Acoustic output device

Abstract

Acoustic output device, comprising: a case; a first loudspeaker arranged in the housing, the first loudspeaker comprising a first diaphragm, wherein a first front chamber and a first rear chamber are provided on a front and a rear side of the first diaphragm, respectively, wherein the first front chamber and the first rear chamber are acoustically coupled to a first perforation section and a second perforation section in the housing, respectively, and wherein the first loudspeaker, driven by a first electrical signal via the first perforation section and the second perforation section, emits a first sound wave and a second sound wave, respectively, between which there is a phase difference; and a second loudspeaker arranged in the housing, wherein the second loudspeaker comprises a second diaphragm, wherein a second front chamber or a second rear chamber is provided on a front or rear side of the second diaphragm, wherein the second front chamber is acoustically coupled to the second hole section in the housing, and wherein the second loudspeaker emits a third sound wave under the drive of a second electrical signal via the second hole section.

Description

Cross-reference

[0001] The present utility model claims priority over the Chinese patent application filed on November 21, 2022, with application number 202211455122.0. Technical field

[0002] The present description concerns the field of acoustics, in particular an acoustic output device. State of the art

[0003] To solve the problem of sound loss in acoustic output devices, two or more sound sources are typically used, emitting two acoustic signals with opposite phases. Under far-field conditions, the sound path difference between the two sound sources with opposite phases to a point in the far field is generally negligible, allowing the two acoustic signals to cancel each other out and reduce sound loss in the far field. While this can reduce sound loss to some extent, certain limitations exist. For example, due to the shorter wavelength of high-frequency sound, the distance between the two sound sources is not negligible compared to the wavelength under far-field conditions, meaning that the sound signals emitted by the two sources cannot cancel each other out.Another example is that when an acoustic transmission structure of the acoustic output device is at resonance, the sound signals actually emitted from a sound outlet of the acoustic output device exhibit a certain phase difference from the original phase at the point of sound wave generation, and additional resonance peaks are added to the transmitted sound waves. This leads to a chaotic sound field distribution, makes it more difficult to ensure the reduction of sound losses at high frequencies in the far field, and could even increase sound losses.

[0004] Therefore, it is desirable to provide an acoustic output device with good sound field directional characteristics. Disclosure of the invention

[0005] Exemplary embodiments of the present description provide an acoustic output device. It comprises a housing; a first loudspeaker arranged in the housing, wherein the first loudspeaker is acoustically coupled to a first perforated section and a second perforated section on the housing, and wherein the first loudspeaker, driven by a first electrical signal via the first perforated section or the second perforated section, emits a first sound wave or a first sound wave, respectively.a second sound wave, between which there is a phase difference; and a second loudspeaker arranged in the housing, wherein the second loudspeaker, driven by a second electrical signal, emits a third sound wave, wherein in a target frequency range the first sound wave, the second sound wave and the third sound wave superimpose on each other, such that the far-field radiation of the acoustic output device has a directional characteristic.

[0006] In some embodiments, the first loudspeaker comprises a first diaphragm, wherein a front chamber and a rear chamber are provided inside the housing in front of and behind the first diaphragm respectively, the front chamber and the rear chamber being acoustically coupled to the first hole section and the second hole section respectively; and the second loudspeaker is arranged in the rear chamber, the second loudspeaker emitting the third sound wave via the second hole section acoustically coupled to the rear chamber.

[0007] In some embodiments, the first loudspeaker comprises a first diaphragm, wherein a front chamber and a rear chamber are provided inside the housing in front of and behind the first diaphragm, respectively, the front chamber and the rear chamber being acoustically coupled to the first perforation section and the second perforation section, respectively; that a third perforation section is provided on the housing through which the second loudspeaker emits the third sound wave; and that the distance from the third perforation section to the second perforation section acoustically coupled to the rear chamber is greater than 0 mm and not greater than 10 mm.

[0008] In some embodiments, the acoustic output device further comprises a modulator which modulates the second electrical signal driving the second loudspeaker according to a preset adjustment method for amplitudes and frequencies.

[0009] In some embodiments, a microphone array is provided on the housing for estimating a sound signal at a preset position, the acoustic output device further comprising a modulator which modulates the second electrical signal driving the second loudspeaker based on the sound signal detected by the microphone array.

[0010] In some embodiments, it is provided that in the range of 100 Hz to 800 Hz the difference between the sound pressure level of the second sound wave emitted by the first loudspeaker at the second hole section and the sound pressure level of the third sound wave emitted by the second loudspeaker at the second hole section or the third hole section is not less than 6 dB.

[0011] In some embodiments, the second loudspeaker has a first resonant frequency and the rear chamber has a second resonant frequency, wherein the phase difference between the second electrical signal and the first electrical signal is not less than 150° between the first resonant frequency and the second resonant frequency.

[0012] In some embodiments, the frequency range between the first resonant frequency and the second resonant frequency covers a range from 1 kHz to 4 kHz.

[0013] In some embodiments, it is provided that at a frequency point of 1 kHz the phase difference between the second electrical signal and the first electrical signal is not less than 200°; and that at a frequency point of 4 kHz the phase difference between the second electrical signal and the first electrical signal is not less than 150°.

[0014] In some embodiments, it is provided that the second loudspeaker outputs the third sound wave via the second hole section or the third hole section, wherein the rear chamber has a second resonant frequency, and wherein at two frequency points before and after the second resonant frequency the phase difference of the second electrical signal is not less than 100°.

[0015] In some embodiments, the second resonant frequency is provided to be between 3 kHz and 5 kHz, and the phase difference of the second electrical signal between the frequency points of 3 kHz and 5 kHz is in a range of 100° to 240°.

[0016] In some embodiments, the phase difference of the second electrical signal between the frequency points of 3 kHz and 5 kHz is provided to be in a range of 138° to 160°.

[0017] In some embodiments, the front chamber is provided to have a third resonant frequency, wherein at two frequency points before and after the third resonant frequency the phase difference of the second electrical signal is not less than 100°.

[0018] In some embodiments, the third resonant frequency is provided to be between 5 kHz and 8 kHz, with the phase difference of the second electrical signal between the frequency points of 5 kHz and 8 kHz being in a range of 100° to 200°.

[0019] In some embodiments, the phase difference of the second electrical signal between the frequency points of 5 kHz and 8 kHz is provided to be in a range of 115° to 160°.

[0020] In some embodiments, the directional characteristic is manifested as follows: the absolute value of the sound pressure level difference of the far-field radiation of the acoustic output device in at least one pair of opposite directions is not less than a preset sound pressure level threshold.

[0021] In some embodiments, the directional characteristic is manifested as follows: the absolute value of the sound pressure level difference of the far-field radiation of the acoustic output device in at least one pair of opposite directions is not less than 6 dB.

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

[0023] The present description is further illustrated by exemplary embodiments, which are described in detail by the accompanying drawings. These embodiments are not limiting. In the embodiments, the same structure is designated with the same reference numeral. These show: Fig. 1 a schematic representation of the position of an acoustic output device according to some embodiments of the present description relative to the user's ear; Fig. 2A a schematic representation of the sound pressure level sound field distribution of the acoustic output device according to Fig. 1 at medium-low frequencies; Fig. 2B a schematic representation of the sound pressure level sound field distribution of the acoustic output device according to Fig. 1 at high frequencies; Fig. 3 a representation of the frequency response curve of the acoustic output device according to Fig. 1; Fig. 4 a schematic representation of the directional characteristic according to some embodiments of the present description; Fig. Figures 5A to 5D each show a schematic structural view of the acoustic output device comprising a first loudspeaker and a second loudspeaker arranged in various ways, according to some embodiments described in the present description; Fig. 6 a schematic representation of the relationship between the resonance frequency of a common cavity and its volume according to some embodiments of the present description; Fig. 7 a schematic representation of the relationship between the resonance frequency of the common cavity and the area of ​​an acoustically coupled hole section according to some embodiments of the present description; Fig. 8 a schematic representation of the relationship between the resonance frequency of a closed cavity and its volume according to some embodiments of the present description; Fig. 9 a schematic structural view of the acoustic output device according to some other embodiments of the present description; Fig. 10A to 10D each show a schematic representation of the acoustic output device with different arrangements of sound outlet hole sections according to some embodiments of the present application description; Fig. 11A to 11D each show a schematic representation of the directional characteristic of the far-field radiation of the in Fig. acoustic output devices shown in 10A to 10D; Fig. 12A and Fig. 12B each a schematic representation of the directional characteristic of the far-field radiation of the acoustic output device with exemplary arrangement positions of hole sections according to some embodiments of the present description; Fig. 13 a schematic representation of another acoustic output device according to some embodiments of the present description; Fig. 14 a schematic representation of the acoustic transmission in the acoustic output device which is provided with a second loudspeaker, according to some embodiments of the present description; Fig. 15 a schematic exemplary flowchart of the adaptation of a second electrical signal according to some embodiments of the present description; Fig. 16 a schematic representation of the frequency response curves when excited separately by a single sound source or by a dual sound source according to some embodiments of the present description; Fig. 17 a schematic representation of the directional characteristic of the far-field radiation of the acoustic output device after adjustment of the second electrical signal according to some embodiments of the present description; Fig. 18A and Fig. 18B each a representation of the directional characteristic measurement curves of the acoustic output device according to some embodiments of the present description; Fig. 19 a schematic representation of an equivalent model of the adaptation of the acoustic output device according to some embodiments of the present description using a preset algorithm; Fig. 20 a schematic representation of an equivalent model of the adaptation of the acoustic output device according to some embodiments of the present description using an active algorithm; and Fig. 21 a schematic block diagram of an amplitude-phase matching algorithm according to some embodiments of the present description. Detailed descriptions

[0024] To further explain the technical solutions of the embodiments described in this document, the drawings required for describing these embodiments are briefly summarized below. Naturally, the following drawings merely represent some examples or embodiments of the present description, and a person skilled in the art can apply the present description to other similar scenarios based on these drawings without inventive step. Unless otherwise stated or understood from the context, the same reference numerals in the figures represent the same structures or operations.

[0025] It is understood that the terms "system," "device," "unit," and / or "module," as used herein, are a method for distinguishing between different components, elements, parts, or assemblies at different levels. However, where other words can serve the same purpose, these terms may be substituted.

[0026] As shown in the present description and in the claims, the terms "a" and / or "the" need not necessarily refer to the singular form, but may also include the plural form unless clearly indicated otherwise in the context. In general, the expressions "comprise" and "contain" only indicate that the specifically identified steps and elements are included, that these steps and elements do not constitute an exclusive list, and that further steps or elements may be included in the method or apparatus.

[0027] In this description, flowcharts are used to illustrate the processes performed by the system according to the embodiments described. It should be understood that preceding or subsequent processes do not necessarily have to be performed exactly in the order shown. Rather, the individual steps can be processed in reverse order or concurrently. Furthermore, additional processes can be added to these processes, or one or more steps can be removed from them.

[0028] In some embodiments, to solve the problem of sound loss in acoustic output devices, two sound sources with opposite phases can be used to emit two sound signals with opposite phases. Under far-field conditions, the sound path difference of the two sound sources with opposite phases to a point in the far field is generally negligible, so that the two sound signals can cancel each other out, thus reducing sound loss in the far field.

[0029] Fig. Figure 1 shows a schematic representation of the position of an acoustic output device according to some embodiments of the present description relative to the user's ear. As in Fig. As shown in Figure 1, the acoustic output device 100 can comprise a housing 110 and a loudspeaker 120. The loudspeaker 120 can be arranged in a cavity formed by the housing 110. The loudspeaker 120 comprises a diaphragm (not shown). Within the chamber of the housing 110, a front chamber 130 and a rear chamber 140, respectively, are provided in front of and behind the diaphragm, respectively, for sound radiation. A first perforated section 111 and a second perforated section 112 are provided on the housing 110. The front chamber 130 can be acoustically coupled to the first perforated section 111, and the rear chamber 140 can be acoustically coupled to the second perforated section 112.When the loudspeaker 120 emits sound waves, the sound wave in front of the diaphragm (also referred to as the first sound wave) can be emitted from the first hole section 111 via the front chamber 130, while the sound wave behind the diaphragm (also referred to as the second sound wave) can be emitted from the second hole section 112 via the rear chamber 140. In this case, the first hole section 111 and the second hole section 112 can be considered a group of two sound sources capable of emitting two sound signals with the same amplitude but opposite phases. For clarity, in some embodiments of this description, the front of the diaphragm refers to the side of the diaphragm facing away from a magnetic circuit arrangement (not shown); the back of the diaphragm refers to the side of the diaphragm facing the magnetic circuit arrangement.Of course, in certain scenarios the front and back of the membrane can be reversed, that is, the side of the membrane facing away from the magnetic circuit arrangement can be considered the back, while the side facing away from the membrane of the magnetic circuit arrangement can be considered the front.

[0030] In some embodiments, the acoustic output device 100 can be positioned near the user's ear when a user wears or uses the acoustic output device 100, as shown in Fig. Figure 1 shows the first hole section 111 facing the user's ear canal opening 201, so that the sound transmitted by the first hole section 111 can be directed towards the user's ear canal. The second hole section 112 can be located further away from the ear canal opening 201 relative to the first hole section 111, with the distance between the first hole section 111 and the ear canal opening being smaller than the distance between the second hole section 112 and the ear canal opening.

[0031] In some embodiments, when the loudspeaker 120 vibrates, its front and rear surfaces can each function as sound wave-generating structures, producing sound waves with the same amplitude but opposite phases. In some embodiments, these sound waves with the same amplitude and opposite phases can be radiated outwards via the first perforated section 111 and the second perforated section 112, respectively, thus forming two sound sources. These two sound sources can interfere at a point in space (e.g., in the far field) and cancel each other out, effectively improving the problem of far-field sound loss of the acoustic output device 100.

[0032] Fig. Figure 2A shows a schematic representation of the sound pressure level sound field distribution of the acoustic output device according to Fig. 1 at medium-low frequencies. As in Fig. As shown in Figure 2A, the sound field distribution of the acoustic output device 100 exhibits good dual-source directional characteristics in the mid-low frequency range (e.g., 50 Hz–1 kHz), thereby significantly reducing sound losses. This means that in the mid-low frequency range, the two sound sources formed by the first perforation section 111 and the second perforation section 112 of the acoustic output device 100 emit sound waves with opposite phases (i.e., the first sound wave and the second sound wave). The sound field forms a distribution in space with two petal-shaped structures. The sound pressure level is higher in the two opposite directions along the line connecting the two sound sources, while the sound pressure level is lower in a direction perpendicular to the line connecting the two sound sources.However, one of the two petal-shaped structures is located far from the user's ear in the sound field, resulting in greater sound loss and impairing the effectiveness of the acoustic output device's sound loss reduction.

[0033] In some embodiments, the wavelength of the first and second sound waves is relatively short in the higher frequency range, meaning that the distance between the two sound sources formed by the first hole section 111 and the second hole section 112 is not negligible compared to the wavelength. For example, the distance between the first hole section 111 and the second hole section 112 can cause the sound paths of the first and second sound waves to a point in space (e.g., in the far field) to be different. This reduces the phase difference between the first and second sound waves at this point in space (e.g., with the same or similar phase), so that the first and second sound waves cannot interfere destructively at this point in space, but may instead superimpose and increase the amplitude of the sound wave at this point.In some embodiments, the shading of high-frequency sound waves by structures such as the auricle 210 and / or the influence of reflected sound waves can also lead to a chaotic sound field distribution of the acoustic output device 100.

