Acoustic control device, program, and method

Abstract

To provide an acoustic control device which easily transmits only sound in a specific direction, a program, and a method.SOLUTION: An acoustic control device comprises an acoustic filter coefficient calculation section and an audio signal processing section. The acoustic filter coefficient calculation section calculates acoustic filter coefficients less than the number of sound sources, based on a first relational expression which is based on amplification control rules and applied to audio signals including information on sounds reproduced by a plurality of sound sources, and a second relational expression which is based on acoustic power minimization control rules between acoustic filters. The audio signal processing section applies the calculated acoustic filter coefficients to the inputted audio signals, branches and outputs an audio signal to which a common acoustic filter coefficient is applied, to at least two sound sources of the plurality of sound sources.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to an acoustic control device, a program, and a method. [Background technology]

[0002] Various voice-based services are in use, such as voice guidance in public spaces, voice guidance in car navigation systems, and voice conversations in online conference systems. The voice in this type of service is useful for people who need guidance and want to talk, but can be just noise for people who do not need guidance and do not want to talk. In other words, the area in which you want to convey voice or the area in which you do not want to convey voice changes depending on the place and time of use. Therefore, there is a demand for sound field control technology that makes it easier to convey sound only in a specific direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-048468 Summary of the Invention [Problem to be solved by the invention]

[0004] The embodiments provide an acoustic control device, a program, and a method that facilitate transmission of sound only in a specific direction. [Means for solving the problem]

[0005] An acoustic control device according to one embodiment includes an acoustic filter coefficient calculation unit and an audio signal processing unit. The acoustic filter coefficient calculation unit calculates acoustic filter coefficients, the number of which is less than the number of sound sources, based on a first relational expression between acoustic filters applied to an audio signal including information on sounds reproduced by each of the multiple sound sources, based on a sound increase control rule that increases the sound pressure at a sound increase control point by the sounds reproduced by the multiple sound sources, and a second relational expression between the acoustic filters, based on an acoustic power minimization control rule that minimizes the acoustic power for the sounds reproduced by the multiple sound sources. The audio signal processing unit applies the calculated acoustic filter coefficients to the input audio signal, and branches and outputs the audio signal to which the common acoustic filter coefficient has been applied to at least two of the multiple sound sources. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of an acoustic control device according to the first embodiment. [Diagram 2] FIG. 2 is an external view showing an example of the configuration of a speaker. [Diagram 3] FIG. 3 is a block diagram showing elements included in the control device. [Figure 4] FIG. 4 is a diagram showing an example of setting the volume increase area and the volume decrease area. [Diagram 5] FIG. 5 is a diagram showing the calculation results of the relationship between frequency and sound pressure level in the sound increase area and sound decrease area of ​​FIG. [Figure 6] FIG. 6 is a diagram showing the sound pressure level gradient in the sound increase area and the sound decrease area when sound is radiated from an acoustic filter set according to the result of equation (1). [Figure 7] FIG. 7 shows an example of the distribution of sound pressure levels in each area when sound is radiated with acoustic filter coefficients set according to the results of equation (1). [Figure 8] FIG. 8 is a diagram illustrating an example of the configuration of an acoustic control device according to Modification 2 of the first embodiment. [Figure 9]FIG. 9 is a diagram showing the calculation results of the relationship between frequency and sound pressure level when sound increase areas and sound decrease areas are set in the configuration of FIG. 8 in the same manner as in FIG. [Figure 10] FIG. 10 is a diagram showing a modified example in which speakers are arranged on a spherical surface. [Figure 11] FIG. 11 is a diagram illustrating an example of the configuration of the acoustic control device according to the second embodiment. [Figure 12] FIG. 12 is a diagram showing the sound pressure level gradient in the sound increase area and the sound decrease area when sound is radiated from an acoustic filter set according to the result of equation (3). [Figure 13] FIG. 13 is a diagram showing an example of the distribution of sound pressure levels when sound is emitted with acoustic filter coefficients set according to the result of equation (1). [Figure 14A] FIG. 14A is a diagram showing the results of actual measurements of the relationship between the azimuth angle and the sound pressure level with respect to the two speaker groups when the arrangement of the speaker groups is changed. [Figure 14B] FIG. 14B is a diagram showing the results of actual measurements of the relationship between the azimuth angle and the sound pressure level with respect to the speaker groups when the arrangement of the two speaker groups is changed. [Figure 14C] FIG. 14C is a diagram showing the results of actual measurements of the relationship between the azimuth angle and the sound pressure level with respect to the speaker groups when the arrangement of the two speaker groups is changed. [Figure 14D] FIG. 14D is a diagram showing the results of actual measurements of the relationship between the azimuth angle and the sound pressure level with respect to the speaker groups when the arrangement of the two speaker groups is changed. [Figure 14E] FIG. 14E is a diagram showing the results of actual measurements of the relationship between the azimuth angle and the sound pressure level with respect to the speaker groups when the arrangement of the two speaker groups is changed. [Figure 14F] FIG. 14F is a diagram showing the results of actual measurements of the relationship between the azimuth angle and the sound pressure level with respect to the speaker groups when the arrangement of the two speaker groups is changed. [Figure 14G] FIG. 14G is a diagram showing the results of actual measurements of the relationship between the azimuth angle and the sound pressure level with respect to the speaker groups when the arrangement of the two speaker groups is changed. [Figure 14H]FIG. 14H is a diagram showing the results of actual measurements of the relationship between the azimuth angle and the sound pressure level with respect to the speaker groups when the arrangement of the two speaker groups is changed. [Figure 15A] FIG. 15A is a diagram showing an example of a 3-ch 1-set speaker group. [Figure 15B] FIG. 15B is a diagram showing an example of a 3ch 2set speaker group. [Figure 16] FIG. 16 is an external view showing a group of speakers embedded in a baffle board. [Figure 17A] FIG. 17A is a conceptual diagram for finding an arrangement of a group of speakers with optimal directivity. [Figure 17B] FIG. 17B is a conceptual diagram for finding an arrangement of a group of speakers with optimal directivity. [Figure 18] FIG. 18 is a diagram illustrating an example of the configuration of an acoustic control device according to Modification 1 of the second embodiment. [Figure 19] FIG. 19 is a diagram illustrating an example of a hardware configuration of the acoustic control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, an embodiment will be described with reference to the drawings. (First embodiment) A first embodiment will be described. FIG. 1 is a diagram showing an example of the configuration of an acoustic control device according to the first embodiment. The acoustic control device 100 has an audio signal input unit 101, an audio signal processing device 102, a control device 103, and speakers 104L1, 104L2, 104C, and 104R. In the embodiment, the speakers 104L1, 104L2, 104C, and 104R are stored side by side in a horizontally long housing as shown in FIG. 2. Here, the speakers 104L1 and 104L2 are vertically and closely arranged so as to be symmetrical with respect to the straight line on which the speakers 104C and 104R are arranged, and can operate as one speaker virtually arranged at the intermediate position, that is, on the straight line on which the speakers 104C and 104R are arranged. In FIG. 2, the speakers 104L1 and 104L2 viewed as one are represented as the speaker 104L. In the following description, the speakers 104L1 and 104L2 may be collectively referred to as the speaker 104L.

