WO2024100818A1

WO2024100818A1 - Acoustic signal outputting device

Info

Publication number: WO2024100818A1
Application number: PCT/JP2022/041807
Authority: WO
Inventors: 大将千葉; 達也加古
Original assignee: 日本電信電話株式会社
Priority date: 2022-11-10
Filing date: 2022-11-10
Publication date: 2024-05-16

Abstract

This acoustic signal outputting device comprises: a speaker unit; and a collar that serves as a housing accommodating a portion of the speaker unit so as to make an opposite-phase sound emitted from the speaker unit toward the back of the speaker unit go around toward the front of the speaker unit. A first opposite-phase sound emitting hole for emitting the opposite-phase sound toward the front of the speaker unit is provided to the collar. The collar accommodates the portion of the speaker unit in such a manner that the opposite-phase sound emitted from the first opposite-phase sound emitting hole has a relation of approximately opposite phase to a regular-phase sound emitted from the speaker unit toward the front of the speaker unit.

Description

Audio signal output device

The present invention relates to an audio signal output technology that can be used in audio systems installed in seats of aircraft, automobiles, etc.

　Traditionally, users have used earphones or headphones to watch movies or listen to music on airplanes. This is because when using speakers, the playback sound reaches the user's surroundings, causing a nuisance to other users. However, wearing earphones or headphones can be bothersome for users. Some users do not like wearing them because they mess up their hair. Others dislike the pressure that they put on their ears. Furthermore, wearing earphones or headphones for long periods of time can cause users to feel tired when listening.

In order to eliminate the need to wear earphones or headphones, it is possible to synthesize a virtual sound field using wave field synthesis technology, but this would require the preparation of a large-scale speaker array, which is not realistic. Therefore, Patent Document 1 discloses an audio signal output technology for users occupying seats on an aircraft, which can reproduce sounds that cannot be heard by surrounding users without the need for earphones or headphones.

Patent No. 6958763

However, the technology of Patent Document 1 has the problem that the sweet spot, which is the area in which the emitted sound can be heard, is narrow. In addition, the technology of Patent Document 1 also has the problem that two speaker units are always required to emit sound based on one acoustic signal.

The present invention aims to provide an audio signal output technology that can enlarge the sweet spot in a limited area near the speaker unit.

One aspect of the present invention is an audio signal output device that includes a speaker unit and a collar that is a housing that houses a part of the speaker unit so that the sound emitted from the speaker unit in the rear direction of the speaker unit (hereinafter referred to as the anti-phase sound) can be directed in the front direction of the speaker unit, and the collar is provided with a hole (hereinafter referred to as the first anti-phase sound emission hole) for emitting the anti-phase sound in the front direction of the speaker unit, and the collar houses a part of the speaker unit in such a way that the path from the hole of the speaker unit for emitting the anti-phase sound to the first anti-phase sound emission hole is short and the resonance frequency of the internal space of the collar formed between the speaker unit and the collar is high so that the anti-phase sound emitted from the first anti-phase sound emission hole has a substantially anti-phase relationship with the sound emitted from the speaker unit in the front direction of the speaker unit (hereinafter referred to as the normal phase sound) in a predetermined frequency band in the front direction of the speaker unit.

The present invention makes it possible to enlarge the sweet spot in a limited area near the speaker unit.

FIG. 2 is a diagram for explaining a positive phase sound and a negative phase sound. 1 is a diagram illustrating an example of a configuration of an acoustic signal output device 100. 1 is a diagram illustrating an example of a configuration of an acoustic signal output device 100. 1A and 1B are diagrams illustrating how the acoustic signal output device 100 emits a positive phase sound and a negative phase sound. 1 is a diagram for explaining Helmholtz resonance in the acoustic signal output device 100. FIG. FIG. 1 is a diagram showing an example of an acoustic signal output device 100 including a baffle. 1 is a diagram illustrating an example of a configuration of an acoustic signal output device 100. 1 is a diagram illustrating an example of a configuration of an acoustic signal output device 100. FIG. 11 is a diagram relating to a first modified example of the first embodiment. FIG. 11 is a diagram relating to a second modified example of the first embodiment. FIG. 11 is a diagram relating to modified example 3 of the first embodiment. FIG. 11 is a diagram relating to a fourth modified example of the first embodiment. FIG. 13 is a diagram relating to a fifth modified example of the first embodiment. FIG. 13 is a diagram relating to a sixth modified example of the first embodiment. FIG. 13 is a diagram relating to modified example 7 of the first embodiment. FIG. 2 is a diagram showing an acoustic signal output device used in an experiment. FIG. 13 is a diagram showing experimental results. FIG. 2 is a diagram illustrating an example of the configuration of an acoustic signal output device 200. FIG. 2 is a diagram illustrating an example of the configuration of an acoustic signal output device 200. 1A and 1B are diagrams illustrating how the acoustic signal output device 200 emits a positive phase sound and a negative phase sound. FIG. 2 is a diagram showing an example of an acoustic signal output device 200 including a baffle. FIG. 2 is a diagram illustrating an example of the configuration of an acoustic signal output device 200. FIG. 2 is a diagram illustrating an example of the configuration of an acoustic signal output device 200. FIG. 13 is a diagram relating to a first modified example of the second embodiment. FIG. 13 is a diagram relating to modified example 2 of the second embodiment. FIG. 13 is a diagram relating to modified example 3 of the second embodiment. FIG. 13 is a diagram relating to a fourth modified example of the second embodiment. FIG. 13 is a diagram relating to modified example 5 of the second embodiment. FIG. 13 is a diagram relating to a sixth modified example of the second embodiment. FIG. 13 is a diagram relating to modified example 7 of the second embodiment. FIG. 2 is a diagram showing an acoustic signal output device used in an experiment. FIG. 13 is a diagram showing experimental results. FIG. 3 is a diagram illustrating an example of the configuration of an acoustic signal output device 300. FIG. 3 is a diagram illustrating an example of the configuration of an acoustic signal output device 300. 1A and 1B are diagrams illustrating how the acoustic signal output device 300 emits a positive phase sound and a negative phase sound. 11A and 11B are diagrams for explaining Helmholtz resonance in the acoustic signal output device 300. FIG. 2 is a diagram for explaining the vertical and horizontal directions of a baffle. FIG. 13 is a diagram relating to a first modified example of the third embodiment. FIG. 13 is a diagram relating to a first modified example of the third embodiment. FIG. 13 is a diagram relating to a second modified example of the third embodiment. FIG. 13 is a diagram relating to modified example 3 of the third embodiment. FIG. 4 is a diagram illustrating an example of the configuration of an acoustic signal output device 400. FIG. 5 is a diagram illustrating an example of the configuration of an acoustic signal output device 500. FIG. 5 is a diagram illustrating an example of the configuration of an acoustic signal output device 500. FIG. 1 is a diagram illustrating an example of an in-vehicle acoustic signal output device 500. FIG. 6 is a diagram showing an example of the configuration of an acoustic signal output device 600. FIG. 6 is a diagram showing an example of the configuration of an acoustic signal output device 600. FIG. 6 is a diagram showing an example of an acoustic signal output device 600 having a frame. FIG. 7 is a diagram showing an example of the configuration of an acoustic signal output device 700. FIG. 7 is a diagram showing an example of the configuration of an acoustic signal output device 700. FIG. 7 is a diagram showing an example of an audio signal output device 700 equipped with a ring collar having an illumination function. FIG. 7 is a diagram showing an example of the configuration of an acoustic signal output device 700.

Below, an embodiment of the present invention will be described in detail. Components having the same functions will be given the same numbers, and duplicate explanations will be omitted.

First Embodiment
An apparatus that reproduces an acoustic signal obtained based on an object to be reproduced is called an acoustic signal output apparatus. In other words, an acoustic signal output apparatus is an apparatus that reproduces an input acoustic signal as sound (hereinafter, this sound is referred to as sound based on an acoustic signal), and includes a speaker unit. Here, a speaker unit is an apparatus that converts an acoustic signal into sound. Also, an object to be reproduced is data or a signal from which an acoustic signal can be obtained by a predetermined process, such as data recorded on a CD, DVD, or record, data received via the Internet, or a signal received via a radio or television broadcast.

