Audio playback system

Abstract

This audio playback system comprises a controller that causes three-channel sound to be played back from a plurality of speakers. The controller has: an inversion unit for inverting the polarity of one of a left-recording-signal-based input signal to left speakers and a left-recording-signal-based input signal to right speakers, and inverting the polarity of one of a right-recording-signal-based input signal to the right speakers and a right-recording-signal-based input signal to the left speakers; and a division unit for dividing the left recording signal and the right recording signal so as to produce discrete-bandwidth signals. One of the controller and the plurality of speakers includes a delay means that causes a sound pertaining to the discrete-bandwidth signals output from the left speakers and the right speakers to be delayed for each speaker by a prescribed delay time. The delay time is set in advance for each left speaker and right speaker such that crosstalk in a prescribed frequency is cancelled out.

Description

[Technical Field]

[0001] This disclosure relates to an audio reproduction system. [Background technology]

[0002] Patent Document 1 discloses an acoustic reproduction system that three-dimensionally reproduces the direction, distance, and spread of sound. The system reproduces three channels of sound—center channel, left channel, and right channel—from multiple speakers based on a left recording signal corresponding to the listener's left ear and a right recording signal corresponding to the listener's right ear. The system has a center speaker corresponding to the center channel, multiple left speakers corresponding to the left channel, and multiple right speakers corresponding to the right channel. The system determines the frequency band of the output sound for each left speaker and each right speaker, and distributes signals of the appropriate frequency band to the appropriate speakers. The system configures a filter for each speaker to cancel crosstalk. Crosstalk is the sound component that reaches the ear other than the ear being controlled. Specifically, the system measures the entire transmission system of the plant matrix from the speaker to both ears and calculates its inverse matrix (inverse system) to achieve independent control of both ears. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2010-532614 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The system described in Patent Document 1 requires detailed design using digital signal processing because it strictly configures and controls an inverse system for all frequencies. Therefore, the system described in Patent Document 1 may increase computational costs. Computational costs refer to the effort involved in calculations, the number of tasks, and the complexity. This disclosure provides a technology that can reduce the computational costs associated with independent control of both ears. [Means for solving the problem]

[0005] An acoustic reproduction system relating to one aspect of this disclosure reproduces sound in a listening space where a listener is present. The acoustic reproduction system comprises a plurality of speakers and a controller. The plurality of speakers are arranged in the listening space. The controller reproduces three channels of sound—center channel, left channel, and right channel—from the plurality of speakers based on a left recording signal corresponding to the listener's left ear and a right recording signal corresponding to the listener's right ear. The plurality of speakers include a center speaker corresponding to the center channel, a plurality of left speakers corresponding to the left channel, and a plurality of right speakers corresponding to the right channel. The bandwidth of each of the plurality of left speakers and the plurality of right speakers is preset so that they can output different bandwidths of sound. The controller includes an inversion unit and a splitting unit. The inverting unit inverts the polarity of either the input signal to the left speaker based on the left recording signal or the input signal to the right speaker based on the left recording signal, so that the phase difference between them is 180 degrees at all frequencies, and also inverts the polarity of either the input signal to the right speaker based on the right recording signal or the input signal to the left speaker based on the right recording signal, so that the phase difference between them is 180 degrees at all frequencies. The splitting unit splits the left recording signal and the right recording signal into signals with discrete bandwidths. The controller reproduces the sound related to the discrete bandwidth signals through the center speaker and the right and left speakers, each with a corresponding bandwidth set. Either of the multiple speakers or the controller includes a delay means that delays the sound related to the discrete bandwidth signals output from each left speaker and each right speaker by a predetermined relative delay time with respect to the center speaker for each left speaker and each right speaker. The delay time is pre-set for each left and right speaker so that crosstalk is canceled at predetermined frequencies within the pre-set bandwidth for each left and right speaker.

