Acoustic 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 audio systems installed in seats of aircraft, automobiles, etc. [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 surroundings of the user, 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 bothersome for users. Some users do not like 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 users to feel tired after listening to them.

[0005] To eliminate the need to wear earphones or headphones, it is possible to synthesize a virtual sound field using wave field synthesis technology; however, 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 a user seated in an airplane, automobile, etc., that reproduces sounds that cannot be heard by surrounding users without the need for earphones or headphones. [Means for solving the problem]

[0007] One aspect of the present invention is an acoustic system including a speaker system including 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 having a plurality of holes, the direction in which the speaker unit pair faces a user is defined as the user direction, and the positive speaker unit and the negative speaker unit of the speaker unit pair are positioned such that sound emitted from the positive speaker unit in a direction opposite to the user direction and sound emitted from the negative speaker unit in a direction opposite to the user direction are transmitted in the user direction by wraparound. Effect 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 description of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram for explaining the directivity of a sound emitted from a speaker. [Diagram 2] 3A and 3B are diagrams for explaining the directivity of sound emitted from a speaker unit. [Diagram 3] 1A and 1B are diagrams for explaining sounds emitted from a speaker unit pair. [Figure 4] 1A and 1B are diagrams for explaining the directivity of sounds emitted from a speaker unit pair. [Diagram 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 the microphone). [Figure 8] FIG. 13 is a diagram showing the experimental conditions (other measurement positions). [Figure 9] FIG. 13 is a diagram showing experimental results (condition 1). [Figure 10] FIG. 13 is a diagram showing experimental results (condition 2). [Figure 11] FIG. 13 is a diagram showing experimental results (condition 3). [Figure 12] FIG. 13 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 audio 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 audio 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 audio system 300. [Figure 20] FIG. 2 is a block diagram showing an example of the configuration of an audio 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 audio system 108. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail. Note that components having the same functions are given the same reference 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 effect of the speaker unit pair of the present invention will be described.

[0012] 1: Directivity of sound emitted from a speaker Typically, a speaker is made up of a speaker unit and a speaker box. The speaker unit is a component that includes a diaphragm that converts an acoustic signal, which is an electrical signal, 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 vibration of the diaphragm. Here, sound waves emitted to the outside of the speaker box (i.e., toward the front of the speaker unit) are called positive sound waves, and sound waves emitted to the inside of the speaker box (i.e., toward the back of the speaker unit) are called negative sound waves. Negative sound waves are sound waves with a phase opposite to that of positive sound waves. Figure 1 is a diagram for 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 go outside 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 pair of speaker units Here, we will first explain the directivity of sound emitted from a speaker unit, which is a bare speaker. Figure 2 is a diagram for explaining the directivity of sound emitted from a speaker unit. In the case of only a speaker unit, unlike the case of a speaker, negative sound waves are emitted from the back of the speaker unit hidden inside the speaker box. Therefore, as shown in Figure 2, the sound emitted from the speaker unit has a bidirectional characteristic.

[0015] In the present invention, this bidirectionality is utilized. A specific description will be given below. First, as shown in FIG. 3, two speaker units are arranged to form a speaker unit pair. When acoustic signals with opposite positive and negative relationships are input to the speaker unit pair, the diaphragms of the two speaker units vibrate and emit sounds based on these two acoustic signals. Then, as shown in FIG. 4, sounds are eliminated in all directions except for the vicinity of the speaker unit pair. In other words, sounds are eliminated only at positions sufficiently far away from the speaker unit pair, and sounds are not eliminated in the vicinity of the speaker unit pair. The reason why sounds are not eliminated in the vicinity of the speaker unit pair is because the phases of the sound waves radiated from the front of the speaker unit and the sound waves wrapping around from the back are not aligned in the vicinity of 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 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. In the experiment, the following speakers, speaker units, and speaker unit pairs were used: a speaker with a diaphragm with a diameter of 4.5 cm (see Fig. 5), a speaker with the speaker box removed leaving only the speaker unit (see Fig. 6), and two of the speaker units arranged side by side (see Fig. 7). In addition, microphones were placed under the following four conditions to measure the frequency characteristics near the speaker, speaker unit, and speaker unit pair.

