Sound system

Abstract

Provided is an acoustic system for reproducing such sounds that cannot be heard around a user, while reducing the shift of the position of a speaker system or the position of the user's head. The acoustic system comprises: a directivity control device; and a speaker system that includes at least one speaker unit pair including a positive speaker for releasing a sound based on a first processed acoustic signal and a negative speaker for releasing a sound based on a second processed acoustic signal. The positive speaker and the negative speaker include no speaker box. The signal processing executed by the directivity control unit causes the sounds that are to be released by the speaker unit pair to have directivities. The directivities of the sounds that are to be released by the speaker unit pair are controlled in accordance with the positions where the user's hearing organs exist and with the position where the speaker unit pair exists.

Description

[Technical Field]

[0001] The present invention relates to a technology for localized sound reproduction. [Background technology]

[0002] There is a technique for pairing at least two speakers to realize local reproduction of an acoustic signal (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 192166 Summary of the Invention [Problem to be solved by the invention]

[0004] Non-Patent Document 1 discloses a technique that utilizes the bidirectionality of multiple speakers without using speaker boxes, allowing users to listen only locally in the vicinity of the speaker system. The technology described in Non-Patent Document 1 allows users to listen only in the immediate vicinity of the speaker system, so the audible range must be set taking into account the position of the speaker system and the position of the user's head (especially the position of the ears) for listening.

[0005] Therefore, an object of the present invention is to provide an audio system that reproduces sound so that it cannot be heard around the user, while reducing movement of the speaker system position or the user's head position. [Means for solving the problem]

[0006] In one aspect of the present invention, an acoustic system includes: a directivity control device including at least one directivity control unit that performs predetermined signal processing to generate a first processed acoustic signal from an acoustic signal of a predetermined sound source (hereinafter referred to as a first acoustic signal) and generate a second processed acoustic signal from an acoustic signal that is out-of-phase with the first acoustic signal (hereinafter referred to as a second acoustic signal); and a speaker system including at least one speaker unit pair including a speaker (hereinafter referred to as a positive speaker) that emits sound based on the first processed acoustic signal and a speaker (hereinafter referred to as a negative speaker). The positive speaker and the negative speaker do not include speaker boxes, and the signal processing performed by the directivity control unit is processing that imparts directionality to the sound emitted by the speaker unit pair, and the directivity of the sound emitted by the speaker unit pair is controlled according to the positions of the user's auditory organs and the positions of the speaker unit pair.

[0007] [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce movement of the speaker system position or the user position, while reproducing sounds that can be heard only in a very limited range. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram illustrating the directivity of sound emitted from a speaker. [Figure 2] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 3] 10A and 10B are diagrams for explaining sounds emitted from a speaker unit pair. [Figure 4] 10A and 10B are diagrams for explaining the directivity of sounds emitted from a speaker unit pair. [Figure 5] FIG. 1 shows the experimental setup (the relative positions of the speaker and microphone). [Figure 6] FIG. 1 shows the experimental setup (the relative positions of the speaker unit and microphone). [Figure 7] FIG. 1 shows the experimental setup (the relative positions of the speaker unit pair and microphone). [Figure 8] FIG. 10 is a diagram showing the experimental conditions (other measurement positions). [Figure 9] FIG. 10 is a diagram showing experimental results (condition 1). [Figure 10] FIG. 10 is a diagram showing experimental results (condition 2). [Figure 11] FIG. 10 is a diagram showing experimental results (condition 3). [Figure 12] FIG. 10 is a diagram showing experimental results (condition 4). [Figure 13] FIG. 1 is a diagram showing an example of an audio system installed in an aircraft seat. [Figure 14] 1 is a block diagram showing an example of the configuration of an acoustic system 100. FIG. [Figure 15] 10A and 10B are diagrams illustrating sounds emitted from a pair of speaker units. [Figure 16] FIG. 2 is a block diagram showing an example of the configuration of an acoustic system 200. [Figure 17] FIG. 2 is a block diagram showing an example of the configuration of an acoustic system 202. [Figure 18] 12 is a diagram showing an example of the configuration of a speaker unit pair 122 to which a member 1224 is attached. [Figure 19] FIG. 1 is a diagram showing an example of an audio system installed in a car seat. [Figure 20] FIG. 1 is a diagram showing an example of an audio system installed in a car seat. [Figure 21] FIG. 1 is a diagram showing an example of an audio system installed in an aircraft seat. [Figure 22] FIG. 2 is a block diagram showing an example of the configuration of an acoustic system 300. [Figure 23] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 24] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 25]3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 26] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 27] FIG. 1 is a diagram showing an example of an audio system installed in an aircraft seat. [Figure 28] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 29] FIG. 1 is a diagram showing an example of an audio system installed in an aircraft seat. [Figure 30] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 31] FIG. 1 is a diagram showing an example of an audio system installed in an aircraft seat. [Figure 32] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 33] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 34] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 35] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 36] FIG. 1 is a diagram showing an example of an audio system installed in an aircraft seat. [Figure 37] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 38] FIG. 1 is a diagram showing an example of an audio system installed in an aircraft seat. [Figure 39] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 40] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 41] 3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 42]3A and 3B are diagrams for explaining the directionality of sound emitted from a speaker unit. [Figure 43] FIG. 1 is a diagram showing an example of an audio system installed in an aircraft seat. [Figure 44] FIG. 1 is a diagram showing an example of an audio system installed in an aircraft seat. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail. Components having the same functions are given the same numbers, and duplicated explanations will be omitted.

[0011] <Technical background> First, the directivity of the sound emitted from the speaker will be described. Next, the directivity of the sound emitted from the speaker unit pair of the present invention will be described. Finally, the results of an experiment to confirm the effects of the speaker unit pair of the present invention will be described.

[0012] 1: Directionality of sound emitted from a speaker Typically, a speaker consists of a speaker unit and a speaker box. The speaker unit is a component that includes a diaphragm that converts electrical acoustic signals into vibrations in the air (i.e., generates sound waves). The speaker box is a component that houses the speaker unit.