[0006] In order to achieve independent control of both ears in a 3-channel system, the phase difference between the left channel signal and the center channel signal, and the phase difference between the center channel signal and the right channel signal, must be shifted by a predetermined value (e.g., 90 degrees) at all frequencies during the processing of the recording signal for one side. Furthermore, the phase difference between the left channel signal and the right channel signal must be shifted by a predetermined value (e.g., 180 degrees) at all frequencies. In this acoustic reproduction system, the above-mentioned phase differences are approximately achieved by delay time and polarity inversion.

[0007] In this sound reproduction system, each left speaker and each right speaker is pre-set with a relative delay time relative to the center speaker. The sound related to discrete bandwidth signals output from each left speaker and each right speaker is delayed by the pre-set relative delay time relative to the center speaker for each left speaker and each right speaker. The delay time is pre-set for each left speaker and each right speaker so that crosstalk is canceled at predetermined frequencies included in the pre-set bandwidth for each left speaker and each right speaker. By providing such delay times, the phase difference between the signal related to the left channel and the signal related to the center channel, and between the signal related to the center channel and the signal related to the right channel, is processed so that it is shifted by a predetermined value (e.g., 90 degrees) at predetermined frequencies included in each bandwidth. Furthermore, the phase difference between the input signal to the left speaker based on the left recording signal and the input signal to the right speaker based on the left recording signal is processed so that it is shifted by 180 degrees at predetermined frequencies included in each bandwidth by inverting the polarity of the two input signals so that their polarities are different. Similarly, the phase difference between the input signal to the right speaker based on the right recording signal and the input signal to the left speaker based on the right recording signal is processed so that the polarities of the two input signals are reversed, resulting in a 180-degree shift at predetermined frequencies within each band.

[0008] Thus, instead of calculating the inverse system for all frequencies, this audio playback system cancels crosstalk at a representative frequency (predetermined frequency) within the frequency band assigned to the speaker, while reversing the polarity of either one of the input signals to the left speaker and the right speaker based on the left recording signal, and either one of the input signals to the right speaker and the left speaker based on the right recording signal, and creating a time difference (simple delay) between the sound of the center speaker and the sounds of the left and right speakers. That is, the calculation of a predetermined frequency included in the frequency band represents the calculation of the frequency band assigned to the speaker. Therefore, although the accuracy of crosstalk cancellation for sounds of frequencies deviated from the representative frequency is somewhat reduced compared to the case of calculating the inverse system for all frequencies, this audio playback system can significantly reduce the calculation cost.

[0009] In one embodiment, the delay time may be preset for each of the left and right speakers so that, at a predetermined frequency, the phase difference between the sound of the left channel and the sound of the center channel is shifted by 90 degrees, and the phase difference between the sound of the center channel and the sound of the right channel is shifted by 90 degrees. In this case, the audio playback system can process the phase differences between the signal related to the left channel and the signal related to the center channel, and between the signal related to the center channel and the signal related to the right channel so as to be shifted by 90 degrees at the predetermined frequency included in each band.

[0010] In one embodiment, the delay means provided in the controller may be a delay unit that delays a signal with a discrete bandwidth by signal processing. In this case, the audio playback system can create a time difference (simple delay) with respect to the sound of the center speaker by signal processing.

[0011] In one embodiment, the delay time Δτ may be predetermined for each left and right speaker, such that, in a coordinate system where the origin is the center point of both ears of a listener viewed from a plan view, θ is the angle between the line connecting the position of the right or left speaker and the origin, and the line connecting the position of the center speaker and the origin, Δr is the equivalent distance between the two ears, and c is the speed of sound, and Δτ = (Δr·sinθ) / (2·c).

[0012] In one embodiment, the delay means provided for multiple speakers may be implemented by arranging the center speaker, multiple right speakers, and multiple left speakers such that the sound relating to discrete bandwidth signals reaching the listener is delayed by a predetermined delay time for each right speaker and each left speaker. In this case, the sound reproduction system can introduce a time difference (simple delay) relative to the sound from the center speaker by arranging each right speaker and each left speaker.