[0034] In some embodiments, different structures and parameters (e.g., volume) of the front chamber 130 and the rear chamber 140 result in the front chamber 130 and the rear chamber 140 exhibiting different resonant frequencies. In some embodiments, the front chamber 130 and / or the rear chamber 140 may additionally be provided with a special acoustic structure (e.g., a sound-conducting tube) to adjust the resonant frequency. When sound waves resonate in the front chamber 130 and / or the rear chamber 140, this can change the frequency components of the sound waves transmitted in the front chamber 130 and / or the rear chamber 140 (e.g., adding additional resonance peaks to the transmitted sound waves) or change the phase of the transmitted sound waves.Compared to the non-resonant state, the phase and / or amplitude of the sound waves emitted by the first hole section 111 and / or the second hole section 112 change. These changes in phase and / or amplitude can lead to a chaotic sound field of the dual sound source in the high-frequency range and impair the destructive interference of the sound waves emitted by the first hole section 111 and the second hole section 112 at a point in space. For example, at resonance, the phase difference of the sound waves emitted by the first hole section 111 and the second hole section 112 can change. If the phase difference of the sound waves emitted by the first hole section 111 and the second hole section 112 is small (e.g., less than 120°, less than 90°, or 0°, etc.), the destructive interference of the sound waves at the point in space is weakened, making it more difficult to reduce sound losses.In another case, sound waves with a small phase difference can superimpose at a point in space and increase the sound wave amplitude near the resonance frequency at that point (e.g., in the far field), thereby amplifying the far-field sound losses of the acoustic output device 100. As a further example, resonance can increase the amplitude of the transmitted sound waves near the resonance frequency of the acoustic transmission structure (e.g., in the form of a resonance peak near the resonance frequency), resulting in a chaotic sound field of the dual sound source near the resonance frequency. In this case, the amplitudes of the sound waves emitted by the first hole section 111 and the second hole section 112 differ considerably, which weakens the destructive interference of the sound waves at the point in space and makes it more difficult to reduce sound losses.

[0035] Fig. Figure 2B shows a schematic representation of the sound pressure level sound field distribution of the acoustic output device according to Fig. 1 at high frequencies. Fig. Figure 3 shows a representation of the frequency response curve of the acoustic output device according to Fig. 1. As in Fig. As shown in Figure 2B, in the higher frequency range the sound signal emitted outwards by the second hole section 112 of the acoustic output device 100 dominates the entire sound field distribution, and the sound field distribution is relatively chaotic. There is a certain difference between the actual emitted sound wave amplitude / phase of the second hole section 112 of the acoustic output device 100 and the original amplitude / phase of the sound waves emitted by the loudspeaker 120. This results in the two sound waves emitted by the first hole section 111 and the second hole section 112 not reducing the sound losses at certain positions in the far field, but rather amplifying them.

[0036] As in Fig. As shown in Figure 3, curve L3 represents the frequency response curve diagram of the front chamber 130 (e.g., at the first hole section 111) of the acoustic output device 100, and curve L3' represents the frequency response curve diagram of the rear chamber 140 (e.g., at the second hole section 112) of the acoustic output device 100. Fig. Figure 3 shows that in the high-frequency range, the front chamber 130 of the acoustic output device 100 (with a resonance peak at approximately 6 kHz) and the rear chamber 140 (with a resonance peak at approximately 4 kHz) exhibit significantly different resonance peaks. Comparing curves L3 and L3' reveals that the output volume of the front and rear chambers of the acoustic output device 100 is approximately equal in the mid-low frequency range (e.g., 50 Hz–1500 Hz), resulting in a good reduction of sound losses. However, in the high-frequency range (e.g., 1500 Hz–20 kHz), the output volumes of the front and rear chambers differ considerably, and the reduction of sound losses is significantly diminished. In conjunction with Fig. 2B and Fig. Figure 3 shows that in the high-frequency range, the dual sound source sound field distribution is relatively chaotic, may not be able to reduce far-field sound losses, and could even increase them. In some embodiments, the dual sound source sound field distribution can be adjusted by modifying the structure of the acoustic output device 100 to obtain a well-directed sound field and thereby improve the problem of increased far-field sound losses of the acoustic output device 100.

[0037] In some embodiments, a second loudspeaker can be provided in the acoustic output device, such that the sound waves of the second loudspeaker and the sound waves generated by the loudspeaker 120 (also referred to as the first loudspeaker) cancel each other out. This can suppress the sound field chaos of the dual sound source structure (e.g., in the high-frequency range) and reduce or eliminate the sound losses of the acoustic output device in the far field. In some embodiments, the acoustic output device can comprise a housing, a first loudspeaker, and a second loudspeaker. The first loudspeaker is arranged in the housing and acoustically coupled to two perforated sections on the housing (e.g., the first perforated section and the second perforated section) to output a first sound wave and a second sound wave with a phase difference, respectively.In some embodiments, the first loudspeaker comprises a first diaphragm. A first front chamber and a first rear chamber are provided in the housing in front of and behind the first diaphragm, respectively. The first front chamber and the first rear chamber are acoustically coupled to one of the two perforated sections (e.g., a first perforated section and a second perforated section) to output the first sound wave and the second sound wave with a phase difference, respectively. In some embodiments, the first loudspeaker, driven by a first electrical signal, can output the first sound wave and the second sound wave with a phase difference via the two perforated sections (e.g., the first perforated section and the second perforated section). The second loudspeaker is arranged in the housing and acoustically coupled to a perforated section provided in the housing (e.g.,a third perforated section; the third perforated section can be one of the perforated sections (first and second perforated sections) or a different perforated section (different from the first and second perforated sections). In some embodiments, the second loudspeaker comprises a second diaphragm. In the housing, a second front chamber and a second rear chamber are provided in front of and behind the second diaphragm, respectively, only one of which is acoustically coupled to the one perforated section (e.g., the third perforated section) to output a third sound wave. In some embodiments, the second loudspeaker can output the third sound wave by being driven by a second electrical signal via the one perforated section (e.g., the third perforated section). In this case, the first loudspeaker outputs the first sound wave and the second sound wave via two perforated sections (e.g., the first perforated section and the third perforated section).the second hole section), thus forming a dual sound source; while the second loudspeaker outputs only the third sound wave via one hole section (e.g., the third hole section), thus forming a single sound source. In some embodiments, in the target frequency range, the third sound wave output by the second loudspeaker and the first and second sound waves output by the first loudspeaker can superimpose and cancel each other out at a far-field position in a certain direction of the acoustic output device, with the sound pressure at this position being low after superposition and cancellation (e.g., close to zero).Simultaneously, the sound pressure at the corresponding far-field position in the opposite direction to this specific direction is high, such that the absolute value of the sound pressure level difference between the two positions is at least as high as a preset sound pressure level threshold. This gives the far-field radiation of the acoustic output device a directional characteristic. The two corresponding far-field positions in the specified direction and its opposite direction are equidistant from the acoustic output device. In some embodiments, the sound pressure levels at the two far-field positions in the specified direction and the corresponding opposite direction can be measured by using a test microphone positioned at each of the two far-field positions to detect the sound pressure at that position.The sound pressure can be used to determine the corresponding sound pressure level, in order to ultimately obtain the sound pressure level difference between the two far-field positions in the specified direction or the corresponding opposite direction.

[0038] To ensure that the sound waves emitted by the first loudspeaker (e.g., the superimposed sound wave of the first and second sound waves) and the sound waves emitted by the second loudspeaker (e.g., the third sound wave) can effectively cancel each other out at the far-field position, the amplitudes of the sound waves emitted by the first loudspeaker and the sound waves emitted by the second loudspeaker at the far-field position should be equal or similar, and their phases should be opposite or approximately opposite.Considering that the frequency responses of the first and second loudspeakers can vary at the far-field position when driven with the same electrical signal due to their different structures, electrical signals of different strengths can be applied to the first and second loudspeakers to compensate for these frequency response differences. This ensures that the final sound waves emitted by the first and second loudspeakers have the same or similar amplitudes at the far-field position. For example, a processing circuit can apply different gain levels to the two electrical signals driving the first and second loudspeakers, respectively, to compensate for the frequency response differences.To reduce the effort required to adapt the electrical signals and increase their stability, the differences in the frequency response of the first and second loudspeakers at the far-field position can be reduced. For example, by adjusting the structure of the first and second loudspeakers, such as the volume of the cavity, the dimensions and positioning of the perforated sections, etc., the differences in their frequency response at the far-field position can be reduced. Regarding the adjustment of the structural parameters of the first and second loudspeakers, reference can be made to the descriptions elsewhere in this document. The "reduction of the differences in the frequency response of the first and second loudspeakers at the far-field position" described here can be understood as follows: In the target frequency range and when driven with the same electrical signal (i.e.,(The first and second electrical signals are identical) the sound pressure level difference between the superimposed sound wave from the first and second sound waves emitted by the first loudspeaker and the third sound wave emitted by the second loudspeaker is less than 14 dB at the far-field position in the specified direction of the acoustic output device. Therefore, after the first or second electrical signal has undergone suitable amplitude-frequency matching, the first and second sound waves emitted by the first loudspeaker, as well as the third sound wave emitted by the second loudspeaker, can superimpose and cancel each other out at the far-field position in the specified direction of the acoustic output device, so that the sound pressure at this far-field position is low, for example, close to zero.In some embodiments, in order to reduce the sound pressure at the far-field position in the specified direction of the acoustic output device and to improve the reduction of sound losses of the acoustic output device, in the target frequency range, when driven with the same electrical signal (i.e., the first and second electrical signals are identical), the sound pressure level difference between the superimposed sound wave from the first and second sound waves emitted by the first loudspeaker and the third sound wave emitted by the second loudspeaker can be less than 10 dB at the far-field position in the specified direction of the acoustic output device.In some embodiments, to further reduce the sound pressure at the far-field position in the specified direction of the acoustic output device and to further improve the reduction of sound losses of the acoustic output device, in the target frequency range, when driven with the same electrical signal (i.e., the first and second electrical signals are identical), the sound pressure level difference between the superimposed sound wave from the first and second sound waves emitted by the first loudspeaker and the third sound wave emitted by the second loudspeaker can be less than 6 dB at the far-field position in the specified direction of the acoustic output device. In some embodiments, the target frequency range can include a first frequency range.In the first frequency range, the first, second, and third sound waves overlap, resulting in a heart-shaped directional characteristic for the far-field radiation of the acoustic output device. In some embodiments, the target frequency range can include a second frequency range. In this second frequency range, the sound pressure level of the third sound wave is significantly lower than that of the second sound wave. When the first, second, and third sound waves overlap, the influence of the third sound wave can be neglected, and the first and second sound waves can be considered as two overlapping sound sources, resulting in a dual-source directional characteristic for the far-field radiation of the acoustic output device.In some embodiments, the first frequency range can encompass the mid-high frequency range (e.g., 800 Hz–10 kHz, etc.), and the second frequency range can encompass the mid-low frequency range (e.g., 100 Hz–800 Hz, etc.). Further information on the directional characteristics of the acoustic output device and the heart-shaped directional pattern can be found in [reference to be inserted here]. Fig. 4 and the associated descriptions; further information on the dual sound source directional characteristics can be found in Fig. 2A and the corresponding descriptions above.

[0039] In some embodiments, the acoustic output device may comprise at least one neckband earphone, one earhook earphone, one in-ear earphone, or eyeglasses. When worn, the opposite direction of the intended direction may point towards the user's ear canal opening. Fig. Figure 4 shows a schematic representation of the directional characteristic according to some embodiments described in this document. It refers to Fig. 4 pointed out. Fig. Figure 4 shows the acoustic output device in the worn state, with AS1 representing a sound outlet hole section of the front chamber of the acoustic output device and AS2 representing a sound outlet hole section of the rear chamber of the acoustic output device. In some embodiments, the directed far-field radiation of the acoustic output device means that the output direction of the sound of the acoustic output device lies within a certain directional range, i.e., the far-field radiation of the acoustic output device is significantly greater within this certain directional range than outside this certain directional range. In some embodiments, in the worn state of the acoustic output device, the direction X1 points from the sound-output hole section AS2 of the rear chamber to the sound-output hole section AS1 of the front chamber (i.e.,The direction X1, which points from sound outlet section AS2 of the posterior chamber to sound outlet section AS1 of the anterior chamber, and adjacent directions (e.g., direction X2, direction X3) point towards the user's ear canal opening. That is, when worn, the sound outlet section AS1 of the anterior chamber of the acoustic output device is closer to the user's ear canal opening. The direction X1', which points from sound outlet section AS1 of the anterior chamber to sound outlet section AS2 of the posterior chamber, and adjacent directions (e.g., direction X2', direction X3') point away from the user's ear canal opening.In some embodiments, the direction X1, pointing from the sound outlet section AS2 of the rear chamber towards the sound outlet section AS1 of the front chamber, and adjacent directions can form the aforementioned defined directional range, both when worn and / or when not worn. The far-field radiation of the acoustic output device in direction X1 and adjacent directions is significantly greater than in other directional ranges (e.g., in directional ranges perpendicular to X1 and adjacent directions, directional ranges opposite to X1 and adjacent directions, etc.).In some embodiments, the directional characteristic of the acoustic output device can manifest itself as follows: The absolute value of the difference in sound pressure levels at the two corresponding far-field positions in the specified direction and its opposite direction of the acoustic output device is no less than a preset sound pressure level threshold. When worn, the specified direction can be the direction in which the acoustic output device points away from the user's ear canal opening, and its opposite direction can be the direction in which the acoustic output device points towards the user's ear canal.In some embodiments, the defined direction can be direction X1', pointing from sound outlet section AS1 of the front chamber to sound outlet section AS2 of the rear chamber, and adjacent directions; the opposite direction to the defined direction can be direction X1, pointing from sound outlet section AS2 of the rear chamber to sound outlet section AS1 of the front chamber, and adjacent directions. In some embodiments, adjacent directions to direction X1' can be understood as directions whose angle to direction X1' is less than 60°. It should be noted that, for a better understanding of the directional characteristics, only the two outlet sections AS1 and AS2 are used here for illustrative purposes.If the acoustic output device has several different hole sections, AS1 can be understood as an equivalent hole section formed by a subset of the hole sections, and AS2 as an equivalent hole section formed by a different subset. In this case, the direction of the directional characteristic is determined by the positions of the equivalent hole sections. In some embodiments, the position of each equivalent hole section formed by several hole sections can be determined as follows: The centers of adjacent hole sections are successively connected to form a polygon or polyhedron. The center point of this polygon or polyhedron corresponds to the center point of the equivalent hole section and can be used to represent its position.