[0008] The acoustic control device 100 combines sound increase control using multiple speakers with sound power minimization control to make it easier for sound to be transmitted only to a specific sound increase area A2 while quieting a sound reduction area A1 around the speakers. Sound increase control is a control that increases sound pressure in a specific direction by controlling the amplitude of sound emitted from multiple speakers. On the other hand, sound power minimization control is a control that minimizes the sound power when multiple speakers are viewed as one speaker by controlling the amplitude and phase of sound emitted from multiple speakers.

[0009] The audio signal input unit 101 inputs an audio signal to the audio signal processing device 102. The audio signal input unit 101 may also input the audio signal to the control device 103. The audio signal is a signal that includes sound information. The audio signal is prepared in advance for playback, for example. The audio signal may be generated sequentially for each playback, or may be input by the user or the control device 103, for example.

[0010] The audio signal processing device 102 processes an audio signal and includes an amplifier 1021 and acoustic filters 1022L, 1022C, and 1022R.

[0011] The amplifier 1021 amplifies the audio signal input from the audio signal input unit 101 with a gain G. The gain G may be a fixed value, for example, 1, or may be specified by the control device 103.

[0012] The acoustic filter 1022L filters the audio signal output from the amplifier 1021 according to an acoustic filter coefficient qL designated by the control device 103. Then, the acoustic filter 1022L branches the filtered audio signal and outputs it to the speakers 104L1 and 104L2. In this case, the speakers 104L1 and 104L2 emit sounds of the same amplitude and phase. Also, the acoustic filter 1022C filters the audio signal output from the amplifier 1021 according to an acoustic filter coefficient qC designated by the control device 103. Then, the acoustic filter 1022C outputs the filtered audio signal to the speaker 104C. Also, the acoustic filter 1022R filters the audio signal output from the amplifier 1021 according to an acoustic filter coefficient qR designated by the control device 103. Then, the acoustic filter 1022R outputs the filtered audio signal to the speaker 104R. These acoustic filters are intended to pass only sounds in a specific band of the audio signal. The acoustic filter coefficients qL, qC, qR may be set equal to the complex volume velocities of the speakers 104L, 104C, 104R.

[0013] The control device 103 is a device for determining acoustic filter coefficients qL, qC, and qR to be applied to the acoustic filters 1022L, 1022C, and 1022R based on the frequency of the audio signal and the respective intervals between the speakers 104L, 104C, and 104R. The control device 103 may also set a gain G. The control device 103 will be described in detail later.

[0014] The speakers 104L1 and L2, 104C, and 104R are sound sources that emit sounds corresponding to filtered audio signals output from the corresponding acoustic filters. The speaker 104L operates as a left speaker, the speaker 104C operates as a center speaker, and the speaker 104R operates as a right speaker. In the configuration of FIG. 2, the intervals between the speakers 104L, 104C, and 104R are fixed values. Here, the speakers 104L, 104C, and 104R do not necessarily have to be configured as one unit. On the other hand, for the acoustic power minimization control and the sound increase control, it is desirable that the speakers 104L, 104C, and 104R are arranged to some extent close to each other. In addition, the housing shown in FIG. 2 may also house the audio signal input unit 101, the audio signal processing device 102, and the control device 103. The distance d between the speaker 104L, the speaker 104C, and the speaker 104R is determined according to the frequency band in which a sound pressure level gradient is generated by the sound increase control and the sound power minimization control.

[0015] Next, a description will be given of the control device 103. Fig. 3 is a block diagram showing elements included in the control device 103. The control device 103 has an acquisition unit 1031, an acoustic filter coefficient calculation unit 1032, an acoustic filter coefficient storage unit 1033, and an acoustic filter setting unit 1034.

[0016] The acquisition unit 1031 acquires various pieces of information necessary for calculating the acoustic filter coefficients. Then, the acquisition unit 1031 inputs the acquired information to the acoustic filter coefficient calculation unit 1032. The information acquired by the acquisition unit 1031 includes, for example, information on the frequency, the speaker interval, and the transfer function.

[0017] The frequency is the frequency of the audio signal input from the audio signal input unit 101. The acquisition unit 1031 acquires, for example, frequency information from the audio signal input unit 101. If the sound speed c is known, the frequency can be converted into a wave number. Since the wave number is used to calculate the acoustic filter coefficient, the acquisition unit 1031 may acquire the wave number information from the audio signal input unit 101. If the frequency of the audio signal is a fixed value, the acquisition unit 1031 may input pre-stored information on the fixed value of the frequency to the acoustic filter coefficient calculation unit 1032.

[0018] The speaker spacing is the spacing between each of a plurality of speakers. The acquisition unit 1031 acquires the speaker spacing based on, for example, an input from a user. The speaker spacing may be equal or different. If the speakers are fixed, the speaker spacing may be treated as a fixed value. In this case, the acquisition unit 1031 may input information on the speaker spacing of the fixed value stored in advance to the acoustic filter coefficient calculation unit 1032.

[0019] The transfer function is a function that represents the transfer characteristic of the sound between each of the speakers 104L, 104C, and 104R and the sound increase control point, and is determined by the positional relationship between the speakers 104L, 104C, and 104R and the sound increase control point. The sound increase control point is a control target position for sound increase control. The transfer function is expressed as a matrix whose elements are the spatial transfer characteristic CL of the sound transferred from the speaker 104L to the sound increase control point, the spatial transfer characteristic CC of the sound transferred from the speaker 104C to the sound increase control point, and the spatial transfer characteristic CR of the sound transferred from the speaker 104R to the sound increase control point. Each spatial transfer characteristic can be measured from a microphone acquisition signal obtained by emitting a sound based on a random signal or a sound based on a TSP (Time stretched Pulse) signal from the speakers 104L1, 104L2, 104C, and 104R in an anechoic room or listening room with little sound reflection, and collecting this sound with a microphone arranged at the position of the sound increase control point. The acquisition unit 1031 acquires the transfer function measured in this manner. Note that, if the positions of the speakers 104L1, L2, 104C, and 104R and the positions of the volume increase control points are fixed, the transfer function may be treated as a fixed transfer function. In this case, the acquisition unit 1031 may input the fixed transfer function stored in advance to the acoustic filter coefficient calculation unit 1032.