Here, we will explain an audio signal output device that reproduces sound based on an audio signal obtained from an object to be reproduced so that only users in the vicinity of the speaker unit can hear it. In other words, the sound reproduced by the audio signal output device cannot be heard by users other than the user in the vicinity of the speaker unit. If such an audio signal output device is used as an audio system for a user using a seat on an airplane, for example, it is possible to provide a system in which only the user using that seat can hear the reproduced sound. Note that such an audio system can also be installed in seats and reclining chairs of vehicles other than airplanes, such as automobiles and trains, and can also be installed in a wearable form, such as worn on the shoulder.

As shown in Figure 1, sound emitted from a speaker unit in the front direction of the speaker unit is called positive phase sound, and sound emitted from a speaker unit in the rear direction of the speaker unit is called negative phase sound. Negative phase sound is sound with a phase opposite to that of positive phase sound, in other words, sound with a phase that is 180 degrees inverted from that of positive phase sound, so positive phase sound and negative phase sound are in an opposite phase relationship. The direction perpendicular to the front and rear directions is called the lateral direction.

The acoustic signal output device 100 will be described below with reference to Figures 2 to 8. Figures 2 and 3 are both diagrams showing the configuration of the acoustic signal output device 100, with Figure 2 showing the acoustic signal output device 100 as viewed from the side, and Figure 3 showing the acoustic signal output device 100 as viewed from the front. As shown in Figure 2, the acoustic signal output device 100 includes a speaker unit 111 and a collar 112. The speaker unit 111 is a component that includes a diaphragm (not shown) that converts an acoustic signal into vibrations in the air (i.e., generates sound waves). In other words, the speaker unit 111 is a component that reproduces an input acoustic signal as sound. The collar 112 is a housing that houses a part of the speaker unit 111. Note that in Figure 2, a part of the speaker unit 111 (the part housed in the collar 112) is shown by a dotted line because it cannot be seen from the side. In addition, in FIG. 2, the part of the speaker unit 111 that emits the positive and negative phase sounds and the collar 112 are shaped like a cone and a bowl, respectively.

It is preferable that the plane that forms the front of the speaker unit 111 and the plane that forms the front of the collar 112 are substantially parallel, as shown in FIG. 2. In FIG. 2, the two planes are substantially the same.

Collar 112 is a housing for directing the out-of-phase sound, which is the sound emitted from speaker unit 111 toward the rear of speaker unit 111, toward the front of speaker unit 111, and collar 112 is provided with a hole (hereinafter referred to as the first out-of-phase sound emission hole) for emitting the out-of-phase sound that has been directed toward the front of speaker unit 111. Note that in FIG. 2, the first out-of-phase sound emission hole is indicated by a dashed line because it cannot be seen from the side.

4 is a diagram showing how the audio signal output device 100 emits a positive phase sound and a negative phase sound. More specifically, the audio signal output device 100 emits a positive phase sound from the speaker unit 111 in the front direction of the speaker unit 111, and emits a negative phase sound from the first negative phase sound emission hole in the front direction of the speaker unit 111. At this time, in order to ensure that only users in the vicinity of the speaker unit 111 can hear the sound and that other users cannot hear the sound, it is preferable that the positive phase sound and the negative phase sound are in an approximately opposite phase relationship on the plane in front of the speaker unit 111. In other words, it is preferable that the positive phase sound, which is the sound emitted from the speaker unit 111 in the front direction of the speaker unit 111, and the negative phase sound emitted from the first negative phase sound emission hole in the front direction of the speaker unit 111 are in an approximately opposite phase relationship. More specifically, in a predetermined frequency band in the front direction of the speaker unit 111, it is preferable that the positive phase sound emitted from the speaker unit 111 in the front direction of the speaker unit 111 and the negative phase sound emitted from the first negative phase sound emission hole in the front direction of the speaker unit 111 have a substantially opposite phase relationship. Here, it is preferable that the predetermined frequency band is a band below a frequency (hereinafter referred to as a resonant frequency) at which resonance occurs in the internal space of the collar 112 formed between the speaker unit 111 and the collar 112.

For this purpose, the collar 112 accommodates a part of the speaker unit 111 in such a manner that the path from the hole of the speaker unit 111 for emitting the anti-phase sound to the first anti-phase sound emitting hole is short and the resonance frequency of the internal space of the collar 112 formed between the speaker unit 111 and the collar 112 is high so that the anti-phase sound emitted from the first anti-phase sound emitting hole in the front direction of the speaker unit 111 has a substantially anti-phase relationship with the positive phase sound emitted from the speaker unit 111 in the front direction of the speaker unit 111 in a predetermined frequency band in the front direction of the speaker unit 111. In order to shorten the path from the hole of the speaker unit 111 for emitting the anti-phase sound to the first anti-phase sound emitting hole, if the speaker unit 111 is a speaker unit used in a dynamic speaker, the magnet part constituting the speaker unit 111 may be not accommodated in the collar 112. Furthermore, in order to increase the resonant frequency of the internal space of collar 112 formed between collar 112 and speaker unit 111, the resonant frequency can be adjusted using one or more of the following three methods, taking into consideration the following equation related to the resonant frequency _fH of Helmholtz resonance, thereby making collar 112 accommodate a portion of speaker unit 111 (see FIG. 5 ): increasing the area S of the first anti-phase sound emitting hole, decreasing the volume V of the internal space, or shortening the length L of the first anti-phase sound emitting hole.

Here, c represents the speed of sound.

The lower frequency sound output by the audio signal output device 100 becomes harder to hear the further away from the speaker unit. This is because in the higher frequency range, the phases of the out-of-phase sound and the positive phase sound do not align as they move away from the speaker unit, and so they do not cancel each other out. In contrast, in the lower frequency range, the phases of the out-of-phase sound and the positive phase sound are relatively aligned and cancel each other out even if they move away from the speaker unit. Therefore, a member (hereinafter referred to as a baffle) is attached to the speaker unit to adjust the position where the out-of-phase sound and the positive phase sound cancel each other out in the lower frequency range to a position far from the speaker unit, thereby adjusting the sweet spot position in front of the speaker unit (see FIG. 6). In other words, the speaker unit 111 may be attached with a baffle 113, which is a member for preventing the out-of-phase sound emitted from the first out-of-phase sound emission hole and the positive phase sound emitted from the speaker unit 111 from canceling each other out at the sweet spot position in front of the speaker unit 111. 7 and 8 are both diagrams showing the configuration of the acoustic signal output device 100, with FIG. 7 showing the acoustic signal output device 100 as seen from the side, and FIG. 8 showing the acoustic signal output device 100 as seen from the front.

In FIG. 7, the part of the speaker unit 111 that emits the positive and negative phase sounds, the collar 112, and the baffle 113 are shaped like a cone, a bowl, and a plate, respectively.

It is preferable that the plane that forms the front of the speaker unit 111, the plane that forms the front of the collar 112, and the plane that forms the front of the baffle 113 are substantially parallel, as shown in FIG. 7. In FIG. 7, the three planes are substantially the same.

According to an embodiment of the present invention, it is possible to enlarge the sweet spot in a limited area near the speaker unit.

(Variation 1)
As shown in Fig. 9, the collar 112 may be provided with a hole (hereinafter referred to as a second negative phase sound emitting hole) different from the first negative phase sound emitting hole in order to emit the negative phase sound in a direction other than the front direction of the speaker unit 111 (i.e., a side direction or a rear direction). Fig. 9 is a diagram showing the acoustic signal output device 100 as viewed from the side direction. The second negative phase sound emitting hole may have any shape as long as it is capable of emitting the negative phase sound outside the collar 112. The shape of the second negative phase sound emitting hole may be, for example, a notch shape (see Fig. 9(A)). In addition, the second negative phase sound emitting holes may be provided at regular intervals on the side surface of the collar 112 (see Fig. 9(B)).

By emitting the anti-phase sound from the second anti-phase sound emission hole outside the collar 112, the sound pressure of the anti-phase sound can be released in a direction other than the front direction of the speaker unit 111, and the wave characteristics of the anti-phase sound emitted from the first anti-phase sound emission hole change. By suppressing the cancellation of the anti-phase sound and the positive phase sound in the front direction of the speaker unit 111, it becomes possible to control the size and directivity of the sweet spot in the front direction of the speaker unit 111.