[0013] In one embodiment, the placement of each speaker may be determined such that, in a coordinate system where the origin is the center point of both ears of a listener viewed from above, the angle between the line connecting the placement of the right speaker or left speaker to the origin and the line connecting the placement of the center speaker to the origin is θ, the equivalent distance between the two ears is Δr, the speed of sound is c, and the path difference between the right speaker or left speaker and the center speaker is Δl, then Δl = (Δr·sinθ) / 2. [Effects of the Invention]

[0014] This disclosure provides a technology that can reduce the computational cost associated with the independent control of both ears. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram showing an example of an audio reproduction system according to the embodiment. [Figure 2] This is a block diagram showing an example of an audio reproduction system according to the embodiment. [Figure 3]This is a block diagram illustrating binaural synthesis using a speaker with a 3-channel inverse system. [Figure 4] This diagram illustrates the geometric positional relationship between the sound source and the listener. [Figure 5] This is a diagram explaining the definition of azimuth interval. [Figure 6] This diagram illustrates the concept of a pair of monopole sound sources in which the azimuth angle continuously changes as a function of frequency. [Figure 7] This graph shows the relationship between azimuth angle spacing and frequency in multiple left speakers. [Figure 8] This diagram illustrates binaural control in a 3-channel audio playback system. [Figure 9] This is a schematic diagram showing an example of a modified sound reproduction system. [Figure 10] This block shows an example of a modified sound reproduction system. [Figure 11] This is the result of simulating the sound pressure distribution of an acoustic reproduction system in which time delay is achieved through signal processing. [Figure 12] This is the result of simulating the sound pressure distribution of an acoustic reproduction system in which time delay is achieved by speaker placement. [Modes for carrying out the invention]

[0016] Embodiments of the present disclosure will be described below with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numeral, and redundant descriptions will not be repeated. The dimensional ratios in the drawings do not necessarily correspond to those in the description. The terms "top," "bottom," "left," and "right" are based on the illustrated state and are for convenience only.

[0017] [Configuration of the audio playback system] Figure 1 is a schematic diagram showing an example of an acoustic reproduction system according to an embodiment. The acoustic reproduction system 1 shown in Figure 1 reproduces sound in a listening space 10 where a listener 11 is present. As shown in Figure 1, the acoustic reproduction system 1 includes a multiway speaker unit 2 (an example of multiple speakers) and a controller 3, which are arranged in the listening space 10.

[0018] Controller 3 is connected to controllable multiway speaker unit 2. Controller 3 is configured as a computer system including, for example, a processor such as a CPU (Central Processing Unit), memory such as RAM (Random Access Memory) and ROM (Read Only Memory), input / output devices such as a touch panel, mouse, keyboard, and display, and communication devices such as a network card. Controller 3 realizes the functions of Controller 3, described later, by having the processor operate each piece of hardware based on a program stored in memory or the like.

[0019] The controller 3 may be configured to access the database 4. The database 4 stores the sounds to be provided to the listener 11. For example, the database 4 stores a left recording signal 41 corresponding to the listener 11's left ear 11L and a right recording signal 42 corresponding to the listener 11's right ear 11R.

[0020] The controller 3 reproduces three channels of sound from the multi-way speaker unit 2 based on the left recording signal 41 and the right recording signal 42. The three channels are the center channel Cch, the left channel Lch, and the right channel Rch, and further details will be described in the explanation of Figure 3. The multi-way speaker unit 2 includes a center speaker 20 corresponding to the center channel Cch, multiple left speakers LW corresponding to the left channel Lch, and multiple right speakers RW corresponding to the right channel Rch. The number of speakers corresponding to each channel is arbitrary.