[0020] The acoustic filter coefficient calculation unit 1032 receives various information from the acquisition unit 1031, and also receives an acoustic filter coefficient for at least one speaker from the acoustic filter coefficient storage unit 1033 to calculate acoustic filter coefficients for the remaining speakers. Then, the acoustic filter coefficient calculation unit 1032 inputs the acoustic filter coefficient to the acoustic filter setting unit 1034. The acoustic filter is calculated as shown in the following formula (1) by a first relational expression and a second relational expression obtained based on the sound increase control law and the acoustic power minimization control law, respectively.

number

[0021] The acoustic filter coefficient storage unit 1033 stores an acoustic filter coefficient for at least one of the speakers 104L, 104C, and 104R. For example, the acoustic filter coefficient storage unit 1033 stores the acoustic filter coefficient of the speaker 104C. The acoustic filter coefficient storage unit 1033 may be provided when the number of speakers is three or more. When the number of speakers is l (l≧3), the acoustic filter coefficient storage unit 1033 stores at least (l−2) acoustic filter coefficients. As described above, in the embodiment, the speakers 104L1 and 104L2 are regarded as one speaker 104L. In this case, the acoustic filter coefficient storage unit 1033 may store the acoustic filter coefficient of one speaker, for example, the speaker 104C.

[0022] An acoustic filter setting unit 1034 sets the acoustic filter coefficients calculated by the acoustic filter coefficient calculation unit 1032 to the acoustic filters 1022L, 1022C, and 1022R, respectively.

[0023] Here, based on the sound boost control rule, the sound boost volume is determined by the overlapping of sounds from the sound sources. Therefore, if the number of sound sources increases, the sound boost effect improves. In the embodiment, two speakers 104L1 and 104L2 function as one left speaker 104L. Therefore, the sound boost effect can be improved compared to when one speaker functions as the left speaker.

[0024] In addition, based on the acoustic power minimization control, the amount of reduction in acoustic power is determined by the sum of the amounts of reduction in acoustic power between the sound sources. Even if the total volume velocity of the sound sources is the same, the new sum (radiation resistance) increases when the sound source is divided into two, resulting in a larger reduction in acoustic power.

[0025] In other words, by dividing the left speaker into two speakers 104L1 and 104L2, it is expected that both the effect of sound increase control and the effect of sound power minimization control will be improved.

[0026] Fig. 4 is a diagram showing an example of setting sound increase areas and sound reduction areas. In Fig. 4, a sound increase area is set to the right of speakers 104L, 104C, and 104R arranged side by side. In the case of the speaker arrangement in Fig. 4, the front direction, rear direction, and left direction of speakers 104L, 104C, and 104R become sound reduction areas. In Fig. 4, the front direction of speakers 104L, 104C, and 104R is sound reduction area 1, the left direction of speakers 104L, 104C, and 104R is sound reduction area 2, and the rear direction of speakers 104L, 104C, and 104R is sound reduction area 3.

[0027] FIG. 5 is a diagram showing the calculation results of the relationship between frequency and sound pressure level in the sound increase area and sound reduction area of ​​FIG. 4. The horizontal axis of FIG. 5 is frequency. The vertical axis of FIG. 5 is sound pressure level in the sound increase area and sound reduction areas 1, 2, and 3. Here, in FIG. 5, the speaker interval is 0.1 m. Then, the sound pressure level of the sound collected by the microphone placed at a position 0.5 m away from the speaker 104C in each of the sound increase area and sound reduction areas 1, 2, and 3 is calculated. Also, in FIG. 5, a diagram of a state in which the change in sound pressure level is emphasized by multiplying the sound pressure level in the applicable band, which is a frequency band in which the effect of the reduction of sound power is particularly large according to the principle of sound power minimization control, by a gain is shown. The applicable band is determined based on the speaker interval. For example, when the speaker interval is 0.1 m, the applicable band is 400 Hz to 1250 Hz in 1 / 3 octave band. Furthermore, in obtaining the calculation results in Fig. 5, the positions of sound reduction area 1 and sound reduction area 3 are slightly shifted from the front and back positions of the speakers due to adjustment of the speaker placement. This is to create a difference between the calculation results of sound reduction area 2 and the calculation results of sound reduction area 3. If sound reduction area 1 and sound reduction area 3 are positioned symmetrically with respect to the speaker, theoretically the calculation results of sound reduction area 1 and the calculation results of sound reduction area 3 will match.

[0028] As shown in FIG. 5, the sound pressure level in the sound-increasing area is almost constant in the frequency band from 400 Hz to 1250 Hz. In contrast, the sound pressure level in the sound-reducing areas 1 and 3 is lower than that in the sound-increasing area from 400 Hz to 1250 Hz, and is particularly significantly lower near 400 Hz. The sound pressure level in the sound-reducing area 2, which is located symmetrically to the sound-increasing area with respect to the speaker, is lower than that in the sound-increasing area from 400 Hz to 1250 Hz, although the amount of decrease is smaller than that in the sound-reducing areas 1 and 3, and is particularly significantly lower near 700 Hz. The decrease in the sound pressure level in the sound-reducing area 2 is smaller than that in the sound-reducing areas 1 and 3 because the interference between the sounds emitted from the speakers 104L and 104R is large in the sound-reducing areas 1 and 3. In the sound power minimization control, when a reduction in the sound pressure level occurs at one point, the sound pressure level increases at another point. This increase in sound pressure level occurs in the sound-reducing area 2. On the other hand, in the embodiment, a sufficient reduction in sound pressure level can be ensured even in the sound reduction area 2 compared to the sound increase area.

[0029] Fig. 6 shows the sound pressure level gradient in the sound increase area and the sound reduction area when sound is radiated by an acoustic filter set according to the result of formula (1). Here, Fig. 6 shows an example where the speaker interval is 0.1 m and the frequency of the radiated sound is 700 Hz. The x-axis and y-axis in Fig. 6 represent the distance from the origin when the position of speaker 104C is taken as the origin. The vertical axis in Fig. 6 represents the sound pressure level.

[0030] As shown in Fig. 6, the area with particularly high sound pressure levels, for example, +0.75≦x≦+1 and 0≦y≦0.5 (both in meters), is the sound increase area. On the other hand, the areas other than the sound increase areas shown in Fig. 6 are sound reduction areas. As also shown in Fig. 5, under the conditions of a speaker spacing of 0.1 m and a frequency of 700 Hz, the difference in sound pressure levels between the sound increase area and the sound reduction area becomes large, so a large sound pressure level gradient is created in a small area, for example, 2 m x 2 m.

