Acoustic control device, program and method

Abstract

To provide an acoustic control apparatus, a program, and a method that facilitate transmitting a sound in only a specific direction.SOLUTION: An acoustic control apparatus includes an acoustic filter coefficient calculation unit. The acoustic filter coefficient calculation unit calculates a first relational expression between acoustic filter coefficients of acoustic filters to be applied to voice signals containing information of sounds played back by two or more sound sources, on the basis of an amplification magnification in a sound amplification control point with respect to the sounds played back by the two or more sound sources, and of transfer functions between the sound amplification control point and the two or more sound sources. The acoustic filter coefficient calculation unit calculates a second relational expression between the acoustic filter coefficients, on the basis of information of a frequency of the voice signals and of an interval between the two or more sound sources. The acoustic filter coefficient calculation unit calculates the respective acoustic filter coefficients on the basis of the first relational expression and the second relational expression.SELECTED DRAWING: Figure 3

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 such as 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 where you want to convey voice or the area where 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. The acoustic filter coefficient calculation unit calculates a first relational expression between acoustic filter coefficients of an acoustic filter to be applied to an audio signal including information of a sound reproduced by each of two or more sound sources, based on a multiplication factor at a sound increase control point for the sound reproduced by two or more sound sources and a transfer function between each of the two or more sound sources and the sound increase control point. The acoustic filter coefficient calculation unit calculates a second relational expression between the acoustic filter coefficients, based on information on the frequency of the audio signal and an interval between the two or more sound sources. The acoustic filter coefficient calculation unit calculates each acoustic filter coefficient based on the first relational expression and the second relational expression. [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 conceptual diagram of the sound increase control. [Diagram 5] FIG. 5 is a conceptual diagram of acoustic power minimization control. [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 with the acoustic filter coefficient set according to the result of equation (9). [Figure 7A] FIG. 7A is a diagram showing an example of setting a volume increase area and a volume decrease area. [Figure 7B] FIG. 7B is a diagram showing an example of the distribution of sound pressure levels in each area when sound is emitted with acoustic filter coefficients set according to the result of equation (9) when sound increase areas and sound decrease areas are set as in FIG. 7A. [Figure 8] FIG. 8 is a diagram showing the relationship between the sound increase control and the sound power minimization control with respect to the speaker interval. [Figure 9]FIG. 9 is a flowchart showing the flow of spatial sound field design, including the determination of speaker intervals and frequencies. [Figure 10] FIG. 10 is a diagram showing the relationship between the speaker interval for each frequency and the amount of acoustic power reduction in acoustic power minimization control. [Figure 11] FIG. 11 is a diagram showing the calculation results of the relationship between frequency and sound pressure level in the sound increase area and the sound decrease area. [Figure 12] FIG. 12 is a diagram showing the relationship between the frequency and each speaker interval. [Figure 13A] FIG. 13A shows the results of an experiment in which white noise was used as a sound source, sound was emitted from a speaker, the sound was collected by a microphone placed in a sound-augmented area, and the noise level of the collected sound was measured. [Figure 13B] FIG. 13B shows the results of an experiment in which white noise was used as a sound source, sound was emitted from a speaker, the sound was collected by a microphone placed in sound reduction area 1, and the noise level of the collected sound was measured. [Figure 13C] FIG. 13C shows the results of an experiment in which white noise was used as a sound source, sound was emitted from a speaker, the sound was collected by a microphone placed in sound reduction area 3, and the noise level of the collected sound was measured. [Figure 13D] FIG. 13D shows the results of an experiment in which white noise was used as a sound source, sound was emitted from a speaker, the sound was collected by a microphone placed in sound reduction area 2, and the noise level of the collected sound was measured. [Figure 14] FIG. 14 is a diagram illustrating an example of the configuration of the acoustic control device according to the second embodiment. [Figure 15] FIG. 15 is a diagram showing an example of the distribution of sound pressure levels in each area when sound is radiated as a traveling wave with acoustic filter coefficients set according to the result of equation (9) when sound increase areas and sound decrease areas are set as shown in FIG. 7A. [Figure 16A] FIG. 16A is a diagram showing the results of an experiment similar to that shown in FIG. 13A, in which the sound radiated from the speaker is converted into a traveling wave. [Figure 16B]FIG. 16B is a diagram showing the results of an experiment similar to that shown in FIG. 13B, in which the sound radiated from the speaker is converted into a traveling wave. [Figure 16C] FIG. 16C is a diagram showing the results of an experiment similar to that shown in FIG. 13C, in which the sound radiated from the speaker is converted into a traveling wave. [Figure 16D] FIG. 16D is a diagram showing the results of an experiment similar to that shown in FIG. 13D, in which the sound radiated from the speaker is converted into a traveling wave. [Figure 17] FIG. 17 is a diagram illustrating an example of the configuration of an acoustic control device according to the third embodiment. [Figure 18A] FIG. 18A is a diagram showing the calculation results regarding the relationship between the sound pressure levels of the sound increase area and the sound reduction areas 1, 2, and 3 for each frequency when the gain correction of the acoustic filter coefficient qL is not taken into consideration. [Figure 18B] FIG. 18B is a diagram showing the calculation results regarding the relationship between the sound pressure levels of the sound increase area and the sound reduction areas 1, 2, and 3 for each frequency when the gain correction of the acoustic filter coefficient qL is taken into consideration. [Figure 19] FIG. 19 is a diagram showing an example of setting the volume increase control points when the number of speakers is four. [Figure 20] FIG. 20 is a diagram illustrating an example of a hardware configuration of the acoustic control device described in each embodiment. 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 104L, 104C, and 104R. The acoustic control device 100 combines sound increase control using multiple speakers 104L, 104C, and 104R and sound power minimization control to make it easier to transmit sound only to a specific sound increase area A2 while quieting a sound reduction area A1 around the speakers 104L, 104C, and 104R. The sound increase control is a control that increases the sound pressure in a specific direction by controlling the amplitude of the sound emitted from multiple speakers. On the other hand, the sound power minimization control is a control that minimizes the acoustic power when multiple speakers are viewed as one speaker by controlling the amplitude and phase of the sound emitted from multiple speakers.