[0013] When an acoustic signal is input to a speaker, the diaphragm of the speaker unit vibrates, and sound waves are emitted in both directions of the diaphragm's vibration. Here, sound waves emitted outside the speaker box (i.e., toward the front of the speaker unit) are called positive sound waves, and sound waves emitted inside the speaker box (i.e., toward the back of the speaker unit) are called negative sound waves. Negative sound waves are sound waves with the opposite phase to positive sound waves. Figure 1 is a diagram explaining the directionality of sound emitted from a speaker. As shown in Figure 1, positive sound waves are emitted from the speaker in all directions, while negative sound waves do not leave the speaker box. As a result, the sound emitted from the speaker can be heard over a wide range.

[0014] 2: Directivity of sound emitted from a speaker unit pair Here, we will first explain the directionality of sound emitted from a speaker unit, which is a bare speaker. Figure 2 is a diagram for explaining the directionality of sound emitted from a speaker unit. Unlike the case of a speaker unit alone, negative sound waves are emitted from the back of the speaker unit, which is hidden inside the speaker box. Therefore, as shown in Figure 2, the sound emitted from the speaker unit has a bidirectional characteristic.

[0015] The present invention utilizes this bidirectionality. A more detailed explanation follows. First, as shown in FIG. 3, two speaker units are arranged to form a speaker unit pair. The two speaker units are arranged so that they emit sound in approximately the same direction. When acoustic signals of approximately the same magnitude but in opposite phase are input to the speaker unit pair, the diaphragms of the two speaker units vibrate, emitting sounds based on these two acoustic signals. As a result, the sound emitted from the speaker unit pair is greatly suppressed except in the vicinity of the speaker unit pair, and the sound pressure approaches zero. For example, in FIG. 4, sound is not eliminated in the point area near the speaker unit, but is inaudible outside the point area. In other words, sound is eliminated only at positions sufficiently far from the speaker unit pair, and sound is not eliminated in the vicinity of the speaker unit pair. The reason why sounds are not cancelled near the speaker unit pair is that when the sound waves emitted from each of the speaker unit pair overlap at the observation point, the distance based on the arrival path from each speaker unit to the observation point has a large effect. At distances where the influence of path differences due to the spacing between the speaker unit pair and wraparound is small, the positive and negative phases overlap and cancel each other out, but near the speaker unit pair, the difference in the path taken by the sound waves emitted from the front of the speaker unit and the sound waves wraparound from the back is large, so the positive and negative phases are in a completely opposite relationship and do not overlap.

[0016] In other words, by taking advantage of the property that when a specified acoustic signal is input to one speaker unit that makes up a speaker unit pair and an acoustic signal of the opposite phase to the specified acoustic signal is input to the other speaker unit, the sound can only be heard in the vicinity of the speaker unit pair, it is possible to create a situation in which the sound can only be heard by users in the vicinity of the speaker unit pair, and cannot be heard by other users.

[0017] 3. Experimental Results Here we explain the results of an experiment to measure the frequency characteristics of a speaker, speaker unit, and speaker unit pair. The speakers, speaker units, and speaker unit pairs used in the experiment were a speaker with a 4.5 cm diameter diaphragm (see Figure 5), a speaker with the speaker box removed, leaving only the speaker unit (see Figure 6), and two of these speaker units lined up (see Figure 7). In addition, to measure the frequency characteristics near the speaker, speaker unit, and speaker unit pair, microphones were placed under the following four conditions.

[0018] (Condition 1) 5cm from the front of the speaker (Condition 2) 5cm from the front of the speaker unit (Condition 3) 2 cm from the front of the speaker unit (Condition 4) 2 cm from the front of the speaker unit pair In addition, for comparison purposes, microphones were placed 100 cm from the front, back, and side of the speaker, speaker unit, and speaker unit pair under all conditions (see Figure 8).

[0019] The experimental results are explained below. Figures 9, 10, 11, and 12 show the experimental results, illustrating the relationship between frequency and attenuation under Conditions 1, 2, 3, and 4, respectively. Each figure shows four curves. The curve indicated by the arrow represents sound picked up by a microphone positioned 5 cm or 2 cm from the front, while the other three curves represent sound picked up by microphones positioned 100 cm from the front, back, and side. Note that the curves positioned 5 cm or 2 cm from the front are located near the speaker, so the gain is very large. Therefore, for ease of viewing, the curve positioned 5 cm from the front is plotted at a -25 dB offset from the three curves positioned 100 cm from the front. Similarly, the curve positioned 2 cm from the front is plotted at a -32 dB offset. Comparing Figures 9 and 10, when a speaker is used, there is almost no difference between the four curves. However, when a speaker unit is used, there is a difference between the curve positioned 5 cm from the front and the other three curves. This difference is more pronounced in the low frequency range. Also, comparing Figure 11 and Figure 12, it can be seen that the difference between the curve 2 cm from the front and the other three curves is greater for the speaker unit pair than for the speaker unit itself.

[0020] As described above, it has been confirmed through experiments that the sound emitted from the speaker unit pair of the present invention can be heard only in the vicinity of the speaker unit pair.

[0021] First Embodiment A system that reproduces an acoustic signal obtained based on a reproduction object is called an acoustic system. An acoustic system includes a speaker system for emitting the acoustic signal as sound (hereinafter, this sound will be referred to as sound based on the acoustic signal). Here, a speaker system is a device that converts an analog acoustic signal into sound. Furthermore, a reproduction object refers to data or signals from which an acoustic signal can be obtained by predetermined processing, such as data recorded on a CD, DVD, or record, data received via the Internet, or signals received via radio or television broadcasts.

