Sound system

Abstract

To provide an acoustic system, for a user who uses a seat of an aircraft, an automobile, etc., which uses neither an earphone nor headphones and reproduces a sound that circumferential users cannot hear.SOLUTION: The present invention relates to an acoustic system that includes a speaker system including at least one speaker unit pair including a positive speaker unit radiating a sound based upon an acoustic signal of a predetermined sound source and a negative speaker unit radiating a sound based upon an acoustic signal having the opposite phase from the acoustic signal. The positive speaker unit and negative speaker unit of the speaker unit pair are each housed in a speaker box having a plurality of holes bored, and when the direction in which the speaker unit pair faces a user is defined as a user direction, the positive speaker unit and negative speaker unit of the speaker unit pair are so arranged that sounds radiated from the two speaker units in the opposite direction from the user direction travel around to be transmitted in the user direction.SELECTED DRAWING: Figure 22

Description

[Technical Field]

[0001] The present invention relates to a sound reproduction technology that can be used in an audio system installed in a seat of an aircraft, automobile, or the like. [Background technology]

[0002] Conventionally, users have used earphones or headphones to watch movies or listen to music on airplanes (see Non-Patent Document 1). This is because when speakers are used, the playback sound reaches the user's surroundings, causing a nuisance to other users. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] In-flight entertainment / JAL First Class, [online], [searched on March 10, 2020], Internet<URL: https: / / www.jal.co.jp / jp / ja / inter / service / first / entertainment / index.html> Summary of the Invention [Problem to be solved by the invention]

[0004] However, wearing earphones or headphones can be a hassle for users. Some users dislike wearing them because they mess up their hair. Others dislike the pressure they put on their ears. Furthermore, wearing earphones or headphones for long periods of time can cause listening fatigue.

[0005] To eliminate the need to wear earphones or headphones, it is possible to synthesize a virtual sound field using wave field synthesis technology, but this would require the preparation of a large-scale speaker array, which is not realistic.

[0006] Therefore, an object of the present invention is to provide an audio system for users seated in an airplane, automobile, etc., that reproduces sounds that cannot be heard by surrounding users without using earphones or headphones. [Means for solving the problem]

[0007] One aspect of the present invention is an acoustic system including a speaker system that includes at least one speaker unit pair including a speaker unit (hereinafter referred to as a positive speaker unit) that emits sound based on an acoustic signal of a predetermined sound source and a speaker unit (hereinafter referred to as a negative speaker unit) that emits sound based on an acoustic signal that is in phase with the acoustic signal, wherein the positive speaker unit and the negative speaker unit of the speaker unit pair are both housed in a speaker box with a plurality of holes, the direction in which the speaker unit pair faces the user is defined as the user direction, and the positive speaker unit and the negative speaker unit of the speaker unit pair are positioned so that the sound emitted from the positive speaker unit in a direction opposite to the user direction and the sound emitted from the negative speaker unit in a direction opposite to the user direction are transmitted to the user direction by wraparound. [Effects of the Invention]

[0008] According to the present invention, it is possible to reproduce sounds that can only be heard 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] FIG. 2 is a block diagram showing an example of the configuration of an acoustic system 102. [Figure 16] 12 is a diagram showing an example of the configuration of a speaker unit pair 122 to which a member 1222 is attached. [Figure 17] FIG. 2 is a block diagram showing an example of the configuration of an acoustic system 104. [Figure 18] FIG. 2 is a block diagram showing an example of the configuration of an acoustic system 200. [Figure 19] FIG. 2 is a block diagram showing an example of the configuration of an acoustic system 300. [Figure 20] FIG. 2 is a block diagram showing an example of the configuration of an acoustic system 106. [Figure 21] 12 is a diagram showing an example of the configuration of a speaker unit pair 122 to which a member 1224 is attached. [Figure 22] FIG. 2 is a block diagram showing an example of the configuration of an acoustic system 108. 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 side by side to form a speaker unit pair. When acoustic signals with opposite positive and negative polarities are input to this speaker unit pair, the diaphragms of the two speaker units vibrate, emitting sounds based on these two acoustic signals. Then, as shown in FIG. 4, sound is eliminated in all directions except for the vicinity of the speaker unit pair. In other words, sound is eliminated only at positions sufficiently far from the speaker unit pair, and sound is not eliminated near the speaker unit pair. The reason sound is not eliminated near the speaker unit pair is because the phases of the sound waves emitted from the front of the speaker units and the sound waves coming around from the back are not aligned near the speaker unit pair.