[0008] 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.

[0009] The audio signal processing device 102 processes an audio signal and includes an amplifier 1021 and acoustic filters 1022L, 1022C, and 1022R.

[0010] 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.

[0011] 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 outputs the filtered audio signal to the speaker 104L. 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 for passing only sounds in a specific band of the audio signal. The acoustic filter coefficients qL, qC, and qR can be set to be equal to the complex volume velocities of the speakers 104L, 104C, and 104R.

[0012] 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.

[0013] The speakers 104L, 104C, and 104R are sound sources that emit sounds corresponding to filtered audio signals output from the corresponding acoustic filters. The speakers 104L, 104C, and 104R are housed side by side as one unit in a horizontally long housing as shown in FIG. 2, for example. When the direction shown in FIG. 2 is the front, the speaker 104L operates as the left speaker, the speaker 104C operates as the center speaker, and the speaker 104R operates as the right speaker. In the configuration of FIG. 2, the interval between the speakers 104L, 104C, and 104R is a fixed value. Here, the speakers 104L, 104C, and 104R do not necessarily need to be configured as one unit. On the other hand, for the purpose of acoustic power minimization control and sound increase control, it is desirable that the speakers 104L, 104C, and 104R are arranged to some extent close to each other. The housing shown in FIG. 2 may also house an audio signal input unit 101, an audio signal processing device 102, and a control device 103.

[0014] 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.

[0015] 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.

[0016] 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 speed of sound is known, the frequency can be converted into a wave number. As will be described later, 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.

[0017] 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.

[0018] 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 of the sound increase control. The transfer function is expressed as a matrix whose elements are the spatial transfer characteristic CR 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 104L, 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. If the positions of the speakers 104L, 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.

[0019] 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. The acoustic filter coefficient calculation unit 1032 then inputs the acoustic filter coefficients to the acoustic filter setting unit 1034. The calculation of the acoustic filter coefficient will be described in detail later.

[0020] 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 m (m≧3), the acoustic filter coefficient storage unit 1033 stores at least (m−2) acoustic filter coefficients.

[0021] 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.