[0022] Here, we will describe an acoustic system that reproduces sound based on an acoustic signal obtained from a playback target so that only users near the speaker system can hear it. In other words, the sound reproduced by the acoustic system cannot be heard by users other than those near the speaker system. If such an acoustic system is used as an acoustic system for a user using a seat on an airplane, for example, a system can be provided in which the reproduced sound can only be heard by the user using that seat. FIG. 13 is a diagram showing an example of an acoustic system installed on an airplane seat. The acoustic system of FIG. 13 is installed on the seat so as to sandwich the head of a seated user, with two speaker unit pairs positioned near the left and right ears. Note that such an acoustic system can also be installed in vehicles other than airplanes, such as automobiles and trains, or in reclining chairs, and can also be installed in a wearable form, such as on the shoulder. Furthermore, a driver unit pair consisting of two driver units arranged side by side, corresponding to the above-mentioned speaker unit pair, may be installed in each of the left and right units of headphones or earphones. Headphones are generally divided into two main types: open-air and closed-air. Applying the above technology to open-air headphones, which are particularly susceptible to sound leakage, is expected to reduce sound leakage.

[0023] The acoustic system 100 will be described below with reference to FIG. 14. FIG. 14 is a block diagram showing the configuration of the acoustic system 100. As shown in FIG. 14, the acoustic system 100 includes a playback device 110 and a speaker system 120. The playback device 110 includes N (where N is an integer equal to or greater than 1) playback units 112 (i.e., first playback unit 112, ..., Nth playback unit 112). The speaker system 120 includes N speaker unit pairs 122 (i.e., first speaker unit pair 122, ..., Nth speaker unit pair 122). Each speaker unit pair 122 includes two speaker units (i.e., a positive speaker unit 1221 and a negative speaker unit 1221). An acoustic signal having an opposite phase to that input to the positive speaker unit 1221 is input to the negative speaker unit 1221. The speaker system 120 is installed near the head of a user using the seat.

[0024] The direction in which the nth speaker unit pair 122 faces the user is defined as the nth user direction (n=1, ..., N), and the positive speaker unit 1221 and the negative speaker unit 1221 of the nth speaker unit pair 122 (n=1, ..., N) are arranged so that sound emitted from the positive speaker unit 1221 in the direction opposite to the nth user direction and sound emitted from the negative speaker unit 1221 in the direction opposite to the nth user direction are transmitted to the nth user direction by wraparound. Here, the nth user direction refers to the front direction of the positive speaker unit 1221 and the negative speaker unit 1221 of the nth speaker unit pair 122. Furthermore, the direction opposite to the nth user direction refers to the rear direction of the positive speaker unit 1221 and the negative speaker unit 1221 of the nth speaker unit pair 122.

[0025] In addition, the positive speaker unit 1221 and the negative speaker unit 1221 of the nth speaker unit pair 122 (n=1, ..., N) are positioned in a positional relationship such that the sounds emitted from the positive speaker unit 1221 and the negative speaker unit 1221 cancel each other out so that they cannot be heard by users using other seats.

[0026] The operation of the acoustic system 100 will be described below with reference to FIG.

[0027] The playback device 110 receives as input a first acoustic signal, a third acoustic signal, ..., a 2N-1th acoustic signal, which are acoustic signals obtained based on a playback object, and outputs the first acoustic signal, the second acoustic signal, ..., the 2Nth acoustic signal. More specifically, the nth playback unit 112 (n = 1, ..., N) receives as input the 2n-1th acoustic signal, generates from the 2n-1th acoustic signal a 2nth acoustic signal that is an acoustic signal of opposite phase to the 2n-1th acoustic signal, and outputs the 2n-1th acoustic signal and the 2nth acoustic signal. The 2n-1th acoustic signal and the 2nth acoustic signal are input to the positive speaker unit 1221 and the negative speaker unit 1221 of the nth speaker unit pair 122, respectively.

[0028] The speaker system 120 receives as input the first acoustic signal, the second acoustic signal, ..., the 2Nth acoustic signal output by the playback device 110, and emits a sound based on the first acoustic signal, a sound based on the second acoustic signal, ..., a sound based on the 2Nth acoustic signal. More specifically, the nth speaker unit pair 122 (n = 1, ..., N) receives as input the 2n-1th acoustic signal and the 2nth acoustic signal, and emits a sound based on the 2n-1th acoustic signal from the positive speaker unit 1221, and emits a sound based on the 2nth acoustic signal from the negative speaker unit 1221. Because the 2n-1th acoustic signal and the 2nth acoustic signal are in opposite phase to each other, as described in <Technical Background>, the sounds can be heard only in the vicinity of the seat where the speaker system 120 is installed. For example, when N=2, if the first acoustic signal and the third acoustic signal are the right channel acoustic signal and the left channel acoustic signal of a certain sound source, respectively, stereo sound can be heard only in the vicinity of the seat where the speaker system 120 is installed.

[0029] Note that the sound emitted from the positive speaker unit 1221 of the n-th speaker unit pair 122 in the n-th user direction and the sound emitted from the positive speaker unit 1221 of the n-th speaker unit pair 122 in the direction opposite to the n-th user direction have opposite phases to each other. Similarly, the sound emitted from the negative speaker unit 1221 of the n-th speaker unit pair 122 in the n-th user direction and the sound emitted from the negative speaker unit 1221 of the n-th speaker unit pair 122 in the direction opposite to the n-th user direction have opposite phases to each other.

[0030] According to an embodiment of the present invention, it is possible to reproduce a sound that can only be heard within a very narrow range, namely, the vicinity of the speaker system. The term "vicinity" refers to a distance defined based on the environment and experimental results, in accordance with the frequency and the degree of sound attenuation. For example, in <3: Experimental Results>, if the state of sound at a distance where the sound pressure at a position approximately the diameter of the speaker diaphragm from the center of the speaker diaphragm gradually decreases to a sound pressure equivalent to background noise, and this state is considered to be sound attenuation, then "vicinity" is defined as, for example, a distance of approximately twice the diameter of the speaker diaphragm from the center of the speaker diaphragm. In other words, assuming an environment with a certain level of background noise, such as the inside of a car, the vicinity range is set so that the speaker system 120 can be heard by a person sitting in the seat where it is installed, but cannot be heard by a person sitting in the seat next to it. For example, in (3: Experimental Results), if we consider the state in which sound emitted from a speaker unit is radiated into the surrounding area and reaches a sound pressure equivalent to that of background noise to be sound elimination, then "nearby" can be considered to be up to a distance of approximately twice the user's shoulder width from the center of the speaker diaphragm.