[0021] In the example shown in Figure 1, the multiple left speakers LW include, in order from a position close to the center speaker 20 to a position further away, a first left speaker 21L, a second left speaker 22L, a third left speaker 23L, a fourth left speaker 24L, a fifth left speaker 25L, and a sixth left speaker 26L. The multiple right speakers RW include, in order from a position close to the center speaker 20 to a position further away, a first right speaker 21R, a second right speaker 22R, a third right speaker 23R, a fourth right speaker 24R, a fifth right speaker 25R, and a sixth right speaker 26R.

[0022] Each of the multiple left speakers (LW) and multiple right speakers (RW) has a preset bandwidth so that they can output different sound frequencies. For example, the bandwidth of the sound frequencies that can be output decreases as the distance from the center speaker 20 increases. The center speaker 20 reproduces sound in its full range. As a result, when the multi-way speaker unit 2 reproduces high-frequency sounds, sound is output from the center speaker 20 and the left and right speakers that are close to the center speaker 20. When the multi-way speaker unit 2 reproduces low-frequency sounds, sound is output from the center speaker 20 and the left and right speakers that are farther from the center speaker 20.

[0023] [Controller Details] Figure 2 is a block diagram showing an example of an audio playback system according to an embodiment. As shown in Figure 2, the controller 3 is equipped with input terminals for inputting a left recording signal 41 and a right recording signal 42, and is connected to a multiway speaker unit 2. The controller 3 includes a polarity inversion unit 31 (an example of an inversion unit), a band division unit 32 (an example of a division unit), a simple delay unit 33 (an example of a delay means), and an amplifier 34.

[0024] The polarity inversion unit 31 inverts the polarity of either the input signals to the left speaker LW based on the left recording signal 41 or the input signals to the right speaker RW based on the left recording signal 41 so that their polarities are different. Similarly, the polarity inversion unit 31 inverts the polarity of either the input signals to the right speaker RW based on the right recording signal 42 or the input signals to the left speaker LW based on the right recording signal 42 so that their polarities are different. By inverting the polarity, the phase difference between the signal related to the left channel Lch and the signal related to the right channel Rch is adjusted. As a specific example, if the input signals to the left speaker LW based on the left recording signal 41 take a positive value, the polarity inversion unit 31 multiplies either the signal related to the left channel Lch or the signal related to the right channel Rch by a negative value so that the input signals to the right speaker RW based on the left recording signal 41 take a negative value.

[0025] The band splitting unit 32 divides the left recording signal 41 and the right recording signal 42 into separate bands. As described above, the bandwidths of the multiple left speakers LW and multiple right speakers RW are pre-set so that each has a different bandwidth for the sound frequencies it can output. Hereafter, the signals split by the band splitting unit 32 will be referred to as discrete bandwidth signals. The discrete bandwidth signals are distributed to the speakers that can output them and played back.

[0026] The simple delay unit 33 delays the sound related to discrete bandwidth signals output from each left speaker and each right speaker by a delay time relative to the center speaker that is preset for each left speaker and each right speaker. The delay time is preset for each left speaker and each right speaker so that crosstalk is canceled at a predetermined frequency included in the bandwidth that is preset for each left speaker and each right speaker. The simple delay unit 33 delays the signal uniformly by the same amount of time for each speaker, that is, for each corresponding bandwidth, using signal processing. The signal processing may be digital signal processing or analog signal processing. Details of the delay time will be described later.

[0027] The amplifier 34 amplifies the signal output from the controller 3 to the multiway speaker unit 2. The multiway speaker unit 2 converts the amplified signal into sound and provides it to the listener 11. The polarity inversion unit 31 may be placed between the amplifier 34 and the multiway speaker unit 2. When placed between the amplifier 34 and the multiway speaker unit 2, the polarity inversion unit 31 is configured as a switch circuit that reverses the positive and negative terminals of either the left speaker or the right speaker.

[0028] [Details on independent control of both ears] To explain the independent control of both ears by controller 3, we will first describe binaural synthesis using a speaker with a 3-channel inverse system. Figure 3 is a block diagram illustrating binaural synthesis using a speaker with a 3-channel inverse system. As shown in Figure 3, the input signal for the right ear is d R (jω), input signal for the left ear is d L Let (jω) be the angular frequency.

