Acoustic signal output device

Abstract

The present invention comprises: a speaker unit pair that is composed of two speaker units; a collar that is a housing for accommodating part of the speaker unit pair in order to direct reverse-phase sound emitted in the rear direction of the speaker unit pair from the two speaker units constituting the speaker unit pair around the speaker units to travel in the front direction of the speaker unit pair, and is provided with a first reverse-phase-sound-emitting hole for emitting the reverse-phase sound in the front direction of the speaker unit pair; a baffle that is a member which is attached to the speaker unit pair in order to prevent the reverse-phase sound emitted from the first reverse-phase-sound-emitting hole and positive-phase sound emitted from the two speaker units constituting the speaker unit pair in the front direction of the speaker unit pair from cancelling one another out at a position that is to be the sweet spot in the front direction of the speaker unit pair; and an acoustic signal generation unit that, on the basis of a right-channel acoustic signal and a left-channel acoustic signal, generates a first output acoustic signal and a second output acoustic signal.

Description

Technical Field

[0001] The present invention relates to an acoustic signal output technology that can be used in acoustic systems installed in seats of aircraft, automobiles, and the like. Background Art

[0002] Conventionally, users have used earphones or headphones to watch movies or listen to music inside aircraft. This is because when speakers are used, the reproduced sound reaches the surrounding area of the user and disturbs other users. However, wearing earphones or headphones is cumbersome for users. There are also users who do not prefer wearing them for reasons such as that it messes up their hairstyle. Some users dislike the pressure on the ears caused by wearing. Furthermore, wearing earphones or headphones for a long time may cause listening fatigue to users.

[0003] To eliminate the need for wearing earphones or headphones, it is also conceivable to synthesize a virtual sound field using wavefront synthesis technology, but in this case, a large-scale speaker array needs to be prepared, which is not practical. Accordingly, Patent Document 1 discloses an acoustic signal output technology for users using seats inside aircraft, which can reproduce sound that cannot be heard by surrounding users without using earphones or headphones. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Patent No. 6958763 Summary of the Invention Problem to be Solved by the Invention

[0005] However, the technology of Patent Document 1 has a problem that the sweet spot, which is the region where the emitted sound can be heard, is narrow. The technology of Patent Document 1 also has a problem that two speaker units are always required to emit sound based on one acoustic signal.

[0006] Therefore, the present invention aims to provide an acoustic signal output technology that can enlarge the sweet spot in a limited area near the speaker unit. [Means for solving the problem]

[0007] One aspect of the present invention comprises a speaker unit pair consisting of two speaker units, a housing that accommodates a part of the speaker unit pair in order to allow sound emitted from the two speaker units constituting the speaker unit pair toward the rear of the speaker unit pair (hereinafter referred to as out-of-phase sound) to wrap around toward the front of the speaker unit pair, a collar provided with a hole for emitting the out-of-phase sound toward the front of the speaker unit pair (hereinafter referred to as the first out-of-phase sound emission hole), a baffle which is a member attached to the speaker unit pair in order to prevent the out-of-phase sound emitted from the first out-of-phase sound emission hole and sound emitted from the two speaker units constituting the speaker unit pair toward the front of the speaker unit pair (hereinafter referred to as the in-phase sound) from canceling each other out at a position that is to be the sweet spot toward the front of the speaker unit pair, and inputs the right channel sound signal and the left channel sound signal, and the right channel sound signal and the left channel An acoustic signal output device including an acoustic signal generation unit that generates a first output acoustic signal and a second output acoustic signal using an acoustic signal, outputs the first output acoustic signal to one speaker unit constituting the speaker unit pair, and outputs the second output acoustic signal to the other speaker unit constituting the speaker unit pair, wherein the collar accommodates a part of the speaker unit pair such that, in a predetermined frequency band in the front direction of the speaker unit pair, the out-of-phase sound emitted from the first out-of-phase sound emission hole is in approximately opposite phase to the in-phase sound, the path from the hole of each speaker unit constituting the speaker unit pair for emitting the out-of-phase sound to the first out-of-phase sound emission hole is short, and the resonant frequency of the internal space of the collar formed between the speaker unit pair and the speaker unit pair is high, and the baffle is attached to the speaker unit pair so that the region between the front directions of each speaker unit constituting the speaker unit pair is the sweet spot. [Effects of the Invention]

[0008] According to the present invention, it is possible to enlarge the sweet spot in a limited area near the speaker unit. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram to explain in-phase and out-of-phase sounds. [Figure 2] This figure shows an example of the configuration of the acoustic signal output device 100. [Figure 3] This figure shows an example of the configuration of the acoustic signal output device 100. [Figure 4] This diagram shows how the acoustic signal output device 100 emits in-phase and out-of-phase sounds. [Figure 5] This is a diagram illustrating Helmholtz resonance in the acoustic signal output device 100. [Figure 6] This figure shows an example of an acoustic signal output device 100 equipped with a baffle. [Figure 7] This figure shows an example of the configuration of the acoustic signal output device 100. [Figure 8] This figure shows an example of the configuration of the acoustic signal output device 100. [Figure 9] This is a diagram relating to a modified example 1 of the first embodiment. [Figure 10] This figure shows a modified example 2 of the first embodiment. [Figure 11] This is a diagram relating to a third modified example of the first embodiment. [Figure 12] This figure shows a modified example 4 of the first embodiment. [Figure 13] This is a diagram relating to a modified example 5 of the first embodiment. [Figure 14] This is a diagram relating to a modified example 6 of the first embodiment. [Figure 15] This is a diagram relating to a modified example 7 of the first embodiment. [Figure 16] This figure shows the acoustic signal output device used in the experiment. [Figure 17] This figure shows the experimental results. [Figure 18]It is a diagram showing an example configuration of the acoustic signal output device 200. [Figure 19] It is a diagram showing an example configuration of the acoustic signal output device 200. [Figure 20] It is a diagram showing how the acoustic signal output device 200 emits in-phase sound and anti-phase sound. [Figure 21] It is a diagram showing an example of the acoustic signal output device 200 provided with a baffle. [Figure 22] It is a diagram showing an example configuration of the acoustic signal output device 200. [Figure 23] It is a diagram showing an example configuration of the acoustic signal output device 200. [Figure 24] It is a diagram related to Modification 1 of the second embodiment. [Figure 25] It is a diagram related to Modification 2 of the second embodiment. [Figure 26] It is a diagram related to Modification 3 of the second embodiment. [Figure 27] It is a diagram related to Modification 4 of the second embodiment. [Figure 28] It is a diagram related to Modification 5 of the second embodiment. [Figure 29] It is a diagram related to Modification 6 of the second embodiment. [Figure 30] It is a diagram related to Modification 7 of the second embodiment. [Figure 31] It is a diagram showing the acoustic signal output device used in the experiment. [Figure 32] It is a diagram showing the experimental results. [Figure 33] It is a diagram showing an example configuration of the acoustic signal output device 300. [Figure 34] It is a diagram showing an example configuration of the acoustic signal output device 300. [Figure 35] It is a diagram showing how the acoustic signal output device 300 emits in-phase sound and anti-phase sound. [Figure 36] It is a diagram for explaining Helmholtz resonance in the acoustic signal output device 300. [Figure 37] It is a diagram for explaining the vertical direction and the horizontal direction of the baffle. [Figure 38]This is a diagram relating to a modified example 1 of the third embodiment. [Figure 39] This is a diagram relating to a modified example 1 of the third embodiment. [Figure 40] This is a diagram relating to a modified example 2 of the third embodiment. [Figure 41] This is a diagram relating to a third modified example of the third embodiment. [Figure 42] This figure shows an example of the configuration of the acoustic signal output device 400. [Figure 43] This figure shows an example of the configuration of the acoustic signal output device 500. [Figure 44] This figure shows an example of the configuration of the acoustic signal output device 500. [Figure 45] This figure shows an example of an in-vehicle audio signal output device 500. [Figure 46] This figure shows an example of the configuration of the acoustic signal output device 600. [Figure 47] This figure shows an example of the configuration of the acoustic signal output device 600. [Figure 48] This figure shows an example of an acoustic signal output device 600 equipped with a frame. [Figure 49] This figure shows an example of the configuration of the acoustic signal output device 700. [Figure 50] This figure shows an example of the configuration of the acoustic signal output device 700. [Figure 51] This figure shows an example of an acoustic signal output device 700 equipped with a ring color that has a lighting function. [Figure 52] This figure shows an example of the configuration of the acoustic signal output device 700. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described in detail below. Components having the same function will be given the same number, and redundant explanations will be omitted.

