Acoustic signal output device

Abstract

Provided is an acoustic signal output device having a driver unit 11 that sends out an acoustic signal AC1 in a D1 direction, and a driver unit 12 that sends out an acoustic signal AC2 in the D1 direction. The driver unit 11 and the driver unit 12 are positioned along the same virtual plane, and the driver unit 12 is positioned annularly around the driver unit 11. The present invention is designed so that when the acoustic signal AC1 is sent out from the driver unit 11 and the acoustic signal AC2 is sent out from the driver unit 12, the rate of attenuation of the first acoustic signal, relative to a predetermined first point reached by the first acoustic signal AC1, at a second point farther from the acoustic signal output device than the first point will be less than or equal to a predetermined value that is less than the rate of air-propagation attenuation relative to the first point of the acoustic signal at the second point. Alternatively, the acoustic signal output device is designed so that the amount of attenuation of the first acoustic signal relative to the first point at the second point is greater than or equal to a predetermined value that is greater than the amount of air-propagation attenuation the acoustic signal at the second point.

Description

Acoustic signal output device

[0001] The present invention relates to an acoustic signal output device, and more particularly to an acoustic signal output device that does not seal the ear canal.

[0002] In recent years, the increased strain on the ears caused by wearing earphones and headphones has become a problem. Open-ear earphones and headphones, which do not block the ear canal, are known as devices that reduce strain on the ears.

[0003] “WHAT ARE OPEN-EAR HEADPHONES?”, [online], Bose Corporation, [Retrieved November 21, 2022], Internet <https: / / www.bose.com / en_us / better_with_bose / open-ear-headphones.html>

[0004] However, open-ear earphones and headphones have the problem of significant sound leakage to the surroundings. This problem is not limited to open-ear earphones and headphones, but is a common problem with any acoustic signal output device that does not seal the ear canal, including installed speakers and built-in speakers.

[0005] The present invention has been made in view of the above points, and has an object to provide an acoustic signal output device that does not seal the ear canal and is capable of suppressing sound leakage to the surroundings.

[0006] An acoustic signal output device is provided that has one or more first driver units that emit a first acoustic signal in a first direction and one or more second driver units that emit a second acoustic signal in the first direction. Here, the first driver unit and the second driver unit are arranged along the same imaginary plane, and the second driver unit is arranged in a ring shape around the first driver unit. The device is designed so that when the first acoustic signal is emitted from the first driver unit and the second acoustic signal is emitted from the second driver unit, the attenuation rate of the first acoustic signal at a second point farther from the acoustic signal output device than the first point, based on a predetermined first point where the first acoustic signal arrives, is equal to or less than a predetermined value that is smaller than the attenuation rate of the acoustic signal due to air propagation at the second point based on the first point. Alternatively, the device is designed so that the attenuation amount of the first acoustic signal at the second point based on the first point is equal to or greater than a predetermined value that is greater than the attenuation amount of the acoustic signal due to air propagation at the second point based on the first point.

[0007] This structure helps prevent sound from leaking into the surrounding area.

[0008] FIG. 1 is a transparent perspective view illustrating the configuration of an acoustic signal output device of a first embodiment. FIG. 2A is a transparent plan view illustrating the configuration of the acoustic signal output device of the first embodiment. FIG. 2B is a transparent front view illustrating the configuration of the acoustic signal output device of the first embodiment. FIG. 3 is a diagram for explaining the supply of an electric signal to the acoustic signal output device of the first embodiment. FIG. 4A is a diagram for illustrating the use state of the acoustic signal output device of the first embodiment. FIG. 4B is a diagram for illustrating the state of an acoustic signal emitted from the acoustic signal output device of the first embodiment. FIG. 5A is a diagram for illustrating a numerical analysis model in the case where multiple sound emitting surfaces that emit acoustic signals are not on the same plane. FIG. 5B is an enlarged view of region R1 in FIG. 5A. FIG. 6 is a diagram for illustrating a numerical analysis model of acoustic radiation in the case where multiple sound emitting surfaces that emit acoustic signals are not on the same plane. FIG. 7A is a diagram for illustrating a numerical analysis model in the case where multiple sound emitting surfaces that emit acoustic signals are on the same plane, and other sound emitting surfaces are arranged coaxially and annularly around one sound emitting surface. Fig. 7B is an enlarged view of region R1 in Fig. 7A. Fig. 8 is a diagram illustrating a numerical analysis model of acoustic radiation in a case where multiple sound emitting surfaces that emit acoustic signals are on the same plane and other sound emitting surfaces are arranged coaxially and annularly around one sound emitting surface. Fig. 9A is a diagram illustrating a numerical analysis model in a case where multiple sound emitting surfaces that emit acoustic signals are not on the same plane. Fig. 9B is a diagram illustrating a numerical analysis model in a case where multiple sound emitting surfaces that emit acoustic signals are on the same plane and other sound emitting surfaces are arranged coaxially and annularly around one sound emitting surface. Fig. 10A is a graph illustrating acoustic characteristics in a case where multiple sound emitting surfaces that emit acoustic signals are not on the same plane. Fig. 10B is a graph illustrating acoustic characteristics in a case where multiple sound emitting surfaces that emit acoustic signals are on the same plane and other sound emitting surfaces are arranged coaxially and annularly around one sound emitting surface. Figs. 11A and 11B are transparent plan views illustrating the configuration of an acoustic signal output device of a second embodiment. FIG. 12 is a transparent plan view illustrating the configuration of an acoustic signal output device according to the third embodiment.