[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 sounds that can be heard only in a very limited narrow range, namely, in the vicinity of the speaker system.

[0031] Second Embodiment The acoustic system 100 of the first embodiment has a narrow sweet spot, which is the range in which emitted sound can be heard. Here, an acoustic system having a structure that enlarges the sweet spot will be described.

[0032] The acoustic system 102 will be described below with reference to Fig. 15. Fig. 15 is a block diagram showing the configuration of the acoustic system 102. As shown in Fig. 15, the acoustic system 102, like the acoustic system 100, includes a playback device 110 and a speaker system 120. However, the acoustic system 102 differs from the acoustic system 100 in that a member 1222 is attached to the speaker unit pair 122.

[0033] The structure of the n-th speaker unit pair 122 (n=1, . . . , N) will be described below with reference to FIG.

[0034] A component 1222 is attached to the nth speaker unit pair 122 to lengthen the path of sound that is 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 and that returns toward the user (see FIG. 16). The component 1222 may be, for example, a component such as a partition plate that prevents sound from leaking in from the back of the speaker unit. This component 1222 is attached not to prevent sound from leaking in, but to increase the phase difference between sound that leaks in from the back and sound from the front, in other words, to lengthen the path of the sound that leaks in.

[0035] The nth speaker unit pair 122 to which the member 1222 is attached has a larger sweet spot than the nth speaker unit pair 122 of the first embodiment.

[0036] According to an embodiment of the present invention, it is possible to reproduce sounds that can be heard only in a very limited narrow range, namely, in the vicinity of the speaker system.

[0037] Third Embodiment Because high-frequency sounds have short wavelengths, it is difficult for the phases of sounds coming around from the back to align with those of sounds coming from the front. Therefore, high-frequency sounds are less likely to be eliminated than low-frequency sounds, both near the speaker units and at relatively distant locations. Because neither the positive speaker unit 1221 nor the negative speaker unit 1221 of the speaker unit pair 122 constituting the acoustic system 100 of the first embodiment is housed in a speaker box, the above-mentioned feature widens the range in which high-frequency sounds can be heard, which can lead to sound leakage. Here, we will explain an acoustic system with a structure that makes it difficult for high-frequency sounds to leak outside the vicinity of the speaker system.

[0038] The acoustic system 104 will be described below with reference to FIG. 17. FIG. 17 is a block diagram showing the configuration of the acoustic system 104. As shown in FIG. 17, the acoustic system 104 includes a playback device 110 and a speaker system 120, similar to the acoustic system 100. However, the acoustic system 104 differs from the acoustic system 100 in that a tweeter 1223 is attached to each of the positive speaker unit 1221 and the negative speaker unit 1221 of the speaker unit pair 122. Here, a tweeter is a speaker unit for reproducing high-frequency signals. The tweeter 1223 is attached to the positive speaker unit 1221 and the negative speaker unit 1221 in a manner that prevents sound from leaking from the back, as if it were housed in a speaker box.

[0039] The operation of the speaker system 120 will be described below with reference to FIG.

[0040] 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 sound based on the first acoustic signal, sound based on the second acoustic signal, ..., 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 sound based on the 2n-1th acoustic signal from the positive speaker unit 1221 and the tweeter 1223 attached to the positive speaker unit 1221, and emits sound based on the 2nth acoustic signal from the negative speaker unit 1221 and the tweeter 1223 attached to the negative speaker unit 1221.