[0011] <First Embodiment> A device that reproduces an acoustic signal obtained based on a playback target is called an acoustic signal output device. In other words, an acoustic signal output device is a device that reproduces an input acoustic signal as sound (hereinafter, this sound will be referred to as sound based on an acoustic signal), and includes a speaker unit. Here, a speaker unit is a device that converts an acoustic signal into sound. Furthermore, the playback target refers to data or signals from which an acoustic signal can be obtained through predetermined processing, such as data recorded on CDs, DVDs, or records, data received via the internet, or signals received via radio broadcasts or television broadcasts.

[0012] This section describes an acoustic signal output device that reproduces sound based on acoustic signals obtained from an object so that only users near the speaker unit can hear it. In other words, the sound reproduced by the acoustic signal output device is inaudible to users other than those near the speaker unit. If such an acoustic signal output device is used, for example, as an acoustic system for users of an airplane seat, it is possible to provide a system in which only users of that seat can hear the reproduced sound. Such an acoustic system can also be installed in seats or recliners of vehicles other than airplanes, such as cars and trains, and can also be installed in a wearable form, such as by being placed on the shoulders.

[0013] As shown in Figure 1, sound emitted from a speaker unit in the direction of the front of the speaker unit is called in-phase sound, and sound emitted from a speaker unit in the direction of the rear of the speaker unit is called out-of-phase sound. Out-of-phase sound is sound with the opposite phase to that of in-phase sound, that is, sound with a phase that is 180 degrees inverted from that of in-phase sound, and in-phase sound and out-of-phase sound are in opposite phase relationships. Note that the direction perpendicular to the front and rear directions is called the side direction.

[0014] The acoustic signal output device 100 will be described below with reference to Figures 2 to 8. Figures 2 and 3 both show the configuration of the acoustic signal output device 100. Figure 2 shows the acoustic signal output device 100 viewed from the side, and Figure 3 shows the acoustic signal output device 100 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 acoustic signals into air vibrations (i.e., generates sound waves). In other words, the speaker unit 111 is a component that reproduces the 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 not visible from the side, so it is indicated by a dotted line. Furthermore, in Figure 2, the parts of the speaker unit 111 that emit in-phase and out-of-phase sounds, and the shape of the collar 112, are cone-shaped and bowl-shaped, respectively.

[0015] Furthermore, it is preferable that the plane facing the front of the speaker unit 111 and the plane facing the front of the collar 112 are approximately parallel, as shown in Figure 2. In Figure 2, these two planes are approximately identical.

[0016] Color 112 is a housing designed to allow the out-of-phase sound, which is emitted from the speaker unit 111 towards the rear of the speaker unit 111, to wrap around to the front of the speaker unit 111. Color 112 is provided with a hole (hereinafter referred to as the first out-of-phase sound emission hole) for emitting the wrapped out-of-phase sound towards the front of the speaker unit 111. Note that in Figure 2, the first out-of-phase sound emission hole is not visible from the side, so it is indicated by a dashed line.

[0017] Figure 4 shows how the acoustic signal output device 100 emits in-phase and out-of-phase sounds. More specifically, the acoustic signal output device 100 emits in-phase sound from the speaker unit 111 in the direction in front of the speaker unit 111, and emits out-of-phase sound from the first out-of-phase sound emission hole in the direction in front of the speaker unit 111. At this time, in order to ensure that the sound is heard only by users near the speaker unit 111 and not by other users, it is preferable that the in-phase sound and out-of-phase sound are in approximately opposite phases on the plane in front of the speaker unit 111. In other words, it is preferable that the in-phase sound emitted from the speaker unit 111 in the direction in front of the speaker unit 111 and the out-of-phase sound emitted from the first out-of-phase sound emission hole in the direction in front of the speaker unit 111 are in approximately opposite phases. More specifically, it is preferable that, in a predetermined frequency band in the direction in front of the speaker unit 111, the in-phase sound emitted from the speaker unit 111 in the direction in front of the speaker unit 111 and the out-of-phase sound emitted from the first out-of-phase sound emission hole in the direction in front of the speaker unit 111 are in approximately opposite phase relationships. Here, it is desirable that the predetermined frequency band is below the frequency at which resonance occurs in the internal space of the collar 112 between the speaker unit 111 and the collar (hereinafter referred to as the resonance frequency).

[0018] To achieve this, the collar 112 accommodates a portion of the speaker unit 111 such that, in a predetermined frequency band in the front direction of the speaker unit 111, the out-of-phase sound emitted from the first out-of-phase sound emission hole towards the front of the speaker unit 111 is approximately out of phase with the in-phase sound emitted from the speaker unit 111 towards the front of the speaker unit 111. This is done so that the path from the hole in the speaker unit 111 for emitting out-of-phase sound to the first out-of-phase sound emission hole is short, and the resonant frequency of the internal space of the collar 112 between the speaker unit 111 and the speaker unit 111 is high. To shorten the path from the hole in the speaker unit 111 for emitting out-of-phase sound to the first out-of-phase sound emission hole, if the speaker unit 111 is a speaker unit used in a dynamic speaker, the magnet portion constituting the speaker unit 111 should not be housed in the collar 112. Furthermore, in order to increase the resonant frequency of the internal space of the collar 112 that is created between the speaker unit 111 and the collar, the resonant frequency f of the Helmholtz resonance H Considering the following equation, the resonant frequency can be adjusted by using one or more of the following three methods: increasing the area S of the first out-of-phase sound emission hole, decreasing the volume V of the internal space, or shortening the length L of the first out-of-phase sound emission hole, so that the collar 112 accommodates a portion of the speaker unit 111 (see Figure 5).

number

[0019] The low-frequency sound output by the acoustic signal output device 100 becomes harder to hear the further it is from the speaker unit. This is because, in the high-frequency range, the phases of the out-of-phase sound and the in-phase sound do not align as they move away from the speaker unit, thus preventing them from canceling each other out. In contrast, in the low-frequency range, the phases of the out-of-phase sound and the in-phase sound remain relatively aligned even as they move away from the speaker unit, causing them to cancel each other out. Therefore, a component (hereinafter referred to as a baffle) is attached to the speaker unit to adjust the position where the out-of-phase sound and the in-phase sound cancel each other out in the low-frequency range, so that the position is far from the speaker unit, thereby adjusting the desired sweet spot in the front direction of the speaker unit (see Figure 6). In other words, the speaker unit 111 may be fitted with a baffle 113, which is a component that prevents the out-of-phase sound emitted from the first out-of-phase sound emission hole and the in-phase sound emitted from the speaker unit 111 from canceling each other out at the desired sweet spot in the front direction of the speaker unit 111. Figures 7 and 8 both show the configuration of the acoustic signal output device 100. Figure 7 shows the acoustic signal output device 100 viewed from the side, and Figure 8 shows the acoustic signal output device 100 viewed from the front.

[0020] In Figure 7, the shapes of the part of the speaker unit 111 that emits in-phase and out-of-phase sound, the collar 112, and the baffle 113 are cone-shaped, bowl-shaped, and plate-shaped, respectively.

[0021] Furthermore, it is preferable that the plane facing the front of the speaker unit 111, the plane facing the front of the collar 112, and the plane facing the front of the baffle 113 are substantially parallel, as shown in Figure 7. In Figure 7, these three planes are substantially identical.

[0022] According to embodiments of the present invention, it is possible to enlarge the sweet spot in a limited area near the speaker unit.

[0023] (Variation 1) As shown in Figure 9, the collar 112 may be provided with a hole different from the first inverted-phase sound emission hole (hereinafter referred to as the second inverted-phase sound emission hole) for emitting inverted-phase sound in directions other than the front direction of the speaker unit 111 (i.e., the side direction or rear direction). Figure 9 is a diagram showing the acoustic signal output device 100 as viewed from the side. The shape of the second inverted-phase sound emission hole can be arbitrary as long as it is for the purpose of emitting inverted-phase sound outside the collar 112. The shape of the second inverted-phase sound emission hole may be, for example, a notch (see Figure 9(A)). Alternatively, the second inverted-phase sound emission holes may be provided at regular intervals on the side of the collar 112 (see Figure 9(B)).