[0031] Second Embodiment FIG. 15 is a diagram showing the sound emitted from a speaker unit pair. In the diagram, SPU represents a speaker unit. In the case of a speaker unit pair installed near the right ear, the sounds from each speaker unit cancel each other out in the intermediate region between the two speaker units, creating an area where the sound emitted from the speaker unit pair cannot be heard, and the user cannot hear the sound. On the other hand, in the case of a speaker unit pair installed near the left ear, the area where the sound emitted from the speaker unit pair can be heard shifts from the position of the ears, causing the user to be unable to hear the sound. In other words, when (i) both / either of the left and right ears are located in the intermediate region, (ii) both / either of the left and right ears are located outside the audible region, or (iii) one of the left and right ears is located in the intermediate region and the other is located outside the audible region, the user cannot hear the sound or has difficulty hearing it. To solve these problems, the directivity of the sound emitted from the speaker unit pair is controlled. Here, an audio system that performs directivity control processing is described.

[0032] The acoustic system 200 will be described below with reference to Fig. 16. Fig. 16 is a block diagram showing the configuration of the acoustic system 200. As shown in Fig. 16, the acoustic system 200 includes a playback device 110, a directivity control device 210, and a speaker system 120. The directivity control device 210 includes N directivity control units 212 (i.e., a first directivity control unit 212, ..., an Nth directivity control unit 212). The acoustic system 200 differs from the acoustic system 100 in that it includes the directivity control device 210.

[0033] The operations of the directivity control device 210 and the speaker system 120 will be described below with reference to FIG.

[0034] The directivity control device 210 receives the first acoustic signal, the second acoustic signal, ..., the 2Nth acoustic signal output by the playback device 110 as input, and outputs a first-processed acoustic signal obtained by signal processing the first acoustic signal, a second-processed acoustic signal obtained by signal processing the second acoustic signal, ..., a 2Nth-processed acoustic signal obtained by signal processing the 2Nth acoustic signal. More specifically, the nth directivity control unit 212 (n = 1, ..., N) receives the 2n-1th acoustic signal and the 2nth acoustic signal as input, and performs predetermined signal processing to generate a 2n-1th-processed acoustic signal from the 2n-1th acoustic signal, generate a 2nth-processed acoustic signal from the 2nth acoustic signal, and output the 2n-1th-processed acoustic signal and the 2nth-processed acoustic signal. Here, the predetermined signal processing refers to processing for controlling directivity, and can be, for example, the method described in Reference 1 or other directivity control techniques. Needless to say, other directivity control techniques may also be used. In short, any technology may be used as long as it can control the directionality according to the positions of the user's ears and the positions of the speaker unit pair. (Reference 1) Futoshi Asano, "Sound Array Signal Processing - Sound Source Localization, Tracking and Separation", Corona Publishing, 2011, pp. 69-91 The predetermined signal processing is, for example, filtering using an FIR (Finite Impulse Response) filter. The FIR filter used here is designed by placing microphones in an audible range and an inaudible range, respectively, so that the filter coefficient value approaches 1 for the microphones placed in the audible range and the filter coefficient value approaches 0 for the microphones placed in the inaudible range. A specific explanation will be given below. The audible range and the inaudible range need to be designed depending on the case. For example, consider the case of placement in a car seat (hereinafter referred to as seat S). The position where the ear of a user using seat S would be when moving their head or turning their face should be included in the audible range, while the position where the ear of a user using a seat adjacent to seat S (e.g., the seat next to or in front of or behind seat S) would be included in the inaudible range. Therefore, for example, the filter coefficient value approaches 0 for microphones placed in an area that includes seats adjacent to seat S but does not include seat S. As described above, sounds cancel each other out in the intermediate region between the two speaker units, and as a result, sounds may not be heard even at the position where the ears are located when the head is moved or the direction of the face is changed. Taking this into consideration, the filter coefficient value of the microphone placed in the intermediate region is set to approach 1. In essence, the filter coefficient of the microphone placed in the region where the user's ears are assumed to be located can be controlled to approach 1, and / or the filter coefficient of the microphone placed in the region where the user's ears are assumed not to be located can be controlled to approach 0. In other words, the filter can be configured so that the sound arriving in the region where the user's ears are assumed to be located is as loud as possible, and so that the sound arriving in the region where the user's ears are assumed not to be located is reduced as much as possible.

[0035] As a result, the nth directivity control unit (n=1, ..., N) executes signal processing to make the sound emitted from the positive speaker unit of the nth speaker unit pair and the sound emitted from the negative speaker unit of the nth speaker unit pair audible in an area near the nth speaker unit pair that should be audible, but inaudible in an area that should not be audible. Note that the area that should be the audible area includes a point equidistant from the positive speaker unit of the nth speaker unit pair and the negative speaker unit of the nth speaker unit pair, where the sound emitted from the positive speaker unit of the nth speaker unit pair and the sound emitted from the negative speaker unit of the nth speaker unit pair cancel each other out.

[0036] The speaker system 120 receives as input the first processed acoustic signal, the second processed acoustic signal, ..., the 2Nth processed acoustic signal output by the directivity control device 210, and emits sound based on the first processed acoustic signal, the second processed acoustic signal, ..., the 2Nth processed acoustic signal. More specifically, the nth speaker unit pair 122 (n=1, ..., N) receives as input the 2n-1th processed acoustic signal and the 2nth processed acoustic signal, and emits sound based on the 2n-1th processed acoustic signal from the positive speaker unit 1221, and emits sound based on the 2nth processed acoustic signal from the negative speaker unit 1221.

[0037] (Variation) Here, we will explain an acoustic system that uses materials with sound-absorbing properties to prevent high-frequency sounds from leaking.

