from the first hole 111 and the second hole 112 not only do not reduce the sound leakage at a specific position in the far field, but increase the sound leakage at that position.

[0036] As shown in FIG. 3, the curve L3 shows the frequency response curve diagram of the front cavity 130 (for example, the first hole 111) of the acoustic output device 100, and the curve L3' shows the frequency response curve diagram of the rear cavity 140 (for example, 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 the curve L3 and the curve L3', within the mid-low frequency range (for example, 50 Hz to 1500 Hz), the acoustic output device 100 shows a good sound leakage reduction effect with the sound emission volumes of the front cavity and the rear cavity being approximately equal. However, within the high-frequency range (for example, 1500 Hz to 20 kHz), the sound emission volumes of the front cavity and the rear cavity are significantly different, and the sound leakage reduction effect is clearly reduced. As can be seen from FIGS. 2B and 3, within the high-frequency range, the sound field distribution of the dual sound sources is disturbed, and there is a possibility that the sound leakage in the far field cannot be reduced, and thus the sound leakage in the far field may be increased. In some embodiments, by adjusting the structure of the acoustic output device 100, the sound field distribution of the dual sound sources can be adjusted to obtain a sound field with excellent directivity, thereby improving the problem that the sound leakage in the far field of the acoustic output device 100 increases.

[0037] In some embodiments, a second speaker is installed in the acoustic output device, and by mutually canceling the sound wave of the second speaker and the sound wave generated from the speaker 120 (or the first speaker) in the high-frequency range, for example, the disturbance of the sound field of the dual sound source structure can be suppressed, and the sound leakage in the far field of the acoustic output device can be reduced or eliminated. In some embodiments, the acoustic 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 of the housing (for example, the first hole and the second hole) respectively, and outputs a first sound wave and a second sound wave having a phase difference. In some embodiments, the first speaker includes a first diaphragm, and in the housing, a first front cavity and a first rear cavity are correspondingly installed on the front side and the rear side of the first diaphragm respectively. The first front cavity and the first rear cavity are acoustically coupled to the two holes (for example, the first hole and the second hole) respectively, and 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 electrical signal to output a first sound wave and a second sound wave having a phase difference from the two holes (for example, the first hole and the second hole) respectively. The second speaker is installed in the housing and acoustically coupled to one hole installed in the housing (for example, the third hole, and the third hole may be either one of the first hole and the second hole, or another hole different from the first hole and the second hole). In some embodiments, the second speaker includes a second diaphragm, and in the housing, a second front cavity and a second rear cavity are correspondingly 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 is acoustically coupled to the one hole (for example, the third hole) to output a third sound wave. In some embodiments, the second speaker may be driven by a second electrical signal to output a third sound wave from the one hole (for example, the third hole).At this time, the first sound wave and the second sound wave of the first speaker are output from two holes (for example, the first hole and the second hole) respectively to form a dual sound source. In the second speaker, only the third sound wave is output from one hole (for example, the third hole) to form a single sound source. In some embodiments, within the 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 can cancel each other out in superposition at a far-field position in a specific direction of the acoustic output device, and reduce (for example, close to zero) the sound pressure that is cancelled out in superposition at that position, and increase the sound pressure at the corresponding far-field position in the opposite direction of the specific direction, so that the absolute value of the sound pressure level difference between the two above-mentioned positions is not less than a preset sound pressure level threshold value, thereby making the far-field radiation of the acoustic output device exhibit directivity. The two corresponding far-field positions in the specific direction and its opposite direction here are at equal distances from the acoustic output device. In some embodiments, for the sound pressure levels at the two far-field positions in the specific direction and the corresponding opposite direction, the sound pressure at the corresponding far-field position is measured by test microphones installed at the two far-field positions, and then the corresponding sound pressure level is obtained from the sound pressure, and finally the sound pressure level difference between the two far-field positions in the specific direction and its corresponding opposite direction can be obtained.

[0038] In order to ensure that the sound wave output by the first speaker (for example, a sound wave in which the first sound wave and the second sound wave are superimposed) and the sound wave output by the second speaker (for example, the third sound wave) can be effectively canceled at the far-field position, the sound wave output by the first speaker and the sound wave output by the second speaker should have equal or nearly equal amplitudes and opposite or nearly opposite phases at the far-field position. Considering that when driven by the same electrical signal, the first speaker and the second speaker may have differences in their frequency responses at the far-field position due to their different structures, different-intensity electrical signals are provided to the first speaker and the second speaker to compensate for the differences in frequency responses, so that finally the sound wave output by the first speaker and the sound wave output by the second speaker have the same or similar amplitudes at the far-field position. For example, the processing circuit can provide different levels of gain to the two electrical signals driving the first speaker and the second speaker to achieve compensation for the differences in frequency responses. In order to reduce the difficulty of adjusting the electrical signal and improve the stability of the electrical signal, the difference in the frequency responses of the first speaker and the second speaker at the far-field position can be reduced. For example, 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., the difference in the frequency responses of the first speaker and the second speaker at the far-field position can be reduced. For the adjustment of the parameters related to the structures of the first speaker and the second speaker, reference can be made to the descriptions in other parts of this specification.The phrase "reducing the difference in frequency response at the far-field position between the first speaker and the second speaker" as described herein means that within the target frequency range, 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 a specific direction of the acoustic output device, the sound pressure level difference between the sound wave formed by the superposition 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. As a result, after performing appropriate amplitude-frequency adjustment on 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 cancel each other out by superposition at the far-field position in a specific direction of the acoustic output device, and thus the sound pressure at this far-field position is low, for example, it may be understood to be close to zero. In some embodiments, in order to reduce the sound pressure at the 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 the target frequency range, 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 a specific direction of the acoustic output device, the sound pressure level difference between the sound wave formed by the superposition 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 10 dB. In some embodiments, further to reduce the sound pressure at the 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 the target frequency range, 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 a specific direction of the acoustic output device, the sound pressure level difference between the sound wave formed by the superposition 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 6 dB. In some embodiments, the target frequency range may include the first frequency range, and within the first frequency range, the first sound wave, the second sound wave, and the third sound wave superpose on each other, so that the far-field radiation of the acoustic output device exhibits heart-shaped directivity.In some embodiments, the target frequency range may include a second frequency range, within which 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 with each other, the influence of the third sound wave can be ignored. When the first sound wave and the second sound wave are regarded as a double sound source and overlap with each other, the far-field radiation of the acoustic output device exhibits double-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 directivity of the acoustic output device and the heart-shaped directivity, refer to FIG. 4 and its related description. For more information regarding the double-source directivity, refer to FIG. 2A above and its related description.

[0039] In some embodiments, the acoustic output device may include at least one of a neckband type earphone, an earhook type earphone, a canal type earphone, and glasses. In the worn state, the opposite direction of the specific direction may face the user's ear canal opening. FIG. 4 is a schematic diagram of directivity according to some embodiments of the present specification. As shown in FIG. 4, the acoustic output device shown in FIG. 4 is in the worn state, AS1 indicates the sound emission hole portion of the front cavity of the acoustic output device, and AS2 indicates the sound emission hole portion of the rear cavity of the acoustic output device. In some embodiments, the far-field radiation of the acoustic output device exhibiting directivity means that the sound output direction of the acoustic output device is within the specified direction range, that is, the far-field radiation of the acoustic output device within the above-specified direction range is significantly larger than the far-field radiation outside the above-specified direction range. In some embodiments, when the acoustic output device is in the worn state, the direction X1 from the sound emission hole portion AS2 corresponding to the rear cavity of the acoustic output device to the sound emission hole portion AS1 corresponding to the front cavity (that is, the direction X1 from the sound emission hole portion AS2 of the rear cavity to the sound emission hole portion AS1 of the front cavity) and the directions in the vicinity thereof (for example, direction X2, direction X3) face the user's ear canal opening. That is, in the worn state, the sound emission hole portion AS1 corresponding to the front cavity of the acoustic output device is closer to the ear canal opening of the user's ear. The direction X1' from the sound emission hole portion AS1 of the front cavity to the sound emission hole portion AS2 of the rear cavity and the directions in the vicinity thereof (for example, direction X2', direction X3') are the directions in which the acoustic output device is away from the user's ear canal opening. In some embodiments, in the worn state and / or the non-worn state, the direction X1 from the sound emission hole portion AS2 of the rear cavity of the acoustic output device to the sound emission hole portion AS1 of the front cavity and the directions in the vicinity thereof may constitute the above-mentioned specified direction range. The far-field radiation in the direction X1 of the acoustic output device and the directions in the vicinity thereof is significantly larger than the far-field radiation in other direction ranges (for example, the range of directions perpendicular to the direction X1 and the directions in the vicinity thereof, the range of directions opposite to the direction X1 and the directions in the vicinity thereof, etc.). In some embodiments, the directivity of the acoustic output device may be expressed such that the absolute value of the sound pressure level difference between the corresponding two far-field positions in the specific direction of the acoustic output device and the opposite direction thereof is equal to or greater than a preset sound pressure level threshold value.In the mounted state, the specific direction may refer to the direction in which the acoustic output device is away from the user's ear canal opening, and the opposite direction may be the direction in which the acoustic output device faces the user's ear canal. In some embodiments, the specific direction may refer to the direction X1' from the sound emission hole portion AS1 of the front cavity to the sound emission hole portion AS2 of the rear cavity and the directions in the vicinity thereof, and the opposite direction of the specific direction may refer to the direction X1 from the sound emission hole portion AS2 of the rear cavity to the sound emission hole portion AS1 of the front cavity and the directions in the vicinity thereof. In some embodiments, the direction in the vicinity of the direction X1' may be understood as a direction having an included angle of less than 60° with the direction X1'. For the sake of easy understanding of the directivity, here, only the two hole portions AS1 and AS2 are exemplarily described. When there are many different hole portions in the acoustic output device, AS1 can be understood as an equivalent hole portion formed by some of the hole portions, and AS2 can be understood as an equivalent hole portion formed by the hole portions in other parts. At this time, the direction of the directivity may be determined by the position of the equivalent hole portion. In some embodiments, the position of the equivalent hole portion formed by a plurality of hole portions can be determined by the following method: the center points of adjacent hole portions are sequentially connected to form a polygon or polyhedron, and the centroid of the polygon or polyhedron is the center point of the equivalent hole portion and can represent the position of the equivalent hole portion.

[0040] In some embodiments, the far - field radiation of the acoustic output device can exhibit heart - shaped directivity, and within a specified direction range, it is expressed such that the absolute value of the difference in sound pressure levels in at least one pair of opposite directions of the far - field radiated sound of the acoustic output device is equal to or greater than a preset sound pressure level threshold. The at least one pair of opposite directions may each be within the specified direction range and its opposite direction range. In some embodiments, the at least one pair of opposite directions may include the aforementioned specific direction and its opposite direction. That is, the aforementioned specific direction and its opposite direction may each be included within the specified direction range and its opposite direction range described above. In some embodiments, the at least one pair of opposite directions described above includes a pair of opposite directions corresponding to the line connecting the sound - emitting hole portion AS1 (for example, the first hole portion) of the front cavity and the sound - emitting hole portion AS2 (for example, the second hole portion) of the rear cavity. The heart - shaped directivity of the acoustic output device may be expressed such that the sound field intensities in a pair of opposite or substantially opposite two directions within the specified direction range and its opposite direction range are significantly different. Exemplarily, for the pair of opposite or substantially opposite two directions described above, one direction is near the direction X1’ from the sound - emitting hole portion of the front cavity to the sound - emitting hole portion of the rear cavity, and the other direction may be near the direction X1 from the sound - emitting hole portion of the rear cavity to the sound - emitting hole portion of the front cavity. For example, the direction X1’ may be opposite or substantially opposite to the directions X1, X2, and X3.