[0024] When the out-of-phase sound is emitted outside the collar 112 from the second out-of-phase sound emission hole, the sound pressure of the out-of-phase sound can be released in directions other than the front of the speaker unit 111, and the wave characteristics of the out-of-phase sound emitted from the first out-of-phase sound emission hole change. By suppressing the cancellation of out-of-phase and in-phase sounds 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.

[0025] (Modification 2) As shown in Figure 10, the collar 112 may have a cylindrical member extending from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111, or it may have a shape that extends cylindrically from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111. Figure 10 shows the acoustic signal output device 100 as viewed from the side. For example, when viewed from the front of the speaker unit 111, the diaphragm of the speaker unit 111 and the collar 112 are both approximately circular in shape, and their centers are approximately the same. The collar 112 may have a cylindrical member extending from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111, or it may have a shape that extends cylindrically from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111.

[0026] Using the above-described collar 112 makes it difficult for sound to leak outside the collar 112, thus suppressing sound leakage toward the rear of the speaker unit 111.

[0027] (Variation 3) As shown in Figure 11, the baffle 113 may have a cylindrical member extending from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111, or it may have a shape that extends cylindrically from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111. Figure 11 shows the acoustic signal output device 100 as viewed from the side. For example, when viewed from the front of the speaker unit 111, the diaphragm of the speaker unit 111 and the baffle 113 are both approximately circular in shape, and their centers are approximately the same. The baffle 113 may have a cylindrical member extending from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111, or it may have a shape that extends cylindrically from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111.

[0028] By using the baffle 113 described above, the out-of-phase sound and the in-phase sound will merge at a position further away from the speaker unit 111 in the front direction, making it possible to set the sweet spot in the front direction of the speaker unit 111 at a position further away from the speaker unit 111.

[0029] (Modification 4) As shown in Figure 12, the shape of the diaphragm of the speaker unit 111 when viewed from the front is approximately circular, the shape of the collar 112 when viewed from the front is approximately elliptical, and the center of the diaphragm of the speaker unit 111 and the center of the collar 112 when viewed from the front may be approximately the same. Figure 12 is a diagram showing the acoustic signal output device 100 as viewed from the front.

[0030] Using the color 112 described above, the size of the color 112 when viewed from the front of the speaker unit 111 increases in the direction of its major axis, making it possible to suppress sound leakage from the rear of the speaker unit 111.

[0031] (Variation 5) As shown in Figure 13, the shape of the diaphragm of the speaker unit 111 when viewed from the front is approximately circular, the shape of the collar 112 and the baffle 113 when viewed from the front are approximately elliptical, and the centers of the diaphragm, collar 112, and baffle 113 when viewed from the front may be approximately the same. Also, the major axis direction of the collar 112 and the major axis direction of the baffle 113 when viewed from the front may be approximately parallel. Figure 13 is a diagram showing the acoustic signal output device 100 as viewed from the front.

[0032] Using the above-described collar 112 and baffle 113 makes it possible to enlarge the sweet spot in the direction of the long axis of the baffle 113 when viewed from the front of the speaker unit 111.

[0033] (Experimental variation 6) As shown in Figure 14, the collar 112 may be fitted with a vibration-damping material, which is a component for suppressing vibration of the collar 112. Figure 14 is a diagram showing the acoustic signal output device 100 viewed from the side. As a component for suppressing vibration of the collar 112, a sound-absorbing material, which is a component with sound-absorbing properties, may be used.

[0034] By installing vibration-damping material, it becomes possible to prevent the vibration of the collar from causing sound leakage.

[0035] (Example 7) When viewed from the front of the speaker unit 111, the shape of the diaphragm of the speaker unit 111 and the shape of the collar 112 are both approximately circular, and when viewed from the front of the speaker unit 111, the center of the diaphragm of the speaker unit 111 and the center of the collar 112 are approximately the same. Due to the characteristics of the circular shape, namely the equal distance from the center of the circle to a point on the circumference, the peaks and troughs of resonance in the high and mid frequencies in the direction of the front of the speaker unit 111 become sharp, and the changes in the volume of high and mid frequencies as the user moves their head may become noticeable. Therefore, the shape of the collar 112 when viewed from the front of the speaker unit 111 may be approximately square in order to make the peaks and troughs of resonance in the high and mid frequencies gentler. In other words, the shape of the diaphragm of the speaker unit 111 when viewed from the front is approximately circular, the shape of the collar 112 when viewed from the front is approximately square, and the center of the diaphragm of the speaker unit 111 and the center of the collar 112 when viewed from the front are approximately the same (see Figure 15(A)). By making the shape of the collar approximately square, the distance from the center to a point on the side changes. This suppresses changes in the volume of high and mid-range sounds that occur as the user moves their head, making it possible to reduce difficulty in listening and discomfort.

[0036] Furthermore, the center of the diaphragm of the speaker unit 111 and the center of the collar 112 may be offset by a predetermined distance when viewed from the front of the speaker unit 111 (see Figure 15(B)). Doing so makes it possible to further suppress difficulty in listening and discomfort.

[0037] Figure 15 shows the acoustic signal output device 100 as viewed from the front.

[0038] (Experimental results) By housing a portion of the speaker unit within a collar, as in the acoustic signal output device 100, the sweet spot can be made larger than that of the technology described in Patent Document 1. This section describes an experiment to verify the sound leakage performance of the acoustic signal output device 100. The sound leakage performance of the acoustic signal output device 100 (see Figure 16(A)), an acoustic signal output device including only the speaker unit (see Figure 16(B)), and an acoustic signal output device including the speaker unit and a sealed speaker box (see Figure 16(C)) will be compared and verified.

[0039] Figure 17 shows the experimental results. Figures 17(A), 17(B), and 17(C) show the sound leakage of the acoustic signal output device 100, the acoustic signal output device including only the speaker unit, and the acoustic signal output device including the speaker unit and a sealed speaker box, respectively. 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, when comparing the sound pressure levels in the three directions, it can be seen that sound leakage is suppressed to a similar extent in the side and rear directions for the acoustic signal output device 100. Furthermore, it can be seen that sound leakage in the rear direction is not sufficiently suppressed in the acoustic signal output device including only the speaker unit, and that sound leakage in the side direction is not sufficiently suppressed in the acoustic signal output device including the speaker unit and a sealed speaker box. From this, it can be seen that the sound from the acoustic signal output device 100 is clearly audible in the direction in front of the user, while the sound is difficult to hear in the directions to the sides and rear, which is desirable for an acoustic signal output device intended to be heard only by the user.

[0040] <Second Embodiment> In the first embodiment, a collar was used to house a portion of the speaker unit in order to suppress sound leakage in the lateral and rear directions. However, since this covers the speaker unit from the side, resonance can occur, which can cause phase inversion of out-of-phase sound. Therefore, in this embodiment, a configuration in which a member with open sides is used instead of a collar will be described.

[0041] The acoustic signal output device 200 will be described below with reference to Figures 18 to 23. Figures 18 and 19 both show the configuration of the acoustic signal output device 200. Figure 18 shows the acoustic signal output device 200 viewed from the side, and Figure 19 shows the acoustic signal output device 200 viewed from the front. As shown in Figure 18, the acoustic signal output device 200 includes a speaker unit 111 and a color baffle 212. The color baffle 212 is a component attached to the speaker unit 111. In Figure 18, the part of the speaker unit 111 that emits in-phase and out-of-phase sound, and the color baffle 212 are cone-shaped and plate-shaped, respectively.

[0042] Furthermore, it is preferable that the plane facing the front of the speaker unit 111 and the plane facing the front of the color baffle 212 are approximately parallel, as shown in Figure 18.

[0043] The color baffle 212 is a component that directs the out-of-phase sound, which is sound emitted from the speaker unit 111 towards the rear of the speaker unit 111, towards 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 come around 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, resonance that causes the phase of the out-of-phase sound to be reversed can be prevented.