[0029] The inverse system is represented by the inverse filter matrix H. The inverse filter matrix H processes the two input signals and the sound source V corresponding to three channels, in this case the center channel Cch. C , sound source V corresponding to the right channel Rch R , and the sound source V corresponding to the left channel Lch L The filtered signal is output. The inverse filter matrix H is, for example, a 2x3 matrix. The transmission matrix from the sound source to the listener's ear is the plant matrix C. The plant matrix C is, for example, a 2x3 matrix. The signal received by the right ear is w R (jω), the signal received in the left ear w L Let (jω) be the value.

[0030] To mathematically describe the system shown in FIG. 3, the positional relationship between the sound source and the listener 11 is defined as shown in FIGS. 4 and 5. FIG. 4 is a diagram explaining the geometric positional relationship between the sound source and the listener, and FIG. 5 is a diagram explaining the definition of the azimuth interval. As shown in FIG. 4, the geometric positional relationship between the sound source and the listener is expressed in a coordinate system with the center point of both ears of the listener 11 viewed from above as the origin of the x-axis. The sound source V L or the sound source V R The angle formed by the straight line connecting the placement position of and the origin, and the straight line connecting the placement position of the sound source V C and the origin is defined as the azimuth interval θ. As shown in FIG. 5, the azimuth interval θ is the difference in azimuth angles, and is the opening angle between the sound source Vc and the horizontal sound source V viewed from the listener 11 L or the sound source V L The equivalent interval between both ears is Δr. The equivalent interval is the distance obtained by correcting the actual distance between both ears considering the influence of diffraction on the head.

[0031] In the positional relationship in FIGS. 4 and 5, the plant matrix C normalized by the sound pressure of the left ear is generally expressed by the following equation (1).

Equation

[0032] The inverse filter matrix H that ideally realizes independent control of two sound reception points (right ear and left ear) needs to satisfy the relationship of the following equation (2).

Equation

[0033] Note: Some parts of the equations are omitted in the translation for brevity as they are not fully provided in the original text. You can fill in the complete equations according to the actual content.The sound source intensity (maximum amplification) required to reproduce an arbitrary input signal at each frequency can be determined from the 2-norm of H, which is the maximum singular value of the inverse filter matrix H (equation (3) below).

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[0034] In equation (5), when n=2, the 2-norm of H must be minimized if equation (6) is satisfied.

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[0035] Focusing on the inverse filter matrix H expressed by equation (7), H 11 If the phase is shifted by 90 degrees, then H 21 And H 21 If the phase is shifted by 90 degrees, then H 31 This is the result. Also, H 11 If you shift the phase by 180 degrees, that is, reverse the polarity, H 31 This is the result. Based on these relationships, we will outline independent control of both ears based on the principle of optimal sound source distribution. Figure 7 is a diagram illustrating binaural control in a 3-channel sound reproduction system. First, we will explain the case where sound related to the left recording signal 41 is provided to the listener's left ear.

[0036] As shown in Figure 7, the left recording signal 41 is signal d L (jw) is split into 3 channels by the inverse filter matrix H. Signal d L (jw) is the signal corresponding to the left channel Lch, H 11 Filtered by (jw), sound source V L This becomes the input signal to the sound source V. L The sound is delivered to the listener's left ear, and its phase is rotated 180 degrees before being delivered to the listener's right ear. Then, signal dL (jw) is the signal corresponding to the right channel Rch, H 31 Filtered by (jw), sound source V R This becomes the input signal to the sound source V. R The sound is delivered to the listener's right ear, and its phase is rotated 180 degrees before being delivered to the listener's left ear. Furthermore, signal d L (jw) is the signal corresponding to the center channel Cch, H 21 Filtered by (jw), sound source V C This becomes the input signal to the sound source V. C The sound is delivered to both of the listener's ears in phase.