[0041] By installing the acoustic output device so that its far - field radiation exhibits heart - shaped directivity, the sound output from the acoustic output device can be intensively transmitted in the direction of the user's ear canal entrance, reducing the transmission of sound in other directions, improving the problem of sound leakage of the acoustic output device, and improving the user's listening effect.

[0042] In some embodiments, the preset sound pressure level threshold may be 6 dB. For example, the far-field radiation of the acoustic output device presenting a heart-shaped directivity may be expressed as the absolute value of the difference in sound pressure levels in at least a pair of opposite directions (e.g., direction X1 and direction X1') of the far-field radiation sound of the acoustic output device being 6 dB or more. Thereby, a large volume can be received at the user's ear canal opening, and a listening effect that the user can clearly hear can be obtained.

[0043] In some embodiments, the first electrical signal for driving the first speaker and the second electrical signal for driving the second speaker have differences in amplitude and / or phase within the target frequency range. And within the target frequency range, the first sound wave, the second sound wave, and the third sound wave are superimposed and canceled each other at a far-field position in a specific direction of the acoustic output device, so that the sound pressure of the superimposed and canceled sound wave is small, for example, close to zero. Thereby, the far-field radiation of the acoustic output device presents directivity, and the problem of sound leakage in the far field of the acoustic output device is improved. In some embodiments, the first electrical signal may be measured by a measuring instrument (e.g., an oscilloscope, etc.) installed between the first speaker and the corresponding signal generator, and the second electrical signal may be measured by a measuring instrument (e.g., an oscilloscope, etc.) installed between the second speaker and the corresponding signal generator. In some embodiments, the adjusted first electrical signal and / or the second electrical signal may be measured by a measuring instrument installed between the corresponding speaker and the corresponding signal modulator.

[0044] In order to realize the directivity of the far-field radiation of the acoustic output device, the first speaker and the second speaker may be arranged in a plurality of ways. FIGS. 5A to 5D are schematic configuration diagrams of an acoustic output device including the first speaker and the second speaker arranged in different ways according to some embodiments of the present specification. As shown in FIGS. 5A to 5D, in some embodiments, the first diaphragm 521 and the second diaphragm 551 have the same vibration direction (for example, the vertical direction in FIGS. 5A to 5D), and the first diaphragm 521 and the second diaphragm 551 are arranged at intervals along the vibration direction, that is, the first speaker 520 and the second speaker 550 are arranged at intervals along the vibration direction (shown in FIGS. 5A and 5B). In some embodiments, the first diaphragm 521 and the second diaphragm 551 are arranged at intervals along a direction perpendicular to the vibration direction, that is, the first speaker 520 and the second speaker 550 are arranged at intervals along a direction perpendicular to the vibration direction (shown in FIGS. 5C and 5D). Note that it is ideal that 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 mounting error, the first diaphragm 521 and the second diaphragm 551 may not have exactly the same vibration direction and may have a slight difference (for example, the included angle of the vibration direction between the first diaphragm 521 and the second diaphragm 551 is less than 10°). At this time, the arrangement direction of the first speaker 520 and the second speaker 550 or the direction perpendicular to their arrangement direction may be the vibration direction of the first diaphragm 521 or the vibration direction of the second diaphragm 551 or the direction between the included angles formed by the vibration directions of the two diaphragms. In some embodiments, the direction in which the first diaphragm 521 is arranged on the first speaker 520 may be the same as or opposite to the direction in which the second diaphragm 551 is arranged on 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 or communicate with each other. At this time, as shown in FIGS. 5A and 5C, the second front cavity 560 of the second speaker 550 is sealed.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 communicate with each other. At this time, as shown in FIGS. 5B and 5D, the second rear cavity 570 of the second speaker 550 is sealed. In some embodiments, when the volumes of the respective cavities (for example, 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 FIG. 5A may be equivalent to the acoustic output device 500 shown in FIG. 5C, and the acoustic output device 500 shown in FIG. 5B may be equivalent to the acoustic output device 500 shown in FIG. 5D.

[0045] Hereinafter, the acoustic output device will be exemplarily described by taking as an example the case where the first speaker and the second speaker are arranged at intervals along the vibration direction.

[0046] As shown in FIGS. 5A and 5B, in some embodiments, the acoustic output device 500 includes a housing 510, a first speaker 520, and a second speaker 550. The first speaker 520 is installed within the housing 510 and includes a first diaphragm 521. A first front cavity 530 and a first rear cavity 540 are respectively installed on the front side and the rear side of the first diaphragm 521. 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 within the housing 510 and includes a second diaphragm 551. A second front cavity 560 and a second rear cavity 570 are respectively installed on the front side and the rear side of the second diaphragm 551. One of the second front cavity 560 and the second rear cavity 570 is the same cavity as the first rear cavity 540. That is, the second front cavity 560 or the second rear cavity 570 that constitutes the same cavity is acoustically coupled to the second hole 512 of the housing 510. 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. At this time, as shown in FIG. 5B, the first diaphragm 521 and the second diaphragm 551 have the same orientation. In some embodiments, the second rear cavity 570 and the first rear cavity 540 may be the same cavity. At this time, as shown in FIG. 5A, the first diaphragm 521 and the second diaphragm 551 have opposite orientations. Comparing the acoustic output device 500 shown in FIG. 5A with the acoustic output device 500 shown in FIG. 5B, since the first diaphragm 521 and the second diaphragm 551 are installed with different orientations, there are certain differences in the frequency response curves between the acoustic output device 500 shown in FIG. 5A and the acoustic output device 500 shown in FIG. 5B. However, the far-field radiated sounds of both can achieve directivity.Hereinafter, taking as an example the case where the first speaker 520 and the second speaker 550 shown in FIG. 5A are arranged at intervals along the vibration direction and the first diaphragm 521 and the second diaphragm 551 face in opposite directions (that is, the second rear cavity 570 and the first rear cavity 540 are the same cavity), the acoustic output device 500 will be described.

[0047] Accordingly, as shown in FIGS. 4, 5A, and 5B, the first front cavity 530 may be the front cavity of the acoustic output device 500, and the same cavity may be the rear cavity of the acoustic output device 500. At this time, the first hole 511 is the sound emission hole AS1 of the front cavity of the acoustic output device 500, the second hole 512 is the sound emission hole AS2 of the rear cavity of the acoustic output device 500, and at this time, the direction of the extension line of the line connecting the first hole 511 and the second hole 512 is a specific direction.

[0048] In some embodiments, by arranging the first electrical signal and the second electrical signal so that there are differences in amplitude and / or phase within the target frequency range, 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 satisfy certain phase and amplitude conditions at a far-field position in a specific direction of the acoustic output device 500. For example, the superimposed sound wave formed by the first sound wave and the second sound wave at the far-field position in a specific direction and the third sound wave have a phase difference, and after being superimposed and canceled, the sound pressure at the far-field position is small, for example, close to zero. Thereby, 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 of the specific direction is equal to or greater than a preset sound pressure level threshold value, realizing the directivity of the acoustic output device 500. At the same time, by arranging in this way, the disturbance of the sound field within the high-frequency range of the dual sound sources can be suppressed, and the sound wave radiation in the far field of the acoustic output device 500 can be reduced or eliminated.

[0049] To avoid the resonance frequency of each cavity from interfering with the realization of the heart-shaped directivity of the acoustic output device and improve the user's listening effect, by adjusting the structural parameters of each cavity, the resonance frequency of each cavity is outside the frequency range for realizing the heart-shaped directivity. In some embodiments, the target frequency range for the acoustic output device to realize 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 upper frequency limit for easily realizing the heart-shaped directivity is determined by the resonance frequencies of the same cavity of the first speaker 520 and the second speaker 550 (for example, the same cavity composed of the first rear cavity 540 and the second rear cavity 570 in FIG. 5A, the same cavity composed of the first rear cavity 540 and the second front cavity 560 in FIG. 5B). In some embodiments, to improve the user's listening effect, the acoustic output device may have a heart-shaped directivity within the frequency range sensitive to the human ear, for example, near 3 kHz or near 3.5 kHz. At this time, the upper limit of the frequency range for the far-field radiation of the acoustic output device to realize the heart-shaped directivity may be 4 kHz or higher (for example, the frequency range for realizing the heart-shaped directivity may be 1 kHz to 4 kHz). At this time, the resonance frequency of the same cavity is 4 kHz or higher. In some embodiments, since the application scenarios of the acoustic output device are different, the frequency range for realizing the heart-shaped directivity may also be different accordingly. For example, for an acoustic output device mainly operating under mid- and low-frequency conditions, the frequency range for realizing the heart-shaped directivity may be 800 Hz to 2 kHz. At this time, the resonance frequency of the same cavity may be 2 kHz or higher. For an acoustic output device mainly operating under mid- and high-frequency conditions, the upper limit of the frequency range for realizing the heart-shaped directivity may be large, and the resonance frequency of the same cavity is also large accordingly. To improve the output quality of the acoustic output device within the frequency range sensitive to the human ear, the resonance 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, and greater than 5 kHz.At this time, the upper limit of the frequency range for realizing the heart-shaped directivity may be 4 kHz, 4.5 kHz, 5 kHz, etc.

[0050] FIG. 6 is a schematic diagram showing the relationship between the resonance frequency and the volume of the same cavity according to some embodiments of the present specification, and FIG. 7 is a schematic diagram showing the relationship between the resonance frequency of the same cavity and the area of the hole acoustically coupled thereto according to some embodiments of the present specification. As shown in FIGS. 6 and 7, in some embodiments, when adjusting the resonance frequency of the same cavity to 3.8 kHz or more, correspondingly, the volume of the same cavity is 0.38 cm 3 or less, and the area of the second hole 512 acoustically coupled to the same cavity is 17 mm 2 or more. In some embodiments, when adjusting the resonance frequency of the same cavity to 4 kHz or more, correspondingly, the volume of the same cavity is 0.28 cm 3 or less, and the area of the second hole 512 acoustically coupled to the same cavity is 20 mm 2 or more. In some embodiments, when adjusting the resonance frequency of the same cavity to 4.2 kHz or more, correspondingly, the volume of the same cavity is 0.2 cm 3 or less, and the area of the second hole 512 acoustically coupled to the same cavity is 22 mm 2 or more. In some embodiments, when adjusting the resonance frequency of the same cavity to 4.3 kHz or more, correspondingly, the volume of the same cavity is 0.18 cm 3 or less, and the area of the second hole 512 acoustically coupled to the same cavity is 23 mm 2 or more. By adjusting the volume of the same cavity and the area of the hole acoustically coupled to the same cavity, the resonance frequency of the same cavity is further adjusted so that the acoustic output device is outside the frequency range for realizing the heart-shaped directivity, thereby avoiding disturbing the realization of the heart-shaped directivity of the acoustic output device and improving the listening effect of the user.