[0040] In some embodiments, the far-field radiation of the acoustic output device can exhibit a heart-shaped directional characteristic, manifested as follows: Within a specific directional range, the absolute value of the sound pressure level difference of the far-field radiation of the acoustic output device in at least one pair of opposite directions is not less than a preset sound pressure level threshold. The at least one pair of opposite directions can fall within the aforementioned specific directional range or its opposite directional range. In some embodiments, the at least one pair of opposite directions can comprise the aforementioned specific direction and its opposite direction. That is, the aforementioned specific direction and its opposite direction can fall within the aforementioned specific directional range or its opposite direction.whose opposite direction range is included. In some embodiments, the at least one pair of opposite directions comprises a pair of opposite directions corresponding to the connecting line between the sound outlet hole section AS1 of the front chamber (e.g., the first hole section) and the sound outlet hole section AS2 of the rear chamber (e.g., the second hole section). The heart-shaped directional characteristic of the acoustic output device can manifest itself in that the sound field strength in a pair of opposite or nearly opposite directions within the defined direction range and its opposite direction range exhibits a large difference.For example, the pair of opposite or nearly opposite directions can be defined as follows: One direction is close to direction X1', which points from the sound outlet section of the front chamber to the sound outlet section of the rear chamber, and the other direction is close to direction X1, which points from the sound outlet section of the rear chamber to the sound outlet section of the front chamber. For example, direction X1' can be opposite or nearly opposite to directions X1, X2, and X3.

[0041] The heart-shaped directional characteristic of the acoustic output device's far-field radiation allows the sound emitted by the acoustic output device to be focused and transmitted towards the user's ear canal opening. This reduces sound transmission in other directions, improves the problem of sound loss from the acoustic output device, and enhances the sound experience for the user.

[0042] In some embodiments, the preset sound pressure level threshold can be 6 dB. For example, the heart-shaped directional characteristic of the far-field radiation of the acoustic output device can manifest itself as follows: The absolute value of the sound pressure level difference of the far-field radiation of the acoustic output device in at least one pair of opposite directions (e.g., direction X1 and direction X1') is not less than 6 dB. This allows a high volume to be received at the user's ear canal opening, providing the user with a clear sound impression.

[0043] In some embodiments, the first electrical signal driving the first loudspeaker and the second electrical signal driving the second loudspeaker have differences in amplitude and / or phase in the target frequency range. Within the target frequency range, the first, second, and third sound waves superimpose and cancel each other out at the far-field position in the specific direction of the acoustic output device, so that the sound pressure after superposition and cancellation is low, for example, close to zero. This gives the far-field radiation of the acoustic output device a directional characteristic and improves the problem of far-field sound losses of the acoustic output device. In some embodiments, the first electrical signal can be measured using a measuring instrument (e.g., a multimeter).The first electrical signal can be measured using a measuring instrument (e.g., an oscilloscope) located between the first loudspeaker and a corresponding signal generator; the second electrical signal can be measured using a measuring instrument (e.g., an oscilloscope) located between the second loudspeaker and a corresponding signal generator. In some embodiments, the first and / or the second electrical signal, which have been adapted, can be measured using a measuring instrument located between the corresponding loudspeaker and the corresponding signal modulator.

[0044] In order to achieve the directional characteristics of the far-field radiation of the acoustic output device, the first loudspeaker and the second loudspeaker can be arranged in different ways. Fig. Figures 5A to 5D each show a schematic structural view of the acoustic output device, comprising a first loudspeaker and a second loudspeaker arranged in various ways, according to some embodiments described in this document. As in Fig. As shown in Figures 5A to 5D, in some embodiments the direction of vibration of the first diaphragm 521 and the second diaphragm 551 can be the same (e.g. the up-down direction in Figure 5A). Fig. 5A to 5D etc.) and the first diaphragm 521 and the second diaphragm 551 can be spaced apart from each other in the direction of vibration, i.e., the first loudspeaker 520 and the second loudspeaker 550 are spaced apart from each other in the direction of vibration (as in Fig. 5A and Fig. 5B). In some embodiments, the first diaphragm 521 and the second diaphragm 551 can be spaced apart from each other in a direction perpendicular to the direction of vibration, i.e., the first loudspeaker 520 and the second loudspeaker 550 are spaced apart from each other in a direction perpendicular to the direction of vibration (as shown in Fig. 5C and Fig. (5D shown). It should be noted that the same direction of vibration of the first diaphragm 521 and the second diaphragm 551 is an ideal case. In real products, due to structural designs, assembly tolerances, and other factors, the directions of vibration of the first diaphragm 521 and the second diaphragm 551 may not be exactly the same, but slightly different (e.g., the angle between the directions of vibration of the first diaphragm 521 and the second diaphragm 551 may be less than 10°, etc.). In this case, the orientation of the first loudspeaker 520 and the second loudspeaker 550, or the direction perpendicular to their orientation, may be the direction of vibration of the first diaphragm 521, the direction of vibration of the second diaphragm 551, or a direction in the range of the angle between the directions of vibration of the two diaphragms.In some embodiments, the orientation direction of the first diaphragm 521 in the first loudspeaker 520 can be the same as or opposite to the orientation direction of the second diaphragm 551 in the second loudspeaker 550. In some embodiments, the first rear chamber 540 of the first loudspeaker 520 can be adjacent to or connected with the second rear chamber 570 of the second loudspeaker 550. In this case, the second front chamber 560 of the second loudspeaker 550 is closed, as shown in [reference]. Fig. 5A and Fig. 5C shown. In some embodiments, the first rear chamber 540 of the first loudspeaker 520 can be adjacent to or connected with the second front chamber 560 of the second loudspeaker 550. In this case, the second rear chamber 570 of the second loudspeaker 550 is closed, as shown in Fig. 5B and Fig. 5D shown. In some embodiments, if the volumes of the respective cavities (e.g., the first front chamber 530, the first rear chamber 540, the second front chamber 560, the second rear chamber 570, etc.) are equal, the acoustic output device 500 can be arranged according to Fig. 5A and the acoustic output device 500 after Fig. 5C equivalent and the acoustic output device 500 after Fig. 5B and the acoustic output device 500 after Fig. 5D can be equivalent.

[0045] The acoustic output device is explained below using the example of the spaced-apart arrangement of the first and second loudspeakers in the direction of vibration.

[0046] As in Fig. 5A and Fig. As shown in Figure 5B, the acoustic output device 500 comprises, in some embodiments, a housing 510, a first loudspeaker 520, and a second loudspeaker 550. The first loudspeaker 520 is arranged in the housing 510. The first loudspeaker 520 comprises a first diaphragm 521. A first front chamber 530 and a first rear chamber 540 are provided in front of and behind the first diaphragm 521, respectively. The first front chamber 530 and the first rear chamber 540 are acoustically coupled to a first perforated section 511 and a second perforated section 512, respectively, on the housing 510. Driven by a first electrical signal, the first loudspeaker 520 outputs a first sound wave and a second sound wave with a phase difference via the first perforated section 511 and the second perforated section 512, respectively. The second loudspeaker 550 is arranged in the housing 510. The second loudspeaker 550 includes a second diaphragm 551. (Before or...)Behind the second diaphragm 551, a second front chamber 560 or a second rear chamber 570 is provided. One of the cavities, either the second front chamber 560 or the second rear chamber 570, is the same chamber as the first rear chamber 540; that is, the second front chamber 560 or the second rear chamber 570, forming a common cavity, is acoustically coupled to the second perforated section 512 on the housing 510. The second loudspeaker 550, driven by a second electrical signal, emits a third sound wave via the second perforated section 512. In some embodiments, the second front chamber 560 can form a common cavity with the first rear chamber 540. In this case, the orientations of the first diaphragm 521 and the second diaphragm 551 are the same, as shown in [reference missing]. Fig. 5B shown. In some embodiments, the second rear chamber 570 can also form a common cavity with the first rear chamber 540. In this case, the orientations of the first diaphragm 521 and the second diaphragm 551 are opposite, as shown in Fig. 5A shown. When comparing the acoustic output device 500 to Fig. 5A and the acoustic output device 500 according to Fig. In 5B, the orientations of the first diaphragm 521 and the second diaphragm 551 differ. Therefore, the frequency response curves of the in Fig. 5A shown acoustic output device 500 and the one in Fig. The acoustic output device 500 shown in Figure 5B exhibits certain differences, but both can achieve a directional characteristic of the far-field radiation. The acoustic output device 500 is described below using the example of the one shown in Figure 5B. Fig. 5A shows a spaced arrangement of the first loudspeaker 520 and the second loudspeaker 550 in the direction of vibration with opposite orientations of the first diaphragm 521 and the second diaphragm 551 (i.e., the second rear chamber 570 and the first rear chamber 540 form a common cavity).

[0047] Accordingly, with reference to Fig. 4, Fig. 5A and Fig. 5B considers the first front chamber 530 as the front chamber of the acoustic output device 500 and the common cavity as the rear chamber of the acoustic output device 500. In this case, the first hole section 511 serves as sound outlet hole section AS1 of the front chamber of the acoustic output device 500 and the second hole section 512 as sound outlet hole section AS2 of the rear chamber of the acoustic output device 500. The extension line of the connecting line between the first hole section 511 and the second hole section 512 defines the specific direction.

[0048] In some embodiments, by adjusting amplitude and / or phase differences between the first and second electrical signals in the target frequency range, the first sound wave generated by the first loudspeaker 520 in the first front chamber 530, the second sound wave generated by the first loudspeaker 520 in the first rear chamber 540, and the third sound wave generated by the second loudspeaker 550 in the second rear chamber 570 are made to meet specific phase and amplitude conditions at the far-field position in the specified direction of the acoustic output device 500. For example, the resulting sound wave formed by superimposing the first and second sound waves at the far-field position in the specified direction has a phase difference with the third sound wave.After superposition and cancellation, the sound pressure at this far-field position is low, for example, close to zero. This ensures that the absolute value of the sound pressure level difference between the far-field position in a specific direction and the corresponding far-field position in the opposite direction is not less than a preset sound pressure level threshold, thus realizing the directional characteristic of the acoustic output device 500. Simultaneously, this arrangement suppresses the sound field chaos of the dual sound source in the high-frequency range and thus reduces or eliminates the sound wave radiation of the acoustic output device 500 in the far field.

[0049] To prevent the resonant frequencies of the individual cavities from interfering with the realization of the heart-shaped directional characteristic of the acoustic output device, and to improve the sound perception for the user, the structural parameters of the cavities can be adjusted so that their resonant frequencies lie outside the frequency range in which the heart-shaped directional characteristic is realized. In some embodiments, the target frequency range in which the acoustic output device realizes the heart-shaped directional characteristic can lie within the range of relatively flat frequency responses of the first loudspeaker 520 and the second loudspeaker 550. That is, the resonant frequency of the common cavity between the first loudspeaker 520 and the second loudspeaker 550 (such as the common cavity of the first rear chamber 540 and the second rear chamber 570 in Fig. 5A or the common cavity from the first rear chamber 540 and the second front chamber 560 in Fig. 5B) defines the upper frequency limit at which the heart-shaped directional characteristic can be relatively easily achieved. In some embodiments, to improve the sound reception for the user, the acoustic output device may exhibit a heart-shaped directional characteristic in the frequency range sensitive to the human ear, for example, at approximately 3 kHz or approximately 3.5 kHz. In this case, the upper limit of the frequency range in which the far-field radiation of the acoustic output device exhibits a heart-shaped directional characteristic cannot be lower than 4 kHz (e.g., the frequency range for achieving the heart-shaped directional characteristic may be 1 kHz to 4 kHz). The resonant frequency of the common cavity should not be lower than 4 kHz.In some embodiments, the required frequency range for achieving the heart-shaped directional characteristic can vary depending on the application scenario of the acoustic output device. For example, for an acoustic output device operating primarily at mid-low frequencies, the frequency range for achieving the heart-shaped directional characteristic may be 800 Hz to 2 kHz; in this case, the resonant frequency of the common cavity is conceivable to be no lower than 2 kHz. For an acoustic output device operating primarily at mid-high frequencies, the upper limit of the frequency range for achieving the heart-shaped directional characteristic may be higher, and accordingly, the resonant frequency of the common cavity would also be higher.To improve the output quality of the acoustic output device in the frequency range sensitive to the human ear, the resonant frequency of the common cavity should lie outside this range, e.g., greater than 4 kHz, greater than 4.5 kHz, greater than 5 kHz, etc. In this case, the upper limit of the frequency range for achieving the heart-shaped directional characteristic can be 4 kHz, 4.5 kHz, 5 kHz, etc.

[0050] Fig. Figure 6 shows a schematic representation of the relationship between the resonance frequency of the common cavity and its volume according to some embodiments of the present description. Fig. Figure 7 shows a schematic representation of the relationship between the resonant frequency of the common cavity and the area of ​​an acoustically coupled hole section according to some embodiments described in this document. As in Fig. 6 and Fig. As shown in Figure 7, in some embodiments, if the resonant frequency of the common cavity is set to at least 3.8 kHz, the corresponding volume of the common cavity is no more than 0.38 cm³. 3 and the area of ​​the second hole section 512, which is acoustically coupled to the common cavity, is not less than 17 mm 2 If the resonant frequency of the common cavity is set to at least 4 kHz, in some embodiments the corresponding volume of the common cavity is no more than 0.28 cm³. 3 and the area of ​​the second hole section 512, which is acoustically coupled to the common cavity, not less than 20 mm 2 If the resonant frequency of the common cavity is set to at least 4.2 kHz, in some embodiments the corresponding volume of the common cavity is no more than 0.2 cm³. 3and the area of ​​the second hole section 512, which is acoustically coupled to the common cavity, is not less than 22 mm 2 If the resonant frequency of the common cavity is set to at least 4.3 kHz, in some embodiments the corresponding volume of the common cavity is no more than 0.18 cm³. 3 and the area of ​​the second hole section 512, which is acoustically coupled to the common cavity, is not less than 23 mm² 2By adjusting the volume of the shared cavity and the area of ​​the acoustically coupled perforated section, the resonant frequency of the shared cavity can be further controlled so that it lies outside the frequency range in which the acoustic output device achieves its heart-shaped directional characteristic. This avoids interference in the realization of the heart-shaped directional characteristic by the acoustic output device and improves the sound perception for the user.

[0051] In some embodiments, the portion of the second front chamber 560 and the second rear chamber 570 of the second loudspeaker 550 that does not form the common cavity is a closed cavity and is not acoustically coupled to the second hole section 512. For example, in Fig. 5A the second front chamber 560 is a closed cavity and is not acoustically coupled to the second hole section 512. As a further example, in Fig. 5B the second rear chamber 570 is a closed cavity and is not acoustically coupled to the second hole section 512. In some embodiments, the resonant frequency of the closed cavity can be controlled such that it is not higher than the lower frequency limit of the target frequency range for realizing the heart-shaped directional characteristic, in order to ensure that it does not fall within the frequency range in which the acoustic output device realizes the heart-shaped directional characteristic. In some embodiments, it is conceivable that the resonant frequency of the closed cavity is not higher than 1 kHz, so that it is conceivable that the lower frequency limit for realizing the heart-shaped directional characteristic of the acoustic output device is not lower than 1 kHz (e.g.The frequency range for realizing the heart-shaped directional characteristic can encompass 1 kHz to 4 kHz to improve the output quality of the acoustic output device in the frequency range sensitive to the human ear. In some embodiments, the resonant frequency of the closed cavity can be lower than the lower frequency limit of the frequency range in which the acoustic output device realizes the heart-shaped directional characteristic. For example, it is conceivable that the resonant frequency of the closed cavity is not higher than 800 Hz. In some embodiments, it is conceivable that the resonant frequency of the closed cavity, taking into account factors such as structural design, manufacturing and assembly effort, etc., is not higher than 600 Hz.