[0044] Figure 20 shows how the acoustic signal output device 200 emits in-phase and out-of-phase sounds. More specifically, the acoustic signal output device 200 emits in-phase sound from the speaker unit 111 in the direction in front of the speaker unit 111, and emits out-of-phase sound from the opening between the speaker unit 111 and the color baffle 212 in the direction in front of and to the side of the speaker unit 111. At this time, in order to ensure that the sound is heard only by users near the speaker unit 111 and not by other users, it is preferable that the in-phase sound and out-of-phase sound are in approximately opposite phases on the plane in front of the speaker unit 111. In other words, it is preferable that the in-phase sound emitted from the speaker unit 111 in the direction in front of the speaker unit 111 and the out-of-phase sound emitted from the opening between the speaker unit 111 and the color baffle 212 in the direction in front of the speaker unit 111 are in approximately opposite phases.

[0045] Similar to the first embodiment, a component (hereinafter referred to as a baffle) for adjusting the position where the out-of-phase sound and in-phase sound cancel each other out in the low-frequency range may be attached to the speaker unit, thereby adjusting the desired sweet spot in the front direction of the speaker unit (see Figure 21). In other words, the speaker unit 111 may be fitted with a baffle 113, which is a component for preventing the out-of-phase sound emitted from the open area between the speaker unit 111 and the color baffle 212 from canceling each other out at the desired sweet spot in the front direction of the speaker unit 111. Figures 22 and 23 both show the configuration of the acoustic signal output device 200, with Figure 22 showing the acoustic signal output device 200 viewed from the side and Figure 23 showing the acoustic signal output device 200 viewed from the front. In this case, the size of the baffle 113 as viewed from the front of the speaker unit 111 should be smaller than the size of the color baffle 212 as viewed from the front of the speaker unit 111. Furthermore, the size of the baffle 113 as viewed from the front of the speaker unit 111 may be adjustable by the user to change the desired sweet spot position in the front direction of the speaker unit 111. The user's adjustable range should not exceed the size of the color baffle 212 as viewed from the front of the speaker unit 111.

[0046] In Figure 22, the shapes of the parts of the speaker unit 111 that emit in-phase and out-of-phase sounds, the color baffle 212, and the baffle 113 are cone-shaped, plate-shaped, and plate-shaped, respectively.

[0047] Furthermore, it is preferable that the plane facing the front of the speaker unit 111, the plane facing the front of the color baffle 212, and the plane facing the front of the baffle 113 are approximately parallel, as shown in Figure 22. In Figure 22, the plane facing the front of the speaker unit 111 and the plane facing the front of the baffle 113 are approximately the same.

[0048] According to embodiments of the present invention, it is possible to enlarge the sweet spot in a limited area near the speaker unit.

[0049] (Variation 1) As shown in Figure 24, the color baffle 212 may be provided with holes (hereinafter referred to as "out-of-phase sound emission holes") for emitting out-of-phase sound toward the rear of the speaker unit 111. Figure 24 is a diagram showing the acoustic signal output device 200 as viewed from the rear. The shape of the out-of-phase sound emission holes can be arbitrary, as long as they are for emitting out-of-phase sound outside the color baffle 212. The shape of the out-of-phase sound emission holes may be, for example, a notch (see Figure 24(A)). Alternatively, the color baffle 212 may be provided with out-of-phase sound emission holes at regular intervals (see Figure 24(B)).

[0050] When the out-of-phase sound is emitted outside the color baffle 212 through the out-of-phase sound emission hole, the sound pressure of the out-of-phase sound can be released towards the rear of the speaker unit 111, changing the wave characteristics of the out-of-phase sound emitted from the open area between the speaker unit 111 and the color baffle 212. By suppressing the cancellation of out-of-phase and in-phase sounds 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.

[0051] (Modification 2) As shown in Figure 25, the color baffle 212 may have a cylindrical member extending from the plane facing the front of the color baffle 212 toward the front of the speaker unit 111, or it may have a shape that extends cylindrically from the plane facing the front of the color baffle 212 toward the front of the speaker unit 111. However, the length of the cylinder should be such that the opening in the side direction of the speaker unit 111 is maintained. Figure 25 is a diagram showing the acoustic signal output device 200 as seen from the side. For example, when viewed from the front of the speaker unit 111, the diaphragm of the speaker unit 111 and the color baffle 212 are both approximately circular in shape, and their centers are approximately the same. The color baffle 212 may have a cylindrical member extending from the plane facing the front of the color baffle 212 toward the front of the speaker unit 111, or it may have a shape that extends cylindrically from the plane facing the front of the color baffle 212 toward the front of the speaker unit 111.

[0052] Using the color baffle 212 described above makes it difficult for sound to leak out of the color baffle 212, thus suppressing sound leakage toward the rear of the speaker unit 111.

[0053] (Variation 3) As shown in Figure 26, the baffle 113 may have a cylindrical member extending from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111, or it may have a shape that extends cylindrically from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111. Figure 26 is a diagram showing the acoustic signal output device 200 as viewed from the side. For example, when viewed from the front of the speaker unit 111, the diaphragm of the speaker unit 111 and the baffle 113 are both approximately circular in shape, and their centers are approximately the same. The baffle 113 may have a cylindrical member extending from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111, or it may have a shape that extends cylindrically from the plane facing the front of the speaker unit 111 in the direction of the front of the speaker unit 111.

[0054] By using the baffle 113 described above, the out-of-phase sound and the in-phase sound will merge at a position further away from the speaker unit 111 in the front direction, making it possible to set the sweet spot in the front direction of the speaker unit 111 at a position further away from the speaker unit 111.

[0055] (Modification 4) As shown in Figure 27, the shape of the diaphragm of the speaker unit 111 when viewed from the front is approximately circular, the shape of the color baffle 212 when viewed from the front is approximately elliptical, and the center of the diaphragm of the speaker unit 111 and the center of the color baffle 212 when viewed from the front may be approximately the same. Figure 27 is a diagram showing the acoustic signal output device 200 as viewed from the front.

[0056] Using the color baffle 212 described above, the size of the color baffle 212 when viewed from the front of the speaker unit 111 increases in the direction of its major axis, making it possible to suppress sound leakage from the rear of the speaker unit 111.

[0057] (Variation 5) As shown in Figure 28, the shape of the diaphragm of the speaker unit 111 when viewed from the front is approximately circular, the shape of the color baffle 212 and the baffle 113 when viewed from the front is approximately elliptical, and the centers of the diaphragm of the speaker unit 111, the center of the color baffle 212 and the center of the baffle 113 when viewed from the front may be approximately the same. Also, the major axis direction of the color baffle 212 and the major axis direction of the baffle 113 when viewed from the front of the speaker unit 111 may be approximately parallel. Figure 28 is a diagram showing the acoustic signal output device 200 as viewed from the front.

[0058] Using the color baffle 212 and baffle 113 as described above, it is possible to enlarge the sweet spot in the direction of the long axis of baffle 113 when viewed from the front of the speaker unit 111.

[0059] (Experimental variation 6) As shown in Figure 29, the color baffle 212 may be fitted with a vibration-damping material, which is a component for suppressing vibration of the color baffle 212. Figure 29 is a diagram showing the acoustic signal output device 200 viewed from the side. As a component for suppressing vibration of the color baffle 212, a sound-absorbing material, which is a component with sound-absorbing properties, may be used.

[0060] By installing vibration-damping material, it becomes possible to prevent vibrations in the color baffle from causing sound leakage.

[0061] (Example 7) Similar to Modification 7 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 approximately circular, the shape of the color baffle 212 when viewed from the front of the speaker unit 111 may be approximately square, and the center of the diaphragm of the speaker unit 111 and the center of the color baffle 212 when viewed from the front of the speaker unit 111 may be approximately the same (see Figure 30(A)). By making the color approximately square, the distance from the center to a point on the side changes. This suppresses changes in the volume of high and mid-range sounds that occur with the movement of the user's head, making it possible to suppress difficulty in listening and discomfort.

[0062] Furthermore, the center of the diaphragm of the speaker unit 111 and the center of the color baffle 212 may be offset by a predetermined distance when viewed from the front of the speaker unit 111 (see Figure 30(B)). Doing so makes it possible to further suppress difficulty in listening and discomfort.