(Variation 2)
As shown in Fig. 10, the collar 112 may have a cylindrical member extending from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111, or may have a shape that extends in a cylindrical shape from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111. Fig. 10 is a diagram showing the acoustic signal output device 100 as viewed from the side. For example, when viewed from the front of the speaker unit 111, the shapes of the diaphragm of the speaker unit 111 and the collar 112 are both approximately circular and have approximately the same center, and the collar 112 may have a substantially cylindrical member extending from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111, or may have a shape that extends in a substantially cylindrical shape from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111.

By using the collar 112 as described above, sound is less likely to leak outside the collar 112, making it possible to suppress sound leakage toward the rear of the speaker unit 111.

(Variation 3)
As shown in Fig. 11, the baffle 113 may have a cylindrical member extending from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111, or may have a shape that extends in a cylindrical shape from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111. Fig. 11 is a diagram showing the acoustic signal output device 100 as viewed from the side. For example, when viewed from the front of the speaker unit 111, the shapes of the diaphragm of the speaker unit 111 and the baffle 113 are both approximately circular and have approximately the same center, and the baffle 113 may have a substantially cylindrical member extending from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111, or may have a shape that extends in a substantially cylindrical shape from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111.

When the baffle 113 described above is used, the out-of-phase sound and the in-phase sound merge at a position farther in front of the speaker unit 111, making it possible to position the sweet spot in front of the speaker unit 111 farther away from the speaker unit 111.

(Variation 4)
12, the shape of the diaphragm of speaker unit 111 when viewed from the front of speaker unit 111 is approximately circular, the shape of collar 112 when viewed from the front of speaker unit 111 is approximately elliptical, and the center of the diaphragm of speaker unit 111 and the center of collar 112 when viewed from the front of speaker unit 111 may be approximately coincident with each other. Fig. 12 is a diagram showing the acoustic signal output device 100 as viewed from the front.

When using the collar 112 as described above, the size of the collar 112 increases in the long axis direction when viewed from the front of the speaker unit 111, making it possible to suppress sound leakage toward the rear of the speaker unit 111.

(Variation 5)
13, the shape of the diaphragm of speaker unit 111 when viewed from the front of speaker unit 111 is approximately circular, the shapes of collar 112 and baffle 113 when viewed from the front of speaker unit 111 are approximately elliptical, and the center of the diaphragm of speaker unit 111 when viewed from the front of speaker unit 111, the center of collar 112, and the center of baffle 113 may be approximately coincident when viewed from the front of speaker unit 111. Also, the major axis direction of collar 112 and the major axis direction of baffle 113 when viewed from the front of speaker unit 111 may be approximately parallel. Fig. 13 is a diagram showing the acoustic signal output device 100 as viewed from the front.

By using the collar 112 and baffle 113 as described above, it is possible to enlarge the sweet spot in the long diameter direction of the baffle 113 when viewed from the front of the speaker unit 111.

(Variation 6)
As shown in Fig. 14, a vibration-proofing material that is a member for suppressing vibration of the collar 112 may be attached to the collar 112. Fig. 14 is a diagram showing the acoustic signal output device 100 as viewed from the side. A sound-absorbing material that is a member with sound-absorbing properties may be used as a member for suppressing vibration of the collar 112.

By installing vibration-proofing material, it is possible to prevent collar vibrations from causing sound leakage.

(Variation 7)
When the shape of the diaphragm of speaker unit 111 and the shape of collar 112 are each approximately circular when viewed from the front of speaker unit 111, and the center of the diaphragm of speaker unit 111 and the center of collar 112 are approximately the same when viewed from the front of speaker unit 111, the characteristic of the shape of a circle, i.e., the characteristic that the distance from the center of the circle to a point on the circumference is equal, causes sharp peaks and valleys of resonance in the high and mid ranges in the front direction of speaker unit 111, and changes in the volume of high and mid range sounds associated with the movement of the user's head may be noticeable. Therefore, the shape of collar 112 when viewed from the front of speaker unit 111 may be approximately square so that the peaks and valleys of resonance in the high and mid ranges are gentler. That is, the shape of the diaphragm of speaker unit 111 when viewed from the front of speaker unit 111 is approximately circular, the shape of collar 112 when viewed from the front of speaker unit 111 is approximately square, and the center of the diaphragm of speaker unit 111 and the center of collar 112 when viewed from the front of speaker unit 111 are approximately coincident (see FIG. 15(A)). By making the collar approximately square in shape, the distance from the center to a point on the side changes. This suppresses the change in the volume of high and mid-range sounds that accompanies the movement of the user's head, making it possible to suppress difficulty in hearing and discomfort.

Also, the center of the diaphragm of the speaker unit 111 and the center of the collar 112 may be offset by a specified distance when viewed from the front of the speaker unit 111 (see FIG. 15(B)). This makes it possible to further reduce hearing difficulties and discomfort.

Note that FIG. 15 shows the acoustic signal output device 100 as seen from the front.

(Experimental result)
When a part of the speaker unit is housed in a collar as in the audio signal output device 100, the sweet spot can be made larger than the technology of Patent Document 1. Here, an experiment to verify the performance of the audio signal output device 100 with respect to sound leakage will be described. The performance with respect to sound leakage is compared and verified among the audio signal output device 100 (see FIG. 16(A)), an audio signal output device including only a speaker unit (see FIG. 16(B)), and an audio signal output device including a speaker unit and a sealed speaker box (see FIG. 16(C)).

Figure 17 shows the experimental results. Figures 17(A), 17(B), and 17(C) respectively show sound leakage from audio signal output device 100, an audio signal output device including only a speaker unit, and an audio signal output device including a speaker unit and a sealed speaker box, where the horizontal axis is frequency (in Hz) and the vertical axis is sound pressure level (SPL (Sound Pressure Level), in dB). As can be seen from the figures, comparing the sound pressure levels in three directions in audio signal output device 100, it can be seen that sound leakage is suppressed to the same extent in the side and rear directions. It can also be seen that sound leakage in the rear direction is not sufficiently suppressed in the audio signal output device including only a speaker unit, and that sound leakage in the side direction is not sufficiently suppressed in the audio signal output device including a speaker unit and a sealed speaker box. From this, it can be seen that with the audio signal output device 100, sounds can be clearly heard in the front direction where the user is located, but sounds are difficult to hear from the side and rear directions, and this has favorable properties as an audio signal output device that is intended to be heard only by the user.

Second Embodiment
In the first embodiment, a collar is used to house part of the speaker unit in order to suppress sound leakage in the side and rear directions, but since the speaker unit is covered from the side, resonance that causes phase inversion of the anti-phase sound may occur. Therefore, in this embodiment, a form in which a member that opens in the side direction is used instead of the collar will be described.

The acoustic signal output device 200 will be described below with reference to Figs. 18 to 23. Figs. 18 and 19 are both diagrams showing the configuration of the acoustic signal output device 200, with Fig. 18 showing the acoustic signal output device 200 as viewed from the side, and Fig. 19 showing the acoustic signal output device 200 as viewed from the front. As shown in Fig. 18, the acoustic signal output device 200 includes a speaker unit 111 and a color baffle 212. The color baffle 212 is a member attached to the speaker unit 111. In Fig. 18, the part of the speaker unit 111 that emits the positive phase sound and the negative phase sound, the color baffle 212, are shaped like a cone and a plate, respectively.

It is preferable that the plane in front of the speaker unit 111 and the plane in front of the color baffle 212 are approximately parallel, as shown in FIG. 18.

The color baffle 212 is a component for redirecting the out-of-phase sound, which is the sound emitted from the speaker unit 111 toward the rear of the speaker unit 111, toward the front of the speaker unit 111. The color baffle 212 is a component with an open shape on the front and side of the speaker unit 111 so that the out-of-phase sound that has been redirected is emitted in the front and side directions of the speaker unit 111. By using the color baffle 212, which is a component with an open shape on the side of the speaker unit 111, it is possible to prevent resonance that causes the phase of the out-of-phase sound to be inverted.

20 is a diagram showing how the audio signal output device 200 emits a positive phase sound and a negative phase sound. More specifically, the audio signal output device 200 emits a positive phase sound from the speaker unit 111 in the front direction of the speaker unit 111, and emits a negative phase sound from the opening between the speaker unit 111 and the color baffle 212 in the front direction and the side direction of the speaker unit 111. At this time, in order to ensure that only users in the vicinity of the speaker unit 111 can hear the sound and that other users cannot hear the sound, it is preferable that the positive phase sound and the negative phase sound have a relationship of approximately opposite phase on the plane in front of the speaker unit 111. In other words, it is preferable that the positive phase sound, which is the sound emitted from the speaker unit 111 in the front direction of the speaker unit 111, and the negative phase sound emitted from the opening between the speaker unit 111 and the color baffle 212 in the front direction of the speaker unit 111 have a relationship of approximately opposite phase.