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] First, a first embodiment of the present invention will be described. <Configuration> An acoustic signal output device 10 of this embodiment is a device for listening to sound that is worn without sealing the user's ear canal (e.g., open-ear earphones, headphones, installed speakers, embedded speakers, etc.). As illustrated in FIGS. 1 to 3 , the acoustic signal output device 10 of this embodiment includes a driver unit 11 (first driver unit) that converts an output signal (electrical signal representing an acoustic signal) OUT1 output from a signal processing device 100 into an acoustic signal AC1 (first acoustic signal) and emits this acoustic signal AC1 in a direction D1 (first direction), and a driver unit 12 (second driver unit) that converts an output signal OUT2 output from the signal processing device 100 into an acoustic signal AC2 (second acoustic signal) and emits this acoustic signal AC2 in the direction D1 (first direction). The driver unit 11 and the driver unit 12 are arranged along the same imaginary plane P, and the driver unit 12 is arranged in a ring shape around the driver unit 11. Here, when an acoustic signal AC1 is emitted from the driver unit 11 and an acoustic signal AC2 is emitted from the driver unit 12, the attenuation rate of the acoustic signal AC1 at a position P2 (second position) farther from the acoustic signal output device 10 than the position P1, which is based on a predetermined position P1 (first position) where the acoustic signal AC1 arrives, is designed to be equal to or less than a predetermined value that is smaller than the attenuation rate of the acoustic signal due to air propagation at the position P2 based on the position P1. Alternatively, the attenuation amount of the acoustic signal AC1 at the position P2 based on the position P1 is designed to be equal to or greater than a predetermined value that is greater than the attenuation amount of the acoustic signal due to air propagation at the position P2 based on the position P1. This will be explained in detail below.

[0010] <Driver Unit 11> The driver unit (speaker driver unit) 11 is a device (device with speaker function) that emits (sounds) an acoustic signal AC1 (first acoustic signal) based on the input output signal OUT1 to one side (D1 direction), and emits an acoustic signal AC3 (third acoustic signal) that is an inverse phase signal (phase-inverted signal) of the acoustic signal AC1 or a signal approximating the inverse phase signal to the other side (D2 direction). That is, the acoustic signal emitted from the driver unit 11 to one side (D1 direction) is referred to as the acoustic signal AC1 (first acoustic signal), and the acoustic signal emitted from the driver unit 11 to the other side (D2 direction) is referred to as the acoustic signal AC3 (third acoustic signal) ( FIG. 3 ). For example, the driver unit 11 includes a diaphragm 113 that vibrates to emit the acoustic signal AC1 in the D1 direction from one surface 113a and emits the acoustic signal AC3 in the D2 direction from the other surface 113b ( FIG. 2B ). In this example, the driver unit 11 emits an acoustic signal AC1 from one surface 111 in the direction D1 by vibrating the diaphragm 113 based on the input output signal OUT1, and emits an acoustic signal AC3, which is an inverse phase signal of or an approximation of the inverse phase signal of the acoustic signal AC1, from the other surface 112 in the direction D2. That is, the acoustic signal AC3 is emitted secondarily in conjunction with the emission of the acoustic signal AC1. Note that the D2 direction (other side) is, for example, the opposite or approximately opposite direction of the D1 direction (one side), but the D2 direction does not need to be strictly the opposite or approximately opposite direction of the D1 direction; it is sufficient that the D2 direction is different from the D1 direction. Furthermore, depending on the type and shape of the driver unit 11, the acoustic signal AC3 may be strictly an inverse phase signal of the acoustic signal AC1, or the acoustic signal AC3 may be an approximation of the inverse phase signal of the acoustic signal AC1. For example, the approximation signal of the opposite-phase signal of acoustic signal AC1 may be (1) a signal obtained by shifting the phase of the opposite-phase signal of acoustic signal AC1, (2) a signal obtained by changing (amplifying or attenuating) the amplitude of the opposite-phase signal of acoustic signal AC1, or (3) a signal obtained by shifting the phase of the opposite-phase signal of acoustic signal AC1 and then changing the amplitude. The phase difference between the opposite-phase signal of acoustic signal AC1 and its approximation signal is δ of one period of the opposite-phase signal of acoustic signal AC1. １% or less. １ Examples of % are 1%, 3%, 5%, 10%, 20%, etc. Furthermore, it is desirable that the difference between the amplitude of the antiphase signal of acoustic signal AC1 and the amplitude of its approximation signal be δ2% or less of the amplitude of the antiphase signal of acoustic signal AC1. Examples of δ2% are 1%, 3%, 5%, 10%, 20%, etc. Note that examples of the type of driver unit 11 include a dynamic type, a balanced armature type, a hybrid type of a dynamic type and a balanced armature type, and a capacitor type. Furthermore, there are no limitations on the shapes of the driver unit 11 and the diaphragm 113. In this embodiment, for the sake of simplicity, an example is shown in which the outer shape of the driver unit 11 is a substantially cylindrical shape with both end faces and the diaphragm 113 is a substantially disc-shaped, but this does not limit the present invention. For example, the outer shape of the driver unit 11 may be a rectangular parallelepiped shape, or the diaphragm 113 may be a dome-shaped shape. Furthermore, examples of acoustic signals include music, voice, sound effects, environmental sounds, etc.