[0022] Next, the calculation of the acoustic filter coefficient in the acoustic filter coefficient calculation unit 1032 will be described. As described above, the acoustic control device 100 in the embodiment performs a combination of sound increase control and sound power minimization control using the multiple speakers 104L, 104C, and 104R. Below, the sound increase control and sound power minimization control will be described separately.

[0023] First, the sound increase control will be described. Fig. 4 is a conceptual diagram of the sound increase control. Fig. 4 shows the sound increase control using three speakers 104L, 104C, and 104R.

[0024] The sound increase control is a control to increase the sound pressure energy in the sound increase area A2 by n times. In other words, the sound pressure energy in the sound increase area A2 before the sound increase control is increased by Q OFF , the sound pressure energy in the sound-increased area A2 after the sound-increase control is Q on Then, the sounds radiated from the respective speakers 104L, 104C, and 104R are controlled so that the relationship of the following formula (1) is established. Here, in the embodiment, "before sound increase control" refers to a state in which sound is radiated only from the reference speaker 104C. Q on =nQ OFF (1)

[0025] Suppose there are N sound increase control points in the sound increase area A2, the sound pressure at each sound increase control point before the sound increase control is Pj (j=1, 2, ..., N), the sound pressure at each sound increase control point after the sound increase control is P'j (j=1, 2, ..., N), the transfer function between the speaker 104L and each sound increase control point is DLj (j=1, 2, ..., N), the transfer function between the speaker 104C and each sound increase control point is DCj (j=1, 2, ..., N), the transfer function between the speaker 104R and each sound increase control point is DRj (j=1, 2, ..., N), the complex volume velocity of the speaker 104L is qL, the complex volume velocity of the speaker 104C is qC, and the complex volume velocity of the speaker 104R is qR, then the sound pressure energy Q in the sound increase area A2 is OFF and Q ON is the sum of the sound pressure energy at each of the increase control points, and is calculated as shown in the following formulas (2) and (3), respectively. Here, * in formulas (2) and (3) is a symbol representing a complex conjugate. Note that when j is 1, that is, when there is one increase control point, the sound pressure energy is equal to the sound pressure at that increase control point.

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number

[0026] Next, the acoustic power minimization control will be described. Fig. 5 is a conceptual diagram of the acoustic power minimization control. Fig. 5 shows the acoustic power minimization control using three speakers 104L, 104C, and 104R, similar to Fig. 4.

[0027] The acoustic power minimization control is a control that minimizes the acoustic power in the sound reduction area A1 around the speaker. Here, the acoustic power W for one sound source is calculated by the following formula (5). In formula (5), Re is a symbol indicating taking the real part in the parentheses, ω is an angular frequency, ρ is a medium, typically the density of air, k is a wave number, qL, qC, and qR are complex volume velocities of the corresponding sound sources, and dLC, dRL, and dCR are speaker intervals between the corresponding speakers. Also, as in formulas (2) and (3), * is a symbol indicating a complex conjugate. The unit of acoustic power is, for example, W, and the unit of complex volume velocity is, for example, m 3 / s. As the unit indicates, sound power indicates the energy of sound per unit time. Sound power is an absolute value determined by the sound source and does not depend on the position from the sound source.

number

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[0028] As shown in formula (9), qL and qR are functions of the kd value, which is the product of the wave number k and the speaker interval, and the transfer functions DLj, DCj, and DRj between each speaker and each sound increase control point in the sound increase area. The kd value is a dimensionless quantity equivalent to a phase, and can be determined by the frequency of the sound emitted from the speaker and the speaker interval if the sound speed is determined. In addition, the transfer function 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 104L, 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.

[0029] As is clear from equation (6), the acoustic power W is a function of the kd value, so in acoustic power minimization control, the amount of acoustic power reduction is determined by the kd value. Even if the frequency or speaker spacing changes, the same amount of acoustic power reduction can be obtained as long as the kd value is constant.