[0037] Therefore, H 11 (jw) = 1 / 4, H 31 (jw) = -1 / 4, H 21 (jw)=2 1 / 2 We can use j / 4. In other words, for any monopole sound source that satisfies n=2 in equation (5) and whose frequency and opening angle change continuously while maintaining a constant relationship, a complete inverse matrix system can be realized by simple delay operations and polarity inversion.

[0038] Next, let's consider the case of a discretized system. In equation (5), the optimal sound source position that can reproduce the in-phase and out-of-phase components of the desired frequency with minimal effort, as realized when n=2, is given by sound source V. L Or sound source V R The sound output from the sound source V C We consider achieving this by simply delaying it relative to the given time. When the relative delay time is Δτ, equation (7) can be transformed into equation (8) below.

[0039]

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[0040] Figure 8 is a graph showing the relationship between azimuth angle spacing and frequency for multiple left speakers. In the graph in Figure 8, the horizontal axis is azimuth angle spacing and the vertical axis is frequency. Figure 8 shows graphs of equation (5) when n = 0.5, 1, 1.5, 2, and 2.5. The graph for n=1 is for 2 channels, and the graph for n=2 is for 3 channels. As shown in Figure 8, in frequency bands of approximately 2 kHz or higher, the frequency band is allocated to each left speaker such that n=1.5 is the lower limit and n=2.5 is the upper limit. In the example shown in Figure 8, the first left speaker 21L is assigned the first band R1, the second left speaker 22L is assigned the second band R2, the third left speaker 23L is assigned the third band R3, the fourth left speaker 24L is assigned the fourth band R4, and the fifth left speaker 25L is assigned the fifth band R5. In the frequency band generally below 2kHz, the sixth left speaker 26L is assigned the sixth frequency band R6, which includes a band even lower than the value of n=1.5. For the seventh frequency band R7, which is even lower than the sixth frequency band R6, a sound source such as a woofer (not shown) may be assigned.

[0041] [Summary of Embodiments] In the sound reproduction system 1, each left speaker and each right speaker is pre-set with a relative delay time Δτ relative to the center speaker 20. The sound related to discrete bandwidth signals output from each left speaker and each right speaker is delayed by the pre-set relative delay time Δτ relative to the center speaker for each left speaker and each right speaker. The delay time Δτ is pre-set for each left speaker and each right speaker so that crosstalk is canceled at predetermined frequencies included in the pre-set bandwidth for each left speaker and each right speaker. By providing such delay times, the phase difference between the signal related to the left channel Lch and the signal related to the center channel Cch, and between the signal related to the center channel Cch and the signal related to the right channel Rch, is processed so that it is shifted by 90 degrees at predetermined frequencies included in each bandwidth. Furthermore, the phase difference between the signal related to the left channel (Lch) and the signal related to the right channel (Rch) is processed so that it is shifted by 180 degrees at a predetermined frequency included in each band by inverting the polarity of the input signal to the left speaker based on the left recording signal 41 and the input signal to the right speaker based on the left recording signal 41 so that their polarities are different, and also inverting the polarity of the input signal to the right speaker based on the right recording signal 42 and the input signal to the left speaker based on the right recording signal 42 so that their polarities are different.

[0042] Thus, instead of calculating the inverse system for all frequencies, the sound reproduction system 1 reverses the polarity of either the left speaker or the right speaker's sound signal while introducing a time difference (simple delay) between the center speaker's sound and the left and right speaker's sounds, so that crosstalk is canceled at a representative frequency (a predetermined frequency) within the frequency band assigned to the speaker. In other words, the calculation at the predetermined frequency included in the frequency band represents the calculation of the frequency band assigned to the speaker. Therefore, compared to the case where the inverse system is calculated for all frequencies, the sound reproduction system 1 can significantly reduce computational costs, although the accuracy of crosstalk cancellation for sounds at frequencies deviating from the representative frequency is slightly reduced.

[0043] [Differentiation] Although various exemplary embodiments have been described above, the invention is not limited to the above-described exemplary embodiments, and various omissions, substitutions, and modifications may be made.