[0011] <Driver Unit 12> The driver unit (speaker driver unit) 12 is arranged in a ring shape around the driver unit 11 and is a device (device with speaker function) that emits (sounds) an acoustic signal AC2 (second acoustic signal) based on the input output signal OUT2 to one side (D1 direction), and emits an acoustic signal AC4 (fourth acoustic signal) that is an inverse phase signal (phase-inverted signal) of the acoustic signal AC2 or a signal approximating the inverse phase signal to the other side (D2 direction). That is, the acoustic signal emitted from the driver unit 12 to one side (D1 direction) is referred to as the acoustic signal AC2 (second acoustic signal), and the acoustic signal emitted from the driver unit 12 to the other side (D2 direction) is referred to as the acoustic signal AC4 (fourth acoustic signal) (Figure 3). For example, the driver unit 12 includes a diaphragm 123 that vibrates to emit the acoustic signal AC2 from one surface 123a in the D1 direction and emits the acoustic signal AC4 from the other surface 123b in the D2 direction (Figure 2B). In this example, the driver unit 12 emits an acoustic signal AC2 from one surface 121 in the direction D1 by vibrating the diaphragm 123 based on the input output signal OUT2, and emits an acoustic signal AC4, which is an inverse phase signal of or an approximation of the inverse phase signal of the acoustic signal AC2, from the other surface 122 in the direction D2. In other words, the acoustic signal AC4 is emitted secondarily in conjunction with the emission of the acoustic signal AC2. Note that, depending on the type and shape of the driver unit 12, the acoustic signal AC4 may be strictly an inverse phase signal of the acoustic signal AC2, or may be an approximation of the inverse phase signal of the acoustic signal AC2. For example, the approximation of the inverse phase signal of the acoustic signal AC2 may be (1) a signal obtained by shifting the phase of the inverse phase signal of the acoustic signal AC2, (2) a signal obtained by changing (amplifying or attenuating) the amplitude of the inverse phase signal of the acoustic signal AC2, or (3) a signal obtained by shifting the phase of the inverse phase signal of the acoustic signal AC2 and further changing the amplitude. The phase difference between the opposite phase signal of the acoustic signal AC2 and its approximation signal is δ １ % or less. １Examples of % include 1%, 3%, 5%, 10%, and 20%. Furthermore, it is desirable that the difference between the amplitude of the antiphase signal of acoustic signal AC2 and the amplitude of its approximation signal be δ2% or less of the amplitude of the antiphase signal of acoustic signal AC2. Examples of δ2% include 1%, 3%, 5%, 10%, and 20%. Note that examples of the type of driver unit 12 include a dynamic type, a balanced armature type, a hybrid type of a dynamic type and a balanced armature type, and an electrostatic type.

[0012] In this embodiment, at least one of the shapes or sizes of the driver unit 11 (first driver unit) and the driver unit 12 (second driver unit) is different from each other. In this embodiment, for the sake of simplicity, an example is shown in which the driver unit 12 (second driver unit) is a link-type (donut-shaped) driver unit that surrounds the periphery of the driver unit 11 (first driver unit). This makes it possible to expect a uniform and high sound leakage suppression effect. However, this does not limit the present invention, and the shape of the driver unit 12 may be any shape, such as an elliptical ring type or a rectangular frame type, as long as it can be arranged in a ring shape around the driver unit 11.

[0013] Furthermore, driver unit 12 (second driver unit) is arranged in a ring shape around driver unit 11 (first driver unit), and driver unit 11 and driver unit 12 are arranged along the same imaginary plane P (FIGS. 1, 2A, and 2B). For example, driver units 11 and 12 are arranged so that they both pass through imaginary plane P. FIGS. 1, 2A, and 2B show an example in which diaphragm 113 of driver unit 11 and diaphragm 123 of driver unit 12 are arranged so that they both pass through imaginary plane P. However, this does not limit the present invention, as long as driver unit 11 and driver unit 12 are arranged along imaginary plane P. For example, surface 111 of driver unit 11 and surface 121 of driver unit 12 may be arranged so that they pass through imaginary plane P or its vicinity, or surface 112 of driver unit 11 and surface 122 of driver unit 12 may be arranged so that they pass through imaginary plane P or its vicinity. Imaginary plane P may be a plane perpendicular to the D1 direction, a plane approximately perpendicular to the D1 direction, a plane perpendicular to the D2 direction, or a plane approximately perpendicular to the D2 direction. Furthermore, surface 111 of driver unit 11 and surface 121 of driver unit 12 do not have to be arranged on the same plane, and surface 112 of driver unit 11 and surface 122 of driver unit 12 do not have to be arranged on the same plane.

[0014] Preferably, the driver unit 12 (second driver unit) is arranged along an imaginary circle C that is coaxial with the central axis A of the driver unit 11 (first driver unit) (FIGS. 1 and 2A). This makes it possible to expect a sound leakage suppression effect over a wide area. For example, the driver unit 12 may include the imaginary circle C, or the driver unit 12 may be arranged in the vicinity of the imaginary circle C. For example, the central axis A is perpendicular or substantially perpendicular to the imaginary plane P. This makes it possible to expect a high sound leakage suppression effect. However, this does not limit the present invention, and the central axis A does not have to be perpendicular or substantially perpendicular to the imaginary plane P. Furthermore, the imaginary circle C may exist on the imaginary plane P, or may exist on a plane that is parallel or substantially parallel to the imaginary plane P.

[0015] <Phase of Acoustic Signals Emitted from Driver Units 11 and 12> As illustrated in Fig. 3, the signal processing device 100 converts an input signal IN (an electrical signal representing an acoustic signal) into output signals OUT1 and OUT2 and outputs them. The output signal OUT1 is input to the driver unit 11, which emits acoustic signals AC1 and AC3 as described above. The output signal OUT2 is input to the driver unit 12, which emits acoustic signals AC2 and AC4 as described above. Here, the signal processing device 100 converts the input signal into output signals OUT1 and OUT2 so that the amount of sound leakage of the acoustic signals emitted from the driver units 11 and 12 is minimized at predetermined positions. For example, the signal processing device 100 converts the input signal into output signals OUT1 and OUT2 so that the amount of sound leakage of the acoustic signals emitted from the driver units 11 and 12 is minimized at predetermined positions away from the user's ears. For example, signal processing device 100 converts input signal IN so that output signal OUT2 becomes an opposite-phase signal of output signal OUT1 or an approximation of the opposite-phase signal of output signal OUT1. In this case, acoustic signal AC2 emitted from driver unit 12 becomes an opposite-phase signal of acoustic signal AC1 emitted from driver unit 11 or an approximation of the opposite-phase signal of acoustic signal AC1.