[0030] FIG. 6 shows the sound pressure level gradient of the sound increase area and the sound reduction area when sound is emitted with the acoustic filter coefficient set according to the result of formula (9). The x-axis and y-axis in FIG. 6 are distances from the origin when the position of the speaker 104C is the origin. The vertical axis in FIG. 6 is the sound pressure level. The area shown in FIG. 6 where the amount of reduction in sound pressure level is small, for example, the area of ​​+0.75≦x≦+1 and 0≦y≦0.5 (both in meters), is the sound increase area. That is, the acoustic control device 100 of the embodiment can create the sound increase area and the sound reduction area in a relatively narrow space around the speakers 104L, 104C, and 104R, for example, 2m×2m. Here, the larger the sound pressure level gradient between the sound increase area and the sound reduction area shown in FIG. 6, the more the sound emitted from the speaker can be heard only in the sound increase area. The sound pressure level gradient increases as the amount of increase in sound volume due to sound increase control and the amount of decrease in sound power due to sound power minimization control increase.

[0031] Fig. 7A is a diagram showing an example of setting a sound increase area and a sound reduction area. In Fig. 7A, a sound increase area is set to the right of the speakers 104L, 104C, and 104R arranged side by side. In this case, the front direction, rear direction, and left direction of the speakers 104L, 104C, and 104R are sound reduction areas. In Fig. 7A, the front direction of the speakers 104L, 104C, and 104R is sound reduction area 1, the left direction of the speakers 104L, 104C, and 104R is sound reduction area 2, and the rear direction of the speakers 104L, 104C, and 104R is sound reduction area 3.

[0032] FIG. 7B shows an example of the distribution of sound pressure levels in each area when sound is emitted with the acoustic filter coefficient set according to the result of equation (9) when the sound increase area and the sound reduction area are set as in FIG. 7A. Here, the distribution in FIG. 7B represents the magnitude of the sound pressure level according to the concentration. As shown in FIG. 7B, when the sound increase area is set to the right of the speakers 104L, 104C, and 104R, the sound pressure level of the sound increase area becomes high, and the sound pressure level of the sound reduction areas 1, 2, and 3 becomes low. When comparing the sound reduction areas 1, 2, and 3, the sound reduction areas 1 and 3 have a larger reduction in sound pressure level than the sound reduction area 2. When the speaker 104C is used as a reference, the sound of the speaker 104R and the sound of the speaker 104L are in an antiphase relationship. Therefore, the sound reduction areas 1 and 3 have a larger reduction in acoustic power due to interference between the sounds emitted from the speakers 104L and 104R than the sound reduction area 2.

[0033] FIG. 8 is a diagram showing the relationship between the sound increase control and the sound power minimization control for the speaker interval. The horizontal axis of FIG. 8 indicates the speaker interval. Meanwhile, the vertical axis of FIG. 8 indicates the effect amount of the sound increase control and the sound power minimization control. The vertical axis of FIG. 8 is the increase sound volume in the case of the sound increase control, and the sound power reduction amount as the reduction amount of the sound power level in the case of the sound power minimization control. As shown in FIG. 8, there is a trade-off relationship between the effect of the sound increase control and the effect of the sound power minimization control. Specifically, the sound power reduction amount becomes smaller as the speaker interval becomes longer. Meanwhile, the increase sound volume becomes larger as the speaker interval becomes longer. Therefore, in order to increase the sound pressure level gradient shown in FIG. 6, it is important to determine the optimal speaker interval. FIG. 8 shows the relationship between the sound increase control and the sound power minimization control for the speaker interval, and there is also a trade-off relationship between the effect of the sound increase control and the sound power minimization control for the frequency. Specifically, the sound power reduction amount becomes smaller as the frequency becomes higher. Meanwhile, the increase sound volume becomes larger as the frequency becomes higher.

[0034] 9 is a flowchart showing the flow of spatial sound field design including the determination of speaker intervals and frequencies. The process of FIG.

[0035] In step S1, the control device 130 determines a sound increase factor n. The sound increase factor n is appropriately determined according to the usage environment when the acoustic control device 100 is actually used by the user. The sound increase factor n may be a fixed value such as 2, or may be determined by receiving an input from a user or an operator in charge of setting the acoustic control device 100. For example, when the sound increase factor n is set to 2, the acoustic filter coefficient is calculated so that a sound increase of 6 dB is obtained.