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

[0019] The experimental results are explained below. Figures 9, 10, 11, and 12 are diagrams showing the experimental results, and are diagrams showing the relationship between frequency and attenuation under conditions 1, 2, 3, and 4, respectively. Each diagram shows four curves, of which one curve indicated by an arrow is a sound picked up by a microphone located 5 cm or 2 cm from the front, and the other three curves are sounds picked up by microphones located 100 cm from the front, back, and side. The curves located 5 cm or 2 cm from the front are located near a speaker, etc., so the gain is very large. Therefore, to make it easier to see, the curve located 5 cm from the front is plotted at -25 dB lower than the three curves located 100 cm. Similarly, the curve located 2 cm from the front is plotted at -32 dB. Comparing Figures 9 and 10, when a speaker is used, there is almost no difference between the four curves, while when a speaker unit is used, there is a difference between the curve located 5 cm from the front and the other three curves. This difference is more pronounced in the lower frequencies. Also, comparing Figure 11 with Figure 12, we can see that the difference between the curve 2 cm from the front and the other three curves is larger 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 an object to be reproduced is called an acoustic system. An acoustic system includes a speaker system for emitting the acoustic signal as sound (hereinafter, this sound is referred to as sound based on an acoustic signal). Here, a speaker system is a device that converts an analog acoustic signal into sound. An object to be reproduced is data or a signal from which an acoustic signal can be obtained by a predetermined process, such as data recorded on a CD, DVD, or record, data received via the Internet, or a signal received via a radio or television broadcast.

[0022] Here, an acoustic system that reproduces sound based on an acoustic signal obtained from a reproduction target object so that only a user in the vicinity of the speaker system can hear it will be described. In other words, the reproduced sound of the acoustic system cannot be heard by users other than the user in the vicinity of the speaker system. When such an acoustic system is used as an acoustic system for a user using a seat in an aircraft, for example, a system can be provided in which only the user using the seat can hear the reproduced sound. FIG. 13 is a diagram showing an example of an acoustic system installed on an aircraft seat. The acoustic system in FIG. 13 is installed on a seat so as to sandwich the head of a seated user, and two speaker unit pairs are arranged so as to be located near the left and right ears. Note that such an acoustic system can be installed in vehicles other than aircraft, such as automobiles and trains, reclining chairs, and the like, and can also be installed in a wearable form, such as on the shoulder. In addition, a driver unit pair in which two driver units are arranged side by side, which corresponds 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 types: open-air and closed. By applying the above technology to open-air headphones, in which sound leakage is a particular concern, it is expected that sound leakage will be reduced.

[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., a first playback unit 112, ..., an Nth playback unit 112). The speaker system 120 includes N speaker unit pairs 122 (i.e., a first speaker unit pair 122, ..., an Nth speaker unit pair 122). The 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 of an acoustic signal input to the positive speaker unit 1221 is input to the negative speaker unit 1221. The speaker system 120 is installed in a position close to 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 a sound emitted from the positive speaker unit 1221 in the direction opposite to the nth user direction and a 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. Also, 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 are cancelled out by each other 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 reproducing device 110 receives a first acoustic signal, a third acoustic signal, ..., a 2N-1th acoustic signal, which are acoustic signals obtained based on a reproduction target, as input, and outputs a first acoustic signal, a second acoustic signal, ..., a 2Nth acoustic signal. More specifically, the nth reproducing unit 112 (n=1, ..., N) receives the 2n-1th acoustic signal as input, generates a 2nth acoustic signal, which is an acoustic signal in opposite phase to the 2n-1th acoustic signal, from 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 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 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. Since the 2n-1th acoustic signal and the 2nth acoustic signal are in an anti-phase relationship with each other, as described in <Technical Background>, the sound 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 respectively the right channel acoustic signal and the left channel acoustic signal of a certain sound source, the 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 opposite direction to the n-th user direction have an opposite phase relationship. 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 opposite direction to the n-th user direction have an opposite phase relationship.

[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 range in which the emitted sound can be heard, that is, a so-called sweet spot. Here, an acoustic system having a structure for enlarging the sweet spot will be described.

[0032] Hereinafter, the acoustic system 102 will be described 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 includes a playback device 110 and a speaker system 120, similar to the acoustic system 100. 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] Hereinafter, the structure of the n-th speaker unit pair 122 (n=1, . . . , N) will be described with reference to FIG.