[0016] When the acoustic signal output device 10 is placed near the user's ears, controlling the phase relationship between the acoustic signals AC1 and AC2 can minimize the sound pressure of the acoustic signals at multiple positions away from the user's ears. For example, if the acoustic signal AC2 emitted from the driver unit 12 is an opposite-phase signal or an approximate opposite-phase signal of the acoustic signal AC1 emitted from the driver unit 11, the acoustic signals AC1 and AC2 cancel each other out far from the acoustic signal output device 10, minimizing the sound pressure of the acoustic signals at multiple positions away from the user's ears. Meanwhile, the driver units 11 and 12 differ from each other in at least one of their shapes or sizes. Due to this difference in shape or size, the acoustic signals AC1 and AC2 do not completely cancel each other out near the acoustic signal output device 10, ensuring a constant sound pressure near the user's ears. As a result, the necessary sound pressure can be maintained near the user's ears while suppressing sound leakage of the acoustic signal at multiple positions away from the user's ears.

[0017] That is, in the acoustic signal output device 10, when an acoustic signal AC1 (first acoustic signal) is emitted from the driver unit 11 (first driver unit) and an acoustic signal AC2 (second acoustic signal) is emitted from the driver unit 12 (second driver unit), the attenuation rate η of the acoustic signal AC1 (first acoustic signal) at a position P2 (second point) relative to a position P1 (first point) is calculated. １１ Set a predetermined value η ｔｈ The attenuation amount η of the acoustic signal AC1 (first acoustic signal) at the position P2 (second position) relative to the position P1 (first position) can be calculated as follows: １２ a predetermined value ω ｔｈ This makes it possible to suppress sound leakage while ensuring sound pressure in the vicinity of the acoustic signal output device 10.

[0018] Position P1 (first point) is a predetermined point reached by the acoustic signal AC1 (first acoustic signal) emitted from the driver unit 11. Position P2 (second point) is a predetermined point that is farther from the acoustic signal output device 10 than position P1 (first point). ｔｈis the attenuation rate η of an arbitrary or specific acoustic signal (sound) due to air propagation at a position P2 (second position) relative to a position P1 (first position). ２１ The predetermined value ω is a value smaller (lower) than ｔｈ is the attenuation η of an arbitrary or specific acoustic signal (sound) due to air propagation at a position P2 (second position) relative to a position P1 (first position). ２２ That is, the acoustic signal output device 10 of this embodiment has a larger value than the attenuation rate η １１ is the decay rate η ２１ A predetermined value η smaller than ｔｈ It is designed to be equal to or less than the attenuation η １２ is the attenuation η ２２ a predetermined value ω greater than ｔｈ The acoustic signal AC1 is propagated through the air from position P1 to position P2, and is attenuated due to this air propagation and the acoustic signal AC2. The attenuation rate η １１ is the magnitude AMP of the acoustic signal AC1 at the position P1 １ (AC1), the magnitude AMP of the acoustic signal AC1 at the position P2 attenuated due to air propagation and the acoustic signal AC2. ２ (AC1) ratio (AMP ２ (AC1) / AMP １ (AC1)). Also, the attenuation amount η １２ is the magnitude AMP １ (AC1) and size AMP ２ Difference from (AC1) (|AMP １ (AC1)-AMP ２ On the other hand, if the acoustic signal AC2 is not assumed, any or specific acoustic signal AC propagating through the air from the position P1 to the position P2 is ａｒ is attenuated due to air propagation, not due to the acoustic signal AC2. ２１ is the acoustic signal AC at position P1 ａｒ The magnitude of AMP １ (AC ａｒ ) at position P2, which is attenuated due to air propagation (attenuation without being attributable to acoustic signal AC2) ａｒ The magnitude of AMP ２ (AC ａｒ) ratio (AMP ２ (AC ａｒ ) / AMP １ (AC ａｒ )) Also, the attenuation η ２２ is the magnitude AMP １ (AC ａｒ ) and the magnitude AMP ２ (AC ａｒ ) and the difference (|AMP １ (AC ａｒ )-AMP ２ (AC ａｒ ) |). Examples of the magnitude of the acoustic signal include the sound pressure of the acoustic signal or the energy of the acoustic signal. Furthermore, the term "sound leakage component" refers to, for example, a component of the acoustic signal AC1 emitted from the driver unit 11 that is likely to reach an area other than that of the user wearing the acoustic signal output device 10 (for example, a person other than the user wearing the acoustic signal output device 10). For example, the term "sound leakage component" refers to a component of the acoustic signal AC1 that propagates in a direction other than the D1 direction, or a component that propagates in the D1 direction and reaches a position other than that of the user.

[0019] In this embodiment, acoustic signals AC3 and AC4 are also emitted from driver units 11 and 12 in direction D2 ( FIG. 3 ). By controlling acoustic signals AC1, AC2, AC3, and AC4 so as to minimize the sound pressure of the acoustic signals at multiple positions away from the user's ears, it is possible to minimize the sound pressure of the acoustic signals at multiple positions away from the user's ears. For example, if acoustic signal AC2 emitted from driver unit 12 is an opposite-phase signal or an approximation of the opposite-phase signal of acoustic signal AC1 emitted from driver unit 11, and acoustic signal AC4 emitted from driver unit 12 is an opposite-phase signal or an approximation of the opposite-phase signal of acoustic signal AC3 emitted from driver unit 11, then at a distance from acoustic signal output device 10, acoustic signals AC1 and AC2 cancel each other out, acoustic signals AC3 and AC4 cancel each other out, acoustic signals AC1 and AC3 cancel each other out, and acoustic signals AC2 and AC4 cancel each other out, and it is possible to minimize the sound pressure of the acoustic signals at multiple positions away from the user's ears. On the other hand, because driver unit 11 and driver unit 12 differ from each other in at least one of their shapes and sizes, they do not completely cancel each other out near acoustic signal output device 10, and a constant sound pressure can be ensured near the user's ears. As a result, sound leakage of acoustic signals can be suppressed at multiple positions away from the user's ears while ensuring the necessary sound pressure near the user's ears.