[0041] Higher frequency sounds have the tendency to travel in a more directional direction, but because the Tweeter 1223 is designed to prevent sound from leaking out the back, the high frequency sounds emitted from the Tweeter 1223 are prevented from leaking in all directions.

[0042] According to an embodiment of the present invention, it is possible to reproduce sounds that can be heard only in a very limited narrow range, namely, in the vicinity of the speaker system.

[0043] <Fourth embodiment> The tweeter is a speaker unit for reproducing high-frequency signals. Therefore, band splitting processing may be used to input only high-frequency signals to the tweeter. Here, an acoustic system that performs band splitting processing will be described.

[0044] The acoustic system 200 will be described below with reference to Fig. 18. Fig. 18 is a block diagram showing the configuration of the acoustic system 200. As shown in Fig. 18, the acoustic system 200 includes a playback device 110, a band splitting device 210, and a speaker system 120. The band splitting device 210 includes N band splitting sections 212 (i.e., a first band splitting section 212, ..., an Nth band splitting section 212). The acoustic system 200 differs from the acoustic system 104 in that it includes the band splitting device 210.

[0045] The operations of the band splitting device 210 and the speaker system 120 will be described below with reference to FIG.

[0046] The band splitting device 210 receives as input the first acoustic signal, second acoustic signal, ..., 2Nth acoustic signal output by the playback device 110, and outputs a first high-frequency signal that is the high-frequency signal of the first acoustic signal and a first low-frequency signal that is the low-frequency signal, a second high-frequency signal that is the high-frequency signal of the second acoustic signal and a second low-frequency signal that is the low-frequency signal, ..., a 2Nth high-frequency signal that is the high-frequency signal of the 2Nth acoustic signal and a 2Nth low-frequency signal that is the low-frequency signal. More specifically, the nth band splitting unit 212 (n = 1, ..., N) receives the 2n-1th acoustic signal and the 2nth acoustic signal as input, generates a 2n-1th high-frequency signal that is a high-frequency signal of the 2n-1th acoustic signal, and a 2n-1th low-frequency signal that is a low-frequency signal, generates a 2nth high-frequency signal that is a high-frequency signal of the 2nth acoustic signal, and a 2nth low-frequency signal that is a low-frequency signal, and outputs the 2n-1th high-frequency signal, the 2n-1th low-frequency signal, the 2nth high-frequency signal, and the 2nth low-frequency signal.

[0047] The speaker system 120 receives as input the first high-frequency signal, the first low-frequency signal, the second high-frequency signal, the second low-frequency signal, ..., the 2Nth high-frequency signal, and the 2Nth low-frequency signal output by the band splitting device 210, and emits sound based on the first high-frequency signal, sound based on the first low-frequency signal, sound based on the second high-frequency signal, sound based on the second low-frequency signal, ..., sound based on the 2Nth high-frequency signal, and sound based on the 2Nth low-frequency signal. More specifically, the nth speaker unit pair 122 (n = 1, ..., N) receives the 2n-1th high-frequency signal, the 2n-1th low-frequency signal, the 2nth high-frequency signal, and the 2nth low-frequency signal as input, and emits sound based on the 2n-1th low-frequency signal and sound based on the 2n-1th high-frequency signal from the positive speaker unit 1221 and the tweeter 1223 attached to the positive speaker unit 1221, respectively, and emits sound based on the 2nth low-frequency signal and sound based on the 2nth high-frequency signal from the negative speaker unit 1221 and the tweeter 1223 attached to the negative speaker unit 1221, respectively.

[0048] According to an embodiment of the present invention, it is possible to reproduce sounds that can be heard only in a very limited narrow range, namely, in the vicinity of the speaker system.