[0063] Figure 30 shows the acoustic signal output device 200 as viewed from the front.

[0064] (Experimental results) This section describes an experiment to verify the sound leakage performance of the acoustic signal output device 200. The sound leakage performance of the acoustic signal output device 200 with a small baffle size (see Figure 31(A)), an acoustic signal output device 200 with a medium baffle size (see Figure 31(B)), and an acoustic signal output device 200 with a large baffle size (see Figure 31(C)) will be compared and verified. When viewed from the front of the speaker unit, the baffle and color baffle shape of each acoustic signal output device 200 is square. Here, baffle size and color baffle size refer to the length of one side of the square, and the baffle sizes of each acoustic signal output device 200 are 9cm, 13cm, and 17cm, and the color baffle size is 17cm for all of them.

[0065] Figure 32 shows the experimental results. Figures 32(A), 32(B), and 32(C) show the sound leakage of 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, respectively. The horizontal axis is frequency (in Hz), and the vertical axis is sound pressure level (SPL (Sound Pressure Level), in dB). Comparing the three figures, it can be seen that a smaller baffle size is preferable to a larger color baffle size in order to reduce sound leakage in the lateral and rear directions.

[0066] <Third Embodiment> In the first embodiment, only one speaker unit is used, which can result in a narrow sweet spot. Therefore, this embodiment describes a configuration using multiple speaker units.

[0067] The acoustic signal output device 300 will be described below with reference to Figures 33 to 36. Figures 33 and 34 both show the configuration of the acoustic signal output device 300. Figure 33 shows the acoustic signal output device 300 viewed from the side, and Figure 34 shows the acoustic signal output device 300 viewed from the front. As shown in Figure 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 constituting the speaker unit pair 311 are substantially identical, and the same acoustic signal is input to them. Also, the fronts of the two speaker units 111 constituting the speaker unit pair 311 are, for example, substantially on the same plane. The collar 312 is a housing that accommodates a part of the speaker unit pair 311. Note that in Figure 33, a portion of the speaker unit 111 (the part housed in the collar 312) is not visible from the side and is therefore indicated by a dotted line. Also, in Figure 33, the part of the speaker unit 111 that emits in-phase and out-of-phase sound, the shape of the collar 312, and the shape of the baffle 313 are cone-shaped, elongated bowl-shaped, and plate-shaped, respectively.

[0068] Furthermore, it is preferable that the plane facing the front of the speaker unit pair 311, the plane facing the front of the collar 312, and the plane facing the front of the baffle 313 are substantially parallel, as shown in Figure 33. In Figure 33, these three planes are substantially identical.

[0069] Color 312 is a housing designed to allow the out-of-phase sound, which is emitted from the two speaker units 111 constituting the speaker unit pair 311 toward the rear of the speaker unit pair 311, to wrap around toward the front of the speaker unit pair 311. Color 312 is provided with a hole (hereinafter referred to as the first out-of-phase sound emission hole) for emitting the wrapped out-of-phase sound toward the front of the speaker unit pair 311. Note that in Figure 33, the first out-of-phase sound emission hole is not visible from the side and is therefore indicated by a dashed line.

[0070] Figure 35 shows how the acoustic signal output device 300 emits in-phase and out-of-phase sounds. More specifically, the acoustic signal output device 300 emits in-phase sound from speaker unit 111 in the direction in front of speaker unit pair 311, and emits out-of-phase sound from the first out-of-phase sound emission hole in the direction in front of speaker unit pair 311. At this time, in order to ensure that the sound is heard only by users near speaker unit pair 311 and not by other users, it is preferable that the in-phase sound and out-of-phase sound are in approximately opposite phases on the plane in front of speaker unit 111. In other words, it is preferable that the in-phase sound emitted from speaker unit 111 in the direction in front of speaker unit pair 311 and the out-of-phase sound emitted from the first out-of-phase sound emission hole in the direction in front of speaker unit pair 311 are in approximately opposite phases. More specifically, it is preferable that, in a predetermined frequency band in the front direction of the speaker unit pair 311, the in-phase sound emitted from the speaker unit 111 in the front direction of the speaker unit pair 311 and the out-of-phase sound emitted from the first out-of-phase sound emission hole in the front direction of the speaker unit pair 311 are in approximately opposite phase relationships. Here, it is desirable that the predetermined frequency band is below the frequency at which resonance occurs in the internal space of the collar 312 formed between the speaker unit pair 311 and the baffle 313 (hereinafter referred to as the resonance frequency).

[0071] To achieve this, the collar 312 accommodates a portion of the speaker unit 111 such that, in a predetermined frequency band in the front direction of the speaker unit pair 311, the out-of-phase sound emitted from the first out-of-phase sound emission hole towards the front of the speaker unit pair 311 is approximately out of phase with the in-phase sound emitted from the speaker unit 111 towards the front of the speaker unit pair 311. This is done so that the path from the hole in each speaker unit 111 constituting the speaker unit pair 311 for emitting out-of-phase sound to the first out-of-phase sound emission hole is short, and the resonant frequency of the internal space of the collar 312 between the speaker unit pair 311 and the baffle 313 is high. To shorten the path from the hole in the speaker unit 111 for emitting out-of-phase sound to the first out-of-phase sound emission hole, if the speaker unit 111 is a speaker unit used in a dynamic speaker, the magnet portion constituting the speaker unit 111 should not be housed in the collar 312. Furthermore, in order to increase the resonant frequency of the internal space of the collar 312 between the speaker unit pair 311 and the baffle 313, the resonant frequency f of the Helmholtz resonance is set, as in the first embodiment. H Considering equation (1) relating to the resonant frequency, the resonant frequency can be adjusted by using one or more of the following three methods: increasing the area S of the first out-of-phase sound emission hole, decreasing the volume V of the internal space, or shortening the length L of the first out-of-phase sound emission hole, so that the collar 312 accommodates a portion of the speaker unit pair 311 (see Figure 36).

[0072] The speaker unit pair 311 is fitted with a baffle 313, which is a component that prevents the out-of-phase sound emitted from the first out-of-phase sound emission hole and the in-phase sound emitted from the two speaker units 111 constituting the speaker unit pair 311 in the direction in front of the speaker unit pair 311 from canceling each other out at the desired sweet spot in the direction in front of the speaker unit pair 311. The baffle 313 is also fitted to the speaker unit pair 311 to make the region between the frontal directions of each speaker unit 111 constituting the speaker unit pair 311 the sweet spot. For example, the baffle 313 is fitted 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 constituting the speaker unit pair 311. As a result, a baffle 313 is attached to the speaker unit 111 on the side opposite to the other speaker unit 111, while a baffle 313 is not attached to the side opposite to the other speaker unit 111. This makes it possible to reduce sound leakage in the lateral and rear directions, similar to the acoustic signal output device 100. Furthermore, because the collar 312 causes out-of-phase sound to wrap around to the front of the speaker unit pair 311, it is also possible to reduce high-frequency sound leakage in the rear direction of the speaker unit pair 311.

[0073] According to embodiments of the present invention, it is possible to enlarge the sweet spot in a limited area near the speaker unit. Furthermore, it is possible to make the area between the front of the speaker unit, which is difficult to hear in Patent Document 1, the sweet spot.

[0074] (Variation 1) Hereinafter, when viewing the speaker unit pair 311 from the front, the direction connecting the two speaker units 111 that make up 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 make up the speaker unit pair 311 when viewed from the front will be referred to as the horizontal direction of the baffle 313 (see Figure 37).

[0075] As described above, the baffle 313 is attached to the speaker unit pair 311 to create a sweet spot in the area between each speaker unit 111 in the front direction that constitutes the speaker unit pair 311. The size of the sweet spot between each speaker unit 111 in the front direction that constitutes the speaker unit pair 311 depends on the vertical and horizontal lengths of the baffle 313. In other words, increasing the vertical length of the baffle 313 increases the size of the sweet spot vertically, and increasing the horizontal length of the baffle 313 increases the size of the sweet spot horizontally. Therefore, the vertical and horizontal lengths of the baffle 313 may both be determined according to the size of the area between each speaker unit 111 in the front direction that constitutes the speaker unit pair 311 that is to be designated as the sweet spot.