[0020] In other words, in the acoustic signal output device 10, when acoustic signals AC1 and AC3 (first acoustic signal and third acoustic signal) are emitted from the driver unit 11 (first driver unit) and acoustic signals AC2 and AC4 (second acoustic signal and fourth acoustic signal) are emitted from the driver unit 12 (second driver unit), the attenuation rate η of at least one of the acoustic signals AC1, AC2, AC3, AC4 (first acoustic signal to fourth acoustic signal) at position P2 (second point) relative to position P1 (first point) is １１ Set a predetermined value η ｔｈ The attenuation amount η of at least one of the acoustic signals AC1, AC2, AC3, and AC4 (first acoustic signal to fourth acoustic signal) at the position P2 relative to the position P1 can be calculated as follows: １２ a predetermined value ωｔｈ For example, in the acoustic signal output device 10, acoustic signals AC1 and AC3 are emitted from the driver unit 11, and acoustic signals AC2 and AC4 are emitted from the driver unit 12, and the attenuation rates η of the acoustic signals AC1, AC2, AC3, and AC4 at a position P2 relative to a position P1 are calculated. １１ Set a predetermined value η ｔｈ The attenuation amounts η of the acoustic signals AC1, AC2, AC3, and AC4 at the position P2 relative to the position P1 are as follows: １２ a predetermined value ω ｔｈ Here, the acoustic signal ACX (AC1, AC2, AC3, AC4, i.e., X=1, 2, 3, 4) propagates through the air from position P1 to position P2, and is attenuated due to this air propagation and the acoustic signal ACY (Y=1, 2, 3, 4 and Y≠X). Attenuation rate η １１ is the magnitude AMP of the acoustic signal ACX at the position P1 １ (ACX) at position P2, the amplitude AMP of the acoustic signal ACX attenuated due to air propagation and the acoustic signal ACY. ２ (ACX) ratio (AMP ２ (ACX) / AMP １ (ACX)). Also, the attenuation amount η １２ is the magnitude AMP １ (ACX) and magnitude AMP ２ (ACX) and the difference (|AMP １ (ACX)-AMP ２ On the other hand, if the acoustic signal ACY is not assumed, any or specific acoustic signal AC propagating through the air from the position P1 to the position P2 is ａｒ is attenuated due to air propagation, not due to the acoustic signal ACY. ２１ is the acoustic signal AC at position P1 ａｒ The magnitude of AMP １ (AC ａｒ ) at a position P2 attenuated due to air propagation (attenuated without being attributable to the acoustic signal ACY) ａｒ The magnitude of AMP ２ (AC ａｒ ) ratio (AMP ２ (AC ａｒ) / AMP １ (AC ａｒ )) Also, the attenuation η ２２ is the magnitude AMP １ (AC ａｒ ) and the magnitude AMP ２ (AC ａｒ ) and the difference (|AMP １ (AC ａｒ )-AMP ２ (AC ａｒ ) |). This makes it possible to further suppress sound leakage.

[0021] <Usage State> Figures 4A and 4B illustrate an example of how the acoustic signal output device 10 is used. In the example of Figure 4A, one acoustic signal output device 10 is worn on each of the right ear 1010 and left ear 1020 of a user 1000. Any wearing mechanism is used to wear the acoustic signal output devices 10 on the ears. The acoustic signal output devices 10 are each positioned near the right ear 1010 and left ear 1020 of the user 1000, with the D1 direction side facing the user 1000. The driver unit 11 emits an acoustic signal AC1 in the D1 direction and an acoustic signal AC3 in the D2 direction. The driver unit 12 emits an acoustic signal AC2 in the D1 direction and an acoustic signal AC4 in the D2 direction.

[0022] As described above, the sound pressure of the acoustic signals AC1 and AC2 emitted in the direction D1 from the driver units 11 and 12 is ensured at the positions of the right ear 1010 and the left ear 1020 located near the driver units 11 and 12. On the other hand, sound leakage of the acoustic signals can be suppressed at a plurality of positions distant from the right ear 1010 and the left ear 1020. In other words, the attenuation rate η of at least one of the acoustic signals AC1, AC2, AC3, and AC4 at position P2 relative to position P1 is １１ Set a predetermined value η ｔｈ The attenuation amount η of at least one of the acoustic signals AC1, AC2, AC3, and AC4 at the position P2 relative to the position P1 can be expressed as follows: １２ a predetermined value ω ｔｈ 4B shows an example in which the position P2 is spaced 15 cm outward from the position P1, but this does not limit the present invention.

[0023] <Numerical Analysis Example> A numerical analysis example will be shown below, illustrating the sound leakage suppression effect achieved by acoustic signal output device 10 of this embodiment. One of the features of acoustic signal output device 10 of this embodiment is that driver unit 12 is arranged in a ring shape around driver unit 11, and driver unit 11 and driver unit 12 are arranged along the same imaginary plane P. Furthermore, it is preferable that driver unit 12 is arranged along an imaginary circle C that is coaxial with the central axis A of driver unit 11. Here, the sound leakage suppression effect achieved when these features are provided and when they are not provided will be compared by numerical analysis.

[0024] FIG. 5A illustrates a numerical analysis model that does not include the features of this embodiment, and FIG. 5B illustrates an enlarged view of region R1 in FIG. 5A . The horizontal axis H in FIGS. 5A and 5B represents a perfect reflecting surface that models the surface of the user's head, and the vertical axis represents an axis that models the central axis A of the acoustic signal output device. The space of this numerical analysis model is rotationally symmetric about the central axis A. In this example, positions P0, P1, and P2 are located on the central axis A. P0 corresponds to the installation reference position of the acoustic signal output device 10 (e.g., P0 is a point on the surface of the acoustic signal output device 10), position P1 corresponds to the position of the user's ear, and P2 corresponds to a position spaced outward from position P1 of the acoustic signal output device 10. α1 represents an acoustic emission surface that is centered on the central axis A and emits an acoustic signal in direction D1 (toward the perfect reflecting surface, toward position P1) along the central axis A. α2 represents a sound emitting surface that emits sound signals in a direction D3 parallel to the horizontal axis H that is perpendicular to the central axis A. The distance between the position P1 and the sound emitting surface α1 is 20 mm, and the distance between the position P1 and the position P2 is 15 cm.