[0036] In step S2, the control device 130 determines the kd value. The kd value is appropriately determined according to the amount of acoustic power reduction required by the acoustic power minimization control. The kd value may be, for example, a fixed value, or may be determined by receiving an input from a user or an operator in charge of setting the acoustic control device 100. Furthermore, if the speaker interval and frequency are fixed values, the process of step S2 may be omitted.

[0037] In step S3, the control device 130 determines the speaker interval and the frequency based on the kd value. A method for determining the speaker interval and the frequency will be described below.

[0038] Fig. 10 is a diagram showing the relationship between the speaker spacing for each frequency and the amount of acoustic power reduction in acoustic power minimization control. The horizontal axis of Fig. 10 is the speaker spacing. The vertical axis of Fig. 10 is the amount of acoustic power reduction. Each curve in Fig. 10 represents a theoretical calculation value of the amount of acoustic power reduction calculated from equation (6) when the speaker spacing is changed for audio signals of various frequencies. Here, in Fig. 10, the speaker spacing between speakers 104L and 104C is set to be equal to the speaker spacing between speakers 104C and 104R.

[0039] In FIG. 10, the region where the amount of acoustic power reduction is lower than 0 dB is the speaker spacing and frequency region where the effect of acoustic power minimization control is apparent. In other words, if the speaker spacing is constant, the lower the frequency, i.e., the longer the wavelength, the greater the effect of interference between opposite-phase sounds, and the greater the amount of acoustic power reduction. Conversely, if the frequency is constant, the smaller the speaker spacing, the stronger the overlap between opposite-phase sounds, and the greater the amount of acoustic power reduction. In this way, the theoretical limit value of acoustic power, which corresponds to the equipment-specific energy of noise, is determined by the kd value. Therefore, if the theoretical limit value of acoustic power reduction can be understood, the effect of reducing acoustic power can be determined before design.

[0040] Sound pressure is determined by the distance from a sound source having a certain sound power value. Therefore, if the space around the sound source is assumed to be an ideal space, the amount of sound power reduction at the source of the sound corresponds to the amount of sound pressure reduction in that space. For example, assume that the amount of sound power reduction is -7 dB and the amount of sound pressure level reduction at a certain point around the speaker is 15 dB. Such a reduction in sound pressure level at a certain point only occurs locally due to the influence of reflection, etc. Therefore, when a reduction in sound pressure level occurs at a certain point, the sound pressure level increases at another point. In other words, if the theoretical limit value of the amount of sound power reduction due to the constraint of the kd value, etc. is -7 dB, the limit value of the sound pressure level that is uniformly reduced around the speaker is also -7 dB. Therefore, in order to set the sound pressure level gradient, i.e., the amount of sound pressure reduction, to a desired level, it is necessary to select the speaker interval and frequency based on the sound pressure level of the sound increase area increased by the sound increase control and the theoretical limit value of the amount of sound power reduction to realize the sound reduction area around the speaker.

[0041] For example, suppose that the speaker spacing is selected so that the sound pressure level gradient between the sound increase area and the sound reduction area is 10 dB. When the sound increase factor n is 2, a sound pressure level gradient of 10 dB between the sound increase area and the sound reduction area corresponds to an acoustic power reduction of -4 to -10 dB. Therefore, in the example of Fig. 10, the combination of speaker spacing and frequency that can realize the sound pressure level gradient between the sound increase area and the sound reduction area is a combination within the range WR of the acoustic power reduction amount in Fig. 10.

[0042] Therefore, for example, the speaker spacing when the frequency of the audio signal to be reproduced is 1500 Hz can be determined within the range dR1. Similarly, the speaker spacing when the frequency of the audio signal to be reproduced is 1000 Hz can be determined within the range dR2. Similarly, the speaker spacing when the frequency of the audio signal to be reproduced is 500 Hz can be determined within the range dR3.

[0043] FIG. 11 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. The horizontal axis of FIG. 11 is frequency. The vertical axis of FIG. 11 is sound pressure level in the sound increase area and sound reduction areas 1, 2, and 3. In FIG. 11, the speaker interval is 0.1 m. The sound pressure level of the sound collected by a microphone placed 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. FIG. 12 is a diagram showing the relationship between frequency for each speaker interval. The horizontal axis of FIG. 12 is frequency. The vertical axis of FIG. 12 is the amount of sound power reduction.