As in the first embodiment, a member (hereinafter, referred to as a baffle) for adjusting the position where the opposite phase sound and the positive phase sound cancel each other out in the low frequency range may be attached to the speaker unit to adjust the sweet spot in the front direction of the speaker unit (see FIG. 21). In other words, the speaker unit 111 may be attached with a baffle 113, which is a member for preventing the opposite phase sound emitted from the opening between the speaker unit 111 and the color baffle 212 and the positive phase sound emitted from the speaker unit 111 from canceling each other out at the sweet spot in the front direction of the speaker unit 111. Both FIG. 22 and FIG. 23 are diagrams showing the configuration of the acoustic signal output device 200, FIG. 22 is a diagram showing the acoustic signal output device 200 as viewed from the side, and FIG. 23 is a diagram showing the acoustic signal output device 200 as viewed from the front. In this case, the size of the baffle 113 when viewed from the front of the speaker unit 111 should be smaller than the size of the color baffle 212 when viewed from the front of the speaker unit 111. The size of the baffle 113 when viewed from the front of the speaker unit 111 may be adjustable by the user to change the desired position of the sweet spot in the front direction of the speaker unit 111. The range of adjustment by the user should be within a range that does not exceed the size of the color baffle 212 when viewed from the front of the speaker unit 111.

In FIG. 22, the parts of the speaker unit 111 that emit positive and negative phase sounds, the color baffle 212, and the baffle 113 are shaped like a cone, a plate, and a plate, respectively.

It is preferable that the plane that forms the front of the speaker unit 111, the plane that forms the front of the color baffle 212, and the plane that forms the front of the baffle 113 are substantially parallel, as shown in FIG. 22. In FIG. 22, the plane that forms the front of the speaker unit 111 and the plane that forms the front of the baffle 113 are substantially the same.

(Variation 1)
As shown in Fig. 24, the color baffle 212 may be provided with holes (hereinafter, referred to as "reverse phase sound emitting holes") for emitting the reverse phase sound in the rear direction of the speaker unit 111. Fig. 24 is a diagram showing the acoustic signal output device 200 as viewed from the rear direction. The reverse phase sound emitting holes may have any shape as long as they are capable of emitting the reverse phase sound outside the color baffle 212. The shape of the reverse phase sound emitting holes may be, for example, a slit shape (see Fig. 24(A)). In addition, the color baffle 212 may be provided with reverse phase sound emitting holes at regular intervals (see Fig. 24(B)).

By emitting the anti-phase sound from the anti-phase sound emission hole outside the color baffle 212, the sound pressure of the anti-phase sound can be released toward the rear of the speaker unit 111, and the wave characteristics of the anti-phase sound emitted from the opening between the speaker unit 111 and the color baffle 212 change. By suppressing the cancellation of the anti-phase sound and the positive phase sound in the front direction of the speaker unit 111, it becomes possible to control the size and directivity of the sweet spot in the front direction of the speaker unit 111.

(Variation 2)
As shown in Fig. 25, the color baffle 212 may have a cylindrical member extending from a plane that is the front of the color baffle 212 in the front direction of the speaker unit 111, or may have a shape that extends in a cylindrical shape from a plane that is the front of the color baffle 212 in the front direction of the speaker unit 111. However, the length of the cylinder is set to a length that maintains the openness of the side direction of the speaker unit 111. Fig. 25 is a diagram showing the state of the acoustic signal output device 200 as viewed from the side direction. For example, when viewed from the front of the speaker unit 111, the shape of the diaphragm of the speaker unit 111 and the color baffle 212 are both approximately circular, and their centers are approximately the same, and the color baffle 212 may have a substantially cylindrical member extending from a plane that is the front of the color baffle 212 in the front direction of the speaker unit 111, or may have a shape that extends in a substantially cylindrical shape from a plane that is the front of the color baffle 212 in the front direction of the speaker unit 111.

By using the color baffle 212 as described above, sound is less likely to leak outside the color baffle 212, making it possible to suppress sound leakage toward the rear of the speaker unit 111.

(Variation 3)
As shown in Fig. 26, the baffle 113 may have a cylindrical member extending from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111, or may have a shape that extends in a cylindrical shape from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111. Fig. 26 is a diagram showing the acoustic signal output device 200 as viewed from the side. For example, the shapes of the diaphragm of the speaker unit 111 and the baffle 113 when viewed from the front of the speaker unit 111 are both approximately circular and have approximately the same center, and the baffle 113 may have a substantially cylindrical member extending from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111, or may have a shape that extends in a substantially cylindrical shape from a plane that is the front of the speaker unit 111 in the front direction of the speaker unit 111.

(Variation 4)
27, the shape of the diaphragm of speaker unit 111 when viewed from the front of speaker unit 111 is approximately circular, the shape of color baffle 212 when viewed from the front of speaker unit 111 is approximately elliptical, and the center of the diaphragm of speaker unit 111 when viewed from the front of speaker unit 111 and the center of color baffle 212 may be approximately coincident. Fig. 27 is a diagram showing acoustic signal output device 200 as viewed from the front.

When the color baffle 212 as described above is used, the size of the color baffle 212 increases in the long axis direction when viewed from the front of the speaker unit 111, making it possible to suppress sound leakage toward the rear of the speaker unit 111.

(Variation 5)
28, the shape of the diaphragm of speaker unit 111 when viewed from the front of speaker unit 111 is approximately circular, the shapes of color baffle 212 and baffle 113 when viewed from the front of speaker unit 111 are approximately elliptical, and the center of the diaphragm of speaker unit 111 when viewed from the front of speaker unit 111, the center of color baffle 212, and the center of baffle 113 may be approximately coincident. Also, the major axis direction of color baffle 212 and the major axis direction of baffle 113 when viewed from the front of speaker unit 111 may be approximately parallel. Fig. 28 is a diagram showing the acoustic signal output device 200 as viewed from the front.

By using the color baffle 212 and baffle 113 as described above, it is possible to enlarge the sweet spot in the long diameter direction of the baffle 113 when viewed from the front of the speaker unit 111.

(Variation 6)
As shown in Fig. 29, a vibration-proofing material that is a member for suppressing vibration of the color baffle 212 may be attached to the color baffle 212. Fig. 29 is a diagram showing the acoustic signal output device 200 as viewed from the side. A sound-absorbing material that is a member with sound-absorbing properties may be used as a member for suppressing vibration of the color baffle 212.

By installing vibration-proofing material, it is possible to prevent vibrations from the color baffle from causing sound leakage.

(Variation 7)
As in the seventh modified example of the first embodiment, the shape of the diaphragm of the speaker unit 111 when viewed from the front of the speaker unit 111 may be substantially circular, the shape of the color baffle 212 when viewed from the front of the speaker unit 111 may be substantially square, and the center of the diaphragm of the speaker unit 111 when viewed from the front of the speaker unit 111 may be substantially the same as the center of the color baffle 212 (see FIG. 30(A)). By making the color shape substantially square, the distance from the center to a point on the side changes. This suppresses the change in the volume of high and mid-range sounds that accompanies the movement of the user's head, making it possible to suppress difficulty in hearing and discomfort.

Also, the center of the diaphragm of the speaker unit 111 when viewed from the front of the speaker unit 111 may be offset by a specified distance from the center of the color baffle 212 (see FIG. 30(B)). This makes it possible to further reduce hearing difficulties and discomfort.

Note that FIG. 30 shows the acoustic signal output device 200 as seen from the front.

(Experimental result)
Here, an experiment to verify the performance of the acoustic signal output device 200 with respect to sound leakage will be described. The performance of the acoustic signal output device 200 with a small baffle size (see FIG. 31(A)), the acoustic signal output device 200 with a medium baffle size (see FIG. 31(B)), and the acoustic signal output device 200 with a large baffle size (see FIG. 31(C)) will be compared and verified. The baffle and color baffle of each acoustic signal output device 200 are all square shaped when viewed from the front of the speaker unit. Here, the baffle size and color baffle size both refer to the length of one side of a square, and the baffle sizes of each acoustic signal output device 200 are 9 cm, 13 cm, and 17 cm, and the color baffle sizes are all 17 cm.