[0025] FIG. 6 shows the results of a numerical analysis performed without the features of this embodiment. FIG. 6 illustrates the acoustic radiation state from the sound emitting surface α1, the acoustic radiation state from the sound emitting surface α2, and the superposition (mixing) of the acoustic radiation states from the sound emitting surfaces α1 and α2. Here, control is performed to suppress sound leakage at position P2. FIG. 6 also illustrates the acoustic radiation state of a 5120 Hz acoustic signal. The closer to white or black the position, the higher the sound pressure (the closer to white the higher the sound pressure of the positive acoustic signal, and the closer to black the higher the sound pressure of the negative acoustic signal), and the closer to the middle (gray) between white and black, the lower the sound pressure. Even with this configuration, sound leakage can be suppressed to some extent in low-frequency (long wavelength) bands. However, in high-frequency (short wavelength) bands, the spatial distribution of the waves emitted by the sound emitting surface α1 and the sound emitting surface α2 differs, making it difficult to suppress sound leakage over a wide spatial range. For example, as illustrated in Figure 6, the superposition of the acoustic radiation states from the acoustic emission surfaces α1 and α2 at 5120 Hz shows many areas that are close to white or close to black in directions away from the central axis A, and it is clear that sound leakage is occurring in these areas.

[0026] FIG. 7A illustrates a numerical analysis model having the features of this embodiment described above, and FIG. 7B illustrates an enlarged view of region R2 in FIG. 7A. The horizontal axis H in FIGS. 7A and 7B represents a perfect reflection surface modeled on the surface of the user's head, and the vertical axis represents an axis modeled on the central axis A of the acoustic signal output device. The space of this numerical analysis model is rotationally symmetric about the central axis A. In this example, positions P0, P1, and P2 are also located on the central axis A. P0 corresponds to the reference installation position of the acoustic signal output device 10, position P1 corresponds to the position of the user's ear, and P2 corresponds to a position spaced outward from position P1 of the acoustic signal output device 10. β11 represents the acoustic emission surface (corresponding to surface 111 of driver unit 11) that is centered on the central axis A and emits an acoustic signal (corresponding to acoustic signal AC1) in direction D1 (toward the perfect reflection surface, toward position P1). β12 represents a sound emitting surface (corresponding to surface 112 of driver unit 11) that is centered on central axis A and emits an acoustic signal (corresponding to acoustic signal AC3) in direction D2 (the opposite direction to direction D1). β21 represents a sound emitting surface (corresponding to surface 121 of driver unit 12) that emits an acoustic signal (corresponding to acoustic signal AC2) in direction D1 (toward the perfect reflection surface, toward position P1). β22 represents a sound emitting surface (corresponding to surface 122 of driver unit 12) that emits an acoustic signal (corresponding to acoustic signal AC4) in direction D2 (the opposite direction to direction D1). Here, sound emitting surfaces β11, β12, β21, and β22 are arranged along an imaginary plane parallel to horizontal axis H, and sound emitting surfaces β21 and β22 are arranged in a ring shape around sound emitting surfaces β11 and β12. The sound emitting surfaces β21 and β22 are arranged along an imaginary circle coaxial with the central axis A of the sound emitting surfaces β11 and β12. The distance between position P1 and the sound emitting surface β11 is 20 mm, and the distance between position P1 and position P2 is 15 cm.

[0027] FIG. 8 shows the results of numerical analysis when the features of this embodiment described above are included. FIG. 8 illustrates the acoustic radiation state from the sound emitting surfaces β11 and β12, the acoustic radiation state from the sound emitting surfaces β21 and β22, and the superposition (mixing) of the acoustic radiation states from the sound emitting surfaces β11, β12, β21, and β22. Again, control is performed to suppress sound leakage at position P2. FIG. 8 also illustrates the acoustic radiation state of a 5120 Hz acoustic signal. The closer to white or black the position, the higher the sound pressure (the closer to white the higher the sound pressure of the positive acoustic signal, and the closer to black the higher the sound pressure of the negative acoustic signal), and the closer to the middle (gray) between white and black, the lower the sound pressure. To suppress sound leakage over a wide area away from the user's ears, it is necessary that the distribution (1) of the acoustic radiation state from the sound emitting surfaces β11 and β12 and the distribution (2) of the acoustic radiation state from the sound emitting surfaces β21 and β22 be as positively and negatively inverted as possible over a wide area away from the user's ears. Due to the basic nature of acoustic signals, the wavefront spreads spherically. Therefore, the above distributions (1) and (2) have inverted positive and negative shapes far from P1 when the sound emitting surfaces β11, β12, β21, and β22 are arranged along the same imaginary plane and are arranged in a ring shape around the sound emitting surfaces β11 and β12. Furthermore, it is desirable that the sound emitting surfaces β21 and β22 are arranged along an imaginary circle coaxial with the central axis A of the sound emitting surfaces β11 and β12. More preferably, it is desirable that the centers of the spherical wavefronts emitted from the sound emitting surfaces β11, β12, β21, and β22 (the central positions of the motion of each diaphragm) coincide or approximately coincide. When these conditions are met, in a wide range away from the user's ears, the distribution (1) (e.g., area γ11) of the acoustic radiation state from the sound emitting surfaces β11 and β12 and the distribution (2) (e.g., area γ21) of the acoustic radiation state from the sound emitting surfaces β21 and β22 have mutually inverted positive and negative signs, as illustrated in Fig. 8. On the other hand, in the vicinity of the user's ears, the distribution (1) (e.g., area γ12) of the acoustic radiation state from the sound emitting surfaces β11 and β12 and the distribution (2) (e.g., area γ22) of the acoustic radiation state from the sound emitting surfaces β21 and β22 do not mutually inverted positive and negative signs.As a result, the superposition of the acoustic radiation states from the sound emitting surfaces β11, β12, β21, and β22 results in a state in which the sound pressure is low (close to gray) in a wide area away from the user's ears and high (close to black) in the vicinity of the user's ears. In other words, by providing the features of this embodiment described above, it is possible to ensure a constant sound pressure in the vicinity of the user's ears while suppressing sound leakage in a wide area away from the user's ears.