[0044] In the above-described embodiment, an example was explained in which the "delay means" is provided in the controller 3, but the "delay means" may also be realized by arranging multiple speakers. Figure 9 is a schematic diagram showing an example of a modified sound reproduction system. Sound reproduction system 1A differs from sound reproduction system 1 in that it includes a multi-way speaker unit 2A with a different speaker arrangement and a controller 3A that does not include a delay means, but is otherwise identical. Below, we will mainly explain the differences from sound reproduction system 1, and will avoid repeating redundant explanations.

[0045] As shown in Figure 9, the multi-way speaker unit 2A, like the multi-way speaker unit 2, includes a center speaker 20 corresponding to the center channel Cch, multiple left speakers LW corresponding to the left channel Lch, and multiple right speakers RW corresponding to the right channel Rch. The number of speakers corresponding to each channel is arbitrary.

[0046] The center speaker 20, multiple right speakers RW, and multiple left speakers LW are arranged in a positional relationship such that the sound related to discrete bandwidth signals reaching the listener 11 is delayed by a predetermined delay time Δτ for each right speaker and each left speaker. In other words, the distance between the speakers and the listener 11 is adjusted in advance so that the sound output from the left and right speakers is delayed by a delay time Δτ relative to the center speaker 20. The delay time Δτ shown in equation (10) is converted to a path difference Δl using the speed of sound c0.

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[0047] Figure 10 is a block diagram showing an example of a modified sound reproduction system. The controller 3A shown in Figure 10 differs from the controller 3 in that it does not have a simple delay unit 33, but is otherwise identical.

[0048] Furthermore, the number of right speakers and left speakers described in the above embodiment may be changed as appropriate. The number of right speakers and left speakers do not have to be the same. In addition, there only needs to be at least one center speaker 20. That is, there may be a center speaker other than the center speaker 20. The center speaker 20 and the other center speaker are positioned within the midline of the listener 11. When the sound reproduction system has a center speaker 20 and another center speaker, the center speaker 20 does not need to reproduce sound in the full range, but it is sufficient if the center speaker 20 and the other center speaker reproduce sound in the frequency range allocated to each of them, and the multiple center speakers as a whole reproduce sound in the full range (all frequency range).

[0049] In the embodiment described above, an example was explained in which the frequency band is allocated to the speaker such that n=1.5 is the lower limit and n=2.5 is the upper limit. However, the value of n that determines the frequency band is not limited to these values. The value of n that determines the frequency band may be set as appropriate, as long as the condition that n that determines the lower limit is less than 2 and n that determines the upper limit is greater than 2 is met. For example, the frequency band may be determined such that n=1 is the lower limit and n=3 is the upper limit.

[0050] As explained in Figure 7, the frequencies representative of the discrete bandwidths are the intersection points RP1 to RP6 between the graph for n=2 and the allocated bandwidths, but this is not limited to these. Representative frequencies may be appropriately selected for each bandwidth. [Examples]

[0051] The following describes examples implemented by the inventors to illustrate the above-mentioned effects.

[0052] The acoustic reproduction systems 1 and 1A shown in Figures 1 and 9 were used. The sound pressure distribution was simulated assuming that the listener 11 was positioned at the origin in the listening space 10. The results for acoustic reproduction system 1 are shown in Figure 11, and the results for acoustic reproduction system 1A are shown in Figure 12.