[0038] The acoustic system 202 will be described below with reference to Fig. 17. Fig. 17 is a block diagram showing the configuration of the acoustic system 202. As shown in Fig. 17, the acoustic system 202, like the acoustic system 200, includes a playback device 110, a directivity control device 210, and a speaker system 120. However, the acoustic system 202 differs from the acoustic system 200 in that a member 1224 is attached to the speaker unit pair 122.

[0039] The structure of the n-th speaker unit pair 122 (n=1, . . . , N) will be described below with reference to FIG.

[0040] The nth speaker unit pair 122 is fitted with a member 1224 for absorbing sounds emitted from the positive speaker unit 1221 and the negative speaker unit 1221 of the nth speaker unit pair 122 in the direction opposite to the nth user direction (see FIG. 18). The member 1224 may be any member that can prevent high-frequency sounds from being radiated from the rear surface. Note that instead of installing the member 1224 only on the rear surface of the speaker unit pair 122, the member 1224 may be installed so as to surround the speaker unit pair 122 on all sides except the front surface.

[0041] (Example of a car seat-mounted sound system) 19 and 20 are diagrams showing examples of sound systems installed in automobile seats. In the example of FIG. 19, a speaker unit pair is installed in the headrest of the automobile seat. Specifically, N=2, and a first speaker unit pair and a second speaker unit pair are installed in the headrest of the automobile seat. On the other hand, in the example of FIG. 20, a speaker unit pair is installed on arms attached to the automobile seat. Specifically, N=2, and the speaker units are installed on two arms attached to the automobile seat so as to sandwich the head of a user using the automobile seat. The arms may be movable.

[0042] (Other examples) An example other than a car seat, specifically a seat for a gaming machine such as a pachinko or slot machine, will be described. Typically, a user sits in front of the gaming machine and enjoys playing games on the gaming machine. Therefore, the seats for gaming machines may also be provided with arms as described in the example of a car, so that the speaker unit pair is located near the position of the user's ears when seated in the seat. Note that since the seats for gaming machines may not have a backrest, the arms may be provided on the gaming machine instead of the seat. Furthermore, the arms may be movable so that the user can adjust them so that the speaker unit pair is located near the user's ears.

[0043] Third Embodiment In the second embodiment, a case where an ear (hereinafter also referred to as an auditory organ) may be present in a gap or offset between audible regions (see FIG. 15), i.e., a case where the speaker unit pair and the auditory organ are relatively close to each other, is considered, but in this embodiment, attention is focused on the speaker unit pair itself and the position of the auditory organ. In other words, this embodiment considers a more coarse directional control than the second embodiment.

[0044] FIG. 21 is a diagram showing an example of an acoustic system installed in an aircraft seat. The acoustic system in FIG. 21 is installed in the headrest of the seat, with two speaker units included in one speaker unit pair arranged vertically in the center of the headrest. Note that while an aircraft seat will be used as an example here, the present invention may also be applied to a car seat, a train seat, an office chair, or a speaker unit pair installed on a separator or digital signage. In short, this embodiment can be applied to the technology described in the first embodiment when it is necessary to vary the audible range depending on the user's physical characteristics, such as height.

[0045] The acoustic system 300 will be described below with reference to Fig. 22. Fig. 22 is a block diagram showing the configuration of the acoustic system 300. As shown in Fig. 22, the acoustic system 300 includes a playback device 110, a position acquisition unit 330, a directivity control device 210, and a speaker system 120. The acoustic system 300 differs from the acoustic system 200 in that the acoustic system 300 includes the position acquisition unit 330.

[0046] The operation of the position acquisition unit 330 will be described below with reference to FIG. The position acquisition unit 330 changes the directivity of the directivity control process performed by the directivity control device 210 depending on the location of the user's auditory organs and the location of the speaker unit pair, so that the directionality of the sound emitted from the speaker unit pair is directed toward the location of the user's auditory organs. In this embodiment, the speakers are arranged vertically in order to control the viewing area with emphasis on the height at which the user's auditory organs are located. When the height at which the users' auditory organs are located is approximately the same, as in cases where the same user uses the speakers exclusively, the speakers may be arranged horizontally to control the horizontal directivity. Whether the speakers are arranged vertically or horizontally, it is desirable that the speaker closest to the ears be the positive speaker unit and the speaker farthest from the ears be the negative speaker unit. The roles of the positive and negative speakers are switched using a filter used in the directivity control device 210.

[0047] First, the position acquisition unit 330 acquires the position of the user's auditory organs. The position may be acquired by any method. Below, an example in which the position acquisition unit 330 estimates the position and an example in which the user selects the position will be described.

[0048] (Acquisition method 1 (location estimation)) For example, the position acquisition unit 330 estimates the position of the user's head and estimates the position of the auditory organs from the head position. Note that the head position may be estimated by any method.

[0049] For example, a pressure sensor is installed on the headrest, and it is estimated that the user's head is in a position where strong pressure is applied.

[0050] Also, for example, a camera or the like is used to capture an image of the user's head, feature amounts are extracted from the captured image, and the position of the user's head or auditory organs is estimated from the extracted feature amounts.

[0051] Furthermore, for example, if the headrest and backrest of a seat are separate members, a speaker unit pair is installed in the backrest, and the position of the headrest can be freely changed relative to the backrest, the position of the headrest can be detected from physical structures such as the state of belts and gears that operate in conjunction with changes in the position of the headrest, and it is assumed that the user's head is located at the headrest, and the position of the user's head is estimated from the position of the headrest. In this case, it is advisable to arrange the speaker unit pair vertically in the backrest, where the head of a user with an average build would be located when sitting in the seat.

[0052] (Acquisition method 2 (user selection)) For example, the position acquisition unit 330 may have a selection unit such as a button (not shown), and the user may select the position of the head or auditory organs via the selection unit, and the position of the user's auditory organs may be acquired from the selection result. The position acquisition unit 330 may further have a communication function (not shown), and may be configured to allow selection from a terminal carried by the user. The terminal may be configured as an integrated part of the sound system, or may be a terminal carried by the user, such as a smartphone or tablet.