[0028] FIG. 9A shows the results of numerical analysis when the features of the present embodiment described above are not provided (FIGS. 5A and 5B), and FIG. 9B shows the results of numerical analysis when the features of the present embodiment described above are provided (FIGS. 7A and 7B). The conditions are the same as those in FIGS. 5A, 5B, 7A, and 7B. However, in FIGS. 9A and 9A, the sound pressure is represented based on the sound pressure at position P1, which corresponds to the position of the user's ear. The sound pressure at position P1 is represented in white, and the closer to black the position, the lower the sound pressure. As illustrated in FIG. 9A, it can be seen that sound leakage occurs in areas far from the user's ear when the features of the present embodiment are not provided. On the other hand, as illustrated in FIG. 9B, it can be seen that when the features of the present embodiment are provided, sound leakage can be suppressed over a wide area far from the user's ear while maintaining a constant sound pressure near the user's ear.

[0029] FIG. 10A shows the results of numerical analysis when the features of the present embodiment described above are not included (FIGS. 5A and 5B), and FIG. 10B shows the results of numerical analysis when the features of the present embodiment described above are included (FIGS. 7A and 7B). The vertical axis of FIGS. 10A and 10B represents sound pressure (sound pressure level [dB]), and the horizontal axis represents frequency (Frequency [Hz]). The value labeled "ear position" represents the sound pressure at position P1, which corresponds to the ear position, and the value labeled "15 cm θ°" represents the sound pressure at position P3 (the distance between positions P1 and P2 and the distance between positions P1 and P3 are both 15 cm) obtained by rotating position P2 by angle θ (clockwise angle) from the central axis A passing through positions P1 and P2 toward the horizontal axis H representing the perfect reflection surface. 10A and 10B, even when sound leakage at position P2 is controlled to be suppressed, when the feature of the present embodiment described above is provided (FIG. 10B), sound leakage can be suppressed widely at position P3 other than position P2 while ensuring sound pressure near the user's ears, compared to when this feature is not provided (FIG. 10A). Note that, although an example in which the central axis A passes through positions P1 and P2 has been shown here, this does not limit the present invention, and at least one of positions P1 and P2 does not have to pass through the central axis A.

[0030] <Features of this embodiment> As described above, in this embodiment, sound pressure can be ensured near the user's ears, while sound leakage can be suppressed over a wide range away from the user's ears.

[0031] [Second Embodiment] The acoustic signal output device 10 of the first embodiment had one driver unit 11 (first driver unit) and one driver unit 12 (second driver unit) arranged in a ring shape around it. However, the acoustic signal output device may have multiple driver units 11 (first driver units) and one driver unit 12 (second driver unit) arranged in a ring shape around them. The acoustic signal output device 20 illustrated in FIG. 11A has five driver units 21 and one driver unit 12 arranged in a ring shape around it. In this example, one driver unit 21 is arranged on a central axis A, four driver units 21 are arranged around it, and one driver unit 12 is further arranged in a ring shape around them. The central axis passes through the centers of the five driver units 11. The acoustic signal output device 20 illustrated in FIG. 11B has four driver units 21 and one driver unit 12 arranged in a ring shape around it. In this example, four driver units 21 are arranged around a central axis A, and one driver unit 12 is further arranged in a ring shape around them. The central axis passes through the centers of the four driver units 21. In both the examples of FIG. 11A and FIG. 11B, the driver units 21 and 12 are arranged along the same imaginary plane P. For example, the driver units 21 and 12 are arranged so that they both pass through the imaginary plane P. For example, the diaphragms 213 and 123 of the driver units 21 and 12 are arranged so that they both pass through the imaginary plane P. However, this does not limit the present invention; it is sufficient that the driver units 21 and 12 are arranged along the imaginary plane P. Also, for the sake of simplicity, an example is shown in which the outer shape of the driver unit 21 is a substantially cylindrical shape with both end faces, and the diaphragm 213 is a substantially disc-shaped, but this does not limit the present invention. For example, the outer shape of the driver unit 21 may be a rectangular parallelepiped shape, or the diaphragm 213 may be a dome-shaped shape. Also, Figures 11A and 11B are merely examples, and multiple driver units 21 may be arranged in other positions.Furthermore, at least one of the shape and size of the driver units 21 and 12 may be different from each other, or both the shape and size may be the same. Even if the driver units 21 and 12 have the same shape and size, the number of driver units 21 and 12 may differ. Therefore, near the acoustic signal output device 20, the acoustic signals AC1, AC2, AC3, and AC4 do not completely cancel each other out, ensuring a constant sound pressure near the user's ears. On the other hand, far from the acoustic signal output device 20, these cancel each other out, making it possible to suppress sound leakage of acoustic signals at multiple positions away from the user's ears. Also, as in the first embodiment, the driver units 12 (second driver units) are preferably arranged along an imaginary circle C that is coaxial with the central axis A of the multiple driver units 21 (first driver units). For example, the driver unit 12 may include the imaginary circle C, or the driver unit 12 may be arranged near the imaginary circle C. This can be expected to have a sound leakage suppression effect over a wide area.