[0051] In some embodiments, one of the second front cavity 560 and the second rear cavity 570 of the second speaker 550 that does not form the same cavity is a sealed cavity and is not acoustically coupled to the second hole 512. For example, the second front cavity 560 in FIG. 5A is a sealed cavity and is not acoustically coupled to the second hole 512. Also, for example, the second rear cavity 570 in FIG. 5B is a sealed cavity and is not acoustically coupled to the second hole 512. In some embodiments, by adjusting the resonance frequency of the sealed cavity to be below the lower frequency limit of the target frequency range for realizing the heart-shaped directivity, the resonance frequency of the sealed cavity is not within the frequency band in which the acoustic output device realizes the heart-shaped directivity. In some embodiments, the resonance frequency of the sealed cavity is set to 1 kHz or less, and the lower frequency limit for the acoustic output device to realize the heart-shaped directivity is set to 1 kHz or more (for example, the frequency range for realizing the heart-shaped directivity may include 1 kHz to 4 kHz), so that the output performance of the acoustic output device within the frequency range sensitive to the human ear can be improved. In some embodiments, the resonance frequency of the sealed cavity may be lower than the lower frequency limit of the frequency range in which the acoustic output device realizes the heart-shaped directivity. For example, the resonance frequency of the sealed cavity may be 800 Hz or less. In some embodiments, considering factors such as structural design and processing and mounting difficulty, the resonance frequency of the sealed cavity may be 600 Hz or less.

[0052] FIG. 8 is a schematic diagram showing the relationship between the resonance frequency of the sealed cavity and its volume according to some embodiments of the present specification. As shown in FIG. 8, in some embodiments, when the resonance frequency of the sealed cavity of the second speaker 550 is 1 kHz or less, correspondingly, the volume of the sealed cavity is 0.8 cm 3 or more. In some embodiments, when the resonance frequency of the sealed cavity of the second speaker 550 is 1.2 kHz or less, correspondingly, the volume of the sealed cavity is 0.6 cm 3The above is the case. In some embodiments, when the resonance frequency of the sealed cavity of the second speaker 550 is 1.4 kHz or less, accordingly, the volume of the sealed cavity is 0.5 cm 3 The above is the case. In some embodiments, when the resonance frequency of the sealed cavity of the second speaker 550 is 1.6 kHz or less, accordingly, the volume of the sealed cavity is 0.45 cm 3 The above is the case. In some embodiments, when the resonance frequency of the sealed cavity of the second speaker 550 is 0.8 kHz or less, accordingly, the volume of the sealed cavity is 1.1 cm 3 The above is the case. By adjusting the volume of the sealed cavity, the resonance frequency of the sealed cavity is further controlled so that it is below the lower limit of the target frequency range at which the acoustic output device realizes heart-shaped directivity, thereby avoiding interference and improving the user's listening quality and the sound leakage reduction effect of the acoustic output device.

[0053] In some embodiments, since a sealed cavity is installed in the second speaker, it is difficult for the second speaker to output low-frequency sound waves from the holes (e.g., the second hole 512) acoustically coupled thereto. Therefore, within 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 mainly the first speaker outputs the sound waves of the acoustic output device, so that the acoustic output device can achieve dual sound source directivity. Within the mid-high frequency range, since the first speaker and the second speaker cooperate to output the sound waves of the acoustic output device, the acoustic output device can achieve heart-shaped directivity. In some embodiments, the acoustic output device can achieve dual sound source directivity within the frequency range of 100 Hz to 800 Hz and can achieve heart-shaped directivity within the frequency range of 1 kHz to 4 kHz. In some embodiments, the frequency range in which the acoustic output device achieves dual sound source directivity can be designed and adjusted according to the actual situation. For example, the target frequency range in which the acoustic output device achieves dual sound 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, in order to achieve dual sound source directivity within the target frequency range, the amplitude of the second electrical signal for driving the second speaker within the target frequency range can be reduced. For example, the amplitude of the second electrical signal within the target frequency range can be adjusted to 0, that is, the second electrical signal is not provided within the target frequency range. In some embodiments, in order to avoid the disturbance of the sound field of the acoustic output device, the lower frequency limit of the frequency range in which the acoustic output device achieves heart-shaped directivity may be greater than the upper frequency limit of the frequency range in which the acoustic output device achieves dual sound source directivity. When the target frequency range in which the acoustic output device achieves dual sound source directivity is different, accordingly, the mid-high frequency range in which the acoustic output device achieves heart-shaped directivity may also change. Since the resonance frequency of the sealed cavity of the second speaker affects the lower frequency limit of the frequency range in which the heart-shaped directivity is achieved, accordingly, the resonance frequency of the sealed cavity of the second speaker also needs to change.For example, when the acoustic output device realizes dual-source directivity from 100 Hz to 800 Hz and heart-shaped directivity from 1 kHz to 4 kHz, the resonance frequency of the sealed cavity of the second speaker may be 1 kHz or less. Also, for example, when the acoustic output device realizes dual-source directivity from 100 Hz to 1.2 kHz and heart-shaped directivity from 1.5 kHz to 4 kHz, the resonance frequency of the sealed cavity of the second speaker may be 1.5 kHz or less. In some embodiments, in the worn state, the hole acoustically coupled to the first front cavity of the first speaker may be installed close to the user's ear, the hole acoustically coupled to the first rear cavity is installed 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 faces the user's ear, that is, the dual-source directivity formed within the low-frequency range can face the user's ear. In some embodiments, in the worn state, the hole acoustically coupled to the first front cavity of the first speaker may be installed 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 installed 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 holes to the hole acoustically coupled to the first front cavity faces the user's ear, that is, the directivity formed within the mid- to high-frequency range can face the user's ear.

[0054] FIG. 9 is a schematic configuration diagram of an acoustic output device according to some other embodiments of the present specification. In order to prevent the sound wave radiated by the first speaker and the sound wave radiated by the second speaker from interfering with each other and reducing the mutual radiation impedance, the acoustic output device may further be installed such that the first speaker 620 and the second speaker 650 do not have the same cavity as shown in FIG. 9. For example, two accommodation spaces may be provided in the housing of the acoustic output device, and the first speaker 620 and the second speaker 650 may be respectively installed in the two accommodation spaces. Also, for example, the first speaker 620 and the second speaker 650 are installed in the same accommodation space of the housing, but a partition plate is installed between them so that the two cavities corresponding to the two speakers do not communicate with each other. Hereinafter, taking as an example that the first speaker and the second speaker are arranged at intervals along the vibration direction and the directions of the first diaphragm and the second diaphragm are opposite, the acoustic output device 600 according to some other embodiments will be described.

[0055] As shown in FIG. 9, the acoustic 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, and a first front cavity 630 and a first rear cavity 640 are respectively installed on the front side and the rear side of the first diaphragm 621. In the housing 610, 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 are installed. The first hole 611 and the second hole 612 form a dual sound source as the sound emission holes of the first speaker 620. The second speaker 650 includes a second diaphragm 651, and a second front cavity 660 and a second rear cavity 670 are respectively installed on the front side and the rear side 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 of 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 a cavity acoustically coupled to the third hole 613 (for example, 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 respectively located on both sides of the partition plate 614. In some embodiments, in order to avoid the distance between the second hole 612 and the third hole 613 being too large, the distance between the third hole 613 and the second hole 612 may be greater than 0 mm and less than or equal to 10 mm, thereby avoiding the volume of the corresponding cavity being too large, ensuring that the positions of the equivalent holes of the second hole 612 and the third hole 613 are appropriate, and avoiding significantly interfering with the directivity of the acoustic output device 600.

[0056] In some embodiments, within the target frequency range, at a far-field position in a specific direction of the acoustic output device 600, the sound pressure of the sound wave formed by the superposition of the first sound wave and the second sound wave output by the first speaker 620 and the third sound wave output by the second speaker 650 is low, for example, close to zero. Thereby, the far-field radiation of the acoustic output device 600 exhibits directivity, improving the problem of sound leakage in the far field of the acoustic output device 600. In some embodiments, since the acoustic output device 600 has a flat frequency response curve within a wide frequency range and excellent heart-shaped directivity, the target frequency range may include 1 kHz to 4 kHz.

[0057] When indicating the directivity of the acoustic 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 made equivalent to one hole. Specifically, the central position point M between the second hole 612 and the third hole 613 is determined, and the central position point M can represent the position of the equivalent hole. At this time, the first front cavity 630 can be the front cavity of the acoustic 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 acoustic output device 600. The first hole 611 is the sound-emitting hole AS1 of the front cavity of the acoustic output device 600, and the equivalent hole of the second hole 612 and the third hole 613 can be the sound-emitting hole AS2 of the rear cavity of the acoustic output device 600. The direction of the extension line of the line connecting the first hole 611 and the equivalent hole (point M) is the specific direction.

[0058] In some embodiments, the upper limit of the frequency at which the acoustic output device 600 realizes heart-shaped directivity is determined by the resonance frequency of the cavity (the second front cavity 660 or the second rear cavity 670) acoustically coupled to the third hole 613 and the resonance frequency of the first rear cavity 640. If the difference between the above-described two resonance frequencies is too large, one of the resonance frequencies is too small, whereby the upper limit of the frequency at which the acoustic output device 600 realizes heart-shaped directivity is too small, the range of the frequency band at which the acoustic output device 600 realizes heart-shaped directivity is too small, and finally the output performance of the acoustic output device 600 is affected. In some embodiments, the difference between the above-described two resonance frequencies is 3000 Hz or less. Further, in order to increase the upper limit of the frequency of the heart-shaped directivity, in some embodiments, the difference between the above-described two resonance frequencies is 2500 Hz or less. Further, in order to further increase the upper limit of the frequency of the heart-shaped directivity, in some embodiments, the difference between the above-described two resonance frequencies is 2000 Hz or less. Preferably, the difference between the above-described two resonance frequencies is 1500 Hz or less. More preferably, the difference between the above-described two resonance frequencies is 1000 Hz or less.

[0059] In some embodiments, in order to enable the acoustic output device to realize heart-shaped directivity within the voice frequency range sensitive to the human ear, the upper limit of the frequency of the heart-shaped directivity may be 4 kHz or more. In some embodiments, in order to avoid the resonance frequency of the cavity from interfering with the heart-shaped directivity, the resonance frequency of the cavity (the second front cavity 660 or the second rear cavity 670) acoustically coupled to the third hole 613 can be made outside the range of the frequency at which the heart-shaped directivity is realized. For example, the resonance 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 more. In some embodiments, in order to increase the upper limit of the frequency of the heart-shaped directivity, the resonance 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 more.

[0060] In some embodiments, the structure of the first rear cavity 640 and the second hole 612, and the structure of the cavity (the second front cavity 660 or the second rear cavity 670) acoustically coupled to the third hole 613 and the third hole 613 are the same or similar, and the resonance frequencies of both are close (for example, the difference between the resonance frequencies of both is less than 3000 Hz). When the resonance 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 more, the volume of the cavity (for example, the second rear cavity 570 shown in FIG. 9) acoustically coupled to the third hole 613 is 0.3 cm 3 or less, and accordingly, the area of the third hole 613 is 12 mm 2 or more. At this time, the volume of the first rear cavity 640 may also be 0.3 cm 3 or less, and accordingly, the area of the second hole 612 may also be 12 mm 2 or more.

[0061] In some embodiments, among the second front cavity 660 and the second rear cavity 670 of the second speaker 650, the cavity that is not acoustically coupled to the second hole 612 is a sealed cavity. For example, the second front cavity 660 in FIG. 9 is a sealed cavity. The resonance frequency of the sealed cavity can determine the lower frequency limit of the frequency range for realizing heart-shaped directivity. In some embodiments, in order to avoid the resonance frequency of the sealed cavity interfering with the heart-shaped directivity, the resonance frequency of the sealed cavity can be set outside the frequency range for realizing the heart-shaped directivity. For example, the resonance frequency of the sealed cavity (e.g., the second front cavity 660 in FIG. 9) is 1 kHz or less. In some embodiments, the resonance frequency of the sealed cavity may be lower than the lower frequency limit of the frequency range in which the acoustic output device realizes heart-shaped directivity. For example, the resonance frequency of the sealed cavity may be 900 Hz or less. In some embodiments, considering factors such as structural design and processing and installation difficulty, the resonance frequency of the sealed cavity may be 1.1 kHz or less. At this time, the frequency range in which the acoustic output device realizes heart-shaped directivity may be reduced accordingly, and the lower frequency limit for realizing heart-shaped directivity may be 1.1 kHz.