[0052] Fig. Figure 8 shows a schematic representation of the relationship between the resonant frequency of the closed cavity and its volume according to some embodiments described in this document. As in Fig. As shown in Figure 8, in some embodiments the corresponding volume of the closed cavity is not less than 0.8 cm³. 3 , if the resonant frequency of the closed cavity of the second loudspeaker 550 is not higher than 1 kHz. In some embodiments, the corresponding volume of the closed cavity is not less than 0.6 cm³. 3 , if the resonant frequency of the closed cavity of the second loudspeaker 550 is not higher than 1.2 kHz. In some embodiments, the corresponding volume of the closed cavity is not less than 0.5 cm³. 3, if the resonant frequency of the closed cavity of the second loudspeaker 550 is not higher than 1.4 kHz. In some embodiments, the corresponding volume of the closed cavity is not less than 0.45 cm³. 3 , if the resonant frequency of the closed cavity of the second loudspeaker 550 is not higher than 1.6 kHz. In some embodiments, the corresponding volume of the closed cavity is not less than 1.1 cm³. 3, if the resonant frequency of the closed cavity of the second loudspeaker 550 is not higher than 0.8 kHz. By adjusting the volume of the closed cavity, the resonant frequency can be further regulated to ensure that it is not higher than the lower frequency limit of the target frequency range for achieving the heart-shaped directional characteristic of the acoustic output device. This avoids interference and improves the perceived sound quality for the user, while also reducing sound losses in the acoustic output device.

[0053] In some embodiments, due to the arrangement of the closed cavity of the second loudspeaker, the second loudspeaker can only emit low-frequency sound waves with difficulty at its acoustically coupled perforated section (e.g., the second perforated section 512). Therefore, in the low-frequency range, the sound pressure of the sound waves emitted by the second loudspeaker is significantly lower than the sound pressure of the sound waves emitted by the first loudspeaker. In this case, the sound waves emitted by the second loudspeaker can be neglected, and the sound waves are primarily emitted by the first loudspeaker for the acoustic output device, thus enabling the acoustic output device to achieve a dual-source directional characteristic.In the mid-high frequency range, the first and second loudspeakers work together to emit the sound waves for the acoustic output device, which can implement a heart-shaped directional characteristic. In some embodiments, the acoustic output device can implement a dual-source directional characteristic in the frequency range from 100 Hz to 800 Hz and a heart-shaped directional characteristic in the frequency range from 1 kHz to 4 kHz. In some embodiments, the frequency range in which the acoustic output device implements the dual-source directional characteristic can be designed and adapted according to the actual circumstances. For example, the target frequency range for implementing the dual-source directional characteristic of the acoustic output device can be 100 Hz–1.2 kHz, 100 Hz–1.5 kHz, 200 Hz–2 kHz, etc.In some embodiments, to achieve the dual sound source directional characteristic in the target frequency range, the amplitude of the second electrical signal driving the second loudspeaker can be reduced in this target frequency range, for example, by setting the amplitude of the second electrical signal to 0 in this range, i.e., no second electrical signal is provided in this target frequency range. In some embodiments, the lower frequency limit of the frequency range in which the acoustic output device achieves the heart-shaped directional characteristic can be higher than the upper frequency limit of the frequency range in which the dual sound source directional characteristic is achieved, in order to avoid a chaotic sound field distribution of the acoustic output device.If the target frequency range for realizing the dual-source directional characteristic of the acoustic output device varies, the mid-high frequency range in which the acoustic output device realizes the heart-shaped directional characteristic can also change accordingly. Since the resonant frequency of the closed cavity of the second loudspeaker influences the lower frequency limit of the frequency range for realizing the heart-shaped directional characteristic, the resonant frequency of the closed cavity of the second loudspeaker must also be adjusted accordingly. For example, it is conceivable that the resonant frequency of the closed cavity of the second loudspeaker is no higher than 1 kHz if the acoustic output device realizes a dual-source directional characteristic in the range of 100 Hz to 800 Hz and a heart-shaped directional characteristic in the range of 1 kHz to 4 kHz.As another example, it is conceivable that the resonant frequency of the closed cavity of the second loudspeaker is no higher than 1.5 kHz if the acoustic output device implements a dual-source directional characteristic in the range of 100 Hz to 1.2 kHz and a heart-shaped directional characteristic in the range of 1.5 kHz to 4 kHz. In some embodiments, when worn, the perforated section of the first loudspeaker acoustically coupled to the first front chamber can be positioned near the user's ear, while the perforated section acoustically coupled to the first rear chamber is positioned away from the user's ear. The direction from the perforated section acoustically coupled to the perforated section acoustically coupled to the first front chamber points towards the user's ear, i.e.,The dual sound source directional characteristic formed in the low-frequency range can point towards the user's ear. In some embodiments, when worn, the acoustically coupled perforated section of the first loudspeaker is positioned near the user's ear, while the perforated section acoustically coupled to the first rear chamber and the perforated section through which the second loudspeaker emits the third sound wave are positioned away from the user's ear. The perforated section acoustically coupled to the first rear chamber and the perforated section through which the second loudspeaker emits the third sound wave have an equivalent perforated section. The direction from this equivalent perforated section to the perforated section acoustically coupled to the first front chamber points towards the user's ear, i.e.,, the directional characteristic formed in the mid-high frequency range can point towards the user's ear.

[0054] Fig. Figure 9 shows a schematic structural view of the acoustic output device according to some other embodiments described in this document. To ensure that the sound waves of the first and second loudspeakers do not interfere with each other and that the mutual radiation impedance is reduced, the acoustic output device may further comprise an arrangement in which—as shown in Fig. Figure 9 shows that there is no common cavity between the first loudspeaker 620 and the second loudspeaker 650. For example, the housing of the acoustic output device can have two receiving spaces, with the first loudspeaker 620 and the second loudspeaker 650 being housed in these two receiving spaces. As another example, the first loudspeaker 620 and the second loudspeaker 650 can be arranged in the same receiving space of the housing, but a partition plate is provided between them so that the two opposing cavities of the two loudspeakers are not connected. The acoustic output device 600 is further explained below using the example of a spaced-apart arrangement of the first and second loudspeakers in the direction of vibration with opposite orientations of the first and second diaphragms.

[0055] As in Fig. As shown in Figure 9, the acoustic output device 600 can comprise a housing 610, a first loudspeaker 620, and a second loudspeaker 650. The first loudspeaker 620 comprises a first diaphragm 621. A first front chamber 630 and a first rear chamber 640 are provided in front of and behind the first diaphragm 621, respectively. The housing 610 has a first perforated section 611, which is acoustically coupled to the first front chamber 630, and a second perforated section 612, which is acoustically coupled to the first rear chamber 640. The first perforated section 611 and the second perforated section 612 serve as sound outlets of the first loudspeaker 620 and form a dual sound source. The second loudspeaker 650 comprises a second diaphragm 651. A second front chamber 660 and a second rear chamber 670 are provided in front of and behind the second diaphragm 651, respectively.One of the second front chambers 660 and the second rear chamber 670 is acoustically coupled to a third perforated section 613 on the housing 610, while the other serves as a closed cavity. The third perforated section 613 is different from the first perforated section 611 and the second perforated section 612. In some embodiments, a partition plate 614 is provided in the housing 610. The chamber acoustically coupled to the third perforated section 613 (e.g., the second rear chamber 570 in ) Fig. 9) and the first rear chamber 640 are separated from each other by the partition plate 614, and the second hole section 612 and the third hole section 613 are located on opposite sides of the partition plate 614. In some embodiments, the distance between the third hole section 613 and the second hole section 612 can be greater than 0 mm but not greater than 10 mm. This avoids an excessively large distance between the second hole section 612 and the third hole section 613, thus preventing an excessively large volume of the corresponding chamber and ensuring a suitable position of the equivalent hole section for the second hole section 612 and the third hole section 613 in order to avoid significant disturbances to the directional characteristics of the acoustic output device 600.

[0056] In some embodiments, the sound pressure at the far-field position in the specified direction of the acoustic output device 600 is low, for example close to zero, in the target frequency range after the superposition of the first and second sound waves emitted by the first loudspeaker 620 and the third sound wave emitted by the second loudspeaker 650. This results in the far-field radiation of the acoustic output device 600 exhibiting a directional characteristic, thus mitigating the problem of far-field sound losses. In some embodiments, the target frequency range can extend from 1 kHz to 4 kHz to enable the acoustic output device 600 to have a flat frequency response curve over a wider frequency range while simultaneously maintaining good heart-shaped directional characteristics.

[0057] It should be noted that when representing the directional characteristics of the acoustic output device 600, the second hole section 612 acoustically coupled to the first rear chamber 640 of the first loudspeaker 620 and the third hole section 613 acoustically coupled to the second rear chamber 670 of the second loudspeaker 650 can be considered as a single equivalent hole section. Specifically, the midpoint M between the second hole section 612 and the third hole section 613 is determined. This midpoint M can represent the position of the equivalent hole section. In this case, the first front chamber 630 can serve as the front chamber of the acoustic output device 600, while the first rear chamber 640 and the chamber acoustically coupled to the third hole section 613 (e.g., the second rear chamber 670 in the second loudspeaker 650) Fig. 9) can function as the rear chamber of the acoustic output device 600. The first hole section 611 serves as sound outlet hole section AS1 of the front chamber of the acoustic output device 600, and the equivalent hole section of the second hole section 612 and the third hole section 613 can function as sound outlet hole section AS2 of the rear chamber of the acoustic output device 600. The extension line of the connecting line between the first hole section 611 and the equivalent hole section (point M) then defines the specific direction.

[0058] In some embodiments, the upper frequency limit up to which the acoustic output device 600 can realize a heart-shaped directional characteristic is determined by the resonant frequency of the chamber acoustically coupled to the third perforation section 613 (the second front chamber 660 or the second rear chamber 670) and the resonant frequency of the first rear chamber 640. If the difference between these two resonant frequencies is too large, one of the resonant frequencies becomes too low, resulting in an upper frequency limit that is too low for realizing the heart-shaped directional characteristic of the acoustic output device 600. This would excessively reduce the frequency range in which the acoustic output device 600 can realize the heart-shaped directional characteristic and ultimately impair the output performance of the acoustic output device 600.In some embodiments, the difference between the two aforementioned resonant frequencies is no more than 3000 Hz. To achieve the highest possible upper frequency limit for the heart-shaped directional characteristic, the difference between the two resonant frequencies is no more than 2500 Hz in some embodiments. Furthermore, in some embodiments, the difference between the two aforementioned resonant frequencies is no more than 2000 Hz to achieve a higher upper frequency limit for the heart-shaped directional characteristic. Preferably, the difference between the two resonant frequencies is no more than 1500 Hz. Even more preferably, the difference between the two resonant frequencies is no more than 1000 Hz.

[0059] In some embodiments, it is conceivable that the upper frequency limit of the heart-shaped directional characteristic is not lower than 4 kHz, in order to allow the acoustic output device to realize a heart-shaped directional characteristic in the frequency range sensitive to the human ear. In some embodiments, to avoid disturbances of the heart-shaped directional characteristic by the resonance frequencies of the cavities, the resonance frequency of the chamber acoustically coupled to the third hole section 613 (the second front chamber 660 or the second rear chamber 670) can lie outside the frequency range in which the heart-shaped directional characteristic is realized. For example, the resonance frequency of the chamber acoustically coupled to the third hole section 613 (the second front chamber 660 or the second rear chamber 670) is not lower than 4 kHz.In some embodiments, the resonant frequency of the chamber acoustically coupled to the third hole section 613 (the second front chamber 660 or the second rear chamber 670) is not lower than 5 kHz in order to achieve a high upper frequency limit for the heart-shaped directional characteristic.

[0060] In some embodiments, the structure of the first rear chamber 640 and the second hole section 612, as well as the structure of the chamber acoustically coupled to the third hole section 613 (the second front chamber 660 or the second rear chamber 670) and the third hole section 613, are identical or similar, such that their resonant frequencies are close to each other (e.g., the difference between their resonant frequencies is less than 3000 Hz). If the resonant frequency of the chamber acoustically coupled to the third hole section 613 (the second front chamber 660 or the second rear chamber 670) is not lower than 4 kHz, the volume of the chamber acoustically coupled to the third hole section 613 (e.g., the second rear chamber 670) is Fig. 9) not more than 0.3 cm 3 and the area of ​​the corresponding third hole section 613 is not less than 12 mm 2In this case, it is conceivable that the volume of the first rear chamber 640 is also no more than 0.3 cm³. 3 and the area of ​​the corresponding second hole section 612 is also not less than 12 mm 2 amounts.

[0061] In some embodiments, the second front chamber 660 or the second rear chamber 670 of the second loudspeaker 650, which is not acoustically coupled to the second hole section 612, is a closed cavity. For example, in Fig. 9. The second front chamber 660 is a closed cavity. The resonant frequency of this closed cavity can determine the lower frequency limit of the frequency range in which the heart-shaped directional characteristic is realized. In some embodiments, to avoid disturbances of the heart-shaped directional characteristic by the resonant frequency of the closed cavity, the resonant frequency of the closed cavity can lie outside the frequency range in which the heart-shaped directional characteristic is realized. For example, the resonant frequency of the closed cavity (e.g., of the second front chamber 660 in Fig. 9) not higher than 1 kHz. In some embodiments, the resonant frequency of the closed cavity may be lower than the lower frequency limit of the frequency range in which the acoustic output device achieves the heart-shaped directional characteristic. For example, it is conceivable that the resonant frequency of the closed cavity is not higher than 900 Hz. In some embodiments, it is conceivable that the resonant frequency of the closed cavity, taking into account factors such as structural design, manufacturing and assembly effort, etc., is not higher than 1.1 kHz. In this case, the frequency range in which the acoustic output device achieves the heart-shaped directional characteristic could be reduced accordingly, and the lower frequency limit for achieving the heart-shaped directional characteristic could be 1.1 kHz.

[0062] In some embodiments, where the first hole section 611 acoustically coupled to the first front chamber 630 is arranged in a corresponding area of ​​the housing 610 in the direction of vibration of the first loudspeaker 620 (i.e., the connecting line between the geometric center of the first hole section 611 and the geometric center of the shape of the first diaphragm 621 of the first loudspeaker 620 runs parallel to the direction of vibration), the hole sections corresponding to the first rear chamber 640 and an adjacent chamber (the second front chamber 660 or the second rear chamber 670) can be arranged in various ways.The following explains the different arrangements of the hole sections of the acoustic output device 600 using the example of the embodiment in which the first and second loudspeakers do not have a common cavity, are spaced apart from each other in the direction of vibration and the first and second diaphragms are oriented in opposite directions.

[0063] Fig. Figures 10A to 10D each show a schematic representation of the acoustic output device with different arrangements of sound outlet hole sections according to some embodiments of the present application description. Fig. Figures 11A to 11D each show a schematic representation of the directional characteristic of the far-field radiation of the in Fig. The acoustic output devices shown in 10A to 10D. As in Fig. 10A and Fig. As shown in Figure 11A, the directions of the maximum and minimum sound pressure output by the acoustic output device correspond to the directions of its directional characteristics, and the directions of the maximum and minimum are opposite when the first perforation section 611 is located directly above the first loudspeaker 620 in the direction of vibration (i.e., the first perforation section 611 is located on the side wall of the enclosure directly opposite the first diaphragm 621, and the line connecting the geometric center of the first perforation section 611 and the geometric center of the shape of the first diaphragm 621 runs parallel to the direction of vibration of the first loudspeaker 620), and the second perforation section 612 and the third perforation section 613 are located relative to the first perforation section 611 on the same side wall of the enclosure perpendicular to the direction of vibration. The direction of the minimum is the aforementioned specific direction.At the far-field position in this specific direction (minimum direction), the sound pressure of the acoustic output device is low (e.g., close to zero). This specific direction extends from the sound outlet hole of the front chamber of the acoustic output device 600 (e.g., the first hole section 611 in ). Fig. 10A) to the sound outlet hole of the rear chamber (e.g. the equivalent hole section, point M, of the second hole section 612 and third hole section 613 in Fig. 10A).