[0044] As shown in Fig. 11, the sound pressure level in the sound increase area is almost constant in the frequency band from 0 Hz to 2000 Hz. The sound pressure level in the sound reduction areas 1 and 3 increases as the frequency increases. However, the sound pressure level in the sound reduction areas 1 and 3 is sufficiently smaller than the sound pressure level in the sound increase area. Therefore, for the sound reduction areas 1 and 3, the sound power minimization control is effective even in the range from 0 Hz to 2000 Hz.

[0045] In contrast, in the sound reduction area 2, the sound pressure level significantly exceeds 0 dB in the band FR1 from 0 Hz to 350 Hz and in the band FR3 from 1250 Hz to 2000 Hz. In other words, the sound reduction area 2 has increased sound in the bands FR1 and FR3.

[0046] Here, as shown in Fig. 12, the amount of sound power reduction in band FR21, which is almost the same as band FR1, is large. Thus, band FR21 is a band in which the amount of sound power reduction due to sound power minimization control is large, but it is also a band in which sound is increased even at positions away from the sound increase control point due to sound increase control. Due to this increase in sound at positions away from the sound increase control point, the sound pressure level gradient between the sound increase area and sound reduction area 2 in band FR1 becomes small, as shown in Fig. 11.

[0047] Also, as shown in Fig. 12, the amount of sound power reduction in band FR23, which is almost the same as band FR3, is small. This means that, theoretically, sound reduction is hardly performed in band FR23. Therefore, as shown in Fig. 11, the sound pressure level gradient between the sound increase area and sound reduction area 2 in band FR3 is small.

[0048] In this way, similar to the speaker interval, if the frequency is too high or too low, the desired sound pressure level gradient cannot be obtained. Therefore, for example, the frequency at which the acoustic power reduction amount is 0 dB shown in FIG. 12 is used as a reference, and a frequency that is about half of this reference frequency may be set as the lower limit frequency in design. The upper limit frequency in design is about 1400 Hz, which is the lower limit frequency of FR23 shown in FIG. 12. Therefore, for example, if the speaker interval is 0.15 m, the frequency may be set in the range of 400 Hz to 1400 Hz, if the speaker interval is 0.10 m, the frequency may be set in the range of 650 Hz to 1400 Hz, and if the speaker interval is 0.05 m, the frequency may be set in the range of 700 Hz to 1400 Hz.

[0049] Based on the above-mentioned concept, when the frequency is fixed, the control device 130 determines the speaker spacing from within the range of speaker spacing according to the frequency conditions shown in Fig. 10. On the other hand, when the speaker spacing is fixed, the control device 130 determines the frequency from within the range of frequencies according to the speaker spacing conditions shown in Fig. 12.

[0050] Furthermore, when both the speaker spacing and the frequency are fixed, the speaker spacing and the frequency may not be included in the ranges shown in Fig. 10 or 12. In this case, since there is a possibility that the desired quieting may not be achieved, the control device 130 may, for example, adjust the frequency balance of the sound radiated from the speakers so that the energy contribution of the frequency band of the audio signal is increased, or adjust the value of the gain G of the audio signal.

[0051] Returning now to the description of FIG. 9, in step S4 after the speaker interval and frequency have been determined, the control device 130 determines an increase control point. The increase control point may be determined, for example, within a 2m x 2m range based on the speaker 104C. The increase control point may be determined by receiving an input from a user or an operator in charge of setting the acoustic control device 100. In this case, the control device 130 may perform a display or the like for allowing the increase control point to be input. This display is, for example, a 2m x 2m map centered on the speaker 104C. The user or operator may arbitrarily designate, for example, one point on this map as the increase control point.

[0052] In step S5, the control device 130 measures the transfer function. As described above, the transfer function can be measured from a microphone acquired 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 104L, 104C, and 104R in an anechoic room or a listening room with little sound reflection, and collecting this sound with a microphone arranged at the position of the volume increase control point. Here, the transfer functions for a plurality of positions assumed as the volume increase control points may be measured in advance. In this case, the control device 130 acquires a transfer function corresponding to the volume increase control point designated in step S4.