[0031] Figure 7 shows an example of the distribution of sound pressure levels in each area when sound is emitted with the acoustic filter coefficients set according to the results of formula (1). Here, Figure 7 shows an example where the speaker spacing is 0.1 m and the frequency of the emitted sound is 700 Hz. The distribution in Figure 7 also shows the magnitude of the sound pressure level according to the concentration.

[0032] 7, the sound pressure level is high in the sound increase area and low in sound reduction areas 1, 2, and 3. When comparing sound reduction areas 1, 2, and 3, the amount of reduction in sound pressure level is greater in sound reduction areas 1 and 3 than in sound reduction area 2. When speaker 104C is used as the reference, the sound from speaker 104R and the sound from speaker 104L are in anti-phase. Therefore, sound reduction areas 1 and 3 experience a greater reduction in acoustic power due to interference between the sounds emitted from speakers 104L and 104R than sound reduction area 2.

[0033] As described above, in the first embodiment, sound increase control and sound power minimization control are performed in combination. This allows a sharp difference in sound pressure between the sound increase area and the sound reduction area. Also, in the first embodiment, the left speaker is divided into speakers that emit sounds of the same amplitude and phase. Therefore, it is expected that the effects of sound increase control and sound power minimization control will be improved compared to sound increase control and sound power minimization control when the number of speakers and the number of acoustic filter coefficients are the same.

[0034] The configuration of the first embodiment also has commercial and implementation advantages. That is, in the first embodiment, while maintaining the number of acoustic filter coefficients, i.e., the number of speaker control channels, the effect of the sound increase control and the sound power minimization control is expected to improve by increasing the number of speakers. Since the number of control channels can be reduced, the configuration is simplified. In addition, under the condition that the speaker interval is constant, the effect of the sound increase control and the sound power minimization control is improved by increasing the number of speakers. In other words, if the number of speakers is the same and the effect of the sound increase control and the sound power minimization control is the same, the speaker interval can be shortened. Therefore, in the configuration in which the sound signal filtered with the same acoustic filter coefficient is branched and input to two speakers to perform the sound increase control and the sound power minimization control as in the first embodiment, the speaker interval can be shortened compared to the configuration in which the sound signal filtered with the same number of acoustic filter coefficients as the number of speakers is input to separate speakers to perform the sound increase control and the sound power minimization control. As a result, the system is made smaller.

[0035] Here, in the embodiment, the left speaker 104L is divided into a speaker 104L1 and a speaker 104L2. The audio signal processing device 102 branches the audio signal to which the acoustic filter coefficient qL is applied to the speaker 104L1 and the speaker 104L2 and outputs the branched signal. In contrast, the left speaker may be divided into three or more speakers. In this case, the audio signal processing device 102 may branch the audio signal to which the acoustic filter coefficient qL is applied to the three or more speakers and output the branched signal.

[0036] (Modification 1 of the first embodiment) As described above, in the sound increase control and sound power minimization control in the embodiment, the amount of reduction in sound pressure level in the sound reduction area 2 located symmetrically to the sound increase area with respect to the speaker position is smaller than the sound reduction areas 1 and 3.

[0037] On the other hand, for example, a phase shifter is disposed in front of the acoustic filters 1022L, 1022C, and 1022R to shift the phase of the audio signal, thereby increasing the amount of reduction in the sound pressure level in the sound reduction area 2, which is symmetrical to the sound increase area. In this case, the phase of the audio signal input to the acoustic filter 1022L is, for example, 240 degrees, the phase of the audio signal input to the acoustic filter 1022C is, for example, 0 degrees, and the phase of the audio signal input to the acoustic filter 1022R is, for example, 120 degrees. By shifting the phase of the audio signal by 120 degrees each by the phase shifter, the phase of the sound radiated from the speakers 104L, 104C, and 104R is also shifted by 120 degrees each. Therefore, the sound radiated from the speakers 104L, 104C, and 104R becomes a traveling wave and flows, for example, toward the sound increase area. At this time, the sound pressure interference in the sound reduction areas 1 and 3 is reduced. As a result, the amount of reduction in the sound pressure level in the sound reduction area 2 is increased.

[0038] Also, instead of performing phase correction on the audio signal, an effect equivalent to phase correction can be obtained by further reducing the gain of the audio signal input to the speaker closest to the volume increase control point. In the example of Fig. 1, by further reducing the gain of the audio signal input to the acoustic filter 1022R below G, an effect equivalent to shifting the phase of the audio signal can be obtained.

[0039] (Modification 2 of the first embodiment) In the embodiment, the sound increase control and the sound power minimization control are performed using four speakers. However, the number of speakers is not limited to four. Here, when there are three or more speakers, the number of sound increase control points can be two or more. Specifically, when the number of speakers is l, the number of sound increase control points can be a maximum of (l-1).

[0040] FIG. 8 is a diagram showing an example of the configuration of an acoustic control device according to the second modification of the first embodiment. In the example of FIG. 8, four speakers are arranged at equal distances from the speaker 104C arranged in the center, that is, on a circumference with the speaker 104C as the center. More specifically, the speaker 104R is arranged at the 0° azimuth with the speaker 104C as the center, the speaker 104U is arranged at the 90° azimuth, the speaker 104L is arranged at the 180° azimuth, and the speaker 104D is arranged at the 270° azimuth. In this case, the sound increase control points can be set at two positions, for example, at the 0° azimuth and the 180° azimuth. Here, if the increase factor of the sound increase control is smaller than 1, the sound pressure at the sound increase control points can also be reduced. Therefore, if there are two or more sound increase control points, for example, the sound increase control point at the 0° azimuth can be increased, and the sound increase control point at the 180° azimuth can be reduced. Hereinafter, such a sound increase control point where sound is actively reduced is referred to as a sound reduction control point. The sound increase control point in the 180° azimuth is referred to as a sound reduction control point.

[0041] 8, the audio signal processing device 102 has an acoustic filter 1022U in addition to the acoustic filters 1022L, 1022C, and 1022R. The acoustic filter 1022U filters the audio signal output from the amplifier 1021 according to an acoustic filter coefficient qU designated by the control device 103. The acoustic filter 1022U then branches the filtered audio signal and outputs it to the speakers 104U and 104D. In this case, the speakers 104U and 104D emit sounds of the same amplitude and phase.