Figure 32 shows the experimental results. Figures 32(A), 32(B), and 32(C) respectively show sound leakage from an acoustic signal output device 200 with a small baffle size, an acoustic signal output device 200 with a medium baffle size, and an acoustic signal output device 200 with a large baffle size, with the horizontal axis being frequency (in Hz) and the vertical axis being sound pressure level (SPL (Sound Pressure Level), in dB). Comparing the three figures, it can be seen that in order to reduce sound leakage in the side and rear directions, a smaller baffle size is preferable compared to the color baffle size.

Third Embodiment
In the first embodiment, since only one speaker unit is used, the sweet spot may be narrow. Therefore, in the present embodiment, a form using a plurality of speaker units will be described.

The acoustic signal output device 300 will be described below with reference to Figs. 33 to 36. Figs. 33 and 34 are both diagrams showing the configuration of the acoustic signal output device 300, with Fig. 33 showing the acoustic signal output device 300 as viewed from the side, and Fig. 34 showing the acoustic signal output device 300 as viewed from the front. As shown in Fig. 33, the acoustic signal output device 300 includes a speaker unit pair 311 consisting of two speaker units 111, a collar 312, and a baffle 313. The acoustic characteristics of the two speaker units 111 that constitute the speaker unit pair 311 are approximately the same, and the same acoustic signal is input. In addition, the fronts of the two speaker units 111 that constitute the speaker unit pair 311 are, for example, on approximately the same plane. The collar 312 is a housing that houses a part of the speaker unit pair 311. Note that in Fig. 33, a part of the speaker unit 111 (the part housed in the collar 312) is shown by a dotted line because it cannot be seen from the side. In addition, in FIG. 33, the part of the speaker unit 111 that emits the positive and negative phase sounds, the shape of the collar 312, and the shape of the baffle 313 are cone-shaped, elongated bowl-shaped, and plate-shaped, respectively.

It is preferable that the plane in front of the speaker unit pair 311, the plane in front of the collar 312, and the plane in front of the baffle 313 are substantially parallel, as shown in FIG. 33. In FIG. 33, the three planes are substantially the same.

The collar 312 is a housing for directing the out-of-phase sound, which is the sound emitted from the two speaker units 111 constituting the speaker unit pair 311 toward the rear of the speaker unit pair 311, toward the front of the speaker unit pair 311, and the collar 312 is provided with a hole (hereinafter referred to as the first out-of-phase sound emission hole) for emitting the out-of-phase sound that has been directed toward the front of the speaker unit pair 311. Note that the first out-of-phase sound emission hole is indicated by a dashed line in FIG. 33 because it cannot be seen from the side.

35 is a diagram showing how the audio signal output device 300 emits a positive phase sound and a negative phase sound. More specifically, the audio signal output device 300 emits a positive phase sound from the speaker unit 111 in the front direction of the speaker unit pair 311, and emits a negative phase sound from the first negative phase sound emission hole in the front direction of the speaker unit pair 311. At this time, in order to ensure that only users in the vicinity of the speaker unit pair 311 can hear the sound and that other users cannot hear the sound, it is preferable that the positive phase sound and the negative phase sound are in an approximately opposite phase relationship on the plane in front of the speaker unit 111. In other words, it is preferable that the positive phase sound, which is the sound emitted from the speaker unit 111 in the front direction of the speaker unit pair 311, and the negative phase sound emitted from the first negative phase sound emission hole in the front direction of the speaker unit pair 311 are in an approximately opposite phase relationship. More specifically, in a predetermined frequency band in the front direction of the speaker unit pair 311, it is preferable that the positive phase sound emitted from the speaker unit 111 in the front direction of the speaker unit pair 311 and the negative phase sound emitted from the first negative phase sound emission hole in the front direction of the speaker unit pair 311 have a substantially opposite phase relationship. Here, it is preferable that the predetermined frequency band is a band below a frequency (hereinafter referred to as a resonant frequency) at which resonance occurs in the internal space of the collar 312 formed between the speaker unit pair 311 and the baffle 313.

For this purpose, the collar 312 accommodates a part of the speaker unit 111 in such a manner that the path from the hole of each speaker unit 111 constituting the speaker unit pair 311 for emitting the anti-phase sound to the first anti-phase sound emitting hole is short and the resonance frequency of the internal space of the collar 312 formed between the speaker unit pair 311 and the baffle 313 is high so that the anti-phase sound emitted from the first anti-phase sound emitting hole in the front direction of the speaker unit pair 311 has a substantially anti-phase relationship with the positive phase sound emitted from the speaker unit 111 in the front direction of the speaker unit pair 311 in a predetermined frequency band in the front direction of the speaker unit pair 311. In order to shorten the path from the hole of the speaker unit 111 for emitting the anti-phase sound to the first anti-phase sound emitting hole, if the speaker unit 111 is a speaker unit used in a dynamic speaker, the magnet part constituting the speaker unit 111 may be not accommodated in the collar 312. Furthermore, to increase the resonance frequency of the internal space of the collar 312 formed between the speaker unit pair 311 and the baffle 313, as in the first embodiment, the resonance frequency can be adjusted using one or more of the following three methods, taking into consideration equation (1) relating to the resonance frequency _fH of the Helmholtz resonance: increasing the area S of the first anti-phase sound emitting hole, decreasing the volume V of the internal space, or shortening the length L of the first anti-phase sound emitting hole, so that the collar 312 accommodates a part of the speaker unit pair 311 (see FIG. 36 ).

A baffle 313 is attached to the speaker unit pair 311, which is a member for preventing the anti-phase sound emitted from the first anti-phase sound emission hole and the positive-phase sound, which is the sound emitted in the front direction of the speaker unit pair 311 from the two speaker units 111 that constitute the speaker unit pair 311, from canceling each other out at a position that is intended to be the sweet spot in the front direction of the speaker unit pair 311. The baffle 313 is also attached to the speaker unit pair 311 in order to make the area between the front directions of the speaker units 111 that constitute the speaker unit pair 311 the sweet spot. Therefore, for example, the baffle 313 is attached to the speaker unit pair 311 in a manner that connects the opposing sides of one speaker unit 111 and the other speaker unit 111 that constitute the speaker unit pair 311. As a result, the speaker unit 111 has a baffle 313 attached to the side facing the other speaker unit 111, but does not have a baffle 313 attached to the side opposite the side facing the other speaker unit 111, making it possible to reduce sound leakage in the side and rear directions, similar to the acoustic signal output device 100. Note that the collar 312 causes the out-of-phase sound to wrap around to the front of the speaker unit pair 311, making it possible to reduce high-frequency sound leakage in the rear direction of the speaker unit pair 311.

According to an embodiment of the present invention, it is possible to enlarge the sweet spot in a limited area near the speaker unit. Also, it is possible to make the area in front of the speaker unit, which is difficult to hear in Patent Document 1, into a sweet spot.

(Variation 1)
Hereinafter, the direction connecting the two speaker units 111 that constitute the speaker unit pair 311 when viewed from the front of the speaker unit pair 311 will be referred to as the vertical direction of the baffle 313, and the direction perpendicular to the direction connecting the two speaker units 111 that constitute the speaker unit pair 311 when viewed from the front of the speaker unit pair 311 will be referred to as the horizontal direction of the baffle 313 (see Figure 37).

As described above, the baffle 313 is attached to the speaker unit pair 311 in order to make the area between the front faces of the speaker units 111 that make up the speaker unit pair 311 a sweet spot. The size of the sweet spot between the front faces of the speaker units 111 that make up the speaker unit pair 311 depends on the vertical and horizontal lengths of the baffle 313. In other words, if the vertical length of the baffle 313 is increased, the size of the sweet spot will increase vertically, and if the horizontal length of the baffle 313 is increased, the size of the sweet spot will increase horizontally. Therefore, both the vertical length of the baffle 313 and the horizontal length of the baffle 313 may be determined according to the size of the area between the front faces of the speaker units 111 that make up the speaker unit pair 311 that is desired to be the sweet spot.

As shown in FIG. 38, by making the vertical length of the baffle 313 connecting the two speaker units 111 longer and placing the two speaker units 111 apart, it is possible to enlarge the sweet spot in the front direction of the speaker unit pair 311.