[0062] In some embodiments, when the first hole 611 acoustically coupled to the first front cavity 630 is installed in the corresponding region of the housing 610 along the vibration direction of the first speaker 620 (that is, the direction of the line connecting the geometric center of the first hole 611 and the geometric centroid of the first vibrating diaphragm 621 of the first speaker 620 is parallel to the vibration direction), the holes corresponding to the first rear cavity 640 and the adjacent cavity (the second front cavity 660 or the second rear cavity 670) may be installed in a plurality of ways. Hereinafter, taking the example that the first speaker and the second speaker do not have the same cavity and are arranged at intervals along the vibration direction, and the first vibrating diaphragm and the second vibrating diaphragm face in opposite directions, different hole installations of the acoustic output device 600 will be described.

[0063] Figures 10A to 10D are schematic diagrams of acoustic output devices in which sound emission hole portions are installed in different ways according to some embodiments of the specification of the present application, and Figures 11A to 11D are schematic diagrams showing the directivities of far-field radiation of the acoustic output devices shown in Figures 10A to 10D, respectively. As shown in Figures 10A and 11A, when the first hole portion 611 is installed directly above the vibration direction of the first speaker 620 (that is, the first hole portion 611 is located on the side wall of the housing facing the first vibration diaphragm 621, and the line connecting the geometric center of the first hole portion 611 and the geometric center of gravity of the first vibration diaphragm 621 is parallel to the vibration direction of the first speaker 620), and the second hole portion 612 and the third hole portion 613 are installed on the same side wall of the housing in a direction parallel to the vibration direction with respect to the first hole portion 611, the maximum value direction and the minimum value direction of the output sound pressure of the acoustic output device are the directivity directions of the acoustic output device, and the maximum value direction and the minimum value direction are opposite to each other. The minimum value direction is the aforementioned specific direction, and the sound pressure at the far-field position in the specific direction (minimum value direction) of the acoustic output device is small (for example, close to zero). The specific direction is the direction from the sound emission hole portion of the front cavity of the acoustic output device 600 (for example, the first hole portion 611 in Figure 10A) to the sound emission hole portion of the rear cavity (for example, the point M of the equivalent hole portion of the second hole portion 612 and the third hole portion 613 in Figure 10A).

[0064] 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 facing the first diaphragm. 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'). The second hole 612 and the other second hole 612' are respectively installed on two side walls of the housing parallel to the vibration direction with respect to the first hole 611. The second rear cavity 670 is adjacent to the first rear cavity 640. The second rear cavity 670 is acoustically coupled to both of the third hole 613 and the other third hole 613'. The third hole 613 and the other third hole 613' are respectively installed on two side walls of the housing parallel to the vibration direction with respect to the first hole 611. At this time, along the vibration direction, the second hole 612 and the other second hole 612' are symmetric with respect to the first hole 611, and the third hole 613 and the other third hole 613' are symmetric with respect to the first hole 611. At this time, 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' and the first hole 611 is substantially coincident with the vibration direction. As shown in FIG. 10B, point M indicates the position of the equivalent hole. At this time, the line connecting point M and 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 and the geometric center of the third hole 613. For example, when the second hole 612 and the third hole 613 are symmetrically installed 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 direction and the sound pressure minimum direction of the far-field radiation of the acoustic output device 600 are the directivity directions of the acoustic output device, and the maximum value direction and the minimum value direction are opposite. The minimum value direction is a specific direction, that is, the direction from the sound emitting hole of the front cavity of the acoustic output device 600 (for example, the first hole 611 in FIG. 10B) to the sound emitting hole of the rear cavity (for example, point M representing the equivalent holes of the second hole 612, the other second hole 612', the third hole 613 and the other third hole 613' in FIG. 10B).

[0065] As shown in FIGS. 10C and 11C, 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 facing the first diaphragm. The first rear cavity 640 is acoustically coupled to both the second hole 612 and the other second hole 612'. The second hole 612 and the other second hole 612' are respectively installed on two side walls of the housing parallel to the vibration direction with respect to the first hole 611. The second rear cavity 670 is adjacent to the first rear cavity 640. At this time, the second rear cavity 670 is a sealed cavity. The second front cavity 660 is acoustically coupled to the third hole 613. Along the vibration direction, the third hole 613 is installed on the housing facing the first hole 611. That is, it is installed directly below the geometric center of gravity of the second diaphragm 651 of the second speaker 650. That is, the third hole 613 is located on the side wall of the housing facing 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' and the first hole 611 is substantially coincident 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 (that is, the maximum value direction) is the direction from point M representing the equivalent holes 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 representing the equivalent holes 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 minimum value direction is 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.

[0066] As shown in FIGS. 10D and 11D, 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 facing the first diaphragm. The first rear cavity 640 is acoustically coupled to both the second hole 612 and the other second hole 612'. The second hole 612 and the other second hole 612' are respectively installed on two side walls of the housing parallel to the vibration direction with respect to the first hole 611. The second rear cavity 670 is adjacent to the first rear cavity 640. 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 two side walls of the housing parallel to the vibration direction with respect to the first hole 611. The second front cavity 660 is acoustically coupled to the fourth hole 615. Along the vibration direction, the fourth hole 615 is installed directly below the housing corresponding to the position of the first hole 611. That is, the fourth hole 615 is located on the side wall of the housing facing the geometric center of gravity of the second diaphragm. At this time, the first hole 611 of the first speaker 620 and the equivalent holes of the second hole 612 and the other second hole 612' are regarded as a set of double sound sources. The equivalent holes of the third hole 613 and the other third hole 613' of the second speaker 650 and the fourth hole 615 are regarded as a set of double sound sources. At this time, 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. The four of the second hole 612, the other second hole 612', the third hole 613 and the other third hole 613' have a point M3 representing the equivalent hole. For the position of the point M3, the position of the point M in FIG. 10B can be referred to, and the description is omitted here. The direction of the line connecting the point M3 representing the equivalent hole and the first hole 611 is substantially 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 value) and side lobes. The direction of the main lobe (that is, the maximum value direction) is the direction from the point M3 representing the equivalent hole to the first hole 611. The direction of the side lobe is the direction from the point M3 representing the equivalent hole to the fourth hole 615.As can be seen from FIGS. 10D and 11D, the minimum value directions are the directions from the point M1 representing the equivalent hole portion to the fourth hole portion 615 and from the point M2 representing the equivalent hole portion to the fourth hole portion 615. At this time, 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 minimum value region of the far-field radiation of the acoustic output device 600 shown in FIG. 11D is narrow, the sound pressure levels in the minimum value direction and the directions on both sides of the minimum value direction are large, and the sound pressure levels in the directions near the maximum value direction (the directions of 0° to 180°) are uniform. In some embodiments, the acoustic output device 600 shown in FIG. 10D is applied to scenarios that need to radiate uniformly in the free space.

[0067] In some embodiments, the installation method of the sound-emitting hole portion of the acoustic output device is not limited to the above-described method, and the sound-emitting hole portion may be installed according to actual needs. In some embodiments, the first hole portion corresponding to the first front cavity of the first speaker may be installed in the mounted state so as to correspond to the listening position of the user's ear (for example, installed toward the external auditory canal of the user's ear or installed close to the external auditory canal of the user's ear). In order to reduce the interference of other sound-emitting hole portions with the first sound wave radiated from the first hole portion, the sound-emitting hole portion corresponding to the first rear cavity of the first speaker and the sound-emitting hole portion of the second speaker should be as far away as possible from the first hole portion. In some embodiments, according to the actual application scenario, the listening quality of the acoustic output device, or the need to reduce sound leakage, the region where it is necessary to reduce the sound leakage of the acoustic output device (for example, a 30° fan-shaped region 10 cm away from the user's ear) can be determined, thereby determining the maximum value direction and the minimum value direction of the sound pressure of the directivity of the far-field radiation of the acoustic output device, and further determining the installation positions of the corresponding sound-emitting hole portions.

[0068] In order to reduce the overall dimensions of the audio output device, the dimensions of the speaker serving as a single sound source must not be too large. Otherwise, the fundamental resonance frequency of the speaker serving as a single sound source (i.e., the resonance frequency of the sealed cavity of the speaker serving as a single sound source) is high, and it is difficult for the lower frequency limit of the frequency range in which the audio output device realizes heart-shaped directivity to reach the frequency band of human voices. FIGS. 12A and 12B are schematic diagrams showing the directivity of far-field radiation of an audio output device having exemplary hole installation positions according to some embodiments of the present specification. As shown in FIGS. 12A and 12B, the audio output device 700 includes a first speaker 710 and a second speaker 720. The front cavity and the rear cavity of the first speaker 710 are acoustically coupled to a first hole 711 and a second hole 712, respectively, and serve as a dual sound source. The second speaker 720 has one cavity sealed and the other cavity acoustically coupled to a third hole 713, and serves as a single sound source. In order to always reduce sound leakage to the side of the user's head in the entire frequency band, as shown in FIGS. 12A and 12B, the second speaker 720 serving as a single sound source is smaller in size and has a length close to the thickness of the first speaker 710 compared to the first speaker 710 serving as a dual sound source. The first hole 711 is installed facing the user's ear canal opening, and both the second hole 712 and the third hole 713 are installed away from the first hole 711. At this time, within the frequency range of the mid-low frequency band (for example, 1 kHz or less), since the output sound pressure level of the single sound source is smaller than that of the dual sound source, the output of the single sound source at this time can be ignored, and the audio output device 700 operates almost as a dual sound source alone, and as shown in FIG. 12A, it can realize an "8"-shaped dual sound source directivity to reduce 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 source cooperate to operate, and as shown in FIG. 12B, heart-shaped directivity is realized.

[0069] In some embodiments, by filling an acoustic particle material into a sealed cavity (e.g., the second front cavity 560 shown in FIG. 5A, the second rear cavity 570 shown in FIG. 5B, etc.) that is not acoustically coupled to the hole of the second speaker of the acoustic output device, the virtual volume of the sealed cavity can be increased, the resonance frequency of the sealed cavity can be decreased, the lower frequency limit of the heart-shaped directivity of the acoustic output device can be decreased, and the frequency range of the heart-shaped directivity can be increased.

[0070] FIG. 13 is a schematic diagram of another acoustic output device according to some embodiments of the present specification. As shown in FIG. 13, in some embodiments, the acoustic output device 800 may include a separately installed first speaker 810, a second speaker 820, and a third speaker 830. The first speaker 810 can emit a first sound wave, the second speaker 820 can emit a second sound wave, and the first sound wave and the second sound wave emitted by both can satisfy certain phase and amplitude conditions (e.g., the amplitudes are the same and the phases are opposite), thereby forming a dual sound source structure. The third speaker 830 can emit a third sound wave, and the third sound wave emitted by the third speaker 830 can satisfy certain phase and amplitude conditions at a far-field position in a specific direction of the acoustic output device 800 with respect to the second sound wave emitted by the second speaker 820 and the first sound wave emitted by the first speaker 810. Thereby, the third sound wave, the first sound wave, and the second sound wave are superimposed and canceled at the far-field position, realizing the directivity of the far-field of the acoustic output device 800. In some embodiments, the first speaker 810, the second speaker 820, and the third speaker 830 may be speakers that derive sound only from a non-sealed cavity with a sealed front cavity or rear cavity. In some embodiments, the acoustic output device 800 may include an acoustic enclosure.