[0076] As shown in Figure 38, by making the vertical length of the baffle 313 connecting the two speaker units 111 longer and installing the two speaker units 111 further apart, it is possible to enlarge the sweet spot of the speaker unit pair 311 in the front direction.

[0077] Furthermore, as shown in Figure 39, by installing the baffle 313 with a longer lateral 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 the same time, it is possible to move the sweet spot further away from the front of the speaker unit pair 311.

[0078] (Modification 2) As shown in Figure 40, the speaker units 111 that make up the speaker unit pair 311 may be arranged such that the planes facing each speaker unit 111 are not on the same plane. In the example in Figure 40, the two speaker units 111 are arranged such that the angle between them in the front direction is an acute angle less than 45 degrees.

[0079] (Variation 3) As shown in Figure 41, the number of speaker units included in the acoustic signal output device 300 may be, for example, 4.

[0080] As shown in the modified examples above, the size of the sweet spot can be adjusted 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 acoustic signal output device 300.

[0081] <Fourth Embodiment> When reproducing a stereo audio signal using two audio signal output devices 100, the audible range for each channel is the same as the sweet spot of the audio signal output device 100, which may result in an insufficient sweet spot size. Furthermore, when reproducing a stereo audio signal using two audio signal output devices 300, four speaker units are required, increasing the installation space. Therefore, this embodiment describes a stereo audio signal reproduction method using a single audio signal output device 300, which results in a larger sweet spot than when using two audio signal output devices 100.

[0082] The acoustic signal output device 400 will be described below with reference to Figure 42. Figure 42 is a diagram showing the configuration of the acoustic signal output device 400. As shown in Figure 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 implemented 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 necessary for processing the program into RAM as needed, and processing it appropriately with the CPU. In other words, the acoustic signal generation unit 420 may be configured by a processing circuit.

[0083] The acoustic signal generation unit 420 takes the right channel acoustic signal and the left channel acoustic signal as input, generates a first output acoustic signal and a second output acoustic signal using the right channel acoustic signal and the left channel acoustic signal, 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 generation unit 420 may also output the input right channel acoustic signal and left channel acoustic signal as they are without signal processing. In other words, the first output acoustic signal is the right channel acoustic signal, and the second output acoustic signal is the left channel acoustic signal. In this way, in a typical stereo sound source, the correlation between channels is high in the low frequency range, so the sweet spot is enlarged, while sound leakage at more distant positions in the front direction and sound leakage in the side and rear directions are suppressed. On the other hand, the correlation between channels is not as high in the high frequency range as in the low frequency range. However, because high-frequency sounds have a stronger directional property than low-frequency sounds, sound leakage in the side and rear directions is suppressed.

[0084] Further, the acoustic signal generation unit 420 may generate and output a first output acoustic signal and a second output acoustic signal as acoustic signals that increase the size of the sweet spot from the input right-channel acoustic signal and left-channel acoustic signal. To this end, the acoustic signal generation unit 420 generates the first output acoustic signal and the second output acoustic signal by performing signal processing to mix the input right-channel acoustic signal and left-channel acoustic signal to obtain a new acoustic signal. For example, letting r (where r satisfies 0<r<1) be a mixing coefficient, the acoustic signal generation unit 420 sets an acoustic signal obtained by mixing the right-channel acoustic signal and the left-channel acoustic signal at a ratio of r:1-r as the first output acoustic signal, and generates an acoustic signal obtained by mixing the right-channel acoustic signal and the left-channel acoustic signal at a ratio of 1-r:r as the second output acoustic signal. That is, the first output acoustic signal = right-channel acoustic signal × r + left-channel acoustic signal × (1-r), and the second output acoustic signal = right-channel acoustic signal × (1-r) + left-channel acoustic signal × r, thereby generating the first output acoustic signal and the second output acoustic signal. Note that the mixing coefficient r may be a frequency-dependent value, and a different mixing coefficient may be used for each frequency.

[0085] 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 receiving the right-channel acoustic signal and the left-channel acoustic signal as inputs, it becomes possible to enlarge the sweet spot.

[0086] <Fifth Embodiment> As described in the first embodiment, in low frequency ranges, even when far from the speaker unit, the phases of the out-of-phase sound and the in-phase sound are relatively aligned and cancel each other out, so low-frequency sound may be perceived as weak. Accordingly, the present embodiment describes a configuration using a woofer that is a speaker unit for low-frequency reproduction and a tweeter that is a speaker unit for high-frequency reproduction.

[0087] The acoustic signal output device 500 will be described below with reference to Figures 43 to 45. Figures 43 and 44 both show the configuration of the acoustic signal output device 500. Figure 43 shows the acoustic signal output device 500 viewed from the side, and Figure 44 shows the acoustic signal output device 500 viewed from the front. As shown in Figure 43, the acoustic signal output device 500 includes a first acoustic signal output unit 510 and a second acoustic signal output unit 520. The first acoustic signal output unit 510 includes a woofer 511, which is a speaker unit for reproducing low-frequency sounds, and a first color 512. The first color 512 is a housing that houses a part of the woofer 511. The second acoustic signal output unit 520 includes a tweeter 521, which is a speaker unit for reproducing high-frequency sounds, and a second color 522. The second color 522 is a housing that houses a part of the tweeter 521. In Figure 43, a portion of the woofer 511 (the part housed in the first color 512) and a portion of the tweeter 521 (the part housed in the second color 522) are not visible from the side, and are therefore indicated by dotted lines. Also, in Figure 43, the parts of the woofer 511 that emit in-phase and out-of-phase sounds, and the shape of the first color 512 are cone-shaped and bowl-shaped, respectively. Similarly, the parts of the tweeter 521 that emit in-phase and out-of-phase sounds, and the shape of the second color 522 are cone-shaped and bowl-shaped, respectively.

[0088] Furthermore, it is preferable that the plane facing the woofer 511 and the plane facing the first color 512 are approximately parallel, as shown in Figure 43. Similarly, it is preferable that the plane facing the tweeter 521 and the plane facing the second color 522 are approximately parallel, as shown in Figure 43. In Figure 43, these four planes are approximately identical.

[0089] The first color 512 is an enclosure for directing the out-of-phase sound (hereinafter referred to as the first out-of-phase sound), which is emitted from the woofer 511 towards the rear of the woofer 511, to the front of the woofer 511. The first color 512 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 wrapped around to the front of the woofer 511. The second color 522 is an enclosure for directing the out-of-phase sound (hereinafter referred to as the second out-of-phase sound), which is emitted from the tweeter 521 towards the rear of the tweeter 521, to the front of the tweeter 521. The second color 522 is provided with a hole (hereinafter referred to as the second out-of-phase sound emission hole) for emitting the out-of-phase sound that has wrapped around to the front of the tweeter 521. Note that in Figure 43, the first out-of-phase sound emission hole and the second out-of-phase sound emission hole are not visible from the side and are therefore indicated with dashed lines.