[0053] Next, the position acquisition unit 330 selects a filter that directs the directionality of the sound emitted by the speaker unit pair toward the position where the user's auditory organs are located, and sets the selected filter as the filter to be used in the directivity control device 210. In essence, the position acquisition unit 330 changes the filter to be used in the directivity control device 210 according to the positional relationship between the speaker unit pair and the position where the user's auditory organs are located, thereby changing the area that should be audible and the area that should not be audible, so that the position where the user's auditory organs are located (the position where they are assumed to exist) becomes the area that should be audible, and the position where the user's auditory organs are not located (the position where they are assumed not to exist) becomes the area that should not be audible. Note that the positional relationship may be determined based on the estimated or selected positions of the head and auditory organs and a reference point of the speaker unit pair (for example, the center position of the speaker unit pair, the center or bottom position of a speaker close to the ground, etc.).

[0054] The filters may be calculated in advance through simulations or experiments and stored in a storage unit (not shown) in association with the positional relationship between the speaker unit pair and the position of the user's auditory organs. Instead of selecting a filter, filters may be calculated sequentially so that the directionality of the sound emitted by the speaker unit pair is directed toward the position of the user's auditory organs.

[0055] (Example of directivity control) As shown in FIG. 23, when the position where the user's auditory organs are located is lower than the position where the speaker unit pair is located, the speaker unit pair is controlled so that the directivity of the sounds emitted is directed in a lower direction.

[0056] As shown in FIG. 24, when the position where the user's auditory organs are located is higher than the position where the speaker unit pair is located, the speaker unit pair is controlled so that the directivity of the sound emitted from the speaker unit pair is directed in a high direction.

[0057] As shown in FIG. 25, when the position where the user's auditory organs are located is approximately the same height as the position where the speaker unit pair is located, the directivity of the sound emitted by the speaker unit pair is controlled so that the user can hear the sound at a point equidistant from the positive speaker and the negative speaker. Note that when the position where the user's auditory organs are located is approximately the same height as the position where the speaker unit pair is located, this means that the position where the user's auditory organs are located is on a plane formed by points equidistant from the positive speaker and the negative speaker (i.e., the intermediate region in the second embodiment). A filter designed to minimize the area where the directivity is not suitable (the area where sound pressure is low) between the positive speaker and the negative speaker is selected. Note that in this case, there is a trade-off: the smaller the area where the directivity is not suitable (the area where sound pressure is low), the greater the sound leakage to the surroundings.

[0058] As shown in Fig. 26, when the position of the user's auditory organs is at approximately the same height as the position of the positive speaker or the negative speaker, the directivity of the sound emitted by the speaker unit pair is controlled so that the area that the user can hear is reduced. By controlling in this way, it is possible to reduce sound leakage to the surroundings.

[0059] For example, filters for realizing directivity such as those shown in FIGS. 23 to 26 are calculated in advance through simulations or experiments, and stored in a memory unit (not shown) in association with the positions of the auditory organs. The position acquisition unit 330 acquires the positions of the user's auditory organs, selects a corresponding filter from the memory unit (not shown) based on the positional relationship between the speaker unit pair and the acquired positions of the user's auditory organs, and sets the selected file in the directivity control device 210.

[0060] The directivity control device 210 performs processing using the filter selected by the position acquisition unit 330. The processing itself in the directivity control device 210 is the same as in the second embodiment, and therefore a description thereof will be omitted.

[0061] As explained in the second embodiment, the positive speaker and the negative speaker emit sounds in predetermined directions so that they are in opposite phase to each other in a region that should not be audible. Also, as explained in the first embodiment, the positive speaker unit and the negative speaker unit are speakers without the speaker box, and are arranged so that the sound emitted from the positive speaker unit in the direction opposite to the nth user direction and the sound emitted from the negative speaker unit in the direction opposite to the nth user direction are transmitted to the nth user direction by wraparound.

[0062] According to an embodiment of the present invention, it is possible to reproduce sounds that can only be heard in a very limited range, such as in the vicinity of the speaker system, and to appropriately control the directionality to match the location of the user's auditory organs.

[0063] The present embodiment may be combined with the modified example of the second embodiment. Furthermore, in this embodiment, an example where N=1 has been described, but N may be any integer greater than or equal to 2. Even when N is an integer greater than or equal to 2, local playback is possible, and the directivity can be appropriately controlled according to the position of the user's auditory organs.

[0064] <Variation 1> In this embodiment, one speaker unit pair is installed in the headrest of the seat, but two speaker unit pairs may be installed near the positions of the left and right auditory organs on the headrest as shown in Fig. 27. As shown in Fig. 28, directivity control similar to that of the third embodiment can be performed for each channel. Local reproduction can be performed for each auditory organ from each speaker unit pair, and directivity can be appropriately controlled according to the positions of the user's auditory organs.

[0065] <Variation 2> Furthermore, while two speaker unit pairs are installed in the headrest of the seat in FIG. 27, as shown in FIG. 29, two speaker unit pairs may be installed on two arms that are not adjustable to attach the speaker unit pairs to the seat. As shown in the figure, directivity control similar to that of the third embodiment can be performed for each channel. Note that in this embodiment, a speaker unit pair is installed in the backrest, and the position of the headrest relative to the backrest can be freely adjusted. In this case, however, the headrest may interfere with the sound output from the speaker unit pair. On the other hand, in the case of FIG. 30, the speaker unit pair is installed on the arm, which has the advantage that the sound output from the speaker unit pair is not obstructed.

[0066] <Variation 3> In Fig. 29 of Modification 2, the two speaker units included in each speaker unit pair are arranged vertically on each arm, but they may also be arranged horizontally as shown in Fig. 31. With this configuration, the directivity can be controlled in the front-to-back direction as shown in Fig. 32. Therefore, if the position of the ears moves forward or backward (leaning forward / throwing one's body against the backrest), it is better to arrange the two speaker units horizontally.