[0064] As in Fig. 10B and Fig. As shown in Figure 11B, the first perforated section 611 is arranged directly above the first loudspeaker 620 in the direction of vibration; that is, the first perforated section 611 is located on the side wall of the enclosure directly opposite the first diaphragm. The first rear chamber 640 is acoustically coupled to two acoustic perforated sections (the second perforated section 612 and a further second perforated section 612'), with the second perforated section 612 and the further second perforated section 612' being arranged relative to the first perforated section 611 on both side walls of the enclosure perpendicular to the direction of vibration.The second rear chamber 670 adjoins the first rear chamber 640. The second rear chamber 670 is acoustically coupled to the third perforated section 613 and a further third perforated section 613', wherein the third perforated section 613 and the further third perforated section 613' are arranged relative to the first perforated section 611 on two side walls of the housing perpendicular to the direction of vibration. In this case, the second perforated section 612 and the further second perforated section 612' are arranged symmetrically left-right in the direction of vibration with respect to the first perforated section 611, and the third perforated section 613 and the further third perforated section 613' are also arranged symmetrically left-right with respect to the first perforated section 611.The connecting line between the equivalent hole section of the second hole section 612, the further second hole section 612', the third hole section 613 and the further third hole section 613' and the first hole section 611 then lies in a direction that essentially coincides with the direction of oscillation. As in . Fig. As shown in Figure 10B, point M indicates the position of the equivalent hole section. In this case, the connecting line between point M and the geometric center of the first hole section 611 runs parallel to the direction of vibration of the first loudspeaker 620, and point M lies on the midline between the geometric centers of the second hole section 612 and the third hole section 613. For example, if the second hole section 612 and the third hole section 613 are arranged symmetrically with respect to the partition plate 614, point M can be located at the geometric center of the partition plate 614. The directions of the maximum and minimum sound pressure of the far-field radiation of the acoustic output device 600 correspond to the directions of the directional characteristic of the acoustic output device, with the maximum and minimum directions being opposite. Here, the minimum direction is the specific direction, i.e.,the direction from the sound outlet hole of the front chamber of the acoustic output device 600 (e.g. the first hole section 611 in . Fig. 10B) to the sound outlet hole of the rear chamber (e.g. the equivalent hole section, namely point M, of the second hole section 612, of the further second hole section 612', of the third hole section 613 and of the further third hole section 613' in Fig. 10B).

[0065] As in Fig. 10C and Fig. As shown in Figure 11C, the first perforated section 611 is arranged directly above the first loudspeaker 620 in the direction of vibration; that is, the first perforated section 611 is located on the side wall of the enclosure directly opposite the first diaphragm. The first rear chamber 640 is acoustically coupled to the second perforated section 612 and the further second perforated section 612', the second perforated section 612 and the further second perforated section 612' being arranged relative to the first perforated section 611 on both side walls of the enclosure perpendicular to the direction of vibration. The second rear chamber 670 adjoins the first rear chamber 640, the second rear chamber 670 being a closed cavity in this case. The second front chamber 660 is acoustically coupled to the third perforated section 613.In the direction of vibration, the third hole section 613 is located on the side of the housing opposite the first hole section 611, i.e., directly below the geometric center of the shape of the second diaphragm 651 of the second loudspeaker 650. That is, the third hole section 613 is located on the side wall of the housing that is directly opposite the geometric center of the shape of the second diaphragm 651. In this case, the direction of the connecting line between the equivalent hole section of the second hole section 612 and the further second hole section 612' and the first hole section 611 essentially coincides with the direction of vibration. As in . Fig. As shown in Figure 10C, point M indicates the position of the equivalent hole section. In this case, the far-field radiation of the acoustic output device 600 has a principal petal (corresponding to the direction of maximum sound pressure) and a secondary petal. The direction of the principal petal (i.e., the maximum direction) extends from the equivalent hole section, namely point M, of the second hole section 612 and the further second hole section 612' to the first hole section 611. The direction of the secondary petal extends from the equivalent hole section, namely point M, of the second hole section 612 and the further second hole section 612' to the third hole section 613. With reference to Fig. 10C and Fig. 11C shows that the minimum direction is in the direction from the second hole section 612 to the third hole section 613 or in the direction from the further second hole section 612' to the third hole section 613.

[0066] As in Fig. 10D and Fig. As shown in Figure 11D, the first perforated section 611 is arranged directly above the first loudspeaker 620 in the direction of vibration; that is, the first perforated section 611 is located on the side wall of the enclosure directly opposite the first diaphragm. The first rear chamber 640 is acoustically coupled to the second perforated section 612 and the further second perforated section 612', the second perforated section 612 and the further second perforated section 612' being arranged relative to the first perforated section 611 on both side walls of the enclosure perpendicular to the direction of vibration. The second rear chamber 670 adjoins the first rear chamber 640.The second rear chamber 670 is acoustically coupled to the third perforated section 613 and the further third perforated section 613', the third perforated section 613 and the further third perforated section 613' being arranged relative to the first perforated section 611 on both side walls of the housing perpendicular to the direction of vibration. The second front chamber 660 is acoustically coupled to a fourth perforated section 615. In the direction of vibration, the fourth perforated section 615 is located directly below the position of the housing where the first perforated section 611 is located; that is, the fourth perforated section 615 is located on the side wall of the housing directly opposite the geometric center of the shape of the second diaphragm.In this case, in the first loudspeaker 620, the first hole section 611 and the equivalent hole section of the second hole section 612 and the further second hole section 612' form a dual sound source, and in the second loudspeaker 650, the equivalent hole section of the third hole section 613 and the further third hole section 613', as well as the fourth hole section 615, form another dual sound source. In this case, the second hole section 612 and the third hole section 613 have an equivalent hole section point M1, the further second hole section 612' and the further third hole section 613' have an equivalent hole section point M2, and the four hole sections, namely the second hole section 612, the further second hole section 612', the third hole section 613, and the further third hole section 613', have an equivalent hole section point M3. The position of point M3 can be determined by referring to the position of point M in . Fig. 10B is taken as an example, and further explanation is unnecessary here. The direction of the connecting line between the equivalent hole section point M3 and the first hole section 611 essentially coincides with the direction of oscillation. In this case, the far-field radiation of the acoustic output device 600 has a principal petal (corresponding to the direction of maximum sound pressure) and a secondary petal. The direction of the principal petal (i.e., the maximum direction) runs from the equivalent hole section point M3 to the first hole section 611. The direction of the secondary petal runs from the equivalent hole section point M3 to the fourth hole section 615. Based on Fig. 10D and Fig. Figure 11D shows that the minimum direction lies in the direction from the equivalent hole section point M1 to the fourth hole section 615, or in the direction from the equivalent hole section point M2 to the fourth hole section 615. In this case, the far-field radiation of the acoustic output device 600 can also realize a weak heart-shaped directional characteristic, as shown in Fig. 11D shown. In comparison to the heart-shaped directional characteristic in Fig. 11A and Fig. 11B is the region of minimum in the far-field radiation of the in Fig. In the acoustic output device shown in Figure 11D, the sound pressure level is 600 mm narrower, the sound pressure level is higher in the minimum direction and in the adjacent directions, and the sound pressure level is relatively uniform in the directions near the maximum direction (directions from 0° to 180°). In some embodiments, the [description of the acoustic output device] shown in Figure 11D is suitable. Fig. 10D shows the acoustic output device 600 for applications requiring uniform radiation in a half-space.

[0067] In some embodiments, the arrangement of the sound outlet sections of the acoustic output device is not limited to the possibilities mentioned above; rather, the sound outlet sections can be arranged according to actual requirements. In some embodiments, the first outlet section corresponding to the first front chamber of the first loudspeaker can be adjusted so that, when worn, it corresponds to the listening position of the user's ear (e.g., aligned with or located near the opening of the user's ear canal). The outlet section corresponding to the first rear chamber of the first loudspeaker and the single sound outlet section of the second loudspeaker should be located as far away as possible from the first outlet section in order to reduce interference between the other sound outlet sections and the first sound wave emitted by the first outlet section.Based on the actual application scenario, the requirements for the perceived sound quality of the acoustic output device, or the reduction of sound losses, the area in which the acoustic output device must reduce sound losses can be determined in some embodiments (e.g., a 30° circular sector area at a distance of 10 cm from the user's ear). This allows the directions of the maximum and minimum sound pressure of the far-field radiation pattern of the acoustic output device to be determined, in order to then establish the arrangement positions of the respective sound outlet hole sections.

[0068] To reduce the overall dimensions of the acoustic output device, the dimensions of the loudspeaker serving as the single sound source should not be too large. Otherwise, the fundamental resonant frequency of the loudspeaker of the single sound source (i.e., the resonant frequency of the closed cavity of the loudspeaker of the single sound source) would become too high, making it difficult to lower the lower frequency limit of the area in which the acoustic output device achieves the heart-shaped directional characteristic into the frequency range of the human voice. Fig. 12A and Fig. Figure 12B shows a schematic representation of the directional characteristic of the far-field radiation of the acoustic output device with exemplary arrangement positions of hole sections according to some embodiments of the present description. As in Fig. 12A and Fig. As shown in Figure 12B, the acoustic output device 700 has a first loudspeaker 710 and a second loudspeaker 720. The front and rear chambers of the first loudspeaker 710 are acoustically coupled to the first perforated section 711 and the second perforated section 712, respectively, and function as a dual source. One chamber of the second loudspeaker 720 is closed, while the other chamber is acoustically coupled to the third perforated section 713 and serves as a single sound source. To ensure that the sound losses of the acoustic output device 700 are always low at the sides of the user's head across the entire frequency range, as shown in Figure 12B, the following configuration is used: Fig. 12A and Fig. As shown in Figure 12B, the second loudspeaker 720, which serves as a single sound source, is smaller than the first loudspeaker 710, which serves as a dual sound source. The length of the second loudspeaker 720 is similar to the thickness of the first loudspeaker 710. The first perforation section 711 is oriented towards the user's ear canal opening, while the second perforation section 712 and the third perforation section 713 are both located far from the first perforation section 711. In this case, in the mid-low frequency range (e.g., below 1 kHz), the output of the single sound source can be neglected due to the lower sound pressure level compared to the dual sound source. The acoustic output device 700 then operates approximately only with the dual sound source and implements a figure-eight dual sound source directional characteristic to reduce sound losses, as shown in Figure 12B. Fig. 12A is shown. In the mid-high frequency range (e.g., 1 kHz–4 kHz), the single and dual sound sources work together to achieve a heart-shaped directional characteristic, as shown in Fig. 12B shown.

[0069] In some embodiments, the closed cavity of the second loudspeaker, which is not acoustically coupled to a hole section, can be used in the acoustic output device (e.g., the second front chamber 560 in Fig. 5A, the second rear chamber 570 in Fig. 5B etc.), are filled with acoustic granular material. This increases the virtual volume of the closed cavity and lowers the resonant frequency of the closed cavity, which in turn reduces the lower frequency limit of the heart-shaped directional characteristic of the acoustic output device and extends the frequency range of the heart-shaped directional characteristic.

[0070] Fig. Figure 13 shows a schematic representation of another acoustic output device according to some embodiments described in the present description. As in Fig. As shown in Figure 13, the acoustic output device 800 can, in some embodiments, comprise a first loudspeaker 810, a second loudspeaker 820, and a third loudspeaker 830, which are arranged separately. The first loudspeaker 810 can emit a first sound wave, and the second loudspeaker 820 can emit a second sound wave. The first and second sound waves emitted by both loudspeakers can satisfy certain phase and amplitude conditions (e.g., same amplitude, opposite phase) and thus form a dual sound source structure.The third loudspeaker 830 can emit a third sound wave, and this third sound wave, together with the second sound wave emitted by the second loudspeaker 820 and the first sound wave emitted by the first loudspeaker 810, can fulfill specific phase and amplitude conditions at the far-field position in the direction of the acoustic output device 800, such that the third sound wave, as well as the first and second sound waves, superimpose and cancel each other out at this far-field position. This achieves the directional characteristic of the acoustic output device 800 in the far field.In some embodiments, the first loudspeaker 810, the second loudspeaker 820, and the third loudspeaker 830 can be loudspeakers in which either the front or the rear chamber is closed and the sound is directed only from the open cavity. In some embodiments, the acoustic output device 800 can comprise a loudspeaker box.

[0071] In some embodiments, the output of the acoustic output device can be measured with a test microphone. In some embodiments, a test microphone can be provided at the far-field position in the specified direction of the acoustic output device and at the corresponding far-field position in the opposite direction to measure the sound pressure levels at both far-field positions. This yields the magnitude of the sound pressure level difference between the two corresponding far-field positions. By comparing the absolute value of this difference with a preset sound pressure level threshold, it can be determined whether the acoustic output device exhibits a directional characteristic in the specified direction and its opposite direction.

[0072] Fig. Figure 14 shows a schematic representation of the acoustic transmission in the acoustic output device, which is equipped with a second loudspeaker, according to some embodiments described in this document. It refers to Fig. 14. In some embodiments, one of the test microphones can be positioned at the far-field position in the specified direction of the acoustic output device. In some embodiments, the far-field position of the acoustic output device can be a position greater than a preset distance threshold from the acoustic output device, for example, a position more than 25 cm away. In some embodiments, for a frequency range of 1 kHz to 4 kHz, the far-field position of the acoustic output device can be more than 5.5 cm away from the acoustic output device. In some embodiments, the test microphone can be positioned at a distance of 30 cm from the acoustic output device in the specified direction.The specified direction is the direction from the sound outlet hole section of the front chamber of the acoustic output device (e.g., the first hole section) to the sound outlet hole section of the rear chamber (e.g., the second hole section) and their adjacent directions. In some embodiments, the front chamber of the acoustic output device may refer to the first front chamber of the first loudspeaker, and the rear chamber of the acoustic output device may refer to the first rear chamber of the first loudspeaker as well as an equivalent chamber or the common cavity of the output chamber of the second loudspeaker. When the acoustic output device is in the worn state, the specified direction may also be the direction in which the acoustic output device is facing away from the user's ear.In some embodiments, the absolute value of the difference in sound pressure levels measured by the test microphones at the two corresponding far-field positions in the specified direction and the opposite direction of the acoustic output device is no less than a preset sound pressure level threshold value to achieve the directional characteristic. The sound pressure measured by the test microphone at the far-field position in the specified direction may be low, for example, close to zero.