[0053] In step S6, the control device 130 calculates filter coefficients qL, qC, and qR based on the sound boost ratio, speaker interval, frequency, and transfer function based on equation (9). Then, the control device 130 sets the filter coefficients qL, qC, and qR to the acoustic filters 1022L, 1022C, and 1022R, respectively. After that, the control device 130 ends the process of FIG. 9.

[0054] 13A, 13B, 13C, and 13D are diagrams showing the results of an experiment in which, in the settings of the sound increase area and sound reduction area shown in FIG. 7A, white noise is used as a sound source and emitted from a speaker, the sound is collected by a microphone placed in each area, and the noise level of the collected sound is measured. The speaker interval in the experiment is 10 cm. The microphone is placed at a position 50 cm from the speaker 104C in each area. Furthermore, as described above, the white noise sound emitted from the sound source has a constant sound pressure level in the applicable frequency band of 400 Hz to 1600 Hz, where the sound pressure level gradient determined by the speaker interval is realized. FIG. 13A shows the results in the sound increase area. FIG. 13B shows the results in the sound reduction area 1. FIG. 13C shows the results in the sound reduction area 3. FIG. 13D shows the results in the sound reduction area 2. The horizontal axis of Fig. 13A, Fig. 13B, Fig. 13C, Fig. 13D is the center frequency of the 1 / 3 octave band. The vertical axis of Fig. 13A, Fig. 13B, Fig. 13C, Fig. 13D is the 1 / 3 octave band level. The OFF results of Fig. 13A, Fig. 13B, Fig. 13C, Fig. 13D show the results before the sound increase control and the sound power minimization control, that is, the results when sound is emitted only from the speaker 104C. On the other hand, the ON results of Fig. 13A, Fig. 13B, Fig. 13C, Fig. 13D show the results after the sound increase control and the sound power minimization control, that is, the results when sound is emitted from each of the speakers 104L, 104C, and 104R.

[0055] When the control is off, the reduction in sound pressure level in sound reduction areas 1, 2, and 3 compared to the sound pressure level in the sound increase area is -0.6 dB, 0.1 dB, and -0.4 dB, respectively. On the other hand, when the control is on, the reduction in sound pressure level in sound reduction areas 1, 2, and 3 compared to the sound pressure level in the sound increase area is 14.1 dB, 12.7 dB, and 17.2 dB, respectively. In this way, it can be seen that by combining sound increase control and sound power minimization control, a sharp difference in sound pressure level is achieved even at close range.

[0056] As described above, in the first embodiment, sound increase control and sound power minimization control are combined and executed. This allows a sharp difference in sound pressure to be created between the sound increase area and the sound reduction area. Therefore, in the first embodiment, it is possible to make it easier for sound to be transmitted only in a specific direction.

[0057] In the first embodiment, when the positions of the speaker, which is the sound source, and the sound increase control point are determined, the acoustic filter coefficient can be calculated if a transfer function corresponding to the positions is obtained. Therefore, the sound increase control point does not need to be fixed. Also, sound increase control and acoustic power minimization control can be performed simply by adjusting the acoustic filter coefficient. Therefore, the acoustic control device of the embodiment can be applied to environments where listeners are not limited, such as online conference systems and public announcements.

[0058] In the first embodiment, the speaker interval and frequency for sound boosting and sound power minimization control can be designed based on the theoretical limit value of the sound power reduction amount based on the kd value. That is, in the first embodiment, excessive engineering for designing the speaker interval and frequency is not required. Furthermore, when the calculated acoustic filter coefficient is set in the acoustic filter, the user of the acoustic control device does not need to change the acoustic filter setting even if the characteristics of the surrounding room to be used change. Furthermore, it is possible to use multiple acoustic filter coefficients separately, such as using an acoustic filter coefficient calculated from the characteristics actually measured with speaker A in one band and using an acoustic filter calculated from the characteristics actually measured with speaker B in another band. For example, when the acoustic filter calculated from the characteristics actually measured with speaker A has a poor effect of reducing the sound power level, it is possible to use an acoustic filter calculated from the characteristics actually measured with speaker B.

[0059] Second embodiment Next, a second embodiment will be described. In the second embodiment, the description that overlaps with the first embodiment will be omitted or simplified.