[0071] In some embodiments, the output of the acoustic output device can be measured using a test microphone. In some embodiments, test microphones are respectively installed at the far-field positions in a specific direction of the acoustic output device and the corresponding far-field positions in the opposite direction thereof, and the sound pressure levels at the two far-field positions are measured to obtain the sound pressure level difference between the two corresponding far-field positions described above, and by comparing the absolute value of the sound pressure level difference with a preset sound pressure level threshold, it can be determined whether the acoustic output device has directivity in the specific direction and the opposite direction thereof.

[0072] FIG. 14 is a schematic diagram of the acoustic transmission of an acoustic output device provided with a second speaker according to some embodiments of the present specification. 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 acoustic output device. In some embodiments, the far-field position of the acoustic output device may be a position where the distance from the acoustic output device is greater than a preset distance threshold, for example, a position greater than 25 cm. In some embodiments, when the frequency range is 1 kHz to 4 kHz, the far-field position of the acoustic output device may be a position where the distance from the acoustic 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 acoustic output device in a specific direction. The specific direction is the direction from the sound-emitting hole portion (for example, the first hole portion) of the front cavity of the acoustic output device to the sound-emitting hole portion (for example, the second hole portion) of the rear cavity and the directions 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 the equivalent cavity or the same cavity of the first rear cavity of the first speaker and the output cavity of the second speaker. When the acoustic output device is in a mounted state, the specific direction may be the direction away from the user's ear of the acoustic output device. In some embodiments, in order to achieve directivity, the absolute value of the difference in sound pressure levels measured by the test microphone at two corresponding far-field positions in the specific direction and the opposite direction of the acoustic output device is set to be equal to or greater than a preset 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.

[0073] In some embodiments, the sound pressure received by the test microphone includes two sets of sound waves. One is the sound wave radiated from the hole acoustically coupled to the front cavity (e.g., the first sound wave), and its transfer function is z(1). The other is the sound wave radiated from the hole acoustically coupled to the rear cavity (e.g., the second and third sound waves), and their transfer functions are z(2). In order to make the far-field radiation of the acoustic output device directional, it is necessary to cancel out the two sets of sound waves received by the test microphone, that is, the two sets of sound waves need to have equal sound pressure amplitudes and opposite phases at the position of the test microphone. The received signal p of the test microphone mic is as follows.

[0074] p mic =p(1)*z(1)+[p(2)+p(3)]*z(2)=0 (1) where p(1) is the sound pressure radiated from the front cavity by the dual sound source (i.e., the first speaker, e.g., 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, e.g., 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, e.g., SPK2 in FIG. 14).

[0075] In some embodiments, when measuring p(1), p(2), and p(3), it is necessary to avoid their mutual interference. Therefore, when measuring p(1), the first speaker is operated, the second speaker is turned off, and the holes communicating with the rear cavity (for example, the second hole) are temporarily blocked with cotton, rubber, etc., and it can be measured by the other test microphone installed inside or near (for example, within the range of 2 mm to 3 mm away) the hole communicating with the front cavity (for example, the first hole). When measuring p(2), the first speaker is operated, the second speaker is turned off, and the holes communicating with the front cavity (for example, the first hole) are temporarily blocked with cotton, rubber, etc., and it can be measured by the other test microphone installed inside or near the hole communicating with the rear cavity of the first speaker (for example, the second hole). When measuring p(3), the second speaker is operated, the first speaker is turned off, and it can be measured by the other test microphone installed inside or near the hole communicating with the rear cavity of the second speaker (for example, the second hole or the third hole to be described later).

[0076] In some embodiments, a baffle with a large size (for example, a diameter of 1 m) may be installed on the peripheral side of the acoustic output device. The baffle is installed around the acoustic output device and is tightly connected to the acoustic output device. The sound-emitting holes of the front cavity (that is, the holes communicating with the front cavity) and the sound-emitting holes of the rear cavity (that is, the holes communicating with the rear cavity) are located on both sides of the baffle respectively. By installing the baffle, the mutual interference between the first sound wave radiated from the sound-emitting hole of the front cavity, the second sound wave and the third sound wave radiated from the sound-emitting hole of the rear cavity is significantly reduced and thus mutually separated, and the measurement accuracy of p(1), p(2), and p(3) is improved. In some embodiments, when the baffle is installed, the first speaker is operated, the second speaker is turned off, and test microphones are installed in the holes communicating with the front cavity and the holes communicating with the rear cavity, so that p(1) and p(2) can be measured simultaneously.

[0077] Based on the distributive law of convolution, Equation (1) may be expressed as follows.

[0078] p mic = [p(1)*z(1) + p(2)*z(2)] + p(3)*z(2) = 0 (2) In the formula, [p(1)*z(1) + p(2)*z(2)] represents the sound pressure at the test microphone of the sound waves (for example, the first sound wave and the second sound wave) radiated from the dual sound sources (that is, the first speaker, for example, SPK1 in FIG. 14), and p(3)*z(2) represents the sound pressure at the test microphone of the sound wave (for example, the third sound wave) radiated from the single sound source (that is, the second speaker, for example, SPK2 in FIG. 14). Therefore, by adjusting the first electrical signal and the second electrical signal, the dual sound source (that is, the first speaker) and the single sound source (that is, the second speaker) are excited respectively, and the amplitudes and phases of the sound pressures 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 (that is, SPK2 of the second speaker) and / or the amplitude and phase of the first electrical signal driving the dual sound source (that is, SPK1 of the first speaker), the sound wave (that is, the third sound wave) radiated from the single sound source (that is, the second speaker) and the sound wave (that is, the superimposed sound wave of the first sound wave and the second sound wave) radiated from the dual sound source (that is, the first speaker) have the same amplitude of the sound pressure at the test microphone (that is, the same amplitude of the sound pressure level), and the phases are opposite, that is, the sound pressure at the far-field position in a specific direction of the acoustic output device becomes zero, whereby the sound pressure level at the far-field position in a specific direction of the acoustic output device becomes zero, and the absolute value of the difference in the sound pressure levels between the far-field positions in at least one pair of opposite directions of the acoustic output device is greater than or equal to a preset sound pressure level threshold, and the directivity of the far-field radiation of the acoustic output device can be realized.

[0079] FIG. 15 is a schematic diagram showing an exemplary process of a method for adjusting a second electrical signal according to some embodiments of the present specification. As shown in FIG. 15, process 900 may include the following steps 910 to 940.

[0080] In step 910, the dual sound sources are excited separately, and the first sound pressure level amplitude and the first phase of the test microphone are recorded.

[0081] In some embodiments, the dual sound sources may be the first speakers. The installation position of the test microphone may be a far-field position in a specific direction of the acoustic output device. In some embodiments, the specific direction may be within a specified direction range, and may be the direction from the sound emission hole portion of the front cavity to the sound emission hole portion of the rear cavity and directions in the vicinity thereof. At this time, 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 on the test microphone.

[0082] In some embodiments, by providing the first electrical signal only to the first speaker and not providing the second electrical signal to the second speaker so that the first speaker operates and the second speaker does not operate, it is possible to realize exciting the dual sound sources separately.

[0083] In step 920, the single sound source is excited separately, and the second sound pressure level amplitude and the second phase of the test microphone are recorded.

[0084] In some embodiments, the single sound source may be the second speaker. The installation position of the test microphone is a far-field position in a specific direction of the acoustic output device, and may be the same as the position of the test microphone in step 910. At this time, the sound pressure level amplitude and the phase measured by the test microphone may be the second sound pressure level amplitude and the second phase of the third sound wave generated from the second speaker at the test microphone.

[0085] In some embodiments, by providing a second electrical signal only to the second speaker and not providing a first electrical signal to the first speaker so that the second speaker operates and the first speaker does not operate, it is possible to achieve exciting a single sound source alone.

[0086] In step 930, calculate the sound pressure level amplitude difference and phase difference between the single sound source and the dual sound sources.

[0087] Compare the second sound pressure level amplitude of the single sound source measured by the test microphone with the first sound pressure level amplitude of the dual sound sources to obtain the sound pressure level amplitude difference between the two. Compare the second phase of the single sound source measured by the test microphone with the first phase of the dual sound sources to obtain the phase difference between the two.

[0088] In step 940, adjust the second electrical signal so that the sound wave radiated from the single sound source has the same sound pressure level amplitude at the test microphone as that of the dual sound sources and the opposite phase to that of the dual sound sources.

[0089] 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, by adjusting the second electrical signal that drives the single sound source, the sound wave radiated from the single sound source has the same sound pressure level amplitude at the test microphone as that of the dual sound sources and the opposite phase to that of the dual sound sources. Thereby, the third sound wave radiated from the single sound source, the first sound wave and the second sound wave radiated from the dual sound sources are superimposed and canceled at the position of the test microphone, the far-field radiation of the acoustic output device exhibits directivity (e.g., heart-shaped directivity), and the sound leakage in the far field of the acoustic output device is reduced.

[0090] In some embodiments, based on the sound pressure level amplitude difference and the phase difference between the single sound source and the dual sound sources obtained in step 930, by adjusting the first electrical signal that drives the dual sound sources, the sound wave radiated from the single sound source and the sound wave radiated from the dual sound sources have the same sound pressure level amplitude and opposite phases at the test microphone, thereby enabling the far-field radiation of the acoustic output device to exhibit directivity (e.g., heart-shaped directivity) and reducing the sound leakage in the far field of the acoustic output device.

[0091] FIG. 16 is a schematic diagram of the frequency response curves when the single sound source and the dual sound sources are excited separately according to some embodiments of the present specification. As a mere example, the single sound source (i.e., the second speaker) and the dual sound sources (i.e., the first speaker) share the rear cavity of the acoustic output device (e.g., the structure shown in FIG. 5A), and the volume of the rear cavity of the acoustic 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 equal areas. The second electrical signal that excites the single sound source and the first electrical signal that excites the dual sound sources both have an amplitude of 1V and a phase of 0°. As shown in FIG. 16, under the above-described conditions, curve L 101 shows the frequency response curve measured by the test microphone when the dual sound sources are excited alone, and curve L 102 shows the frequency response curve measured by the test microphone when the single sound source is excited alone.

[0092] Under the above-described conditions, by means of process 900, the sound pressure level amplitude difference and the phase difference at the positions of the test microphone (i.e., the far field of the acoustic output device) at different frequencies of the single sound source and the dual sound sources can be measured. Then, by comparing curve L 101 and curve L 102 in FIG. 16, the sound pressure level amplitude difference at the positions of the test microphone (i.e., the far field of the acoustic output device) at different frequencies of the single sound source and the dual sound sources can be determined.

[0093] In some embodiments, by adjusting the amplitudes and phases of the first electrical signal and the second electrical signal such that there are certain amplitude and / or phase differences within the target frequency range, the sound wave (the third sound wave) generated from a single sound source (the second speaker) and the sound waves (the first sound wave, the second sound wave) generated from a dual sound source (the first speaker) overlap with each other, and the far-field radiation of the acoustic output device exhibits directivity. In some embodiments, the target frequency range may include 100 Hz to 10 kHz. In some embodiments, an acoustic output device composed of a single sound source and a dual sound source can reduce sound leakage in a wide frequency band of 100 Hz to 10 kHz. The target frequency range may include a first frequency range, and the first frequency range may include some mid-high frequency bands, for example, 800 Hz to 10,000 Hz. Within the first frequency range, the acoustic output device can reduce sound leakage using the principle of heart-shaped directivity, that is, the far-field radiation of the acoustic output device exhibits heart-shaped directivity. The target frequency range may include a second frequency range, and the second frequency range may include some mid-low frequency bands. Within the second frequency range, for example, at 100 Hz to 800 Hz, the acoustic output device can reduce sound leakage using the principle of dual sound source directivity. Specifically, refer to FIG. 1 and its related description.