[0073] In some embodiments, the sound pressure received by the test microphone comprises two groups of sound waves: the first group includes sound waves emitted from a hole section acoustically coupled to the front chamber (e.g., the first sound wave), and its transfer function is z(1); the second group includes sound waves emitted from a hole section acoustically coupled to the rear chamber (e.g., the second and third sound waves), and its transfer function is z(2). To ensure that the far-field radiation of the acoustic output device has a directional characteristic, the two groups of sound waves received by the test microphone must cancel each other out. That is, the sound pressure amplitudes of the two groups of sound waves at the location of the test microphone must be equal, and their phases must be opposite. The received signal p",, « The test microphone's specifications are then as follows: pmic=p(1)∗z(1)+[p(2)+p(3)]∗z(2)=0

[0074] Here, p(1) represents the sound pressure generated by the dual sound source (i.e., the first loudspeaker, SPK1 in Fig. 14) is radiated at the front chamber, p(2) for the sound pressure emitted by the dual sound source (i.e. the first loudspeaker, SPK1 in Fig. 14) is radiated at the rear chamber, and p(3) for the sound pressure radiated from the single sound source (i.e. the second loudspeaker, SPK2 in Fig. 14) is emitted from the rear chamber.

[0075] In some embodiments, mutual interference must be avoided when measuring p(1), p(2), and p(3). Therefore, when measuring p(1), the first loudspeaker can be switched on and the second loudspeaker switched off. Simultaneously, a perforation section connected to the rear chamber (e.g., the second perforation section) can be temporarily blocked with cotton wool, rubber, etc. The measurement is then performed with another test microphone positioned inside or near (e.g., at a distance of 2 mm to 3 mm) a perforation section connected to the front chamber (e.g., the first perforation section). When measuring p(2), the first loudspeaker can be switched on and the second loudspeaker switched off. Simultaneously, a perforation section connected to the front chamber (e.g., the first perforation section) can be temporarily blocked with cotton wool, rubber, etc.The measurement is then performed with another test microphone positioned inside or near a perforation section (e.g., the second perforation section) connected to the rear chamber of the first loudspeaker. During the measurement of p(3), the second loudspeaker can be switched on and the first loudspeaker switched off. The measurement is performed with another test microphone positioned inside or near a perforation section (e.g., the second perforation section or a third perforation section mentioned later, etc.) connected to the rear chamber of the second loudspeaker.

[0076] In some embodiments, a larger shielding plate (e.g., with a diameter of 1 m) can also be provided around the acoustic output device. The shielding plate is arranged around the acoustic output device and rigidly connected to it. The sound outlet section of the front chamber (i.e., the hole section connected to the front chamber) and the sound outlet section of the rear chamber (i.e., the hole section connected to the rear chamber) are located on opposite sides of the shielding plate. By providing the shielding plate, the mutual interference between the first sound wave emitted from the sound outlet section of the front chamber and the second and third sound waves emitted from the sound outlet section of the rear chamber is significantly reduced or even isolated, thus increasing the measurement accuracy of p(1), p(2), and p(3).In some embodiments, if such a shielding plate is present, the first loudspeaker can be switched on and the second loudspeaker switched off, while at the same time test microphones are provided on the hole section connected to the front chamber and on the hole section connected to the rear chamber in order to measure p(1) and p(2) simultaneously.

[0077] According to the distributive law of convolution, formula (1) can be expressed as follows: pmic=[p(1)∗z(1)+p(2)∗z(2)]+p(3)∗z(2)=0

[0078] Here, [p(1) * z(1) + p(2) * z(2)] represents the sound pressure of the sound waves emitted by the dual sound source (i.e., the first loudspeaker, SPK1 in Fig. 14) are radiated (e.g., the first and second sound waves), at the test microphone and p(3) * z(2) represents the sound pressure of the sound waves emitted by the single sound source (i.e., the second loudspeaker, SPK2 in Fig. 14) are radiated (e.g., the third sound wave) at the microphone. Therefore, by adjusting the first and second electrical signals, the dual sound source (the first loudspeaker) and the single sound source (the second loudspeaker) can be excited separately, and the sound pressure amplitude and phase of the sound waves arriving at the test microphone, radiated by both sound sources, can be recorded. By adjusting the amplitude and phase of the second electrical signal driving the single sound source (the second loudspeaker, SPK2) and / or the amplitude and phase of the first electrical signal driving the dual sound source (first loudspeaker, SPK1), it is possible to obtain a precise measurement of the sound pressure amplitude (i.e., the sound pressure amplitude).The sound pressure level amplitude of the sound wave (namely the third sound wave) emitted by the single sound source (namely the second loudspeaker) and the sound wave (namely the superimposed sound wave of the first and second sound waves) emitted by the dual sound source (namely the first loudspeaker) are equal at the test microphone, and their phases are opposite. This results in the sound pressure at the far-field position in the specified direction of the acoustic output device being zero. Thus, the sound pressure level at this far-field position is zero, and the absolute value of the sound pressure level difference between the far-field positions in at least one pair of opposite directions is not less than the preset sound pressure level threshold. This achieves the directional characteristic of the far-field radiation of the acoustic output device.

[0079] Fig. Figure 15 shows a schematic example flowchart of the adaptation of a second electrical signal according to some embodiments of the present description. As in Fig. As shown in 15, the 900 process can include the following steps:

[0080] Step 910: Separate excitation of the dual sound source and recording of a first sound pressure level amplitude and a first phase at the test microphone.

[0081] In some embodiments, the dual sound source can be the first loudspeaker. The arrangement position of the test microphone can be the far-field position in the specified direction of the acoustic output device. In some embodiments, the specified direction can be the direction from the sound outlet section of the front chamber to the sound outlet section of the rear chamber and their adjacent directions within a specified directional range. In this case, the first sound pressure level amplitude and the first phase measured by the test microphone can be the first sound pressure level amplitude and the first phase, respectively, after superposition of the first and second sound waves generated by the first loudspeaker at the test microphone.

[0082] In some embodiments, the dual sound source can be excited separately by supplying the first electrical signal only to the first loudspeaker and not supplying a second electrical signal to the second loudspeaker, so that the first loudspeaker works and the second loudspeaker does not work.

[0083] Step 920: Separate excitation of the single sound source and recording of a second sound pressure level amplitude and a second phase at the test microphone.

[0084] In some embodiments, the single sound source can be the second loudspeaker. The arrangement position of the test microphone can be the far-field position in the specified direction of the acoustic output device, the same as the position of the test microphone in step 910. In this case, the sound pressure level amplitude and phase measured by the test microphone can be the second sound pressure level amplitude and the second phase, respectively, of the third sound wave generated by the second loudspeaker at the test microphone.

[0085] In some embodiments, the individual sound source can be excited separately by supplying the second electrical signal only to the second loudspeaker and not supplying a first electrical signal to the first loudspeaker, so that the second loudspeaker works and the first loudspeaker does not work.

[0086] Step 930: Calculating the sound pressure amplitude difference and the phase difference between the single sound source and the dual sound source.

[0087] Compare the second sound pressure level amplitude of the single sound source and the first sound pressure level amplitude of the dual sound source, as measured by the test microphone, to obtain the sound pressure level amplitude difference between them. Compare the second phase of the single sound source and the first phase of the dual sound source, as measured by the test microphone, to obtain the phase difference between them.

[0088] Step 940: Adjusting the second electrical signal so that the sound pressure level amplitude of the sound wave emitted by the single sound source at the test microphone is equal to that of the dual sound source and its phase is opposite to that of the dual sound source.

[0089] Based on the sound pressure amplitude difference and the phase difference obtained in step 930 between the single and dual sound sources, the second electrical signal driving the single sound source is adjusted. This ensures that the sound pressure level amplitude of the sound wave emitted by the single sound source at the test microphone is equal to that of the dual sound source, and its phase is opposite to that of the dual sound source. Consequently, the third sound wave emitted by the single sound source, as well as the first and second sound waves emitted by the dual sound source, can superimpose and cancel each other out at the test microphone. This gives the far-field radiation of the acoustic output device a directional characteristic (e.g., a heart-shaped directional characteristic) and reduces the far-field sound losses of the acoustic output device.

[0090] In some embodiments, based on the sound pressure amplitude difference and the phase difference obtained in step 930 between the single and dual sound sources, the first electrical signal driving the dual sound source can also be adjusted. This ensures that the sound pressure level amplitudes of the sound waves emitted by the single and dual sound sources at the test microphone are equal and their phases are opposite, thus giving the far-field radiation of the acoustic output device a directional characteristic (e.g., a heart-shaped directional characteristic) and reducing the far-field sound losses of the acoustic output device.

[0091] Fig. Figure 16 shows a schematic representation of the frequency response curves when the single sound source or the dual sound sources are excited separately, according to some embodiments described in this document. For example, it is assumed that the single sound source (i.e., the second loudspeaker) and the dual sound source (i.e., the first loudspeaker) share the rear chamber of the acoustic output device (e.g., in the configuration described in [reference to relevant document]. Fig. (structure shown in 5A) and the volume of the rear chamber of the acoustic output device is equal to that of the front chamber. In this case, the hole section connected to the front chamber is the first hole section and the hole section connected to the rear chamber is the second hole section (e.g., in the structure shown in 5A). Fig. (structure shown in Figure 5A). The areas of the first and second hole sections are equal. The amplitude of both the second electrical signal, which excites the single sound source, and the first electrical signal, which excites the dual sound source, is 1 V, and the phase of both signals is 0°. As shown in Figure 5A. Fig. As shown in 16, under the conditions mentioned above, the curve L represents 101 The frequency response curve measured at the test microphone with separate excitation of the dual sound source is shown, while the curve L 102 The frequency response curve measured at the test microphone is shown when the individual sound source is excited separately.

[0092] Under the conditions mentioned above, the sound pressure level amplitude difference and the phase difference between the single sound source and the dual sound source can be measured at various frequency points at the location of the test microphone (i.e., in the far field of the acoustic output device) using procedure 900. Simultaneously, by comparing the curves L 101 and L 102 in Fig. 16. The sound pressure level amplitude difference between the single sound source and the dual sound source at different frequency points at the location of the test microphone (i.e., in the far field of the acoustic output device) will also be determined.

[0093] In some embodiments, specific amplitude and / or phase differences between the first and second electrical signals are achieved in the target frequency range by adjusting their amplitude and phase. This causes the sound wave (the third sound wave) generated by the single sound source (the second loudspeaker) and the sound waves (the first and second sound waves) generated by the dual sound source (the first loudspeaker) to superimpose in such a way that the far-field radiation of the acoustic output device exhibits a directional characteristic. In some embodiments, the target frequency range can extend from 100 Hz to 10 kHz. In some embodiments, the acoustic output device, consisting of the single and dual sound sources, can reduce sound losses over a wide frequency band from 100 Hz to 10 kHz.The target frequency range can include a first frequency range, which may contain parts of the mid-high frequency range, e.g., 800 Hz to 10,000 Hz. In the first frequency range, the acoustic output device can utilize the principle of heart-shaped directional characteristics to reduce sound losses; that is, the far-field radiation of the acoustic output device exhibits a heart-shaped directional characteristic. The target frequency range can also include a second frequency range, which may contain parts of the mid-low frequency range, e.g., 100 Hz to 800 Hz. In the second frequency range, the acoustic output device can utilize the principle of dual sound source directional characteristics to reduce sound losses. Further details can be found in [reference to be inserted here]. Fig. 1 and the accompanying explanations.

[0094] In some embodiments, the acoustic output device can have a dual sound source directional characteristic in the range of 100 Hz to 800 Hz. This means that in the range of 100 Hz to 800 Hz, the difference between the sound pressure level of the sound wave emitted by the first loudspeaker at the perforation section acoustically coupled to the first rear chamber (e.g., the second perforation section) (e.g., the superimposed sound wave of the first and second sound waves) and the sound pressure level of the third sound wave emitted by the second loudspeaker at the perforation section coupled to it (e.g., the third perforation section) is not less than 6 dB. In some embodiments, if the sound pressure of the sound wave emitted by the single sound source at the rear chamber is significantly lower than the sound pressure of the sound wave emitted by the dual sound source at the rear chamber, i.e.,If p(3) ≤ p(2), and the sound pressure level of the single sound source is extremely low compared to that of the dual sound source, the acoustic output device can implement a dual sound source directional characteristic. For example, if p(2) / p(3) ≥ 2, then it can be assumed that p(3) ≤ p(2). In this case, the difference in sound pressure levels radiated by the dual sound source and the single sound source at the rear chamber is greater than or equal to 6 dB; that is, the difference between the sound pressure level corresponding to p(2) and the sound pressure level corresponding to p(3) is greater than or equal to 6 dB, and the acoustic output device can implement a dual sound source directional characteristic.

[0095] In summary, the single sound source (the second loudspeaker) does not allow free air circulation in the frequency range of 100 Hz to 800 Hz due to its closed front chamber and the fact that only the rear chamber is connected to the ambient air, when the same electrical signal is applied to the single and dual sound sources (i.e., the amplitude and phase of the first and second electrical signals are identical). This results in the single sound source having difficulty emitting low-frequency sound waves at the acoustically coupled section of the hole to the rear chamber.Therefore, in this frequency range, the difference between the sound pressure level of the sound waves emitted by the dual sound source (the first loudspeaker) at the perforated section coupled to the rear chamber and the sound pressure level of the sound waves emitted by the single sound source (the second loudspeaker) at the perforated section coupled to the rear chamber can be greater than or equal to 6 dB. In this case, the acoustic output device can exhibit good dual sound source directional characteristics, which allows for a reduction in sound losses in the mid-low frequency range.To achieve a difference of 6 dB or greater than or equal to the sound pressure level of the sound waves emitted by the dual sound source (the first loudspeaker) at the hole section coupled to the rear chamber, and the sound pressure level of the sound waves emitted by the single sound source (the second loudspeaker) at the hole section coupled to the rear chamber, in the range of 100 Hz to 800 Hz, the amplitude of the second electrical signal driving the single sound source (the second loudspeaker) can, in some embodiments, be further reduced in the range of 100 Hz to 800 Hz. For example, the amplitude of the second electrical signal can be set to 0 in the range of 100 Hz to 800 Hz, i.e., no second electrical signal is supplied to the single sound source in the range of 100 Hz to 800 Hz.In some embodiments, when worn, the acoustically coupled perforated section of the first loudspeaker, connected to the first front chamber, can be positioned near the user's ear, while the acoustically coupled section, connected to the first rear chamber, is positioned away from the user's ear. The direction from the perforated section connected to the rear chamber to the perforated section connected to the front chamber points towards the user's ear; that is, the dual sound source directional characteristic formed in the low-frequency range can point towards the user's ear.