[0053] Figure 11 shows the simulated sound pressure distribution of an acoustic reproduction system in which time delay is achieved by signal processing. Figure 12 shows the simulated sound pressure distribution of an acoustic reproduction system in which time delay is achieved by speaker placement. Figures 11 and 12 are diagrams that represent sound pressure level (dB) using shades of gray. As shown in Figures 11 and 12, in both sound pressure distributions, the left ear of listener 11 was approximately 0 dB, and the right ear was approximately -20 dB, confirming that the sound was sufficiently reduced in the right ear. Thus, it was confirmed that independent control of both ears can be achieved using polarity inversion and time delay. Furthermore, it was confirmed that time delay can be achieved by signal processing or by speaker placement. [Explanation of Symbols]

[0054] 1,1A…Sound reproduction system, 2,2A…Multiway speaker unit (an example of multiple speakers), 3,3A…Controller, 10…Listening space, 11…Listener, 20…Center speaker, 41…Left recording signal, 42…Right recording signal, LW…Multiple left speakers, RW…Multiple right speakers.

Claims

1. An acoustic reproduction system that reproduces sound in a listening space where listeners are present, Multiple speakers arranged in the aforementioned listening space, A controller that reproduces three channels of sound—center channel, left channel, and right channel—from the plurality of speakers based on the left recording signal corresponding to the listener's left ear and the right recording signal corresponding to the listener's right ear, Equipped with, The aforementioned multiple speakers are, A center speaker corresponding to the aforementioned center channel, Multiple left speakers corresponding to the aforementioned left channel, Multiple right speakers corresponding to the aforementioned right channel, It has, Each of the aforementioned left speakers and the aforementioned right speakers has a pre-set bandwidth such that it can output a different bandwidth of sound. The aforementioned controller, An inversion unit that inverts the polarity of either the input signal to the left speaker based on the left recording signal or the input signal to the right speaker based on the left recording signal so that the phase difference between them is 180 degrees at all frequencies, and also inverts the polarity of either the input signal to the right speaker based on the right recording signal or the input signal to the left speaker based on the right recording signal so that the phase difference between them is 180 degrees at all frequencies, A splitting unit that divides the left recording signal and the right recording signal into signals with discrete bandwidths, It has, The sound relating to the discrete bandwidth signal is reproduced by the center speaker, and by the right and left speakers, which have corresponding bandwidths set accordingly. Either the plurality of speakers or the controller includes a delay means that delays the sound related to the discrete bandwidth signal output from each left speaker and each right speaker by a predetermined relative delay time with respect to the center speaker for each left speaker and each right speaker. The aforementioned delay time is preset for each left speaker and each right speaker so that crosstalk is canceled at predetermined frequencies included in the bandwidth preset for each left speaker and each right speaker, respectively, in this acoustic reproduction system.

2. The sound reproduction system according to claim 1, wherein the delay time is preset for each of the left and right speakers such that, at the predetermined frequency, the phase difference between the sound of the left channel and the sound of the center channel is shifted by 90 degrees, and the phase difference between the sound of the center channel and the sound of the right channel is shifted by 90 degrees.

3. The sound reproduction system according to claim 2, wherein the delay means provided in the controller is a delay unit that delays the discrete bandwidth signal by signal processing.

4. The sound reproduction system according to claim 3, wherein the delay time Δτ is predetermined for each left speaker and right speaker, such that, in a coordinate system with the center points of both ears of the listener viewed from a plan perspective as the origin, θ is the angle between the line connecting the position of the right speaker or the left speaker and the origin, and the line connecting the position of the center speaker and the origin, Δr is the equivalent distance between the two ears, and c is the speed of sound.

5. The sound reproduction system according to claim 2, wherein the delay means provided in the plurality of speakers is realized by arranging the center speaker, the plurality of right speakers, and the plurality of left speakers such that the sound relating to the discrete bandwidth signal reaching the listener is delayed by a predetermined delay time for each right speaker and each left speaker.

6. The placement of each speaker is determined such that, in a coordinate system with the center point of both ears of the listener viewed from above as the origin, θ is the angle between the line connecting the placement of the right speaker or the left speaker and the origin, and the line connecting the placement of the center speaker and the origin, Δr is the equivalent distance between the two ears, c is the speed of sound, and Δl is the path difference between the right speaker or the left speaker and the center speaker, and Δl is the value of the path between the two ears, such that Δl = (Δr・sinθ) / 2, as described in claim 5.

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