[0049] Fifth Embodiment In the acoustic system 200 of the fourth embodiment, speaker units each having a tweeter 1223 attached to a positive speaker unit 1221 and a negative speaker unit 1221 are used. Here, an acoustic system will be described that uses a speaker unit pair including two speaker units and one tweeter, instead of using a speaker unit pair including two speaker units each having a tweeter attached.

[0050] The acoustic system 300 will be described below with reference to Fig. 19. Fig. 19 is a block diagram showing the configuration of the acoustic system 300. As shown in Fig. 19, the acoustic system 300 includes a playback device 110, a band splitting device 310, and a speaker system 320. The band splitting device 310 includes N band splitting sections 312 (i.e., a first band splitting section 312, ..., an Nth band splitting section 312). The speaker system 320 includes N speaker unit pairs 322 (i.e., a first speaker unit pair 322, ..., an Nth speaker unit pair 322). Each speaker unit pair 322 includes two speaker units (i.e., a positive speaker unit 1221 and a negative speaker unit 1221) and a tweeter 3221. The acoustic system 300 differs from the acoustic system 200 in that it includes a band splitting device 310 and a speaker system 320 instead of the band splitting device 210 and the speaker system 120 .

[0051] Tweeter 3221 is preferably housed in a speaker box to prevent sound from leaking from the rear. Speaker system 320 is also installed near the head of a user using the seat.

[0052] The direction in which the nth speaker unit pair 322 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 322 (n=1, ..., N) are arranged so that sounds emitted from the positive speaker unit 1221 in the direction opposite to the nth user direction and sounds 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, the negative speaker unit 1221, and the tweeter 3221 of the nth speaker unit pair 322. Moreover, the direction opposite to the n-th user direction refers to the rear direction of the positive speaker unit 1221 , the negative speaker unit 1221 , and the tweeter 3221 of the n-th speaker unit pair 322 .

[0053] In addition, the positive speaker unit 1221 and the negative speaker unit 1221 of the nth speaker unit pair 322 (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.

[0054] The operations of the band splitting device 310 and the speaker system 320 will be described below with reference to FIG.

[0055] The band splitting device 310 receives as input the first acoustic signal, second acoustic signal, ..., 2Nth acoustic signal output by the playback device 110, and outputs a first high-frequency signal that is the high-frequency signal of the first acoustic signal, a first low-frequency signal that is the low-frequency signal, a second low-frequency signal that is the low-frequency signal of the second acoustic signal, ..., a 2N-1th high-frequency signal that is the high-frequency signal of the 2N-1th acoustic signal, a 2N-1th low-frequency signal that is the low-frequency signal, and a 2Nth low-frequency signal that is the low-frequency signal of the 2Nth acoustic signal. More specifically, the nth band splitting unit 312 (n = 1, ..., N) receives the 2n-1th acoustic signal and the 2nth acoustic signal as input, generates a 2n-1th high-frequency signal that is a high-frequency signal of the 2n-1th acoustic signal, and a 2n-1th low-frequency signal that is a low-frequency signal of the 2n-1th acoustic signal, generates a 2nth low-frequency signal that is a low-frequency signal of the 2nth acoustic signal, and outputs the 2n-1th high-frequency signal, the 2n-1th low-frequency signal, and the 2nth low-frequency signal.

[0056] The speaker system 320 receives as input the first high-frequency signal, the first low-frequency signal, the second low-frequency signal, ..., the 2N-1th high-frequency signal, the 2N-1th low-frequency signal, and the 2Nth low-frequency signal output by the band splitting device 310, and emits sound based on the first high-frequency signal, sound based on the first low-frequency signal, sound based on the second low-frequency signal, ..., sound based on the 2N-1th high-frequency signal, sound based on the 2N-1th low-frequency signal, and sound based on the 2Nth low-frequency signal. More specifically, the nth speaker unit pair 322 (n=1, ..., N) receives the 2n-1th high-frequency signal, the 2n-1th low-frequency signal, and the 2nth low-frequency signal as input, and emits sound based on the 2n-1th high-frequency signal from the tweeter 3221, emits sound based on the 2n-1th low-frequency signal from the positive speaker unit 1221, and emits sound based on the 2nth low-frequency signal from the negative speaker unit 1221.