[0090] The first color 512 accommodates a portion of the woofer 511 such that, in a predetermined frequency band in the front direction of the woofer 511, the first out-of-phase sound emitted from the first out-of-phase sound emission hole is approximately out of phase with the sound emitted from the woofer 511 in the front direction of the woofer 511 (hereinafter referred to as the first in-phase sound). This is achieved by shortening the path from the hole in the woofer 511 for emitting the first out-of-phase sound to the first out-of-phase sound emission hole, and by increasing the frequency at which resonance occurs in the internal space of the first color 512 between the woofer 511 and the woofer 511 (hereinafter referred to as the resonant frequency). It is desirable that the predetermined frequency band is below the resonant frequency of the internal space of the first color 512 between the woofer 511 and the woofer 511. To shorten the path from the hole in the woofer 511 for emitting the first out-of-phase sound to the first out-of-phase sound emission hole, if the woofer 511 is a woofer used in a dynamic speaker, the magnet portion constituting the woofer 511 should not be housed in the first color 512. Furthermore, in order to increase the resonant frequency of the internal space of the first collar 512 that is created between the woofer 511 and the first collar 512, the resonant frequency of the Helmholtz resonance f HConsidering equation (1) relating to the first phase out-of-phase sound emission hole, the resonant frequency can be adjusted by using one or more of the following three methods: increasing the area S of the first phase out-of-phase sound emission hole, decreasing the volume V of the internal space, or shortening the length L of the first phase out-of-phase sound emission hole, so that the first collar 512 accommodates a portion of the woofer 511. Furthermore, the second collar 522 accommodates a portion of the tweeter 521 in such a way that, in a predetermined frequency band in the front direction of the tweeter 521, the second phase out-of-phase sound emitted from the second phase out-of-phase sound emission hole is approximately out of phase with the sound emitted from the tweeter 521 in the front direction of the tweeter 521 (hereinafter referred to as the second phase in-phase sound), the path from the hole in the tweeter 521 for emitting the second phase out-of-phase sound to the second phase out-of-phase sound emission hole is short, and the frequency at which resonance occurs in the internal space of the second collar 522 between the tweeter 521 and the second collar 522 (hereinafter referred to as the resonant frequency) is high, so that the second phase out-of-phase sound emitted from the second phase out-of-phase sound emission hole is approximately out of phase with the sound emitted from the tweeter 521 in the front direction of the tweeter 521 (hereinafter referred to as the second phase in-phase sound). Furthermore, it is desirable that the predetermined frequency band be below the resonant frequency of the internal space of the second collar 522 formed between the tweeter 521 and the second collar 522. In order to shorten the path from the hole in the tweeter 521 for emitting the second out-of-phase sound to the hole for emitting the second out-of-phase sound, if the tweeter 521 is a tweeter used in a dynamic speaker, the magnet part constituting the tweeter 521 should not be housed in the second collar 522. Also, in order to increase the resonant frequency of the internal space of the second collar 522 formed between the tweeter 521 and the second collar 522, the resonant frequency f of the Helmholtz resonance should be... H Considering equation (1) relating to the second phase out-of-phase sound emission hole, the resonant frequency can be adjusted by using one or more of the following three methods: increasing the area S of the second phase out-of-phase sound emission hole, decreasing the volume V of the internal space, or shortening the length L of the second phase out-of-phase sound emission hole, so that the second collar 522 accommodates a portion of the tweeter 521.

[0091] The second acoustic signal output unit 520 is installed near the user's ear to suppress sound leakage. For example, there are two second acoustic signal output units 520, one for emitting the right channel acoustic signal and the other for emitting the left channel acoustic signal. In this case, the second acoustic signal output unit 520 for emitting the right channel acoustic signal should be installed near the user's right ear, and the second acoustic signal output unit 520 for emitting the left channel acoustic signal should be installed near the user's left ear.

[0092] Similar to the first embodiment, a member (hereinafter referred to as a baffle) may be attached to the woofer to adjust the position that is to be the sweet spot in the front direction of the woofer, so that the position where the out-of-phase sound and the in-phase sound cancel each other out in the low frequency range is far from the woofer. In other words, the woofer 511 may be fitted with a first baffle (not shown), which is a member that prevents 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 position that is to be the sweet spot in the front direction of the woofer 511.

[0093] Furthermore, in order to suppress sound leakage in the lateral and rear directions, a baffle may be attached to the tweeter, similar to the woofer. In other words, the tweeter 521 may be fitted with a second baffle (not shown), which is a component for suppressing sound leakage in the lateral and rear directions of the tweeter 521.

[0094] Furthermore, if a speaker unit capable of reproducing low-frequency sounds of approximately 300 Hz is used as the woofer 511, the first acoustic signal output unit 510, which is equipped with a first baffle, can obtain sufficient low-frequency sound in the vicinity of the woofer 511 by increasing the reproduction voltage. In addition, by using a speaker unit with a diameter of approximately 30 mm as the tweeter 521 and installing the second acoustic signal output unit 520, which is equipped with a second baffle, in a position close to the user's ears, sound leakage can be suppressed.

[0095] Figure 45 shows an example of an in-vehicle audio signal output device 500 installed on the headrest of a car seat. Figure 45(A) shows the device in its uncovered state, and Figure 45(B) shows it with a cover attached. As shown in Figure 45, the in-vehicle audio signal output device 500 has a large woofer in the center, with small tweeters positioned to its lower right and lower left. This arrangement places the large woofer directly behind the user's head, suppressing the cancellation of low-frequency sounds and making it easier for the user to hear low-frequency sounds.

[0096] According to embodiments of the present invention, it is possible to enlarge the sweet spot in a limited area near the speaker unit. By using a two-way configuration of a woofer and a tweeter, it is possible to enhance the low frequencies with the woofer. Specifically, by driving the woofer, which reproduces low-frequency sounds that tend to be difficult to hear due to significant cancellation, independently of the tweeter, it becomes possible to apply a larger voltage to the woofer compared to the tweeter, thereby increasing the output of the woofer. Furthermore, by narrowing the frequency range handled by the tweeter to high frequencies and reducing the size of the tweeter, it is possible to suppress sound leakage by reproducing high-frequency sounds, which are difficult to suppress, only near the user's ears.

[0097] <Sixth Embodiment> When installing the acoustic signal output device 100 in a bedroom, a space where silence is desired, it is convenient to be able to easily change the area in which the sound can be heard so that family members sleeping next to it cannot hear it. Therefore, in this embodiment, a configuration is described in which a member is attached to allow the front direction of the acoustic signal output device 100 to be easily changed.

[0098] The acoustic signal output device 600 will be described below with reference to Figures 46 to 48. Figures 46 and 47 both show the configuration of the acoustic signal output device 600. Figure 46 shows the acoustic signal output device 600 viewed from the side, and Figure 47 shows the acoustic signal output device 600 viewed from the front. As shown in Figure 46, the acoustic signal output device 600 includes an acoustic signal output unit 610 and a direction adjustment unit 614. The acoustic signal output unit 610 includes a speaker unit 111 and a collar 112. The collar 112 is a housing that accommodates a part of the speaker unit 111.

[0099] Color 112 is a housing that allows the out-of-phase sound, which is sound emitted from the speaker unit 111 towards the rear of the speaker unit 111, to wrap around to the front of the speaker unit 111. Color 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 wrapped around to the front of the speaker unit 111.

[0100] The collar 112 accommodates a portion of the speaker unit 111 in such a way that, in a predetermined frequency band in the front direction of the speaker unit 111, the out-of-phase sound emitted from the first out-of-phase sound emission hole towards the front of the speaker unit 111 is approximately out of phase with the in-phase sound emitted from the speaker unit 111 towards the front of the speaker unit 111. This is achieved by shortening the path from the hole in the speaker unit 111 for emitting out-of-phase sound to the first out-of-phase sound emission hole, and by increasing the frequency at which resonance occurs in the internal space of the collar 112 between the speaker unit 111 and the speaker unit 111 (hereinafter referred to as the resonant frequency). It is desirable that the predetermined frequency band is below the resonant frequency of the internal space of the collar 112 between the speaker unit 111 and the speaker unit 111. To shorten the path from the hole in the speaker unit 111 for emitting out-of-phase sound to the first out-of-phase 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 should not be housed in the collar 112. Also, in order to increase the resonant frequency of the internal space of the collar 112 that is created between the speaker unit 111 and the collar, the resonant frequency f of the Helmholtz resonance should be... H By considering equation (1) relating to the resonant frequency, the resonant frequency can be adjusted using one or more of the following three methods: increasing the area S of the first out-of-phase sound emission hole, decreasing the volume V of the internal space, or shortening the length L of the first out-of-phase sound emission hole, so that the collar 112 accommodates a portion of the speaker unit 111.

[0101] The direction adjustment unit 614 is a component attached to the acoustic signal output unit 610 to change the front direction of the acoustic 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 a component such as the arm of a desk lamp (see Figure 46). Alternatively, the direction adjustment unit 614 may be a component such as a frame attached to surround the acoustic signal output unit 610, as shown in Figure 48(A). Note that the acoustic signal output device 600 may include two or more acoustic signal output units 610, in which case a direction adjustment unit 614 may be attached to each acoustic signal output unit 610 so that the front direction of the acoustic signal output unit 610 can be changed (see Figure 48(B)).

[0102] The area where sound cannot be heard is formed in the lateral direction of the acoustic signal output unit 610. Therefore, by changing the front direction of the acoustic signal output unit 610 using the direction adjustment unit 614 so that a user who is not to hear the sound is positioned in the lateral direction of the acoustic signal output unit 610, the sound can be prevented from being heard by that user.