[0042] In the case of a configuration in which four speakers are arranged on a circle centered on the speaker 104C, the acoustic filter coefficients qL, qC, qR, and qU are calculated as shown in the following formula (2).

number

[0043] FIG. 9 is a diagram showing the calculation results of the relationship between frequency and sound pressure level when a sound increase area and a sound reduction area are set in the configuration of FIG. 8 in the same manner as in FIG. 4. To obtain the calculation results of FIG. 9, a sound increase control point is set in the sound increase area of ​​FIG. 4, and a sound reduction control point is set in sound reduction area 2. The multiplication factor n of the sound increase control point is 3. On the other hand, the multiplication factor m of the sound reduction control point is 0.25. The speaker interval d is d=0.1 m, and the speaker interval r is 0.14 m. FIG. 9 also shows a state in which the change in sound pressure level in the 1 / 3 octave band, which is the applicable band, at 400 Hz to 1250 Hz is emphasized.

[0044] Comparing FIG. 9 with FIG. 5, in FIG. 9, the sound pressure level in the sound reduction area 2 changes uniformly regardless of frequency. Also, in FIG. 9, the difference in sound pressure level between the sound increase area and the sound reduction area 2 is about 20 dB in the applicable band of 400 Hz-1250 Hz. Conversely, in FIG. 9, the sound reduction areas 1 and 3 change to a notch characteristic in which the sound pressure level drops sharply at a specific frequency. Meanwhile, in the applicable band of 400 Hz-1250 Hz, the difference in sound pressure level between the sound increase area and the sound reduction areas 1 and 3 is 15 dB or less. In FIG. 5, the amount of drop in the sound pressure level in the sound reduction area 2 near 400 Hz and near 1250 Hz is small, so it can be said that the effect of the sound increase control and sound power minimization control in FIG. 9 is higher than the effect of the sound increase control and sound power minimization control in FIG. 5. Furthermore, in FIG. 9, the sound pressure level drops in the sound reduction areas 1, 2, and 3 even in bands exceeding the applicable band of 1250 Hz. That is, in the configuration of Modification 2, the effects of the sound increase control and the sound power minimization control can be obtained to a certain extent even outside the applicable band. That is, as in the configuration of Modification 2, the effects of the sound increase control and the sound power minimization control can be improved by further increasing the number of speakers.

[0045] (Modification 3 of the first embodiment) In the second modification of the first embodiment, the speakers are arranged two-dimensionally. In contrast, the speakers may be arranged three-dimensionally, for example, at the center of a sphere and on the surface of the sphere as shown in Fig. 10. Alternatively, the speakers may be arranged, for example, at the center of a polyhedron and at the vertices of the polyhedron. The polyhedron is, for example, a regular polyhedron or a truncated polyhedron.

[0046] For example, in Fig. 10, in the arrangement of the speakers shown in Fig. 8, a speaker 104T is arranged vertically above the speaker 104C with a distance d therebetween, and a speaker 104B is arranged vertically below the speaker 104C with a distance d therebetween. In the configuration of Fig. 10, an audio signal filtered with an acoustic filter coefficient qC is input to the speaker 104C, an audio signal filtered with an acoustic filter coefficient qR is input to the speaker 104R, and an audio signal filtered with an acoustic filter coefficient qL is input to the speaker 104L. An audio signal filtered with an acoustic filter coefficient qU is input to the speaker 104U, and an audio signal filtered with an acoustic filter coefficient qD is input to the speaker 104D. Alternatively, an audio signal filtered with the same acoustic filter coefficient qU is branched and input to the speakers 104U and 104D. Also, an audio signal filtered with an acoustic filter coefficient qT is input to the speaker 104T, and an audio signal filtered with an acoustic filter coefficient qB is input to the speaker 104B. Alternatively, an audio signal filtered with the same acoustic filter coefficient qT is branched and input to the speakers 104T and 104B. The acoustic filter coefficients qC, qR, qL, qU, qD, qT, and qB can be calculated based on the sound increase control law and the acoustic power minimization control law, as in the first embodiment and the first modified example.

[0047] Second embodiment Next, a second embodiment will be described. In the first embodiment, an audio signal filtered by a common acoustic filter is branched and input to a plurality of speakers, thereby simplifying the system and improving the effects of sound increase control and sound power minimization control. In contrast, the second embodiment shows an example in which a group of speakers is spaced apart to improve the directivity of sound to a sound increase area.

[0048] 11 is a diagram showing an example of the configuration of an audio control device according to the second embodiment. The audio control device 100 includes an audio signal input unit 101, audio signal processing devices 102a and 102b, a control device 103, a first speaker group, and a second speaker group.

[0049] The first speaker group includes speakers 104L1, 104C1, and 104R1 arranged on a straight line. Similarly, the second speaker group includes speakers 104L2, 104C2, and 104R2 arranged on a straight line. The volume increase control point of the first speaker group is set on the speaker 104R1 side on the straight line on which the speakers 104L1, 104C1, and 104R1 are arranged. In addition, the volume increase control point of the second speaker group is set on the speaker 104R2 side on the straight line on which the speakers 104L2, 104C2, and 104R2 are arranged.

[0050] In the first speaker group, speakers 104R1, 104C1, and 104L1 are arranged in this order from the front to the back. In the second speaker group, speakers 104R2, 104C2, and 104L2 are arranged in this order from the front to the back. The distance between speaker 104R1 and speaker 104R2, the distance between speaker 104C1 and speaker 104C2, and the distance between speaker 104L1 and speaker 104L2 are longer in this order. In other words, the first speaker group and the second speaker group are arranged obliquely from the front to the back. Here, hereinafter, the distance between speaker 104C1 and speaker 104C2 may be referred to as the separation distance L between the first speaker group and the second speaker group. As shown in FIG. 11, the first speaker group and the second speaker group are arranged at a distance from each other, so that the sound amplified areas of the two speaker groups intersect.

[0051] 3, and filters the audio signal input from the audio signal input unit 101 in accordance with acoustic filter coefficients qL1, qC1, and qR1 specified by the control device 103. Then, the audio signal processing device 102a outputs the audio signal filtered with the acoustic filter coefficient qL1 to the speaker 104L1, outputs the audio signal filtered with the acoustic filter coefficient qC1 to the speaker 104C1, and outputs the audio signal filtered with the acoustic filter coefficient qR1 to the speaker 104R1.

[0052] 3, and filters the audio signal input from the audio signal input unit 101 in accordance with acoustic filter coefficients qL2, qC2, and qR2 specified by the control device 103. Then, the audio signal processing device 102b outputs the audio signal filtered with the acoustic filter coefficient qL2 to the speaker 104L2, outputs the audio signal filtered with the acoustic filter coefficient qC2 to the speaker 104C2, and outputs the audio signal filtered with the acoustic filter coefficient qR2 to the speaker 104R2.