[0057] According to an embodiment of the present invention, it is possible to reproduce sounds that can be heard only in a very limited narrow range, namely, in the vicinity of the speaker system.

[0058] Sixth Embodiment The acoustic system 104 of the third embodiment is a system that is less susceptible to leakage of high-frequency sounds by using a speaker unit 1221 equipped with a tweeter 1223. Here, an acoustic system that is less susceptible to leakage of high-frequency sounds will be described, which uses a member with sound-absorbing properties instead of a speaker unit equipped with a tweeter.

[0059] The acoustic system 106 will be described below with reference to Fig. 20. Fig. 20 is a block diagram showing the configuration of the acoustic system 106. As shown in Fig. 20, the acoustic system 106 includes a playback device 110 and a speaker system 120, similar to the acoustic system 104. However, the acoustic system 106 differs from the acoustic system 104 in that it uses a speaker unit 1221 without a tweeter 1223 instead of a speaker unit 1221 with a tweeter 1223, and in that a member 1224 is attached to the speaker unit pair 122.

[0060] The structure of the n-th speaker unit pair 122 (n=1, . . . , N) will be described below with reference to FIG.

[0061] 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. 21). 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.

[0062] According to an embodiment of the present invention, it is possible to reproduce sounds that can be heard only in a very limited narrow range, namely, in the vicinity of the speaker system.

[0063] Seventh Embodiment The acoustic system 106 of the sixth embodiment is a system that is less likely to leak high-frequency sounds by using a speaker unit 1221 attached with a member 1224. Here, we will explain an acoustic system that is less likely to leak high-frequency sounds by storing each speaker unit of a speaker unit pair in a speaker box with holes, instead of using a speaker unit pair attached with sound-absorbing material.

[0064] The acoustic system 108 will be described below with reference to Fig. 22. Fig. 22 is a block diagram showing the configuration of the acoustic system 108. As shown in Fig. 22, the acoustic system 108 includes a playback device 110 and a speaker system 120, similar to the acoustic system 106. The acoustic system 108 differs from the acoustic system 106 in that the acoustic system 108 includes a speaker unit pair 122 including a speaker unit 1221 housed in a speaker box 1225, instead of the speaker unit pair 122 to which a member 1224 is attached.

[0065] The structure of the n-th speaker unit pair 122 (n=1, . . . , N) will be described below with reference to FIG.

[0066] The positive speaker unit 1221 and the negative speaker unit 1221 of the n-th speaker unit pair 122 are each housed in a speaker box 1225. Note that the speaker box 1225 has a large number of holes formed therein.

[0067] According to an embodiment of the present invention, it is possible to reproduce sounds that can be heard only in a very limited narrow range, namely, in the vicinity of the speaker system.

[0068] <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

[Claim 1] A speaker system including at least one speaker unit pair including a speaker unit that emits a sound based on an acoustic signal of a predetermined sound source (hereinafter referred to as a positive speaker unit) and a speaker unit that emits a sound based on an acoustic signal that is in the opposite phase to the acoustic signal (hereinafter referred to as a negative speaker unit). An audio system comprising: The positive speaker unit and the negative speaker unit of the speaker unit pair are both housed in a speaker box having a plurality of holes therein; a direction in which the speaker unit pair faces a user is defined as a user direction; The positive speaker unit and the negative speaker unit of the speaker unit pair are arranged so that the sound emitted from the positive speaker unit in the direction opposite to the user and the sound emitted from the negative speaker unit in the direction opposite to the user are transmitted toward the user by wraparound. Sound system.

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