[0067] Using the direction the user is facing as a reference, if the user's head is in front of the speaker unit pair, the directivity is controlled to be forward, and if the user's head is behind, the directivity is controlled to be backward. In other words, the directivity is directed in the direction of the user's head, especially the ears.

[0068] In this case, the position acquisition unit 330 also acquires the position of the user's auditory organs. Note that the position may be acquired by any method. Below, an example in which the position acquisition unit 330 estimates a position and an example in which the user selects a position will be described.

[0069] (Acquisition method 1 (location estimation)) For example, the position acquisition unit 330 estimates the position of the user's head and estimates the position of the auditory organs from the head position. Note that the head position may be estimated by any method. For example, a tilt sensor is installed on the seat of a chair, and if the front of the chair is downwards and tilted by a predetermined amount or more, it is assumed that the user is leaning their head out and their head is in front of the speaker unit pair.If the back of the chair is downwards and tilted by a predetermined amount or more, it is assumed that the user is leaning their body against the backrest and their head is behind the speaker unit pair.

[0070] Also, for example, a camera or the like is used to photograph the user's head from the side, feature amounts are extracted from the photographed image, and the position of the user's head or auditory organs is estimated from the extracted feature amounts.

[0071] (Acquisition method 2 (user selection)) For example, the position acquisition unit 330 may have a selection unit such as a button (not shown), and the user may select the position of the head or auditory organs via the selection unit, and the position where the user's auditory organs are located may be acquired from the selection result.

[0072] Next, the position acquisition unit 330 selects a filter that directs the directionality of the sound emitted by the speaker unit pair toward the position where the user's auditory organs are located, and sets the selected filter as the filter to be used in the directivity control device 210. The processing itself in the directivity control device 210 is the same as in the second embodiment, except for the direction of the directivity.

[0073] As shown in FIG. 32, when the position where the user's auditory organs are located is in front of the position where the speaker unit pair is located, the directivity of the sound emitted by the speaker unit pair is controlled to be directed forward.

[0074] As shown in FIG. 33, when the position where the user's auditory organs are located is behind the position where the speaker unit pair is located, the directivity of the sound emitted by the speaker unit pair is controlled to be directed backward.

[0075] As shown in FIG. 34, when the position of the user's auditory organs is approximately the same as the position of the speaker unit pair in the front-to-back direction, the directivity of the sound emitted by the speaker unit pair is controlled so that the user can hear the sound at a point equidistant from the positive speaker and the negative speaker. Note that when the position of the user's auditory organs is approximately the same as the position of the speaker unit pair in the front-to-back direction, this means that the position of the user's auditory organs is located on a plane formed by points equidistant from the positive speaker and the negative speaker (i.e., the intermediate region in the second embodiment). A filter designed to minimize the area where the directivity is not suitable (the area where sound pressure is low) between the positive speaker and the negative speaker is selected. Note that in this case, there is a trade-off: the smaller the area where the directivity is not suitable (the area where sound pressure is low), the greater the sound leakage to the surroundings.

[0076] As shown in Figure 35, when the position of the user's auditory organs is approximately the same in the front-to-back direction as the position of the positive speaker or the negative speaker, the directivity of the sound emitted by the speaker unit pair is controlled so that the area that the user can hear is reduced. By controlling in this way, it is possible to reduce sound leakage to the surroundings. The processing itself in the position acquisition unit 330 is the same as in the third embodiment, and therefore a description thereof will be omitted.

[0077] <Variation 4> As shown in Figure 36, two speaker unit pairs may be arranged near the positions where the left and right auditory organs of the headrest are expected to be located, with the two speaker units included in each speaker unit pair lined up horizontally. In this modification, directivity control is performed according to the size of the face and the relative positions of the speaker unit pair.

[0078] In this case, the position acquisition unit 330 estimates the size of the user's face and estimates the position of the auditory organs from the estimated face size. Note that any method may be used to acquire the size of the user's face. Below, an example in which the position acquisition unit 330 estimates the size of the user's face and an example in which the user selects the size of the user's face will be described.

[0079] (Method 1 (Estimation of face size)) For example, the position acquisition unit 330 estimates the size of the user's face and estimates the positions of the auditory organs from the size of the user's face. Note that the size of the face may be acquired by any method.

[0080] For example, pressure sensors may be placed on the inside and outside of the headrest based on the center line, and if the difference between the pressure detected by the pressure sensor placed on the inside and the pressure detected by the pressure sensor placed on the outside is greater than a predetermined value, it may be determined that the person has a small face.

[0081] Also, for example, a camera or the like is used to photograph the user's head, feature amounts are extracted from the photographed image, and the size of the user's face is estimated from the extracted feature amounts.

[0082] (Acquisition method 2 (user selection)) For example, the position acquisition unit 330 may have a selection unit such as a button (not shown), and the user may select the size of the face via the selection unit, and the position where the user's auditory organs are located may be acquired from the selection result.

[0083] Next, the position acquisition unit 330 selects a filter that directs the directionality of the sound emitted by the speaker unit pair toward the position where the user's auditory organs are located, and sets the selected filter as the filter to be used in the directivity control device 210. The processing itself is the same as in the second embodiment, except for the direction of the directivity.

[0084] As shown in Figure 37, if a user has a small face and their face fits between two speaker unit pairs, the direction of the sound emitted by the speaker unit pair located on the left side will be controlled to point to the right, and the direction of the sound emitted by the speaker unit pair located on the right side will be controlled to point to the left, based on the direction the user's face is facing.

[0085] <Variation 5> In this modified example, as shown in FIG. 38, the sound system is installed in the headrest of the seat, with the two speaker units included in one speaker unit pair arranged horizontally side by side in the center of the headrest.

[0086] First, the position acquisition unit 330 acquires the position where the user's auditory organs are located, using the same method as in this embodiment.

[0087] (Example of directivity control) As shown in FIG. 39, when the position of the user's auditory organs is to the left of the position where the speaker unit pair is located, the directivity of the sound emitted by the speaker unit pair is controlled to face leftward.