[0034] A member 1222 is attached to the n-th 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 n-th speaker unit pair 122 in the direction opposite to the n-th user direction and that wraps around toward the user (see FIG. 16). The member 1222 may be, for example, a member such as a partition plate that prevents sound from wrapping around from the back of the speaker unit. This member 1222 is attached not to prevent sound from wrapping around, but to increase the phase difference between sound wrapping around from the back and sound from the front, in other words, to lengthen the path of the wrapping sound.

[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> Since high-frequency sounds have short wavelengths, it is difficult for the phases of the sounds coming around from the back to match with the phases of the sounds coming from the front. Therefore, high-frequency sounds are characterized in that they are less likely to be eliminated in the vicinity of the speaker units or in relatively distant locations other than the vicinity, compared to low-frequency sounds. Since 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 characteristics result in a wide range in which high-frequency sounds can be heard, which may lead to sound leakage. Here, an acoustic system having a structure that makes it difficult for high-frequency sounds to leak outside the vicinity of the speaker system will be described.

[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. Note that 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 stored 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 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 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 a tweeter 1223 attached to the positive speaker unit 1221, and emits a sound based on the 2nth acoustic signal from the negative speaker unit 1221 and a 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, it is possible to input only high-frequency signals to the tweeter by band splitting processing. Here, an audio 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, the second acoustic signal, ..., the 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-1 high-frequency signal that is the high-frequency signal of the 2n-1th acoustic signal and a 2n-1 low-frequency signal that is the low-frequency signal, generates a 2n high-frequency signal that is the high-frequency signal of the 2nth acoustic signal and a 2n low-frequency signal that is the low-frequency signal, and outputs the 2n-1 high-frequency signal, the 2n-1 low-frequency signal, the 2n high-frequency signal, and the 2n 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 associated with 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 associated with 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 the positive speaker unit 1221 and the negative speaker unit 1221 are used. Here, an acoustic system using 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, will be described.

[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 reproduction 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). The 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 audio system 300 differs from the audio 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 installed in a position close to 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 a sound emitted from the positive speaker unit 1221 in the direction opposite to the nth user direction and a 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, 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 are cancelled out by each other 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 which is the high-frequency signal of the first acoustic signal, a first low-frequency signal which is the low-frequency signal, a second low-frequency signal which is the low-frequency signal of the second acoustic signal, ..., a 2N-1 high-frequency signal which is the high-frequency signal of the 2N-1th acoustic signal, a 2N-1 low-frequency signal which is the low-frequency signal, and a 2N low-frequency signal which 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-1 high-frequency signal that is a high-frequency signal of the 2n-1th acoustic signal and a 2n-1 low-frequency signal that is a low-frequency signal, generates a 2n low-frequency signal that is the low-frequency signal of the 2nth acoustic signal, and outputs the 2n-1 high-frequency signal, the 2n-1 low-frequency signal, and the 2n 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, 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 is described, which uses a member with sound-absorbing properties instead of a speaker unit equipped with a tweeter.

[0059] Hereinafter, the acoustic system 106 will be described 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 the acoustic system 106 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] A member 1224 is attached to the n-th speaker unit pair 122 to absorb sounds emitted from the positive speaker unit 1221 and the negative speaker unit 1221 of the n-th speaker unit pair 122 in the direction opposite to the n-th 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 except for 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 susceptible to leakage of high-frequency sounds by using a speaker unit 1221 to which a member 1224 is attached. Here, an acoustic system that is less susceptible to leakage of high-frequency sounds is described by storing each of the speaker units of a speaker unit pair in a speaker box with holes, instead of using a speaker unit pair to which a sound-absorbing material is attached.

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

[0065] Hereinafter, the structure of the n-th speaker unit pair 122 (n=1, . . . , N) will be described 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 invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings. The embodiments have been chosen and depicted to provide a best illustration of the principles of the invention and to enable those skilled in the art to utilize the invention in various embodiments and with various modifications as may be suitable for the practical use contemplated. All such modifications and variations are within the scope of the invention as defined by the appended claims interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

[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 of an 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; 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 a sound emitted from the positive speaker unit in a direction opposite to the user direction and a sound emitted from the negative speaker unit in a direction opposite to the user direction are transmitted to the user direction by wraparound. Sound system.

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