Also, as shown in FIG. 39, by installing the baffle 313 with a longer horizontal length so that the collar 312 and the baffle 313 are in contact, it is possible to enlarge the sweet spot in the front direction of the speaker unit pair 311. At this time, it is also possible to position the sweet spot farther away from the front of the speaker unit pair 311.

(Variation 2)
As shown in Fig. 40, the speaker units 111 constituting a speaker unit pair 311 may be arranged so that the planes that form the front faces of the respective speaker units 111 are not on the same plane. In the example of Fig. 40, the two speaker units 111 are arranged so that the angle formed by the front directions of the two speaker units 111 is an acute angle that is less than 45 degrees.

(Variation 3)
As shown in FIG. 41, the number of speaker units included in the acoustic signal output device 300 may be, for example, four.

As in the modified example described above, it is possible to adjust the size of the sweet spot by adjusting the vertical length of the baffle 313, the horizontal length of the baffle 313, the angle between the two speaker units 111 in the front direction, and the number of speaker units included in the audio signal output device 300.

Fourth Embodiment
When reproducing stereophonic signals using two audio signal output devices 100, the range in which the sound of each channel can be heard is the same as the sweet spot of the audio signal output device 100, so the sweet spot may not be large enough. Also, when reproducing stereophonic signals using two audio signal output devices 300, four speaker units are required, so the space required for installation is large. Therefore, in this embodiment, a form of reproducing stereophonic signals using one audio signal output device 300 in which the sweet spot is larger than when two audio signal output devices 100 are used will be described.

The acoustic signal output device 400 will be described below with reference to FIG. 42. FIG. 42 is a diagram showing the configuration of the acoustic signal output device 400. As shown in FIG. 42, the acoustic signal output device 400 includes a speaker unit pair 311 consisting of two speaker units 111, a collar 312, a baffle 313, and an acoustic signal generation unit 420. In other words, the acoustic signal output device 400 differs from the acoustic signal output device 300 only in that it further includes an acoustic signal generation unit 420. The acoustic signal generation unit 420 can be configured using, for example, a general-purpose computer. The acoustic signal generation unit 420 is realized by a general-purpose computer by storing a program for realizing the functions of the acoustic signal generation unit 420 in an external storage device or ROM, loading the program and data required for processing the program into RAM as necessary, and processing the program appropriately with the CPU. In other words, the acoustic signal generation unit 420 may be configured by a processing circuit.

The acoustic signal generating unit 420 is a component that receives an acoustic signal for the right channel and an acoustic signal for the left channel, generates a first output acoustic signal and a second output acoustic signal using the acoustic signal for the right channel and the acoustic signal for the left channel, outputs the first output acoustic signal to one speaker unit 111 constituting the speaker unit pair 311, and outputs the second output acoustic signal to the other speaker unit 111 constituting the speaker unit pair 311. The acoustic signal generating unit 420 may output the input acoustic signal for the right channel and the acoustic signal for the left channel as is without signal processing. In other words, the first output acoustic signal is an acoustic signal for the right channel, and the second output acoustic signal is an acoustic signal for the left channel. In this way, in a typical stereo sound source, the correlation between channels is high in the low range, so sound leakage from positions farther in the front direction and sound leakage in the side and rear directions is suppressed while enlarging the sweet spot. On the other hand, the correlation between channels is not as high in the high range as in the low range. However, high-frequency sounds tend to travel in a more direct direction than low-frequency sounds, which reduces sound leakage to the sides and rear.

The audio signal generating unit 420 may also generate and output a first output audio signal and a second output audio signal from the input right channel audio signal and left channel audio signal as audio signals that increase the size of the sweet spot. To this end, the audio signal generating unit 420 generates the first output audio signal and the second output audio signal by performing signal processing to mix the input right channel audio signal and left channel audio signal to obtain a new audio signal. For example, with r (where r satisfies 0<r<1) as a mixing coefficient, the audio signal generating unit 420 generates an audio signal obtained by mixing the right channel audio signal and the left channel audio signal in a ratio of r:1-r as the first output audio signal, and an audio signal obtained by mixing the right channel audio signal and the left channel audio signal in a ratio of 1-r:r as the second output audio signal. That is, the first output acoustic signal and the second output acoustic signal are generated by the first output acoustic signal = right channel acoustic signal x r + left channel acoustic signal x (1-r), and the second output acoustic signal = right channel acoustic signal x (1-r) + left channel acoustic signal x r. Note that the mixing coefficient r may be a value that depends on the frequency, and a different mixing coefficient may be used for each frequency.

According to an embodiment of the present invention, it is possible to enlarge the sweet spot in a limited area near the speaker unit. By inputting a right channel acoustic signal and a left channel acoustic signal, it is possible to enlarge the sweet spot.

Fifth Embodiment
As described in the first embodiment, in the low frequency range, the phases of the negative phase sound and the positive phase sound are relatively aligned and cancel each other out even if the speaker unit is far away, so the low frequency sound may be perceived as weak. Therefore, in this embodiment, a configuration using a woofer, which is a speaker unit for reproducing low frequencies, and a tweeter, which is a speaker unit for reproducing high frequencies, will be described.

The acoustic signal output device 500 will be described below with reference to Figs. 43 to 45. Figs. 43 and 44 are both diagrams showing the configuration of the acoustic signal output device 500, with Fig. 43 showing the acoustic signal output device 500 as viewed from the side, and Fig. 44 showing the acoustic signal output device 500 as viewed from the front. As shown in Fig. 43, the acoustic signal output device 500 includes a first acoustic signal output section 510 and a second acoustic signal output section 520. The first acoustic signal output section 510 includes a woofer 511, which is a speaker unit for reproducing low-frequency sounds, and a first collar 512. The first collar 512 is a housing that houses a part of the woofer 511. The second acoustic signal output section 520 includes a tweeter 521, which is a speaker unit for reproducing high-frequency sounds, and a second collar 522. The second collar 522 is a housing that houses a part of the tweeter 521. In addition, in Fig. 43, a part of the woofer 511 (the part housed in the first collar 512) and a part of the tweeter 521 (the part housed in the second collar 522) are shown by dotted lines because they cannot be seen from the side. Also, in Fig. 43, the part of the woofer 511 that emits the in-phase sound and the out-of-phase sound, and the first collar 512 are respectively cone-shaped and bowl-shaped. Similarly, the part of the tweeter 521 that emits the in-phase sound and the out-of-phase sound, and the second collar 522 are respectively cone-shaped and bowl-shaped.

It is preferable that the plane in front of the woofer 511 and the plane in front of the first collar 512 are substantially parallel, as shown in FIG. 43. Similarly, it is preferable that the plane in front of the tweeter 521 and the plane in front of the second collar 522 are substantially parallel, as shown in FIG. 43. In FIG. 43, the four planes are substantially the same.

The first collar 512 is a housing for allowing the out-of-phase sound (hereinafter referred to as the first out-of-phase sound) emitted from the woofer 511 in the direction of the rear of the woofer 511 to go around in the front direction of the woofer 511, and the first collar 512 is provided with a hole (hereinafter referred to as the first out-of-phase sound emission hole) for emitting the first out-of-phase sound that has gone around in the front direction of the woofer 511. The second collar 522 is a housing for allowing the out-of-phase sound (hereinafter referred to as the second out-of-phase sound) emitted from the tweeter 521 in the direction of the rear of the tweeter 521 to go around in the front direction of the tweeter 521, and the second collar 522 is provided with a hole (hereinafter referred to as the second out-of-phase sound emission hole) for emitting the second out-of-phase sound that has gone around in the front direction of the tweeter 521. Note that the first out-of-phase sound emission hole and the second out-of-phase sound emission hole are both shown by dashed lines in FIG. 43 because they cannot be seen from the side.