[0053] The acoustic filter coefficients qL1, qC1, qR1, qL2, qC2, and qR2 are calculated as shown in the following equation (3).

number

[0054] Fig. 12 shows the sound pressure level gradient of the sound increase area and the sound reduction area when sound is radiated by an acoustic filter set according to the result of formula (3). Here, Fig. 12 shows an example in which the speaker interval is 0.1 m, the separation distance between the first speaker group and the second speaker group is 0.2 m, and the frequency of the radiated sound is 700 Hz. The x-axis and y-axis in Fig. 12 are distances from an origin, for example, when the origin is set to the midpoint between the speaker 104C1 and the speaker 104C2. The vertical axis in Fig. 12 is the sound pressure level.

[0055] As mentioned above, by arranging the two speaker groups diagonally from the front to the back, the sound amplified areas of the two speaker groups intersect. The sound pressure level increases sharply at the intersection of the sound amplified areas. In other words, by arranging the two speaker groups at a distance so that their sound amplified areas intersect, the directionality of the sound is improved.

[0056] Figure 13 shows an example of the distribution of sound pressure levels when sound is emitted with acoustic filter coefficients set according to the results of equation (1). The distribution in Figure 13 represents the magnitude of the sound pressure level according to the concentration. As Figure 13 also shows, the sound pressure level in the sound-augmented area located near the center is particularly high, and there are also areas around it where the sound pressure level drops sharply. In other words, Figure 13 also shows that the directionality of the sound can be improved by arranging two speaker groups at a distance so that the sound-augmented areas intersect.

[0057] 14A to 14H are diagrams showing the results of actual measurements of the relationship between the azimuth angle and the sound pressure level with respect to the two speaker groups when the arrangement of the speaker groups is changed.

[0058] Here, the results of 3ch 1set in Fig. 14A-Fig. 14H show the actual measurement results of the relationship between the azimuth angle and the sound pressure level in a single speaker group shown in Fig. 15A. Speakers 104L, 104C, and 104R are installed at positions L, C, and R in Fig. 15A. The speaker interval d is 0.1 m. The azimuth angle θ is an angle based on the speaker 104C. The sound increase control point is set to the 0° azimuth. The results of 3ch-1set are shown for comparison and do not change in Fig. 14A-Fig. 14H. Specifically, the sound pressure level is highest in the 0° azimuth, which is the sound increase area, and the sound pressure level is lowest in the 90° azimuth. The sound pressure level is also lower in the 180° azimuth, which is the opposite side to the sound increase area, compared to the 0° azimuth.

[0059] On the other hand, the results of 3ch 2set in Figures 14A-14H show the actual measurement results of the relationship between azimuth angle and sound pressure level when changing the arrangement of the two speaker groups shown in Figure 15B. Speakers 104L1, 104C1, and 104R1 are installed at positions L1, C1, and R1 in Figure 15B, and speakers 104L2, 104C2, and 104R2 are installed at positions L2, C2, and R2. The speaker interval d is 0.1 m. The azimuth angle θ is an angle based on the midpoint between speakers 104C1 and 104C2. Furthermore, the tilt angles φ of the first speaker group and the second speaker group are the angles formed by speakers 104R1 and 104L1 relative to speaker 104C1, and the angles formed by speakers 104R2 and 104L2 relative to speaker 104C2, respectively. FIG. 14A shows the results when φ is 0°. FIG. 14B shows the results when φ is 10°. FIG. 14C shows the results when φ is 15°. FIG. 14D shows the results when φ is 20°. FIG. 14E shows the results when φ is 30°. FIG. 14F shows the results when φ is 50°. FIG. 14G shows the results when φ is 60°. FIG. 14H shows the results when φ is 90°.

[0060] In all of Figures 14A-14H, the amount of reduction in sound pressure level with respect to the change in azimuth angle is greater in the 3ch 2set results than in the 3ch 1set results. As mentioned above, the 0° azimuth corresponds to the sound-increased area, so the reduction in sound pressure level in azimuths other than the 0° azimuth means that a large sound pressure level gradient is created in a narrow range. In other words, Figures 14A-14H also show that sound directionality can be further improved by arranging the two speaker groups at a distance.

[0061] When comparing the results of 3ch 1set between Figures 14A-14H, the drop in sound pressure level is particularly large in Figure 14C, that is, when φ is 15°. Therefore, under the measurement conditions of Figures 14A-14H, φ is the optimal tilt angle when φ is 15°. However, the actual optimal tilt angle varies depending on the setting of the sound increase control point and the characteristics of the calculated acoustic filter, and 15° is not necessarily optimal. The angle (2φ) between the line on which the first speaker group is arranged and the line on which the second speaker group is arranged is, for example, greater than 0° and less than 180°. The intersection of the two lines is closer to speaker 104R1 than speaker 104L1, and closer to speaker 104R2 than speaker 104L2.

[0062] When the optimal tilt angle is determined, the first speaker group and the second speaker group can be tilted by the tilt angle and spaced apart. In this case, as shown in FIG. 16, the speakers 104R1, 104C1, and 104L1 constituting the first speaker group and the speakers 104R2, 104C2, and 104R2 constituting the second speaker group can be embedded in the baffle board B. As shown in FIG. 13, when the speakers are spaced apart, the sound pressure level is high not only in the front but also behind. This high sound pressure level distribution behind is canceled by embedding the speakers in the baffle board B. Furthermore, the baffle board only doubles the radiated sound pressure, and the effects of the sound boost control and sound power minimization control are the same as when there is no baffle board.

[0063] Moreover, formula (3) is an acoustic filter coefficient calculated taking into consideration the transfer characteristics of the sound emitted from a speaker of one speaker group to the sound increase control point of the other speaker group. On the other hand, as a simpler method, directivity can be improved by arranging two speaker groups whose acoustic filter coefficients are calculated independently based on formula (1). Figures 17A and 17B are conceptual diagrams for finding an arrangement with optimal directivity for multiple speaker groups. A user radiates sound from each speaker group while changing the separation distance L and tilt angle φ between the two speaker groups, and listens to the sound from each speaker group. As shown in Figure 17A, when the separation distance L between the speaker groups is a long distance L1, the sound increase areas of the two speaker groups do not overlap, so the volume of the sound heard by the user does not change much. On the other hand, when the speaker group separation distance L is a short distance L2 as shown in Fig. 17B, the sound boost areas of the two speaker groups overlap, and the volume of the sound heard by the user becomes louder. Here, the applicant's experiments have shown that when the separation distance L satisfies the condition kL<π, the overlapping sound boost areas can provide a high sound boost effect.