[0094] In some embodiments, the acoustic output device can have dual-source directivity in 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 acoustically coupled to the first rear cavity (for example, the second hole) and the sound pressure level of the third sound wave output by the second speaker from the hole acoustically coupled to the second speaker (for example, the third hole) have a difference of 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), the sound pressure level radiated by the single source is extremely small compared to the sound pressure level radiated by the dual source, 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 levels 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.

[0095] From the above, when providing the same electrical signal (i.e., the first electrical signal and the second electrical signal have the same amplitude and phase) to a single sound source and a dual sound source within the frequency band of 100 Hz to 800 Hz, since the front cavity of the single sound source (the second speaker) is sealed and only the rear cavity communicates with the outside air and air cannot flow freely, it is difficult for the single sound source to output low-frequency sound waves from the holes acoustically coupled to the rear cavity. As a result, within this frequency band, the difference in sound pressure level between the sound waves output by the dual sound source (the first speaker) from the holes acoustically coupled to the rear cavity and the sound waves output by the single sound source (the second speaker) from the holes acoustically coupled to the rear cavity can be 6 dB or more. At this time, the acoustic output device can exhibit excellent dual sound source directivity, thereby realizing a design for reducing sound leakage in the mid-low frequency range. In some embodiments, within the range of 100 Hz to 800 Hz, in order to achieve that the difference in sound pressure level between the sound waves output by the dual sound source (the first speaker) from the holes acoustically coupled to the rear cavity and the sound waves output by the single sound source (the second speaker) from the holes acoustically coupled to the rear cavity is 6 dB or more, a method of reducing the amplitude within the range of 100 Hz to 800 Hz of the second electrical signal driving the single sound source (the second speaker) may be used. For example, within the range of 100 Hz to 800 Hz, the amplitude of the second electrical signal may be 0, that is, within the range of 100 Hz to 800 Hz, it may not be necessary to provide the second electrical signal to the single sound source. In some embodiments, in the worn state, the holes acoustically coupled to the first front cavity of the first speaker are installed close to the user's ear, the holes acoustically coupled to the first rear cavity are installed away from the user's ear, and the direction from the holes acoustically coupled to the first rear cavity to the holes acoustically coupled to the first front cavity faces the user's ear, that is, the dual sound source directivity formed within the low-frequency range can face the user's ear.

[0096] In some embodiments, within the frequency range of 1 kHz to 10 kHz, in order to make the first sound wave, the second sound wave, and the third sound wave overlap with each other at a far-field position in a specific direction of the acoustic output device, the sound pressure level at the far-field position is set to zero, and the absolute value of the sound pressure level difference between the far-field positions in at least a pair of opposite directions of the acoustic output device is made equal to or greater than a preset sound pressure level threshold. Thereby, the far-field radiation of the acoustic output device exhibits directivity, and the amplitudes and phases of the first electrical signal and the second electrical signal may be adjusted. In some embodiments, as shown in FIG. 16, since the resonance frequency corresponding to the resonance peak E of the dual sound source is close to the resonance frequency corresponding to the resonance peak D of the single sound source, the dual sound source and the single sound source have a first resonance frequency (i.e., the frequency corresponding to the resonance peak D). The rear cavity shared by the single sound source and the dual sound source has a second resonance frequency (i.e., the frequency corresponding to the resonance peak F). As can be seen from FIG. 16, the frequency response curves of the single sound source and the dual sound source have a flat region between the first resonance frequency and the second resonance frequency. In some embodiments, the frequency band between the first resonance frequency and the second resonance frequency may include the range of 1 kHz to 4 kHz. In some embodiments, the first resonance frequency may be near 1 kHz, and the second resonance frequency may be near 4 kHz, whereby the frequency response curves of the single sound source and the dual sound source have a wide flat region, 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 resonance frequency and the second resonance frequency (for example, 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 resonance frequency (for example, 4 kHz to 10 kHz), the far-field radiation of the acoustic output device can exhibit a heart-shaped directivity.In some embodiments, in the worn state, the hole acoustically coupled to the first front cavity of the first speaker is installed close to the user's ear, and the hole acoustically coupled to the first rear cavity and the hole for outputting the third sound wave of the second speaker are installed 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 holes to the hole acoustically coupled to the first front cavity faces the user's ear. That is, the directivity formed within the mid-high frequency range can face the user's ear.

[0097] In some embodiments, between the first resonance frequency and the second resonance frequency, the phase difference between the second electrical signal and the first electrical signal is 150° or more. In some embodiments, within the range of 1 kHz to 4 kHz, the phase difference between the second electrical signal and the first electrical signal is 150° or more. In some embodiments, at a frequency of 1 kHz, the phase difference between the second electrical signal and the first electrical signal is 200° or more, and at a frequency of 4 kHz, the phase difference between the second electrical signal and the first electrical signal is 150° or more. Exemplarily, for the case shown in FIG. 16, when the amplitude of the first electrical signal is held at 1 V (i.e., 1000 mV) and the phase is held at 0°, in order to make the sound pressure level at the far-field position in a specific direction of the acoustic output device zero and make 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 equal to or greater than a preset sound pressure level threshold, the second electrical signal can be modulated. Within the range of 1 kHz to 4 kHz, the phase and amplitude of the second electrical signal after modulation 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 the far-field position in a specific 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%. Exemplarily, at 1 kHz, the second electrical signal may have an amplitude of 27.5*(1±0.1) mV, and the phase may be 250*(1±0.1)°, that is, the second electrical signal may have an amplitude of 24.75 mV to 30.25 mV and a phase of 225° to 247.5°.

[0098] As can be seen from FIG. 16, the single sound source (i.e., the second speaker) has a first resonance frequency, i.e., a frequency corresponding to the resonance peak D. When passing through the first resonance frequency, the sound wave radiated from the single sound source has its phase inverted. Accordingly, the resonance peak E of the dual sound source near the first resonance frequency is generated when the diaphragm of the single sound source that is not operating is used as a passive diaphragm while the dual sound source is operating. Therefore, at the resonance frequency of the resonance peak E, the sound wave radiated from the dual sound source does not invert. Therefore, it is necessary to compensate for the phase of the sound wave radiated from the single sound source in order to ensure that the sound wave radiated from the single sound source and the sound wave radiated from the dual sound source maintain opposite phases in the far field before and after the first resonance frequency. In some embodiments, at two frequencies before and after the first resonance frequency, the phase difference of the second electrical signal is 100° or more. At the frequency before the first resonance frequency, the phase of the second electrical signal is the phase before compensation, and at the frequency after the first resonance frequency, the phase of the second electrical signal is the phase after compensation. In some embodiments, at two frequencies before and after the first resonance frequency, the phase difference of the second electrical signal may be 100° to 240°. In some embodiments, at two frequencies before and after the first resonance frequency, the phase difference of the second electrical signal may be 120° to 220°. In some embodiments, at two frequencies before and after the first resonance frequency, the phase difference of the second electrical signal may be 140° to 180°. In some embodiments, at two frequencies before and after the first resonance frequency, the phase difference of the second electrical signal may be 150° to 160°.

[0099] In addition, when the phase of the sound wave radiated from only one of the dual sound sources and the single sound source changes by 180° near a certain resonance frequency, in order to avoid the sound wave in the far field being canceled out by such a change, it is necessary to change one of the electrical signals of the dual sound source or the single sound source before and after the resonance frequency (for example, invert by 180° or approximately 180°). However, since the phase difference at each frequency between the first electrical signal and the second electrical signal may be different, based on this, after compensating the phase of one of the electrical signals, finally, the phase difference between the two may not be exactly 180°, but may be close to 180° or approximately 180°.

[0100] In some embodiments, in an actual product, the specifications of the speakers of the acoustic output device may be different, the front cavity and the rear cavity may have different dimensions, the area and depth of the corresponding sound-emitting hole portions may be different, and the front cavity and the rear cavity may have different structural shapes, thereby causing the positions of the resonance peaks (for example, the resonance peaks D and F of the single sound source, the resonance peak G of the dual sound source, etc.) to shift. Therefore, the intervals of the values of the phase difference of the second electrical signal at two frequencies in different frequency ranges before and after the resonance peak may be different.

[0101] In some embodiments, at two frequencies 100 Hz before and after the first resonance frequency, the phase difference of the second electrical signal may be 100° to 240°. In some embodiments, since the dimensions of the single sound source may be different, at two frequencies 500 Hz before and after the first resonance frequency, the phase difference of the second electrical signal may be 120° to 220°. In some embodiments, since the structures of the single sound source may be different, at two frequencies 1000 Hz before and after the first resonance frequency, the phase difference of the second electrical signal may be 140° to 180°.

[0102] In some embodiments, as can be seen from FIG. 16, the first resonance frequency (the frequency corresponding to resonance peak D) is in the range of 800 Hz to 1.2 kHz and is around 1 kHz. In some embodiments, at 800 Hz and 1.2 kHz, the phase difference of the second electrical signal is in the range of 100° to 220°, for example, 130° to 180°. In some embodiments, since the dimensions of the single sound source may be different, at 900 Hz and 1.1 kHz, the phase difference of the second electrical signal may be in the range of 120° to 150°, for example, 130° to 150°. In some embodiments, since the dimensions of the single sound source may be different, at 950 Hz and 1 kHz, the phase difference of the second electrical signal may be in the range of 140° to 170°, for example, 145° to 155°.

[0103] 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 resonance frequency (i.e., the frequency corresponding to resonance peak F). Before and after the second resonance frequency, neither the sound wave radiated from the single sound source nor the sound wave radiated from the dual sound sources undergoes a 180° phase inversion. As can be observed from the vibration mode, the two change from a counter-movement to a relative movement. Therefore, it is still necessary to compensate for the phase of the sound wave radiated from one of the single sound source or the dual sound sources before and after the second resonance frequency. In some embodiments, within the frequency band interval between two frequencies before and after the second resonance frequency, the phase difference of the second electrical signal is 100° or more. In some embodiments, at two frequencies before and after the second resonance frequency, the phase difference of the second electrical signal may be 100° to 260°. In some embodiments, at two frequencies before and after the second resonance frequency, the phase difference of the second electrical signal may be 120° to 170°. In some embodiments, at two frequencies before and after the second resonance frequency, the phase difference of the second electrical signal may be 140° to 160°.

[0104] In some embodiments, at two frequencies of 100 Hz before and after the second resonance frequency, the phase difference of the second electrical signal may be 100° to 260°. In some embodiments, since the dimensions of the rear cavity may be different, at two frequencies of 300 Hz before and after the second resonance frequency, the phase difference of the second electrical signal may be 130° to 180°. In some embodiments, since the area of the sound-emitting hole portion of the rear cavity may be different, at two frequencies of 500 Hz before and after the second resonance frequency, the phase difference of the second electrical signal may be 160° to 170°. In some embodiments, since the depth of the sound-emitting hole portion of the rear cavity may be different, at two frequencies of 700 Hz before and after the second resonance frequency, the phase difference of the second electrical signal may be 140° to 180°. In some embodiments, since the structure of the rear cavity may be different, the volumes are different, and at two frequencies of 700 Hz before and after the second resonance frequency, the phase difference of the second electrical signal may be 170° to 240°.