The first collar 512 accommodates a part of the woofer 511 in such a manner that the path from the hole of the woofer 511 for emitting the first anti-phase sound to the first anti-phase sound emitting hole is short and the frequency at which the internal space of the first collar 512 formed between the woofer 511 and the first collar 512 resonates (hereinafter referred to as the resonant frequency) is high so that the first anti-phase sound emitted from the first anti-phase sound emitting hole has a substantially anti-phase relationship with the sound emitted from the woofer 511 in the front direction of the woofer 511 in a predetermined frequency band in the front direction of the woofer 511. Note that the predetermined frequency band is preferably a band lower than the resonant frequency of the internal space of the first collar 512 formed between the woofer 511 and the first collar 512. In order to shorten the path from the hole of the woofer 511 for emitting the first anti-phase sound to the first anti-phase sound emitting hole, if the woofer 511 is a woofer used in a dynamic speaker, the magnet part constituting the woofer 511 may be not accommodated in the first collar 512. Furthermore, in order to increase the resonant frequency of the internal space of first collar 512 formed between first collar 512 and woofer 511, the resonant frequency can be adjusted using one or more of the following three methods, taking into consideration equation (1) relating to the resonant frequency _fH of Helmholtz resonance: increasing the area S of the first anti-phase sound emitting hole, decreasing the volume V of the internal space, or shortening the length L of the first anti-phase sound emitting hole, so that first collar 512 accommodates a portion of woofer 511. The second collar 522 accommodates a part of the tweeter 521 in such a manner that the path from the hole of the tweeter 521 for emitting the second anti-phase sound to the second anti-phase sound emitting hole is short and the frequency at which resonance occurs in the internal space of the second collar 522 formed between the tweeter 521 and the second collar 522 (hereinafter referred to as the resonant frequency) is high so that the second anti-phase sound emitted from the second anti-phase sound emitting hole has a substantially anti-phase relationship with the sound emitted from the tweeter 521 in the front direction of the tweeter 521 in a predetermined frequency band in the front direction of the tweeter 521. Note that the predetermined frequency band is desirably a band lower than the resonant frequency of the internal space of the second collar 522 formed between the tweeter 521. In order to shorten the path from the hole of the tweeter 521 for emitting the second opposite-phase sound to the second opposite-phase sound emission hole, if the tweeter 521 is a tweeter used in a dynamic speaker, the magnet part constituting the tweeter 521 may be prevented from being housed in the second collar 522. In addition, in order to increase the resonance frequency of the internal space of the second collar 522 formed between the tweeter 521 and the second collar 522, the resonance frequency may be adjusted by using one or more of the following three methods, taking into consideration the equation (1) relating to the resonance frequency _fH of the Helmholtz resonance: increasing the area S of the second opposite-phase sound emission hole, decreasing the volume V of the internal space, and shortening the length L of the second opposite-phase sound emission hole, so that the second collar 522 may house a part of the tweeter 521.

The second acoustic signal output unit 520 is placed near the user's ears to suppress sound leakage. For example, there are two second acoustic signal output units 520, one for emitting a right channel acoustic signal and the other for emitting a left channel acoustic signal. In this case, the second acoustic signal output unit 520 for emitting the right channel acoustic signal may be placed near the user's right ear, and the second acoustic signal output unit 520 for emitting the left channel acoustic signal may be placed near the user's left ear.

As in the first embodiment, a member (hereinafter referred to as a baffle) may be attached to the woofer to adjust the position where the out-of-phase sound and the in-phase sound cancel each other out in the low range so that it is far from the woofer, thereby adjusting the desired sweet spot in the front direction of the woofer. In other words, the woofer 511 may be attached with a first baffle (not shown), which is a member for preventing the first out-of-phase sound emitted from the first out-of-phase sound emission hole and the first in-phase sound emitted from the woofer 511 from canceling each other out at the desired sweet spot in the front direction of the woofer 511.

Furthermore, in order to suppress sound leakage in the side and rear directions, a baffle may be attached to the tweeter, similar to the woofer. In other words, the tweeter 521 may be attached with a second baffle (not shown), which is a member for suppressing sound leakage in the side and rear directions of the tweeter 521.

If a speaker unit that reproduces low-frequency sounds of about 300 Hz is used as the woofer 511, the first acoustic signal output unit 510 equipped with the first baffle can obtain sufficient low-frequency sounds in the vicinity of the woofer 511 by increasing the reproduction voltage. Also, by using a speaker unit with a diameter of about 30 mm as the tweeter 521 and placing the second acoustic signal output unit 520 equipped with the second baffle in a position close to the user's ears, sound leakage can be suppressed.

Figure 45 shows an example of an in-vehicle audio signal output device 500 that is installed on the headrest of a car seat. Figure 45(A) shows the device in its exposed state, and Figure 45(B) shows the device with a cover attached. As shown in Figure 45, the in-vehicle audio signal output device 500 has a large woofer located in the center, with small tweeters located to the lower right and lower left of that. With this type of arrangement, the large woofer is located directly behind the user's head, which reduces the cancellation of low-frequency sounds, making it easier for the user to hear low-frequency sounds.

According to an embodiment of the present invention, it is possible to enlarge the sweet spot in the limited area near the speaker unit. A two-way configuration with a woofer and tweeter allows the woofer to enhance low frequencies. Specifically, by driving the woofer, which reproduces low-frequency sounds that tend to be canceled out and difficult to hear, independently of the tweeter, it is possible to apply a larger voltage than the tweeter, making it possible to increase the woofer's output. In addition, by narrowing the frequency band that the tweeter handles to high frequencies and reducing the size of the tweeter, high-frequency sounds that are difficult to suppress from leaking can be reproduced only near the user's ears, making it possible to suppress sound leakage.

Sixth Embodiment
When installing the audio signal output device 100 in a bedroom where silence is required, it is convenient to be able to easily change the area where the sound can be heard so that the family member sleeping next to the device cannot hear the sound. Therefore, in this embodiment, a form in which a member is attached so that the front direction of the audio signal output device 100 can be easily changed will be described.

The acoustic signal output device 600 will be described below with reference to Figs. 46 to 48. Figs. 46 and 47 are both diagrams showing the configuration of the acoustic signal output device 600, with Fig. 46 showing the acoustic signal output device 600 as viewed from the side, and Fig. 47 showing the acoustic signal output device 600 as viewed from the front. As shown in Fig. 46, the acoustic signal output device 600 includes an acoustic signal output section 610 and a direction adjustment section 614. The acoustic signal output section 610 includes a speaker unit 111 and a collar 112. The collar 112 is a housing that houses part of the speaker unit 111.

The collar 112 is a housing for directing the out-of-phase sound, which is the sound emitted from the speaker unit 111 toward the rear of the speaker unit 111, toward the front of the speaker unit 111, and the collar 112 is provided with a hole (hereinafter referred to as the first out-of-phase sound emission hole) for emitting the out-of-phase sound that has been directed toward the front of the speaker unit 111.

Collar 112 accommodates a part of speaker unit 111 in such a manner that the path from the hole of speaker unit 111 for emitting the anti-phase sound to the first anti-phase sound emitting hole is short and the frequency at which resonance occurs in the internal space of collar 112 formed between collar 112 and speaker unit 111 (hereinafter referred to as the resonant frequency) is high so that the anti-phase sound emitted from the first anti-phase sound emitting hole in the front direction of speaker unit 111 has a substantially anti-phase relationship with the positive phase sound emitted from speaker unit 111 in the front direction of speaker unit 111 in a predetermined frequency band in the front direction of speaker unit 111. Note that the predetermined frequency band is desirably a band lower than the resonant frequency of the internal space of collar 112 formed between collar 112 and speaker unit 111. In order to shorten the path from the hole of the speaker unit 111 for emitting the antiphase sound to the first antiphase sound emission hole, if the speaker unit 111 is a speaker unit used in a dynamic speaker, the magnet part constituting the speaker unit 111 may be prevented from being housed in the collar 112. In addition, in order to increase the resonance frequency of the internal space of the collar 112 formed between the speaker unit 111 and the collar 112, the resonance frequency may be adjusted by using one or more of the following three methods, taking into consideration the equation (1) relating to the resonance frequency _fH of the Helmholtz resonance: increasing the area S of the first antiphase sound emission hole, decreasing the volume V of the internal space, and shortening the length L of the first antiphase sound emission hole, so that the collar 112 accommodates a part of the speaker unit 111.

The direction adjustment unit 614 is a member attached to the audio signal output unit 610 in order to change the front direction of the audio signal output unit 610. By adjusting the direction adjustment unit 614, the user can change the area in which sound leakage is to be suppressed. The direction adjustment unit 614 may be, for example, a member like the arm of a desk lamp (see FIG. 46). The direction adjustment unit 614 may also be a member like a frame attached so as to surround the periphery of the audio signal output unit 610 as shown in FIG. 48(A). The audio signal output device 600 may include two or more audio signal output units 610. In this case, a direction adjustment unit 614 may be attached to each audio signal output unit 610 so that the front direction of the audio signal output unit 610 can be changed (see FIG. 48(B)).