[0064] By using such a search method, the user can place the two speaker groups so that the sound is heard most loudly while listening to the sound. This method also does not require recalculation of the acoustic filter coefficients.

[0065] As described above, according to the second embodiment, the two speaker groups are spaced apart to further increase the directivity of the sound, that is, a more localized sound-increasing area can be set.

[0066] Here, in the second embodiment, the speakers constituting each speaker group are three speakers arranged in a straight line. However, the speakers constituting each speaker group do not necessarily have to be three speakers arranged in a straight line. For example, each speaker group may be four speakers including two speakers arranged vertically as described in FIG. 1 of the first embodiment. That is, the speakers constituting each speaker group only need to include at least two speakers.

[0067] (Modification 1 of the second embodiment) In the example shown in Fig. 11, the first speaker group and the second speaker group are input with the same audio signal filtered by different acoustic filters. Therefore, the sound heard at the volume increase control point is monaural. In contrast, the second embodiment can also be applied to a stereo system.

[0068] 18 is a diagram showing an example of the configuration of an audio control device according to Modification 1 of the second embodiment. The audio control device 100 includes audio signal input units 101a and 101b, audio signal processing devices 102a and 102b, a control device 103, a first speaker group, and a second speaker group.

[0069] The first speaker group and the second speaker group are the same as those in Fig. 11. That is, in the first speaker group, speakers 104R1, 104C1, and 104L1 are arranged diagonally in this order from the front to the rear. Also, in the second speaker group, speakers 104R2, 104C2, and 104L2 are arranged diagonally in this order from the front to the rear.

[0070] In the second modification, two audio signal input units 101a and 101b are provided. The audio signal input unit 101a inputs one of the stereo audio signals, for example, a right audio signal, to the audio signal processing device 102a. The audio signal input unit 101b inputs the other of the stereo audio signals, for example, a left audio signal, to the audio signal processing device 102b. The stereo audio signals may be generated sequentially for each reproduction, or may be input by the user or the control device 103, for example.

[0071] The audio signal processing device 102a has a configuration similar to that of the audio signal processing device 102 shown in Fig. 3, and filters an audio signal input from an audio signal input unit 101a according to acoustic filter coefficients qL1, qC1, and qR1 designated by the control device 103. Then, the audio signal processing device 102a outputs an audio signal filtered with the acoustic filter coefficient qL1 to the speakers 104L1 and 104L2, outputs an audio signal filtered with the acoustic filter coefficient qC1 to the speakers 104C1 and 104C2, and outputs an audio signal filtered with the acoustic filter coefficient qR1 to the speakers 104R1 and 104R2. That is, in the second modification, the audio signal processing device 102a outputs the filtered audio signal to both the first speaker group and the second speaker group.

[0072] The audio signal processing device 102b has a configuration similar to that of the audio signal processing device 102 shown in Fig. 3, and filters the audio signal input from the audio signal input unit 101b according to the acoustic filter coefficients qL2, qC2, and qR2 designated by the control device 103. Then, the audio signal processing device 102b outputs the audio signal filtered with the acoustic filter coefficient qL2 to the speakers 104L2 and 104L1, outputs the audio signal filtered with the acoustic filter coefficient qC2 to the speakers 104C2 and 104C1, and outputs the audio signal filtered with the acoustic filter coefficient qR2 to the speakers 104R2 and 104R1. That is, in the second modification, the audio signal processing device 102b outputs the filtered audio signal to both the first speaker group and the second speaker group.

[0073] The acoustic filter coefficients qL1, qC1, qR1, qL2, qC2, and qR2 may be the acoustic filter coefficients shown in equation (3).

[0074] The configuration of the second modification of the second embodiment described above maintains the effect of the monaural sound source, and also produces a stereo sound image effect by arranging the two speaker groups apart from each other. This realizes the spatial directional distribution of the stereo sound source.

[0075] Next, an example of the hardware configuration of the acoustic control device 100 described in each of the above-mentioned embodiments will be described with reference to Fig. 19. Fig. 19 is a diagram showing an example of the hardware configuration of the acoustic control device 100.

[0076] As shown in FIG. 19, the acoustic control device includes a computer to which a control unit 209, a memory unit 210, a power supply unit 211, a timing device 212, a communication interface (I / F) 205, an input unit 206, an output device 207, and an external interface (I / F) 208 are electrically connected.

[0077] The control unit 209 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and / or a ROM (Read Only Memory), and controls each component in accordance with information processing. The control unit 209 can operate as the audio signal input unit 101, the audio signal processing device 102, and the control device 103. The control unit 209 can call up an execution program stored in the storage unit 210 and execute processing.

[0078] The storage unit 210 is a medium that stores information such as a program so that it can be read by a computer, a machine, etc. The storage unit 210 may also store speaker interval information, audio signal frequency information, and transfer function information. The storage unit 210 may be, for example, an auxiliary storage device such as a hard disk drive or a solid state drive. Furthermore, the storage unit 210 may include a drive. The drive is a device for reading data stored in another auxiliary storage device, a recording medium, etc., and includes, for example, a semiconductor memory drive (flash memory drive), a CD (Compact Disk) drive, a DVD (Digital Versatile Disk) drive, etc. The type of drive may be appropriately selected depending on the type of storage medium.

[0079] The power supply unit 211 supplies power to each element of the audio control device 100. The power supply unit 211 may further supply power to each element of a device including the audio control device 100. The power supply unit 211 may include, for example, a secondary battery or an AC power supply.

[0080] The timing device 212 is a device that measures time. For example, the timing device 212 may be a clock including a calendar, and transmits information on the current year, month, and / or date and time to the control unit 209. The timing device 212 may be used to add a date and time to the reproduced audio signal.

[0081] The communication interface 205 is, for example, a short-distance wireless communication (for example, Bluetooth (registered trademark)) module, a wired LAN (Local Area Network) module, a wireless LAN module, etc., and is an interface for performing wired or wireless communication via a network. The communication via this network may be either wireless or wired. The network may be an internetwork including the Internet, or may be another type of network such as an in-house LAN. Furthermore, the communication interface 205 may perform one-to-one communication using a USB (Universal Serial Bus) cable or the like. Furthermore, the communication interface 205 may include a micro USB connector. The communication interface 205 is an interface for connecting the sound control device to an external device such as, for example, an automobile, a train, an electric device in a house, or various communication devices. The communication interface 205 is controlled by the control unit 209, and receives various information from the external device via the network or the like. The various information includes, for example, information on speaker intervals, information on the frequency of an audio signal, and information on a transfer function set in the external device.