[0105] In some embodiments, as can be seen from FIG. 16, the second resonance frequency (the frequency corresponding to the resonance peak F) is 3 kHz to 5 kHz and is around 4 kHz. In some embodiments, at 3 kHz and 5 kHz, the phase difference of the second electrical signal may be within the range of 100° to 240°, for example, 138° to 160°. In some embodiments, since the volume of the rear cavity may be different, at 3.1 kHz and 4.8 kHz, the phase difference of the second electrical signal may be within the range of 120° to 140°, for example, 130° to 140°. In some embodiments, since the area of the sound-emitting hole portion of the rear cavity may be different, at 3.5 kHz and 4.5 kHz, the phase difference of the second electrical signal may be within the range of 160° to 170°, for example, 162° to 168°. In some embodiments, since the depth of the sound-emitting hole portion of the rear cavity may be different, at 3.8 kHz and 4.2 kHz, the phase difference of the second electrical signal may be within the range of 155° to 180°, for example, 160° to 170°.

[0106] As can be seen from FIG. 16, in some embodiments, the front cavity of the dual sound source (the first speaker) has a third resonance frequency (i.e., the frequency corresponding to the resonance peak G). When passing through the third resonance frequency, the sound wave radiated from the dual sound source has its phase inverted. Accordingly, when the single sound source is excited alone, the resonance peak (not shown) of the single sound source near the third resonance frequency is generated by the diaphragm of the inoperative dual sound source being used as a passive diaphragm, but the sound wave radiated from the single sound source near the third resonance frequency does not have its phase inverted. Therefore, in order to ensure that the sound wave radiated from the single sound source and the sound wave radiated from the dual sound source maintain opposite phases in the far field, it is necessary to compensate for the phase of the sound wave radiated from the single sound source. It is necessary to compensate the second electrical signal within the frequency band interval between two frequencies before and after the third resonance frequency. In some embodiments, at two frequencies before and after the third resonance frequency, the phase difference of the second electrical signal is 100° or more. In some embodiments, at two frequencies before and after the third resonance frequency, the phase difference of the second electrical signal may be 100° to 240°. In some embodiments, at two frequencies before and after the third resonance frequency, the phase difference of the second electrical signal may be 170° to 200°.

[0107] In some embodiments, at two frequencies 100 Hz before and after the third resonance frequency, the phase difference of the second electrical signal may be 175° to 185°. In some embodiments, since the dimensions of the front cavity may be different, at two frequencies 200 Hz before and after the third resonance frequency, the phase difference of the second electrical signal may be 170° to 200°. In some embodiments, since the volume of the front cavity may be different, at two frequencies 600 Hz before and after the third resonance frequency, the phase difference of the second electrical signal may be 150° to 180°. In some embodiments, since the area and / or depth of the sound-emitting hole portion of the front cavity may be different, at two frequencies 1000 Hz before and after the third resonance frequency, the phase difference of the second electrical signal may be 120° to 200°.

[0108] In some embodiments, as can be seen from FIG. 16, the third resonance frequency (the frequency corresponding to resonance peak G) is from 5 kHz to 8 kHz. In some embodiments, at 5 kHz and 8 kHz, the phase difference of the second electrical signal may be within the range of 100° to 200°, for example, 115° to 160°. In some embodiments, since the volume of the front cavity may be different, at 5.1 kHz and 7.5 kHz, the phase difference of the second electrical signal may be within the range of 110° to 150°, for example, 130° to 140°. In some embodiments, since the area of the sound-emitting hole portion of the front cavity may be different, at 5.4 kHz and 7 kHz, the phase difference of the second electrical signal may be within the range of 140° to 170°, for example, 150° to 159°. In some embodiments, since the depth of the sound-emitting hole portion of the front cavity may be different, at 5.8 kHz and 6 kHz, the phase difference of the second electrical signal may be within the range of 170° to 180°, for example, 170° to 176°.

[0109] By adjusting the amplitudes and phases at a plurality of frequencies of the second electrical signal driving a single sound source and / or the first electrical signal driving a dual sound source so that the second electrical signal and the first electrical signal have corresponding amplitude differences and phase differences, the sound pressure at the test microphone of the sound waves radiated from both the single sound source and the dual sound source is small, for example, close to zero, and Equation (1) holds.

[0110] FIG. 17 is a schematic diagram showing the directivity of the far-field radiation of the acoustic output device after the second electrical signal is adjusted according to some embodiments of the present specification. 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 a single sound source (the second speaker) can be adjusted to almost eliminate the output at the far-field position in a specific direction of the acoustic output device. At this time, the far-field radiation of the acoustic output device exhibits directivity. The 0° direction indicates the direction facing the ear canal opening of the user's ear of the acoustic output device. For example, it is the direction from the sound-emitting hole portion AS2 (e.g., the second hole portion) of the rear cavity of the acoustic output device to the sound-emitting hole portion AS1 (e.g., the first hole portion) of the front cavity (the direction X1 shown in FIG. 4). The 180° direction indicates the direction away from the ear canal opening of the user's ear of the acoustic output device. For example, it is the direction from the sound-emitting hole portion AS1 (e.g., the first hole portion) of the front cavity of the acoustic output device to the sound-emitting hole portion AS2 (e.g., the second hole portion) of the rear cavity (the direction X1' shown in FIG. 4). At a frequency of 1 kHz, the far-field radiation of the acoustic output device exhibits a heart-shaped directivity. The maximum point of the sound field is near 15°, and the minimum point is near 180°. 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. The maximum point of the sound field is near 15°, and the minimum point is near 200°. The absolute value of the sound pressure level difference 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. The maximum point of the sound field is near 15°, and the minimum point is near 190°. The absolute value of the sound pressure level difference 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. The maximum point of the sound field is near 30°, and the minimum point is near 200°. The absolute value of the sound pressure level difference 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 side lobes. The direction of the main lobe (i.e., the direction of the maximum value of the sound field) is around 40°, the direction of the side lobes is around 200°, there are minima between the side lobes and the main lobe, and the directions of the minima are around 150° and 250° respectively. The absolute values of the sound pressure level differences between the maxima of the two minima are 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 side lobes. The direction of the main lobe (i.e., the direction of the maximum value of the sound field) is around 10°, the direction of the side lobes is around 200°, there are minima between the side lobes and the main lobe, and the directions of the minima are around 160° and 240° respectively. The absolute values of the sound pressure level differences between the maxima of the two minima are 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 directivity directions of the far-field radiation of the acoustic output device are the directions from 180° and the directions near it to 0° and the directions near it, that is, the direction from the sound emission hole portion AS2 (e.g., the second hole portion) of the rear cavity of the acoustic output device to the sound emission hole portion AS1 (e.g., the first hole portion) of the front cavity (the direction X1 shown in FIG. 4) and the directions near it.

[0111] Figures 18A and 18B are directivity test curve diagrams of an acoustic output device according to some embodiments of this specification. The test signal used in Figure 18A is a white noise signal, and the test signal used in Figure 18B is a sweep signal. The frequency ranges of the white noise signal and the sweep signal are set to 1 kHz to 4 kHz to measure the directivity within the 1 kHz to 4 kHz frequency range of the acoustic output device. 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 time. The white noise signal can simulate complex signal outputs. The sweep signal may be a signal that gradually changes from 1 kHz to 4 kHz. The sweep signal is a signal that includes only a single frequency at any time. The sweep signal can simulate simple signal inputs. As shown in Figures 18A and 18B, the dotted line indicates the frequency response curve in the 0° direction of the acoustic output device, and the solid line indicates the frequency response curve in the 180° direction of the acoustic output device. 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 emission hole portion (for example, the first hole portion) of the front cavity (for example, a location 10 cm away from the sound emission hole portion of the front cavity). 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 emission hole portion (for example, the second hole portion and / or the third hole portion) of the rear cavity (for example, a location 10 cm away from the sound emission hole portion of the rear cavity). In some embodiments, the test microphone, the sound emission hole portion of the front cavity, and the sound emission hole portion of the rear cavity are on the same straight line, and this straight line is the straight line in 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 sound pressure level difference between the 0° direction and the 180° direction of the acoustic output device is 8 dB to 18 dB, and the acoustic 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 sound pressure level difference between the 0° direction and the 180° direction of the acoustic output device is 15 dB to 25 dB, and the acoustic output device has better heart-shaped directivity.

[0112] Note that the above content is for the case where adjustment is performed only on the second electrical signal. In some embodiments, corresponding adjustment may be performed only on the first electrical signal. In some embodiments, corresponding adjustment may be performed on both the first electrical signal and the second electrical signal. Hereinafter, taking the adjustment of the second electrical signal as an example, a specific method for adjusting the electrical signal will be described.

[0113] FIG. 19 is a schematic diagram of an equivalent model obtained by adjusting an acoustic output device according to a preset algorithm in some embodiments of this specification. As shown in FIG. 19, in some embodiments, the acoustic output device may further include a modulator, and the modulator can modulate a second electrical signal for driving a second speaker according to a preset algorithm, so that within a target frequency range, the third sound wave output by the second speaker, the first sound wave output by the first speaker, and the second sound wave are superimposed and canceled 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 a pair of opposite directions of the acoustic output device is not less than a preset sound pressure level threshold (for example, the sound pressure at the far-field position in a specific direction of the acoustic output device is small, for example, close to zero). In some embodiments, the preset algorithm may include a preset amplitude modulation method, a preset frequency (phase) modulation method, and other preset amplitude-frequency adjustment methods. For more content regarding amplitude modulation and phase modulation, refer to the related description in FIG. 21, and the description is omitted here.

[0114] In some embodiments, the principle of FIG. 19 is similar to the principle shown in FIG. 14, and a preset algorithm (for example, the modulation function H0 of the modulator) for modulating the second electrical signal is determined based on the sound pressure measured by a test microphone installed at a far-field position in a specific direction of the acoustic output device. When the acoustic output device operates, the modulator can directly modulate the second electrical signal according to a preset algorithm.

[0115] In some embodiments, the signal Music may include a first electrical signal that drives a first speaker and a second electrical signal that drives a second speaker. The first speaker and the second speaker can each receive the first electrical signal and the second electrical signal in the signal Music and output sound into space. The test microphone is installed at a far-field position in a specific direction of the acoustic output device and measures the sound pressure of the sound at that position. When the sound pressure signal received by the test microphone is zero, it indicates that the sound pressure of the sound 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 above-mentioned acoustic output device) (i.e., the sound after the first sound wave, the second sound wave, and the third sound wave are superimposed) is zero, that is, Music·H1+Music·H0·H2=0 (3)

[0116] where H1 and H2 respectively represent the transfer function that transmits the sound waves (the first sound wave, the second sound wave) generated from the first speaker to the test microphone and the transfer function that transmits 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.

[0117] By turning off the second speaker, the transfer function H1 (the first transfer function) of the first speaker can be measured, H1 = Mic′ / Music′ (4) where Music′ represents the signal (the 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.

[0118] Similarly, by turning off the first speaker, the transfer function H2 (the second transfer function) of the second speaker can be measured, H2=(Mic″) / (Music″) (5)

[0119] In the formula, Music″ represents the signal (the second electrical signal) input when turning off the first speaker, and Mic″ represents the sound pressure signal received by the test microphone when turning off the first speaker.

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

[0121]

Number

[0122] Thereby, for different frequencies, based on the above-mentioned formula (6), the transfer function H0 of the modulator is determined, and by applying the set modulator to the acoustic output device, the acoustic output device can achieve the sound leakage reduction effect at different frequencies. In some alternative embodiments, when there are multiple test microphones, the voices output at any position in space by the first speaker and the second speaker can be measured or simulated. Therefore, at least one pair of test microphones installed in at least one pair of opposite directions can measure the difference in sound pressure levels in at least one pair of opposite directions of the far-field radiated sound of the acoustic output device. According to different frequencies, by adjusting the transfer function of the modulator based on formulas (3) to (6), the difference in sound pressure levels in at least one pair of opposite directions of the far-field radiated sound of the acoustic output device can be not less than a preset sound pressure level threshold.