The area in which sound cannot be heard is formed on the side of the sound signal output unit 610. Therefore, by using the direction adjustment unit 614 to change the front direction of the sound signal output unit 610 so that a user whom you do not want to hear is positioned on the side of the sound signal output unit 610, it is possible to prevent that user from hearing the sound.

As in the first embodiment, a member (hereinafter referred to as a baffle) for adjusting the position where the opposite phase sound and the positive phase sound cancel each other out in the low range may be attached to the speaker unit to adjust the sweet spot in the front direction of the speaker unit. In other words, the speaker unit 111 may be attached with a baffle 113, which is a member for preventing the opposite phase sound emitted from the first opposite phase sound emission hole and the positive phase sound emitted from the speaker unit 111 from canceling each other out at the sweet spot in the front direction of the speaker unit 111.

According to an embodiment of the present invention, it is possible to enlarge the sweet spot in a limited area near the speaker unit. By adjusting the front direction of the acoustic signal output unit 610, the user can change the area in which they want to suppress sound leakage.

Seventh Embodiment
In the first embodiment, sound leakage in the rear direction, particularly in the high frequency range, may be a concern, so in this embodiment, a form for suppressing sound leakage in the rear direction will be described.

The acoustic signal output device 700 will be described below with reference to Figures 49 to 52. Figures 49 and 50 are both diagrams showing the configuration of the acoustic signal output device 700, with Figure 49 showing the acoustic signal output device 700 as viewed from the side, and Figure 50 showing the acoustic signal output device 700 as viewed from the front. As shown in Figure 49, the acoustic signal output device 700 includes a speaker unit 111, a collar 112, and a ring collar 714. The collar 112 is a housing that houses a part of the speaker unit 111. The ring collar 714 is a ring-shaped member having a size that can cover the periphery of the collar 112 in the lateral direction. The shape of the ring collar 714 may be any shape as long as it is large enough to cover the periphery of the collar 112 in the lateral direction. The shape of the ring collar 714 when viewed from the front of the speaker unit 111 may be, for example, approximately circular or approximately elliptical. A baffle (not shown) that is a member for filling the gap may be attached between the collar 112 and the ring collar 714. In this case, it is possible to suppress sound leakage in the direction behind the speaker unit 111. On the other hand, a gap may be provided between the collar 112 and the ring collar 714. In this case, sound can escape in the direction behind the speaker unit 111 from between the collar 112 and the ring collar 714, which results in suppression of sound leakage. In addition, as shown in FIG. 51, the ring collar 714 may have a lighting function.

Also, for example, when viewed from the front of the speaker unit 111, the diaphragm of the speaker unit 111 and the ring collar 714 are both roughly circular in shape and have roughly the same center, and the ring collar 714 may be positioned so as to be located in the lateral direction of the speaker unit 111 (see FIG. 49), or may be positioned so as to be located in the front direction of the speaker unit 111 when viewed from a plane that is the front of the speaker unit 111 (see FIG. 52).

It is preferable that the plane that forms the front of the speaker unit 111, the plane that forms the front of the collar 112, and the plane that forms the front of the ring collar 714 are substantially parallel, as shown in FIG. 49. In FIG. 49, the plane that forms the front of the speaker unit 111 and the plane that forms the front of the collar 112 are substantially the same.

Collar 112 accommodates a part of speaker unit 111 in such a manner that the path from the hole of speaker unit 111 for emitting the anti-phase sound to the first anti-phase sound emitting hole is short and the frequency at which resonance occurs in the internal space of collar 112 formed between collar 112 and speaker unit 111 (hereinafter referred to as the resonant frequency) is high so that the anti-phase sound emitted from the first anti-phase sound emitting hole in the front direction of speaker unit 111 has a substantially anti-phase relationship with the positive phase sound emitted from speaker unit 111 in the front direction of speaker unit 111 in a predetermined frequency band in the front direction of speaker unit 111. Note that the predetermined frequency band is desirably a band lower than the resonant frequency of the internal space of collar 112 formed between collar 112 and speaker unit 111. In order to shorten the path from the hole of the speaker unit 111 for emitting the antiphase sound to the first antiphase sound emitting hole, if the speaker unit 111 is a speaker unit used in a dynamic speaker, the magnet part constituting the speaker unit 111 may be prevented from being housed in the collar 112. In addition, in order to increase the resonance frequency of the internal space of the collar 112 formed between the speaker unit 111 and the collar 112, the resonance frequency may be adjusted by using one or more of the following three methods, taking into consideration the equation (1) relating to the resonance frequency _fH of the Helmholtz resonance: increasing the area S of the first antiphase sound emitting hole, decreasing the volume V of the internal space, and shortening the length L of the first antiphase sound emitting hole, so that the collar 112 houses a part of the speaker unit 111.

According to an embodiment of the present invention, it is possible to enlarge the sweet spot in a limited area near the speaker unit. By using a ring collar, it is possible to suppress sound leakage in the high frequency range. It is also possible to suppress sound leakage in the rear direction.

<Additional Notes>
The foregoing description of the embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings. The embodiments have been chosen and depicted to provide a best illustration of the principles of the invention and to enable those skilled in the art to utilize the invention in various embodiments and with various modifications as may be suitable for the practical use contemplated. All such modifications and variations are within the scope of the invention as defined by the appended claims interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

A speaker unit;
a collar that is a housing that houses a part of the speaker unit so that a sound emitted from the speaker unit in a rear direction of the speaker unit (hereinafter referred to as an inverse phase sound) is directed in a front direction of the speaker unit,
the collar is provided with a hole (hereinafter, referred to as a first anti-phase sound emission hole) for emitting the anti-phase sound in a front direction of the speaker unit,
The collar accommodates a part of the speaker unit in such a manner that the path from the hole of the speaker unit for emitting the anti-phase sound to the first anti-phase sound emission hole is short, and the resonant frequency of the internal space of the collar between the speaker unit and the collar is high, so that the anti-phase sound emitted from the first anti-phase sound emission hole has a substantially anti-phase relationship with the sound emitted from the speaker unit in the front direction of the speaker unit (hereinafter referred to as the positive phase sound) in a predetermined frequency band in the front direction of the speaker unit.
2. The acoustic signal output device according to claim 1,
an acoustic signal output device, characterized in that the resonant frequency of the internal space is increased by using one or more of the following three methods: increasing an area of the first anti-phase sound emitting hole, decreasing a volume of the internal space, and shortening a length of the first anti-phase sound emitting hole.
2. The acoustic signal output device according to claim 1,
an acoustic signal output device, characterized in that a baffle is attached to the speaker unit, which is a member for preventing the anti-phase sound and the positive phase sound emitted from the first anti-phase sound emission hole from canceling each other out at a position that is to be a sweet spot in the front direction of the speaker unit.
2. The acoustic signal output device according to claim 1,
the collar is provided with a hole different from the first anti-phase sound emitting hole for emitting the anti-phase sound in a direction other than the front direction of the speaker unit.
2. The acoustic signal output device according to claim 1,
The acoustic signal output device, characterized in that the collar comprises a cylindrical member extending from a plane that forms the front of the speaker unit toward the front of the speaker unit, or has a cylindrical shape extending from a plane that forms the front of the speaker unit toward the front of the speaker unit.
4. The acoustic signal output device according to claim 3,
The baffle comprises a cylindrical member extending from a plane that forms the front of the speaker unit toward the front of the speaker unit, or has a cylindrical shape extending from a plane that forms the front of the speaker unit toward the front of the speaker unit.
2. The acoustic signal output device according to claim 1,
a shape of the diaphragm of the speaker unit when viewed from the front of the speaker unit is substantially circular, and a shape of the collar when viewed from the front of the speaker unit is substantially elliptical;
11. An acoustic signal output device, wherein a center of a diaphragm of said speaker unit and a center of said collar are substantially aligned when viewed from the front of said speaker unit.
4. The acoustic signal output device according to claim 3,
a shape of a diaphragm of the speaker unit when viewed from the front side of the speaker unit is substantially circular, and a shape of the collar and a shape of the baffle when viewed from the front side of the speaker unit are both substantially elliptical;
an acoustic signal output device, characterized in that a center of a diaphragm of said speaker unit, a center of said collar, and a center of said baffle are substantially coincident when viewed from the front of said speaker unit.
2. The acoustic signal output device according to claim 1,
The acoustic signal output device, wherein a member for suppressing vibration of the collar is attached to the collar.