[0082] The input unit 206 is a device that accepts input, and may be, for example, a touch panel, a physical button, a mouse, a keyboard, etc. The output device 207 is a device that performs output, and may be, for example, a display, a speaker, etc. that outputs information by display, sound, etc. Speaker interval information, sound signal frequency information, and transfer function information may be input via the input unit 206.

[0083] The external interface 208 is for intermediating between the main body of the audio control device and an external device, which may be, for example, a printer, a memory, a communication device, or the like.

[0084] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0085] 100 Acoustic control device, 101, 101a, 101b Audio signal input unit, 102, 102a, 102b Audio signal processing device, 103 Control device, 104L, 104L1, 104L2, 104C, 104C1, 104C2, 104R, 104R1, 104R2, 104U, 104D, 104B, 104T Speaker, 205 Communication interface, 206 Input unit, 207 Output device, 208 External interface, 209 Control unit, 210 Memory unit, 211 Power supply unit, 212 Timer, 1021 Amplifier, 1022L, 1022C, 1022R, 1022U Acoustic filter, 1031 Acquisition unit, 1032 Acoustic filter coefficient calculation unit, 1033 Acoustic filter coefficient storage unit, 1034 acoustic filter setting unit.

Claims

1. an acoustic filter coefficient calculation unit that calculates acoustic filter coefficients whose number is less than the number of the sound sources based on a first relational expression between acoustic filters applied to an audio signal including information of sounds reproduced by each of the multiple sound sources, the first relational expression being based on a sound increase control rule that increases a sound pressure at a sound increase control point by sounds reproduced by the multiple sound sources, and a second relational expression between the acoustic filters based on an acoustic power minimization control rule that minimizes acoustic power for sounds reproduced by the multiple sound sources; an audio signal processing unit that applies the calculated acoustic filter coefficient to an input audio signal, and branches and outputs an audio signal to which a common acoustic filter coefficient has been applied to at least two of the multiple sound sources; An audio control device comprising:

2. the plurality of sound sources include a plurality of sound sources arranged on a straight line and a plurality of sound sources arranged offset from the straight line, the audio signal processing unit outputs an audio signal to which the common acoustic filter coefficient has been applied to a plurality of sound sources arranged offset from the straight line. The acoustic control device according to claim 1 .

3. the plurality of sound sources includes a first sound source disposed at a center and a plurality of second sound sources disposed equidistantly with respect to the first sound source; the audio signal processing unit outputs an audio signal to which the common acoustic filter coefficient is applied to at least two of the second sound sources. The acoustic control device according to claim 1 .

4. an acoustic filter coefficient calculation unit that calculates an acoustic filter coefficient based on a first relational expression between acoustic filters applied to an audio signal including information of sounds reproduced by each of a plurality of sound sources, the first relational expression being based on a sound increase control rule that increases a sound pressure at a sound increase control point by sounds reproduced by the plurality of sound sources, and a second relational expression between the acoustic filters, the second relational expression being based on an acoustic power minimization control rule that minimizes acoustic power for sounds reproduced by the plurality of sound sources; an audio signal processing unit that applies the calculated acoustic filter coefficient to an input audio signal and outputs the audio signal to which the acoustic filter coefficient has been applied to the plurality of sound sources; Equipped with The plurality of sound sources include a first sound source group and a second sound source group each of which is disposed apart from one another and includes at least two sound sources. Sound control device.

5. the first sound source group and the second sound source group are each set with the volume increase control point; the first sound source group and the second sound source group are arranged so that a first sound increase area including a sound increase control point of the first sound source group intersects with a second sound increase area including a sound increase control point of the second sound source group; The acoustic control device according to claim 4.

6. At least two sound sources included in the first sound source group and at least two sound sources included in the second sound source group are arranged on a straight line. The acoustic control device according to claim 4.

7. Calculating acoustic filter coefficients whose number is less than the number of the sound sources based on a first relational expression between acoustic filters applied to an audio signal including information of sounds reproduced by each of the multiple sound sources, the first relational expression being based on a sound increase control rule that increases a sound pressure at a sound increase control point by sounds reproduced by the multiple sound sources, and a second relational expression between the acoustic filters based on an acoustic power minimization control rule that minimizes acoustic power for sounds reproduced by the multiple sound sources; applying the calculated acoustic filter coefficients to an input speech signal; branching an audio signal to which a common acoustic filter coefficient has been applied and outputting the branched audio signal to at least two of the plurality of sound sources; An acoustic control program for causing a computer to execute the above.

8. Calculating acoustic filter coefficients based on a first relational expression between acoustic filters applied to an audio signal including information on sounds reproduced by each of a plurality of sound sources, the first and second sound source groups being arranged apart from each other and including at least two sound sources, the first relational expression being based on a sound increase control rule for increasing a sound pressure at a sound increase control point by sounds reproduced by the plurality of sound sources, and a second relational expression between the acoustic filters being based on an acoustic power minimization control rule for minimizing acoustic power for sounds reproduced by the plurality of sound sources; applying the calculated acoustic filter coefficients to an input speech signal; outputting the audio signal to which the acoustic filter coefficient has been applied to each of the first sound source group and the second sound source group; An acoustic control program for causing a computer to execute the above.

9. Calculating acoustic filter coefficients whose number is less than the number of the sound sources based on a first relational expression between acoustic filters applied to an audio signal including information of sounds reproduced by each of the multiple sound sources, the first relational expression being based on a sound increase control rule that increases a sound pressure at a sound increase control point by sounds reproduced by the multiple sound sources, and a second relational expression between the acoustic filters based on an acoustic power minimization control rule that minimizes acoustic power for sounds reproduced by the multiple sound sources; applying the calculated acoustic filter coefficients to an input speech signal; branching an audio signal to which a common acoustic filter coefficient has been applied and outputting the branched audio signal to at least two of the plurality of sound sources; An acoustic control method comprising:

10. Calculating acoustic filter coefficients based on a first relational expression between acoustic filters applied to an audio signal including information on sounds reproduced by each of a plurality of sound sources, the first and second sound source groups being arranged apart from each other and including at least two sound sources, the first relational expression being based on a sound increase control rule for increasing a sound pressure at a sound increase control point by sounds reproduced by the plurality of sound sources, and a second relational expression between the acoustic filters being based on an acoustic power minimization control rule for minimizing acoustic power for sounds reproduced by the plurality of sound sources; applying the calculated acoustic filter coefficients to an input speech signal; outputting the audio signal to which the acoustic filter coefficient has been applied to each of the first sound source group and the second sound source group; An acoustic control method comprising:

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