[0103] Similar to the first embodiment, a member (hereinafter referred to as a baffle) for adjusting the position where the out-of-phase sound and the in-phase sound cancel each other out in the low-frequency range may be attached to the speaker unit, thereby adjusting the position that is to be the sweet spot in the front direction of the speaker unit. In other words, the speaker unit 111 may be fitted 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 in-phase sound emitted from the speaker unit 111 from canceling each other out at the position that is to be the sweet spot in the front direction of the speaker unit 111.

[0104] According to embodiments 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 sound leakage is to be suppressed.

[0105] <Seventh Embodiment> In the first embodiment, sound leakage from the rear, particularly high-frequency sound leakage, can be a concern. Therefore, this embodiment describes a configuration for suppressing sound leakage from the rear.

[0106] The acoustic signal output device 700 will be described below with reference to Figures 49 to 52. Figures 49 and 50 both show the configuration of the acoustic signal output device 700. Figure 49 shows the acoustic signal output device 700 viewed from the side, and Figure 50 shows the acoustic signal output device 700 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 accommodates a part of the speaker unit 111. The ring collar 714 is a ring-shaped member that is large enough to cover the periphery of the collar 112 in the lateral direction. The shape of the ring collar 714 is arbitrary 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), which is a component used to fill the gap between the collar 112 and the ring collar 714, may be installed. In this case, it is possible to suppress sound leakage in the direction of the rear of 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 from the gap between the collar 112 and the ring collar 714 in the direction of the rear of the speaker unit 111, thereby suppressing sound leakage. Also, as shown in Figure 51, the ring collar 714 may have an illumination function.

[0107] Furthermore, 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 approximately circular in shape, and their centers are approximately the same. The ring collar 714 may be positioned so as to be located in the lateral direction of the speaker unit 111 (see Figure 49), or it may be positioned so as to be located in the front direction of the speaker unit 111 when viewed from the plane that is the front of the speaker unit 111 (see Figure 52).

[0108] Furthermore, it is preferable that the plane facing the front of the speaker unit 111, the plane facing the front of the collar 112, and the plane facing the front of the ring collar 714 are approximately parallel, as shown in Figure 49. In Figure 49, the plane facing the front of the speaker unit 111 and the plane facing the front of the collar 112 are approximately the same.

[0109] Color 112 is a housing that allows the out-of-phase sound, which is sound emitted from the speaker unit 111 towards the rear of the speaker unit 111, to wrap around to the front of the speaker unit 111. Color 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 wrapped around to the front of the speaker unit 111.

[0110] The collar 112 accommodates a portion of the speaker unit 111 in such a way that, in a predetermined frequency band in the front direction of the speaker unit 111, the out-of-phase sound emitted from the first out-of-phase sound emission hole towards the front of the speaker unit 111 is approximately out of phase with the in-phase sound emitted from the speaker unit 111 towards the front of the speaker unit 111. This is achieved by shortening the path from the hole in the speaker unit 111 for emitting out-of-phase sound to the first out-of-phase sound emission hole, and by increasing the frequency at which resonance occurs in the internal space of the collar 112 between the speaker unit 111 and the speaker unit 111 (hereinafter referred to as the resonant frequency). It is desirable that the predetermined frequency band is below the resonant frequency of the internal space of the collar 112 between the speaker unit 111 and the speaker unit 111. To shorten the path from the hole in the speaker unit 111 for emitting out-of-phase sound to the first out-of-phase 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 should not be housed in the collar 112. Also, in order to increase the resonant frequency of the internal space of the collar 112 that is created between the speaker unit 111 and the collar, the resonant frequency f of the Helmholtz resonance should be... H By considering equation (1) relating to the resonant frequency, the resonant frequency can be adjusted using one or more of the following three methods: increasing the area S of the first out-of-phase sound emission hole, decreasing the volume V of the internal space, or shortening the length L of the first out-of-phase sound emission hole, so that the collar 112 accommodates a portion of the speaker unit 111.

[0111] Similar to the first embodiment, a member (hereinafter referred to as a baffle) for adjusting the position where the out-of-phase sound and the in-phase sound cancel each other out in the low-frequency range may be attached to the speaker unit, thereby adjusting the position that is to be the sweet spot in the front direction of the speaker unit. In other words, the speaker unit 111 may be fitted 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 in-phase sound emitted from the speaker unit 111 from canceling each other out at the position that is to be the sweet spot in the front direction of the speaker unit 111.

[0112] According to embodiments 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, sound leakage at high frequencies can be suppressed. Furthermore, sound leakage in the rear direction can be suppressed.

[0113] <Note> The above-described embodiments of the present invention are presented for illustrative and descriptive purposes. They are not intended to be exhaustive, nor are they intended to limit the invention to the strict form disclosed. Modifications and variations are possible from the above teachings. The embodiments are selected and presented to provide the best illustration of the principles of the present invention and to enable those skilled in the art to utilize the invention in various embodiments and with various modifications to suit thoughtful practical use. All such modifications and variations are within the scope of the present invention as defined by the appended claims, interpreted in accordance with the fairly, lawfully, and equitably given width.

Claims

1. A speaker unit pair consisting of two speaker units, A housing that houses a part of the speaker unit pair in order to allow sound emitted from the two speaker units constituting the speaker unit pair toward the rear of the speaker unit pair (hereinafter referred to as out-of-phase sound) to wrap around toward the front of the speaker unit pair, and a collar provided with a hole (hereinafter referred to as the first out-of-phase sound emission hole) for emitting the out-of-phase sound toward the front of the speaker unit pair, In order to prevent the out-of-phase sound emitted from the first out-of-phase sound emission hole and the sound emitted from the two speaker units constituting the speaker unit pair in the direction in front of the speaker unit pair (hereinafter referred to as the in-phase sound) from canceling each other out at the position that is to be the sweet spot in the direction in front of the speaker unit pair, a baffle, which is a member attached to the speaker unit pair, An audio signal generation unit that takes an audio signal for the right channel and an audio signal for the left channel as inputs, generates a first output audio signal and a second output audio signal using the right channel audio signal and the left channel audio signal, outputs the first output audio signal to one speaker unit constituting the speaker unit pair, and outputs the second output audio signal to the other speaker unit constituting the speaker unit pair. An acoustic signal output device including, The collar accommodates a portion of the speaker unit pair such that, in a predetermined frequency band in the front direction of the speaker unit pair, the out-of-phase sound emitted from the first out-of-phase sound emission hole is approximately out of phase with the in-phase sound, the path from the holes of each speaker unit constituting the speaker unit pair for emitting the out-of-phase sound to the first out-of-phase sound emission hole is short, and the resonant frequency of the internal space of the collar formed between the speaker unit pair and the speaker unit pair is high. The baffle is attached to the speaker unit pair in order to make the area between the frontal directions of each speaker unit constituting the speaker unit pair a sweet spot. Said acoustic signal generating unit generates said first output acoustic signal and said second output acoustic signal as acoustic signals that increase the size of the sweet spot, wherein r (where r satisfies 0<r<1) is used as a mixing coefficient, an acoustic signal obtained by mixing said right-channel acoustic signal and said left-channel acoustic signal at a ratio of r:1-r is generated as said first output acoustic signal, and an acoustic signal obtained by mixing said right-channel acoustic signal and said left-channel acoustic signal at a ratio of 1-r:r is generated as said second output acoustic signal An acoustic signal output device.

2. The acoustic signal output device according to claim 1, wherein said baffle is attached to said speaker unit pair in such a manner as to connect opposing sides of one speaker unit and the other speaker unit that constitute said speaker unit pair An acoustic signal output device characterized by the above.

3. The acoustic signal output device according to claim 1, wherein said mixing coefficient r is a value dependent on frequency An acoustic signal output device characterized by the above.

4. The acoustic signal output device according to claim 1, wherein one or more of the three methods including increasing the area of said first reversed-phase sound emission hole, reducing the volume of said internal space, and shortening the length of said first reversed-phase sound emission hole is used to increase the resonance frequency of said internal space An acoustic signal output device characterized by the above.

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