[0032] [Third Embodiment] As illustrated in FIG. 12 , an acoustic signal output device 30 may have one driver unit 11 and multiple driver units 32 arranged in a ring shape around it. The driver unit 11 and the driver unit 32 are arranged along the same imaginary plane P. For example, the driver units 11 and 32 are arranged so that they both pass through the imaginary plane P. For example, the diaphragms 113 and 323 of the driver units 11 and 32 are arranged so that they both pass through the imaginary plane P. However, this does not limit the present invention, and it is sufficient that the driver units 11 and 32 are arranged along the imaginary plane P. For simplicity of explanation, an example is shown in which the outer shape of the driver unit 32 is a substantially cylindrical shape with both end faces, and the diaphragm 323 is a substantially disc shape, but this does not limit the present invention. For example, the outer shape of the driver unit 32 may be a rectangular parallelepiped shape, or the diaphragm 323 may be a dome shape. Also, FIG. 12 is merely an example, and multiple driver units 32 may be arranged in other positions. Furthermore, at least one of the shape and size of the driver unit 11 and the driver unit 32 may be different from each other, or both the shape and size may be the same. Even if the shape and size of the driver unit 11 and the driver unit 32 are the same, because the number of driver units 11 and 32 is different, the acoustic signals AC1, AC2, AC3, and AC4 do not completely cancel each other out near the acoustic signal output device 10, ensuring a constant sound pressure near the user's ears. On the other hand, far from the acoustic signal output device 30, these cancel each other out, making it possible to suppress sound leakage of acoustic signals at multiple positions away from the user's ears. Also, as in the first embodiment, preferably, multiple driver units 32 (second driver units) are arranged along an imaginary circle C that is coaxial with the central axis A of the driver unit 11 (first driver unit). For example, the driver unit 32 may include the imaginary circle C, or the driver unit 12 may be arranged near the imaginary circle C. This can be expected to have a sound leakage suppression effect over a wide area.

[0033] [Fourth embodiment] An acoustic signal output device may have a plurality of driver units 21 (first driver units) and a plurality of driver units 32 (second driver units) arranged in a ring shape around them. For example, the driver unit 11 of the acoustic signal output device 30 illustrated in Fig. 12 may be replaced with a plurality of driver units 21 illustrated in Fig. 11A or 11B.

[0034] [Other Modifications] The present invention is not limited to the above-described embodiments. For example, in the first to third embodiments, at least a portion of the driver units 11, 21 (first driver units) and the driver units 12, 32 (second driver units) may be housed in a housing. For example, the D2-side regions of the driver units 11, 21 and 12, 32 may be housed in a housing, and the D1-side regions may be open to the outside of the housing. As a result, an acoustic signal AC3 may be emitted from the driver units 11, 21 within the housing, and an acoustic signal AC4 may be emitted from the driver units 12, 32 within the housing. The reverberation signals AC3, AC4 emitted within the housing may or may not be emitted to the outside. For example, a sound hole such as a through-hole may be provided in the housing, and the reverberation signals AC3, AC4 emitted within the housing from this sound hole may be emitted to the outside.

[0035] In the above-described embodiments, examples have been shown in which the acoustic signal output devices 10, 20, and 30 are worn on the body of a user. However, the acoustic signal output devices 10, 20, and 30 do not have to be worn on the body of a user. The acoustic signal output devices 10, 20, and 30 may be placed near the ears of a user without being worn on the body of a user. For example, the acoustic signal output devices 10, 20, and 30 may be attached to a chair or the like, and placed near the ears of a user sitting in the chair.

[0036] 10, 20, 30 Acoustic signal output device 11, 12, 21, 32 Driver unit

Claims

1. An acoustic signal output device, one or more first driver units that emit a first acoustic signal in a first direction; a single or multiple second driver units that emit a second acoustic signal in the first direction; the first driver unit and the second driver unit are arranged along the same imaginary plane, the second driver unit is disposed in an annular shape around the first driver unit, When the first acoustic signal is emitted from the first driver unit and the second acoustic signal is emitted from the second driver unit, an attenuation rate of the first acoustic signal at a second point that is farther from the acoustic signal output device than a predetermined first point at which the first acoustic signal arrives is a predetermined value smaller than the attenuation rate of the acoustic signal at the second point relative to the first point due to air propagation; Is designed to be: an attenuation amount of the first acoustic signal at the second point relative to the first point, a predetermined value greater than the attenuation of the acoustic signal due to air propagation at the second point relative to the first point; An acoustic signal output device designed to satisfy the above.

2. 2. The acoustic signal output device of claim 1, the first driver unit emits a third acoustic signal in a second direction that is opposite or substantially opposite to the first direction; the second driver unit emits a fourth acoustic signal in the second direction; When the first acoustic signal and the third acoustic signal are emitted from the first driver unit and the second acoustic signal and the fourth acoustic signal are emitted from the second driver unit, the attenuation rate of at least one of the first acoustic signal to the fourth acoustic signal at the second point relative to the first point is: a predetermined value smaller than the attenuation rate of the acoustic signal at the second point relative to the first point due to air propagation; Is designed to be: an attenuation amount of at least one of the first acoustic signal to the fourth acoustic signal at the second point relative to the first point, a predetermined value greater than the attenuation of the acoustic signal due to air propagation at the second point relative to the first point; An acoustic signal output device designed to satisfy the above.

3. 3. The acoustic signal output device of claim 2, the second acoustic signal is an opposite-phase signal of the first acoustic signal or an approximation signal of the opposite-phase signal of the first acoustic signal, the third acoustic signal is an opposite-phase signal of the first acoustic signal or an approximation signal of the opposite-phase signal of the first acoustic signal, An acoustic signal output device, wherein the fourth acoustic signal is an opposite-phase signal of the second acoustic signal or an approximation signal of the opposite-phase signal of the second acoustic signal.

4. 3. The acoustic signal output device according to claim 1, An acoustic signal output device, wherein the second driver unit is arranged along an imaginary circle coaxial with the central axis of the first driver unit.

5. 3. The acoustic signal output device according to claim 1, An acoustic signal output device, wherein the second driver unit is a ring-shaped driver unit that surrounds the first driver unit.

6. 3. The acoustic signal output device according to claim 1, An acoustic signal output device, wherein the first driver unit and the second driver unit are different from each other in at least one of shape, size, or number.