[0096] In some embodiments, the amplitude and phase of the first and second electrical signals can be adjusted in the frequency range of 1 kHz to 10 kHz so that the first, second, and third sound waves superimpose at the far-field position in the specified direction of the acoustic output device, and the sound pressure level at this far-field position becomes zero. This ensures that the absolute value of the sound pressure level difference of the acoustic output device between the far-field positions in at least one pair of opposite directions will be no less than a preset sound pressure level threshold, thus giving the far-field radiation of the acoustic output device a directional characteristic. In some embodiments, with reference to Fig. 16. The resonance frequencies corresponding to the resonance peak E of the dual sound source and the resonance peak D of the single sound source are close together, such that the dual and single sound sources each have a first resonance frequency (the frequency corresponding to resonance peak D). The rear chamber, shared by the single and dual sound sources, has a second resonance frequency (the frequency corresponding to resonance peak F). From Fig. As can be seen in Figure 16, the frequency response curves of the single and dual sound sources each exhibit a flat region between the first and second resonance frequencies. In some embodiments, the frequency range between the first and second resonance frequencies can span from 1 kHz to 4 kHz. In some embodiments, the first resonance frequency can be at approximately 1 kHz and the second resonance frequency at approximately 4 kHz, so that the frequency response curves of the single and dual sound sources exhibit a broader flat region, thereby improving the acoustic output performance of the output device. In some embodiments, by adjusting the second and / or the first electrical signal, the far-field radiation of the acoustic output device can exhibit a heart-shaped directional characteristic between the first and second resonance frequencies (e.g., 1 kHz to 4 kHz).In some embodiments, the far-field radiation of the acoustic output device can also exhibit a heart-shaped directional characteristic in a frequency range above the second resonant frequency (e.g., 4 kHz–10 kHz) by adjusting the second and / or the first electrical signal. In some embodiments, when worn, the perforation section of the first loudspeaker acoustically coupled to the first anterior chamber is located near the user's ear, while the perforation section acoustically coupled to the first posterior chamber and the perforation section through which the second loudspeaker emits the third sound wave are located away from the user's ear. The perforation section acoustically coupled to the first posterior chamber and the perforation section through which the second loudspeaker emits the third sound wave have an equivalent perforation area.The direction pointing from this equivalent hole section to the hole section acoustically coupled to the first front chamber points towards the user's ear, i.e., the directional characteristic formed in the mid-high frequency range can point towards the user's ear.

[0097] In some embodiments, the phase difference between the second electrical signal and the first electrical signal is at least 150° between the first and second resonant frequencies. In some embodiments, the phase difference between the second electrical signal and the first electrical signal is at least 150° in the range of 1 kHz to 4 kHz. In some embodiments, the phase difference between the second electrical signal and the first electrical signal is at least 200° at a frequency of 1 kHz, with the phase difference between the second electrical signal and the first electrical signal being at least 150° at a frequency of 4 kHz. By way of example, the following is described in Fig. In the situation shown in Figure 16, it is assumed that the amplitude of the first electrical signal is kept constant at 1 V (i.e., 1000 mV) and the phase is kept constant at 0°. To ensure that the sound pressure level at the far-field position in the specified direction of the acoustic output device is zero, and that the absolute value of the sound pressure level difference of the acoustic output device between the far-field positions in at least one pair of opposite directions is not less than a preset sound pressure level threshold, the second electrical signal can be modulated.In the range of 1 kHz to 4 kHz, the phase and amplitude of the modulated second electrical signal at various frequency points are as follows: At 1 kHz, the amplitude of the second electrical signal is 27.5 mV and the phase is 250°; at 1.5 kHz, the amplitude of the second electrical signal is 344.3 mV and the phase is 225°; at 2 kHz, the amplitude of the second electrical signal is 472 mV and the phase is 229°; at 3 kHz, the amplitude of the second electrical signal is 738.7 mV and the phase is 202°; at 4 kHz, the amplitude of the second electrical signal is 708.76 mV and the phase is 179°. It should be noted that in some embodiments, the sound pressure at the far-field position in the specific direction of the acoustic output device may be low, but should not be zero. Therefore, the corresponding amplitude and phase of the second electrical signal may have a deviation of 10%.For example, at 1 kHz the amplitude of the second electrical signal can be 27.5 * (1 ± 0.1) mV and the phase 250 * (1 ± 0.1)°, i.e. the amplitude of the second electrical signal can be between 24.75 mV and 30.25 mV and the phase can be between 225° and 247.5°.

[0098] Out of Fig. Figure 16 shows that the single sound source (the second loudspeaker) has a first resonance frequency, namely the frequency corresponding to the resonance peak D. When passing through the first resonance frequency, the phase of the sound wave emitted by the single sound source is reversed. Accordingly, the resonance peak E of the dual sound source near the first resonance frequency is caused by the diaphragm of the non-operating single sound source, which acts as a passive diaphragm when the dual sound source is operating. Therefore, the phase of the sound wave emitted by the dual sound source is not reversed at the resonance frequency of the resonance peak E. To ensure that the phases of the sound waves emitted by the single and dual sound sources remain opposite in the far field before and after the first resonance frequency, the phase of the sound wave emitted by the single sound source must be compensated.In some embodiments, the phase difference of the second electrical signal at two frequency points before and after the first resonant frequency is at least 100°. The phase of the second electrical signal at the frequency point before the first resonant frequency is the phase before compensation; the phase of the second electrical signal at the frequency point after the first resonant frequency is the phase after compensation. In some embodiments, the phase difference of the second electrical signal at two frequency points before and after the first resonant frequency can be from 100° to 240°. In some embodiments, the phase difference of the second electrical signal at two frequency points before and after the first resonant frequency can be from 120° to 220°. In some embodiments, the phase difference of the second electrical signal at two frequency points before and after the first resonant frequency can be from 140° to 180°.In some embodiments, the phase difference of the second electrical signal at two frequency points before and after the first resonant frequency can be 150° to 160°.

[0099] It should be noted that if the phase of the sound waves from only one of the two sound sources (dual sound source and single sound source) changes by 180° near a certain resonant frequency, and to prevent this change from causing the sound waves to no longer cancel each other out in the far field, the electrical signal of one of the two sound sources (dual sound source and single sound source) must be adjusted before and after the resonant frequency (e.g., phase-shifted by 180° or approximately 180°). However, since the phase difference between the first and second electrical signals can differ at various frequency points, the final phase difference between the two after such phase compensation for one of the electrical signals may not be exactly 180°, but close to or approximately 180°.

[0100] In some embodiments, due to differing loudspeaker specifications of the acoustic output device in actual products, different dimensions of the front and rear chambers, varying surface areas and depths of the corresponding sound outlet hole sections, and different structural shapes of the front and rear chambers, the positions of the resonance peaks (e.g., resonance peaks D and F of the single sound source and resonance peak G of the dual sound source, etc.) may be shifted. Therefore, the range of values ​​of the phase difference of the second electrical signal at two frequency points in different frequency ranges before and after a resonance peak can vary.

[0101] In some embodiments, the phase difference of the second electrical signal at two frequency points located 10 Hz before and after the first resonant frequency can be 100°–240°. In some embodiments, due to possible size differences of the individual sound source, the phase difference of the second electrical signal at two frequency points located 500 Hz before and after the first resonant frequency can be 120°–220°. In some embodiments, due to possible structural differences of the individual sound source, the phase difference of the second electrical signal at two frequency points located 1000 Hz before and after the first resonant frequency can be 140°–180°.

[0102] In some embodiments, as can be seen from Fig. As can be seen from Figure 16, the first resonant frequency (the frequency corresponding to the resonance peak D) is between 800 Hz and 1.2 kHz and close to 1 kHz. In some embodiments, the phase difference of the second electrical signal at 800 Hz and 1.2 kHz can be in the range of 100°–220°, for example, 130°–180°. In some embodiments, due to possible differences in the size of the individual sound source, the phase difference of the second electrical signal at 900 Hz and 1.1 kHz can be in the range of 120°–150°, for example, 130°–150°. In some embodiments, due to possible differences in the size of the individual sound source, the phase difference of the second electrical signal at 950 Hz and 1 kHz can be in the range of 140°–170°, for example, 145°–155°.

[0103] As from Fig. As shown in Figure 16, in some embodiments the rear chamber shared by the single and dual sound sources has a second resonant frequency (i.e., the frequency corresponding to the resonance peak F). Before and after the second resonant frequency, the phase of the sound waves emitted by the single and dual sound sources is not inverted by 180°. Observations of the waveform show that their motion changes from towards each other to relative to each other. Therefore, the phase of the sound waves of either the single or dual sound source must also be compensated before and after the second resonant frequency. In some embodiments, the phase difference of the second electrical signal in the frequency range between two points before and after the second resonant frequency is not less than 100°.In some embodiments, the phase difference of the second electrical signal at two points before and after the second resonant frequency can be 100°–260°. In some embodiments, the phase difference of the second electrical signal at two points before and after the second resonant frequency can be 120°–170°. In some embodiments, the phase difference of the second electrical signal at two points before and after the second resonant frequency can be 140°–160°.

[0104] In some embodiments, the phase difference of the second electrical signal at two points located 100 Hz before and after the second resonant frequency can be 100°–260°. In some embodiments, due to possible size variations of the rear chamber, the phase difference of the second electrical signal at two points located 300 Hz before and after the second resonant frequency can be 130°–180°. In some embodiments, due to possible surface area variations of the sound outlet section of the rear chamber, the phase difference of the second electrical signal at two points located 500 Hz before and after the second resonant frequency can be 160°–170°. In some embodiments, due to possible depth variations of the sound outlet section of the rear chamber, the phase difference of the second electrical signal at two points located 700 Hz before and after the second resonant frequency can be 140°–180°.In some embodiments, due to possible structural differences in the rear chamber leading to volume differences, the phase difference of the second electrical signal at two points located 700 Hz before and after the second resonant frequency can be 170°-240°.

[0105] In some embodiments, as can be seen from Fig. As can be seen from Figure 16, the second resonant frequency (the frequency corresponding to the resonance peak F) is between 3 kHz and 5 kHz and close to 4 kHz. In some embodiments, the phase difference of the second electrical signal at 3 kHz and 5 kHz can be in the range of 100°–240°, for example, 138°–160°. In some embodiments, due to possible volume differences in the rear chamber, the phase difference of the second electrical signal at 3.1 kHz and 4.8 kHz can be in the range of 120°–140°, for example, 130°–140°. In some embodiments, due to possible surface area differences in the sound outlet section of the rear chamber, the phase difference of the second electrical signal at 3.5 kHz and 4.5 kHz can be in the range of 160°–170°, for example, 162°–168°.In some embodiments, due to possible depth differences of the sound exit hole section of the rear chamber, the phase difference of the second electrical signal at 3.8 kHz and 4.2 kHz may be in the range of 155°-180°, for example 160°-170°.

[0106] As from Fig. As shown in Figure 16, in some embodiments the front chamber of the dual sound source (the first loudspeaker) has a third resonant frequency (i.e., the frequency corresponding to the resonance peak G). When passing through the third resonant frequency, the phase of the sound wave radiated by the dual sound source is reversed. Accordingly, when the single sound source is separately excited, the resonance peak of the single sound source near the third resonant frequency (not shown) is caused by the diaphragm of the non-operating dual sound source acting as a passive diaphragm, but the phase of the sound wave radiated by the single sound source near the third resonant frequency is not reversed. Therefore, to ensure that the phases of the sound waves radiated by the single sound source and the dual sound source remain opposite in the far field, the phase of the sound wave radiated by the single sound source must be compensated.In the frequency range between two points before and after the third resonant frequency, the second electrical signal must be compensated. In some embodiments, the phase difference of the second electrical signal at two points before and after the third resonant frequency is at least 100°. In some embodiments, the phase difference of the second electrical signal at two points before and after the third resonant frequency can be 100°–240°. In some embodiments, the phase difference of the second electrical signal at two points before and after the third resonant frequency can be 170°–200°.

[0107] In some embodiments, the phase difference of the second electrical signal at two points located 100 Hz before and after the third resonant frequency can be 175°–185°. In some embodiments, due to possible size differences of the front chamber, the phase difference of the second electrical signal at two points located 200 Hz before and after the third resonant frequency can be 170°–200°. In some embodiments, due to possible volume differences of the front chamber, the phase difference of the second electrical signal at two points located 600 Hz before and after the third resonant frequency can be 150°–180°. In some embodiments, due to possible differences in the area and / or depth of the sound outlet section of the front chamber, the phase difference of the second electrical signal at two points located 1000 Hz before and after the third resonant frequency can be 120°–200°.

[0108] In some embodiments, as can be seen from Fig. As shown in Figure 16, the third resonant frequency (the frequency corresponding to the resonance peak G) is between 5 kHz and 8 kHz. In some embodiments, the phase difference of the second electrical signal at 5 kHz and 8 kHz can be in the range of 100°–200°, for example, 115°–160°. In some embodiments, due to possible volume differences in the front chamber, the phase difference of the second electrical signal at 5.1 kHz and 7.5 kHz can be in the range of 110°–150°, for example, 130°–140°. In some embodiments, due to possible surface area differences in the sound outlet hole section of the front chamber, the phase difference of the second electrical signal at 5.4 kHz and 7 kHz can be in the range of 140°–170°, for example, 150°–159°.In some embodiments, due to possible differences in the depth of the sound outlet hole section of the front chamber, the phase difference of the second electrical signal at 5.8 kHz and 6 kHz may be in the range of 170°-180°, for example 170°-176°.

[0109] By adjusting the amplitude and phase of the second electrical signal driving the single sound source and / or the first electrical signal driving the dual sound source at several frequency points, a corresponding amplitude and phase difference is created between the second and first electrical signals. This results in a low sound pressure level at the test microphone of the sound waves emitted by the single and dual sound sources, for example, close to zero, and equation (1) is satisfied.

[0110] Fig. Figure 17 shows a schematic representation of the directional characteristic of the far-field radiation of the acoustic output device after adjustment of the second electrical signal according to some embodiments of the present description. As in Fig. As shown in Figure 17, by adjusting the second electrical signal at frequencies of 1 kHz, 2 kHz, 3 kHz, 5 kHz, 8 kHz, and 10 kHz, the output (e.g., its phase and / or amplitude) of the single sound source (the second loudspeaker) can be adjusted so that there is virtually no output at the far-field position in the specified direction of the acoustic output device. In this case, the far-field radiation of the acoustic output device exhibits a directional characteristic. The 0° direction denotes the direction in which the acoustic output device points towards the opening of the user's ear canal, for example, the direction (e.g., direction X1 in Figure 17). Fig. 4) from the sound outlet section AS2 of the posterior chamber of the acoustic output device (e.g., the second hole section) to the sound outlet section AS1 of the anterior chamber (e.g., the first hole section); the 180° direction denotes the direction in which the acoustic output device is oriented away from the ear canal opening of the user's ear, for example, the direction (e.g., direction X1' in Fig. 4) from sound outlet section AS1 of the front chamber of the acoustic output device (e.g., the first hole section) to sound outlet section AS2 of the rear chamber (e.g., the second hole section). At a frequency of 1 kHz, the far-field radiation of the acoustic output device exhibits a heart-shaped directional characteristic. The maximum of the sound field is at approximately 15° and the minimum at approximately 180°. The absolute value of the sound pressure level difference between these 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 directional characteristic. The maximum of the sound field is at approximately 15° and the minimum at approximately 200°. The absolute value of the sound pressure level difference between these 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 directional characteristic. The maximum of the sound field is at approximately 15° and the minimum at approximately 190°. The absolute value of the sound pressure level difference between these 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 directional characteristic. The maximum of the sound field is at approximately 30° and the minimum at approximately 200°. The absolute value of the sound pressure level difference between these two directions is approximately 19.6 dB. At 8 kHz, the far-field radiation exhibits a heart-shaped directional characteristic and comprises a primary and a secondary petal. The direction of the primary petal (i.e., the maximum direction of the sound field) is at approximately 40° and the direction of the secondary petal is at approximately 200°.Between the main and secondary petals, there are minima with directions of approximately 150° and 250°, respectively. The absolute values ​​of the sound pressure level differences between these two minima and the maximum are approximately 16.6 dB and 12.9 dB, respectively. At 10 kHz, the far-field radiation exhibits a heart-shaped directional characteristic and encompasses one main and one secondary petal. The direction of the main petal (i.e., the direction of the sound field maxima) is approximately 10°, and the direction of the secondary petal is approximately 200°. Between the main and secondary petals, there are minima with directions of approximately 160° and 240°, respectively. The absolute values ​​of the sound pressure level differences between these two minima and the maximum are approximately 32.4 dB and 19.93 dB, respectively.Thus, at frequencies of 1 kHz, 2 kHz, 3 kHz, 5 kHz, 8 kHz and 10 kHz, the direction of the directional characteristic of the far-field radiation of the acoustic output device points from the 180° direction and its adjacent directions to the 0° direction and its adjacent directions, i.e., the direction from the sound outlet hole section AS2 of the rear chamber of the acoustic output device (e.g., the second hole section) to the sound outlet hole section AS1 of the front chamber (e.g., the first hole section) (e.g., the direction X1 in . Fig. 4) there and their adjacent directions.