[0088] As shown in FIG. 40, when the position of the user's auditory organs is to the right of the position where the speaker unit pair is located, the directivity of the sound emitted by the speaker unit pair is controlled to face rightward.

[0089] As shown in Figure 41, when the position of the user's auditory organs is approximately the same position in the left-right direction as the position of the speaker unit pair, the directionality of the sound emitted by the speaker unit pair is controlled so that the user can hear it at a point equidistant from the positive speaker and the negative speaker.

[0090] As shown in Figure 42, when the position of the user's auditory organs is approximately the same position in the left-right direction as the position of the positive speaker or negative speaker, the directionality of the sound emitted by the speaker unit pair is controlled so that the area that the user can hear is reduced. The processing itself in the position acquisition unit 330 is the same as in the third embodiment, and therefore a description thereof will be omitted.

[0091] <Variation 6> In this modified example, as shown in Figure 43, the audio system has two speaker unit pairs installed on the headrests of the seats, with the two speaker units in one speaker unit pair arranged side by side from the bottom right to the top left, and the two speaker units in the other speaker unit pair arranged side by side from the bottom left to the top right.

[0092] With this arrangement, the speaker unit pair on the right can provide directivity from the lower right to the upper left, and the speaker unit pair on the left can provide directivity from the lower left to the upper right, as shown in Fig. 43. For example, when the user's auditory organs are located between the two speaker unit pairs in the horizontal direction and higher than the two speaker unit pairs in the vertical direction, more flexible directional control becomes possible.

[0093] <Variation 7> In this modified example, as shown in Figure 44, the audio system has two speaker unit pairs installed on the headrests of the seats, with the two speaker units in one speaker unit pair arranged side by side from the upper right to the lower left, and the two speaker units in the other speaker unit pair arranged side by side from the upper left to the lower right.

[0094] With this arrangement, the speaker unit pair on the right can provide directivity from the upper right to the lower left, and the speaker unit pair on the left can provide directivity from the upper left to the lower right, as shown in Fig. 44. For example, when the user's auditory organs are located between the two speaker unit pairs in the horizontal direction and lower than the two speaker unit pairs in the vertical direction, more flexible directional control becomes possible.

[0095] <Additional Notes> The foregoing description of the embodiments of the present 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 were chosen and described to provide the 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 uses 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

1. a directivity control device including at least one directivity control unit that generates a first processed acoustic signal from an acoustic signal of a predetermined sound source (hereinafter referred to as a first acoustic signal) and generates a second processed acoustic signal from an acoustic signal that is in the opposite phase to the first acoustic signal (hereinafter referred to as a second acoustic signal) by executing predetermined signal processing; a speaker system including at least one speaker unit pair including a speaker that emits a sound based on a first processed acoustic signal (hereinafter referred to as a positive speaker) and a speaker that emits a sound based on a second processed acoustic signal (hereinafter referred to as a negative speaker); An audio system comprising: the positive speaker and the negative speaker do not include a speaker box; the signal processing executed by the directivity control unit is processing for imparting directionality to sounds emitted from the speaker unit pair; a directionality of the sound emitted by the speaker unit pair is controlled in accordance with a position of the user's auditory organ and a position of the speaker unit pair; The directionality of the sound emitted by the speaker unit pair is When a position where the user's auditory organs are present is at approximately the same height as a position where the positive speaker or the negative speaker is present, the area that the user can hear is controlled to be small. Sound system.

2. A directivity control device including at least one directivity control unit that generates a first processed acoustic signal from an acoustic signal of a predetermined sound source (hereinafter referred to as a first acoustic signal) by performing predetermined signal processing, and generates a second processed acoustic signal from an acoustic signal that is in the opposite phase to the first acoustic signal (hereinafter referred to as a second acoustic signal); a speaker system including at least one speaker unit pair including a speaker that emits a sound based on a first processed acoustic signal (hereinafter referred to as a positive speaker) and a speaker that emits a sound based on a second processed acoustic signal (hereinafter referred to as a negative speaker); An audio system comprising: the positive speaker and the negative speaker do not include a speaker box; the signal processing executed by the directivity control unit is processing for imparting directionality to sounds emitted from the speaker unit pair; a directionality of the sound emitted by the speaker unit pair is controlled in accordance with a position of the user's auditory organ and a position of the speaker unit pair; The speaker unit pair emits a 1-channel acoustic signal. Sound system.

3. The acoustic system of claim 2, The 1ch acoustic signal is a right channel acoustic signal or a left channel acoustic signal. Sound system.

4. 4. The acoustic system of claim 3, The directionality of the sound emitted by the speaker unit pair is When a position where the user's auditory organs are present is lower than a position where the speaker unit pair is present, the speaker unit is controlled to face in a lower direction; When a position where the user's auditory organs are present is higher than a position where the speaker unit pair is present, the speaker unit pair is controlled to face in a higher direction. Sound system.

5. The acoustic system of claim 3 or claim 4, The directionality of the sound emitted by the speaker unit pair is When a position where the user's auditory organs are present is at approximately the same height as a position where the speaker unit pair is present, the speaker units are controlled so that the user can hear the sound at a point equidistant from the positive speaker and the negative speaker. Sound system.

6. The acoustic system according to any one of claims 3 to 5, The directionality of the sound emitted by the speaker unit pair is When a position where the user's auditory organs are present is at approximately the same height as a position where the positive speaker or the negative speaker is present, the area that the user can hear is controlled to be small. Sound system.

7. 4. The acoustic system of claim 3, The directionality of the sound emitted by the speaker unit pair is When a position where the user's auditory organs are present is in front of a position where the speaker unit pair is present, the speaker unit is controlled to face forward; When a position where the user's auditory organs are present is located behind a position where the speaker unit pair is present, the speaker unit is controlled to face rearward. Sound system.

8. 4. The acoustic system of claim 3, The directionality of the sound emitted by the speaker unit pair is Controlled according to the size of the user's head. Sound system.

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