[0123] In some embodiments, the test microphone may include a microphone array, and the microphone array can measure the voice at the far-field position in a specific direction of the acoustic output device, thereby improving the accuracy of the measurement data.

[0124] FIG. 20 is a schematic diagram of an equivalent model obtained by adjusting an acoustic output device according to an active algorithm in some embodiments of the present specification. 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 installed in the housing of the acoustic output device. The microphone array may estimate an audio signal at a preset position. The preset position may include a far-field position in a specific direction of the acoustic output device. In some embodiments, the preset position may include far-field positions in at least a pair of opposite directions of the acoustic output device. In some embodiments, the controller can determine an active algorithm (for example, an amplitude-frequency active adjustment method) based on the audio signal collected by the microphone array, and the modulator can dynamically modulate a second electrical signal for driving a second speaker based on the active algorithm (for example, 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, the first sound wave output by the first speaker, and the second sound wave are superimposed and canceled 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 a pair of opposite directions of the acoustic output device is equal to or greater than a preset sound pressure level threshold, thereby realizing the directivity of the far-field radiation of the acoustic output device.

[0125] In some embodiments, after the acoustic 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] changes to, and the transfer function corresponding to the second speaker changes from an initial value H2 to

[0128]

Number

[0129] changes to correspond to different users

[0130]

Number

[0131] and

[0132]

Number

[0133] may be different. Accordingly, the above-described formula (3) can be expressed as follows.

[0134]

Number

[0135] In some embodiments, the variable

[0136]

Number

[0137] and

[0138]

Number

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

[0140]

Number

[0141] In the method described in FIG. 20, based on the collected sound waves, H0 can be adjusted in real time to achieve the effect of reducing sound leakage in real time, so that 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 not less than a preset sound pressure level threshold value, realizing the directivity of the far-field radiation of the acoustic output device.

[0142] In some embodiments, for acoustic output devices with different structures, since the transfer functions H1 of the corresponding first speaker and H2 of the second speaker are also different, the adjustment method of the transfer function H0 of the corresponding modulator may also be different. For example, when the first speaker and the second speaker are installed in the same cavity and when they are not installed, the corresponding adjustment methods may be different. Also, for example, when the distance between the sound-emitting hole portion (for example, the second hole portion 912) of the rear cavity of the first speaker and the sound-emitting hole portion (for example, the third hole portion 913) of the second speaker is different, the corresponding adjustment methods may be different. Further, for example, when the acoustic resistance at the sound-emitting hole portion (for example, the first hole portion 911, the second hole portion 912, the third hole portion 913, etc.) is different, the corresponding adjustment methods may be different.

[0143] FIG. 21 is a schematic block diagram of an amplitude-phase adjustment algorithm according to some embodiments of the present specification. As shown in FIG. 21, taking the adjustment of the second electrical signal driving the second speaker as an example, the input signal includes an initial first electrical signal and an initial second electrical signal. The initial first electrical signal and the initial second electrical signal are input to the first speaker and the second speaker respectively. The first speaker and the second speaker vibrate respectively to generate sound waves, which are superimposed on each other. The transfer function H0 of the modulator can be determined according to the principle shown in FIG. 19 and / or FIG. 20. Based on the transfer function H0, the amplitude adjustment value and the phase adjustment value of the initial second electrical signal can be determined. In some embodiments, the amplitude of the initial second electrical signal can be adjusted by a filter. In some embodiments, an infinite impulse response (IIR) filter can be selected as the filter. The IIR filter has a small computational amount and excellent real-time performance. In some embodiments, a finite impulse response (FIR) filter can be selected as the filter. The FIR filter has high stability, controllable phase, can perform amplitude selection, and can synchronously output the synchronously input signal, and can avoid signal distortion. In some embodiments, the phase of the initial second electrical signal can be adjusted by a phase shifter. 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 may be performed synchronously, or either one may be performed first and the other later. The adjusted second electrical signal is output as an output signal together with the initial first electrical signal. The sound wave generated from the second speaker driven by the adjusted second electrical signal can cancel out the sound wave generated from the first speaker driven by the initial first electrical signal at the target position (for example, the far-field position in a specific direction of the acoustic output device), so that 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 not less than a preset sound pressure level threshold (for example, not less than 6 dB), and the directivity of the acoustic output device is realized.

[0144] Although the basic concepts have been described above, it is clear to those skilled in the art that the above detailed disclosure is merely presented as an example and does not limit the present application. Although not explicitly described in this specification, those skilled in the art can make various changes, improvements, and modifications to the present application. Since these changes, improvements, and modifications are intended to be suggested by the present application, they are within the spirit and scope of the exemplary embodiments of the present application.

[0145] Furthermore, specific terms are used in the present application to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" mean specific features, structures, or characteristics related to at least one embodiment of the present application. Therefore, it should be emphasized and understood that two or more references to "an embodiment" or "one embodiment" or "one alternative embodiment" in different parts of this specification do not necessarily refer to the same embodiment. Also, specific features, structures, or characteristics in one or more embodiments of the present application may be appropriately combined.

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

[0147] In some embodiments, numbers are used to describe the number of components and attributes, and it should be understood that the numbers for describing such embodiments are modified by the modifiers "about", "substantially" or "generally" in some examples. Unless otherwise specified, "about", "substantially" or "generally" indicate that the above numbers are allowed a variation of ±20%. Therefore, in some embodiments, the numerical parameters used in the specification and claims are all approximate values that can vary according to the characteristics required by a specific embodiment. In some embodiments, for numerical parameters, the specified number of significant digits should be considered and the normal rounding method should be applied. In some embodiments of the present application, the numerical ranges and parameters for determining the range are approximate values, but in specific embodiments, such numbers are set as accurately as possible.

[0148] All patents, patent applications, published patent gazettes, and other materials such as papers, books, specifications, publications, documents, etc. referred to in the present application are incorporated herein by reference in their entirety, except for those application process documents that do not match or conflict with the content of the present application and those documents that may have a limited impact on the broadest scope of the claims of the present application (currently or later related to the present application). In addition, if the descriptions, definitions, and / or uses of terms in the attached materials of the present application do not match or conflict with the content described in the present application, the descriptions, definitions, and / or uses of terms in the present application shall take precedence.

[0149] Finally, it should be understood that the embodiments described in the present application are merely for explaining the principles of the embodiments of the present application. Other variations may also be within the scope of the present application. Therefore, without limitation, by way of example, alternative configurations of the embodiments of the present application may be considered to be in accordance with the teachings of the present application. Thus, the embodiments of the present application are not limited to the embodiments clearly introduced and described in the present application.

Description of Reference Numerals

[0150] 100 Acoustic output device 110 Housing 111 First hole 112 Second hole portion 120 Speaker 130 Front cavity 140 Rear cavity 521 First diaphragm 551 Second diaphragm 614 Partition plate

Claims

1. An acoustic output device, comprising: a housing; a first speaker installed in the housing, acoustically coupled to a first hole portion and a second hole portion of the housing respectively, driven by a first electrical signal, and outputting a first sound wave and a second sound wave having a phase difference from the first hole portion and the second hole portion respectively; a second speaker installed in the housing, driven by a second electrical signal, and outputting a third sound wave; An acoustic output device, wherein within a target frequency range, the first sound wave, the second sound wave, and the third sound wave overlap with each other, so that the far-field radiation of the acoustic output device exhibits directivity.

2. The first speaker includes a first diaphragm, and in the housing, a front cavity and a rear cavity are respectively installed corresponding to the front side and the rear side of the first diaphragm. The front cavity and the rear cavity are acoustically coupled to the first hole portion and the second hole portion respectively. The second speaker is installed in the rear cavity and outputs the third sound wave from the second hole portion acoustically coupled to the rear cavity. The acoustic output device according to claim 1.

3. The first speaker includes a first diaphragm, and in the housing, a front cavity and a rear cavity are respectively installed corresponding to the front side and the rear side of the first diaphragm. The front cavity and the rear cavity are acoustically coupled to the first hole portion and the second hole portion respectively. A third hole portion is installed in the housing, and the second speaker outputs the third sound wave from the third hole portion. The distance from the third hole portion to the second hole portion acoustically coupled to the rear cavity is greater than 0 mm and less than or equal to 10 mm. The acoustic output device according to claim 1.

4. The acoustic output device according to claim 2 or 3, further comprising a modulator for modulating the second electrical signal for driving the second speaker according to a preset amplitude-frequency adjustment method.

5. A microphone array for estimating an audio signal at a preset position is installed in the housing. The acoustic output device further includes a modulator, and the modulator modulates the second electrical signal for driving the second speaker based on the audio signal collected by the microphone array. The acoustic output device according to claim 2 or 3.

6. In the range of 100 Hz to 800 Hz, the difference between the sound pressure level of the second sound wave output from the first speaker through the second hole and the sound pressure level of the third sound wave output from the second speaker through the second hole or the third hole is 6 dB or more. The acoustic output device according to claim 2 or 3.

7. The second speaker has a first resonance frequency, the rear cavity has a second resonance frequency, and between the first resonance frequency and the second resonance frequency, the phase difference between the second electrical signal and the first electrical signal is 150° or more. The acoustic output device according to claim 2 or 3.

8. The frequency band between the first resonance frequency and the second resonance frequency includes the range of 1 kHz to 4 kHz. The acoustic output device according to claim 7.

9. At a frequency of 1 kHz, the phase difference between the second electrical signal and the first electrical signal is 200° or more, and at a frequency of 4 kHz, the phase difference between the second electrical signal and the first electrical signal is 150° or more. The acoustic output device according to claim 8.

10. The second speaker outputs the third sound wave from the second hole or the third hole, the rear cavity has a second resonance frequency, and at two frequencies before and after the second resonance frequency, the phase difference of the second electrical signal is 100° or more. The acoustic output device according to claim 2 or 3.

11. The second resonance frequency is in the range of 3 kHz to 5 kHz, and at the frequencies of 3 kHz and 5 kHz, the phase difference of the second electrical signal is in the range of 100° to 240°. The acoustic output device according to claim 10.

12. At the frequencies of 3 kHz and 5 kHz, the phase difference of the second electrical signal is in the range of 138° to 160°. The acoustic output device according to claim 11.

13. The front cavity has a third resonance frequency, and at two frequencies before and after the third resonance frequency, the phase difference of the second electrical signal is 100° or more. The acoustic output device according to claim 2 or 3.

14. The third resonance frequency is in the range of 5 kHz to 8 kHz, and at the frequencies of 5 kHz and 8 kHz, the phase difference of the second electrical signal is within the range of 100° to 200°. The acoustic output device according to claim 13.

15. At the frequencies of 5 kHz and 8 kHz, the phase difference of the second electrical signal is within the range of 115° to 160°. The acoustic output device according to claim 14.

16. The directivity is expressed such that the absolute value of the difference in sound pressure levels in at least one pair of opposite directions of the far-field radiated sound of the acoustic output device is equal to or greater than a preset sound pressure level threshold. The acoustic output device according to claim 1.

17. The directivity is expressed such that the absolute value of the difference in sound pressure levels in at least one pair of opposite directions of the far-field radiated sound of the acoustic output device is 6 dB or more. The acoustic output device according to claim 16.

18. The at least one pair of opposite directions includes a pair of opposite directions corresponding to the line connecting the first hole portion and the second hole portion. The acoustic output device according to claim 16.

Images