[0111] Fig. 18A and Fig. Figure 18B shows a representation of the directional characteristic measurement curves of the acoustic output device according to some embodiments described in this document. Fig. 18A a white noise signal as a test signal and Fig. 18B a sweep frequency signal as a test signal. The frequency ranges of the white noise signal and the sweep frequency signal are from 1 kHz to 4 kHz to test the directional characteristics of the acoustic output device in the frequency range of 1 kHz to 4 kHz. In some embodiments, the white noise signal can be a signal that contains all frequencies in the range of 1 kHz to 4 kHz simultaneously at any given time. The white noise signal can simulate complex signal outputs. The sweep frequency signal can be a signal that gradually increases from 1 kHz to 4 kHz. At any given time, the sweep frequency signal contains a signal with only a single frequency. The sweep frequency signal can simulate simple signal inputs. As in Fig. 18A and Fig. As shown in Figure 18B, the dashed line represents the frequency response curve of the acoustic output device in the 0° direction, and the solid line represents the frequency response curve of the acoustic output device in the 180° direction. In some embodiments, the output sound pressure level of the acoustic output device in the 0° direction can be measured with a test microphone positioned near the sound outlet section of the front chamber (e.g., the first hole section) (e.g., 10 cm from the sound outlet section of the front chamber). The output sound pressure level of the acoustic output device in the 180° direction can be measured with a test microphone positioned near the sound outlet section of the rear chamber (e.g., the second and / or third hole section) (e.g., 10 cm from the sound outlet section of the rear chamber).In some embodiments, the test microphone, the sound outlet section of the front chamber, and the sound outlet section of the rear chamber are located on a straight line, this straight line corresponding to the straight line of the 0° and 180° directions. As in . Fig. As shown in Figure 18A, the absolute value of the sound pressure level difference between the 0° and 180° directions of the acoustic output device, using a white noise signal as the test signal, is 8 dB to 18 dB, and the acoustic output device exhibits good heart-shaped directivity. As shown in Fig. As shown in Figure 18B, the absolute value of the sound pressure level difference between the 0° direction and the 180° direction of the acoustic output device when using a sweep signal as a test signal is 15 dB to 25 dB, and the acoustic output device exhibits an even better heart-shaped directivity characteristic.

[0112] It should be noted that the adjustments mentioned above were made specifically for the second electrical signal. In some embodiments, corresponding adjustments can alternatively be made to the first electrical signal only. In some embodiments, corresponding adjustments can also be made to both the first and second electrical signals simultaneously. The following section explains the specific procedure for adjusting the electrical signals using the second electrical signal as an example.

[0113] Fig. Figure 19 shows a schematic representation of an equivalent model for adapting the acoustic output device according to some embodiments of the present description using a preset algorithm. As in Fig. As shown in Figure 19, the acoustic output device may, in some embodiments, further comprise a modulator. According to a preset algorithm, the modulator can modulate the second electrical signal that drives the second loudspeaker. This ensures that, in the target frequency range, the third sound wave emitted by the second loudspeaker, as well as the first and second sound waves emitted by the first loudspeaker, superimpose and cancel each other out at the far-field position in the specified direction of the acoustic output device. This results in the absolute value of the sound pressure level difference of the acoustic output device between the far-field positions in at least one pair of opposite directions being no less than a preset sound pressure level threshold (e.g.,The sound pressure of the acoustic output device at the far-field position in the specified direction is low (for example, close to zero). In some embodiments, the preset algorithm may include a preset matching method for amplitudes and frequencies, for example, a preset matching plan for amplitude modulation, a preset matching plan for frequency or phase modulation, etc. Further information on amplitude modulation and phase modulation can be found in the descriptions of [reference missing]. Fig. 21 can be found here and will not be repeated.

[0114] In some embodiments, the principle is in Fig. 19 similar to the one in Fig. The principle shown in Figure 14 applies. Based on the sound pressure measured by a test microphone at the far-field position in the specified direction of the acoustic output device, the preset algorithm (e.g., the modulation function H0 of the modulator) for modulating the second electrical signal is determined. When the acoustic output device is operating, the modulator can directly modulate the second electrical signal based on the preset algorithm.

[0115] In some embodiments, a signal called Music can comprise the first electrical signal for driving the first loudspeaker and the second electrical signal for driving the second loudspeaker. The first loudspeaker and the second loudspeaker can each receive the first and second electrical signals, respectively, from the Music signal and emit sound into the room. The test microphone is positioned at the far-field position in the specified direction of the acoustic output device and measures the sound pressure at that position. If the sound pressure signal received by the test microphone is zero, this means that the sound pressure of the sound (i.e., the superimposed sound waves of the first, second, and third sound waves) emitted by the first and second loudspeakers to that target position (the aforementioned far-field position in the specified direction of the acoustic output device) is zero, i.e., Music⋅H1+Music⋅H0⋅H2=0

[0116] Here, H1 and H2 represent the transfer functions for the sound waves (the first and second sound waves) generated by the first loudspeaker and transmitted to the test microphone, and the third sound wave generated by the second loudspeaker and transmitted to the test microphone, respectively; H0 represents the transfer function of the modulator used to modulate the second electrical signal that drives the second loudspeaker.

[0117] By testing with the second speaker switched off, the transfer function H1 of the first speaker (the first transfer function) can be obtained: H1=Mic' / Music'

[0118] In this case, 'Music' represents the input signal (the first electrical signal) with the second speaker switched off, and 'Mic' represents the sound pressure signal received at the test microphone with the second speaker switched off.

[0119] Similarly, by testing with the first loudspeaker switched off, the transfer function of the second loudspeaker H2 (the second transfer function) can be obtained: H2=Mic'' / Music''

[0120] In this case, "Music" represents the input signal (the second electrical signal) with the first loudspeaker switched off, and "Mic" represents the sound pressure signal received at the test microphone with the first loudspeaker switched off.

[0121] The transfer function H0 of the modulator can be obtained using formulas (3) to (5): H0=−H1H2=−Mic' / Music'Mic'' / Music''

[0122] Thus, the transfer function H0 of the modulator can be determined for different frequencies using the formula (6) above, and the appropriately adjusted modulator can be used in the acoustic output device to reduce sound losses at various frequencies. In some alternative embodiments, if multiple test microphones are present, the sound emitted by the first and second loudspeakers at arbitrary positions in the room can be measured or simulated. Therefore, by means of test microphones positioned in at least one pair of opposite directions, the sound pressure level difference magnitude of the far-field radiation from the acoustic output device can be measured in at least one pair of opposite directions.For different frequencies, the transfer function of the modulator can be adjusted using formulas (3) to (6) such that the sound pressure level difference magnitude of the far field radiation of the acoustic output device in at least one pair of opposite directions is not less than a preset sound pressure level threshold.

[0123] In some embodiments, the test microphone may comprise a microphone array. By measuring the sound at the far-field position in the specified direction of the acoustic output device using the microphone array, the accuracy of the measurement data can be improved.

[0124] Fig. Figure 20 shows a schematic representation of an equivalent model for adapting the acoustic output device according to some embodiments of the present description using an active algorithm. As in Fig. As shown in Figure 20, the acoustic output device can, in some embodiments, further comprise a controller, a modulator, and a microphone array. The microphone array can be arranged on the housing of the acoustic output device. The microphone array can serve to estimate the sound signal at a preset position. The preset position can include the far-field position in the specified direction of the acoustic output device. In some embodiments, the preset position can also include the far-field positions in at least one pair of opposite directions of the acoustic output device. In some embodiments, the controller can determine an active algorithm (e.g., an active matching method for amplitude and frequency) based on a sound signal detected by the microphone array. The modulator can then, according to the active algorithm determined by the controller (e.g.,The active adjustment method for amplitude and frequency dynamically modulates the second electrical signal driving the second loudspeaker. This ensures that, within the target frequency range, the third sound wave emitted by the second loudspeaker, along with the first and second sound waves emitted by the first loudspeaker, overlap and cancel each other out at the far-field position in the specified direction of the acoustic output device. This results in the absolute value of the sound pressure level difference of the acoustic output device between the far-field positions in at least one pair of opposite directions being no less than a preset sound pressure level threshold, thus achieving the directional characteristic of the far-field radiation of the acoustic output device.

[0125] In some embodiments, the transfer function of the first loudspeaker in a user-worn acoustic output device can change from the initial value H1 to H1' change the transfer function of the second speaker from the initial value H2 to H2', where H1' and H2' The results may differ for different users. Accordingly, the above formula (3) can be represented as follows: Music⋅H1'+Music⋅H0⋅H2'=0

[0126] In some embodiments, the control for H1' and H2' The variable H0 is adjusted based on the sound waves captured by the microphone array to satisfy formula (7) and thus achieve the reduction of sound losses in the specified direction. The adjusted H0 can be determined using formula (6): H0=−H1'H2'

[0127] Based on the in Fig. The method described in section 20 allows H0 to be adjusted in real time based on the detected sound waves to achieve a real-time reduction of sound losses. This ensures that the absolute value of the sound pressure level difference of the acoustic output device between the far-field positions in at least one pair of opposite directions is not less than a preset sound pressure level threshold, thus realizing the directional characteristic of the far-field radiation of the acoustic output device.

[0128] In some embodiments, for acoustic output devices with different structures, the corresponding transfer function H1 of the first loudspeaker and the transfer function H2 of the second loudspeaker can vary. Therefore, the matching method for the transfer function H0 of the modulator can also differ. For example, the matching method can vary depending on whether the first and second loudspeakers are arranged in the same chamber or not. As another example, the corresponding matching method can differ if the distance between the sound outlet of the rear chamber of the first loudspeaker (e.g., the second hole section 912) and the sound outlet of the second loudspeaker (e.g., the third hole section 913) varies. As yet another example, the corresponding matching method can differ if the acoustic resistance at the sound outlets (e.g.,the first hole section 911, the second hole section 912, the third hole section 913, etc.) varies.

[0129] Fig. Figure 21 shows a schematic block diagram of an amplitude-phase matching algorithm according to some embodiments described in the present description. It is based on Fig. 21. Using the example of adjusting the second electrical signal that drives the second loudspeaker, the input signal comprises an initial first electrical signal and an initial second electrical signal. The initial first and second electrical signals are applied to the first and second loudspeakers, respectively, which then vibrate and generate superimposed sound waves. According to the in Fig.The principle illustrated in Figures 19 and / or 20 determines the transfer function H0 of the modulator. Using the transfer function H0, the amplitude matching and phase matching values ​​for the initial second electrical signal can be determined. In some embodiments, the amplitude of the initial second electrical signal can be matched by a filter. In some embodiments, an IIR filter (infinite impulse response) can be selected. An IIR filter is characterized by low computational effort and good real-time capability. In some embodiments, a FIR filter (finite impulse response) can also be selected. An FIR filter is stable and phase-controlled. It can match the amplitude and simultaneously ensure that synchronously input signals are output synchronously to 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 adjustments of the initial second electrical signal by a filter and a phase shifter can be performed synchronously; alternatively, the adjustment by one component can be performed first, followed by the adjustment by the other. The adjusted second electrical signal and the initial first electrical signal are combined and output as a signal. The sound waves generated by the second loudspeaker under the drive from the adjusted second electrical signal and the sound waves generated by the first loudspeaker under the drive from the initial first electrical signal can be combined at the target position (e.g.,The far-field position in the specific direction of the acoustic output device) superimposes and cancels itself out. As a result, the absolute value of the sound pressure level difference of the acoustic output device between the far-field positions in at least one pair of opposite directions is not less than a preset sound pressure level threshold (e.g., not less than 6 dB), thus realizing the directional characteristic of the acoustic output device.

[0130] The basic concept has been described above. It is obvious to the person skilled in the art that the detailed disclosure above is merely an example and does not constitute a limitation of the present application. Although not explicitly stated, a person skilled in the art may make various modifications, improvements, and changes to the application. These modifications, improvements, and changes are indicated in the application so that they are still within the spirit and scope of the exemplary embodiments of the application.

[0131] The present application also uses specific terms to describe embodiments of the present application. The terms "an embodiment" and / or "some embodiments" refer to a feature, structure, or special characteristic associated with at least one embodiment of the present application. It should therefore be emphasized and noted that the terms "an embodiment" or "an alternative embodiment," which appear two or more times in different places in the present description, do not necessarily refer to the same embodiment. Furthermore, some features, structures, or properties of one or more embodiments of the present application can be appropriately combined with one another.

[0132] It should also be noted that in the preceding description of the embodiments of the present application, various features are sometimes grouped together in one embodiment, one figure, or its description(s) in order to simplify the description of the disclosure of the present application and to facilitate the understanding of one or more embodiments of the invention. However, this method of disclosure does not mean that the subject matter of the present application requires more features than those specified in the claims. In fact, the embodiments have fewer features than the totality of features of the individual embodiments disclosed above.

[0133] In some embodiments, numerical values ​​are used to describe the components and properties. It should be understood that in some cases, the numerical values ​​used to describe the embodiments are further specified by terms such as "approximately," "about," or "essentially." Unless otherwise stated, "approximately," "about," or "essentially" indicate that the stated number allows for a variation of ±20%. Accordingly, in some embodiments, the numerical parameters used in the description and claims are approximate values ​​that may vary depending on the requirements of the individual embodiment. In some embodiments, the required number of valid decimal places for the numerical parameters is to be taken into account using a general rounding procedure.Although the numerical ranges and parameters in some embodiments of the present application for determining the width of the associated perimeter are approximate values, such values ​​have been determined as precisely as possible within the practical scope in the specific embodiments.

[0134] Every patent specification, every patent application, every publication of patent applications, and every other material cited in the present application, such as articles, books, descriptions, publications, documents, etc., is hereby incorporated in its entirety into the present application as a reference. Excluded are application history documents that are inconsistent with or conflict with the content of the present application, as well as documents (currently or subsequently attached to the present application) that limit the broadest scope of the claims of the present application. It is hereby clarified that in the event of any discrepancies or conflicts between the description, definition, and / or use of terms in the application and those in accompanying materials, the description, definition, and / or use of terms in the present application shall prevail.

[0135] In conclusion, it should be understood that the embodiments described in this application serve only to illustrate the principle of the embodiments described therein. Other variants could also fall within the scope of this application. Therefore, alternative configurations of the embodiments described in this application may be considered exemplary and not as limiting, as being consistent with the teachings of this application. Accordingly, the embodiments described in this application are not limited to those expressly presented and described herein.

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