[0060] As shown in FIG. 13A, FIG. 13B, FIG. 13C, and FIG. 13D, the first embodiment can generate a difference in sound pressure level between the sound increase area and the sound reduction areas 1, 2, and 3 when the control is on. On the other hand, the difference in sound pressure level between the sound increase area and the sound reduction area 2 is smaller than that between the sound reduction areas 1 and 3. This is because, as described above, the interference between the sounds emitted from the speaker 104L and the speaker 104R is large in the sound reduction areas 1 and 3. In the sound power minimization control, when a reduction in sound pressure level occurs at a certain point, the sound pressure level increases at another point. This increase in sound pressure level occurs in the sound reduction area 2. As shown in FIG. 13D, there is a difference in sound pressure level of 12 dB or more even in the sound reduction area 2, but depending on the usage scene, there are cases where a further difference in sound pressure level is required. In the second embodiment, an attempt is made to obtain a large sound pressure level gradient overall by suppressing the reduction in sound pressure level in the sound reduction area where an excessive reduction in sound pressure level occurs.

[0061] Fig. 14 is a diagram showing an example of the configuration of an acoustic control device according to a second embodiment. Here, in Fig. 14, explanations of parts overlapping with Fig. 1 will be omitted. In the second embodiment, an audio signal processing device 102 has phase shifters 1023L, 1023C, and 1023R. Other configurations are the same between the second embodiment and the first embodiment.

[0062] The sound pressure level in sound reduction areas 1 and 3 has nodes with excessively low sound pressure levels due to sound pressure interference between the sound radiated from speaker 104L and the sound radiated from speaker 104R. Therefore, in the second embodiment, sounds are radiated from the speakers so as to reduce the sound pressure interference in sound reduction areas 1 and 3. Specifically, the sounds radiated from speakers 104L, 104C, and 104R are changed into traveling waves. For this purpose, phase shifters 1023L, 1023C, and 1023R are provided.

[0063] The phase shifter 1023L shifts the phase of the audio signal input from the amplifier 1021 by HL and inputs it to the acoustic filter 1022L. The phase shifter 1023C shifts the phase of the audio signal input from the amplifier 1021 by HC and inputs it to the acoustic filter 1022C. The phase shifter 1023R shifts the phase of the audio signal input from the amplifier 1021 by HR and inputs it to the acoustic filter 1022R. Here, HL is, for example, 240 degrees, HC is, for example, 0 degrees, and HR is, for example, 120 degrees. Since the phases of the audio signals are shifted by 120 degrees each by the phase shifters 1023L, 1023C, and 1023R, the phases of the sounds radiated from the speakers 104L, 104C, and 104R are also shifted by 120 degrees each. Therefore, the sounds radiated from the speakers 104L, 104C, and 104R become traveling waves and flow toward, for example, the sound-increased area. At this time, the sound pressure interference in the sound reduction areas 1 and 3 becomes smaller.

[0064] FIG. 15 shows an example of the distribution of sound pressure levels in each area when sound is emitted as a traveling wave with acoustic filter coefficients set according to the result of equation (9) when sound increase area and sound reduction area are set as in FIG. 7A. Here, as in FIG. 7B, the distribution in FIG. 15 represents the magnitude of the sound pressure level according to the concentration. By modifying the sound emitted from the speaker to a traveling wave, the sound of the opposite phase disappears. Therefore, the nodes of the sound pressure level disappear in sound reduction areas 1 and 3, and the distribution tendency changes. In this state, by also performing sound increase control, the sound pressure level decreases, especially in sound reduction area 2, compared to FIG. 7B.

[0065] 16A, 16B, 16C, and 16D are diagrams showing the results of an experiment similar to that shown in FIGS. 13A, 13B, 13C, and 13D, in which the sound radiated from the speaker was converted into a traveling wave.

[0066] The reduction amounts of the sound pressure level of the sound reduction areas 1, 2, and 3 relative to the sound increase area when the sound reduction area is off are -1.5 dB, 0.3 dB, and -0.7 dB. On the other hand, the reduction amounts of the sound pressure level of the sound reduction areas 1, 2, and 3 relative to the sound increase area when the sound reduction area is on are 10.2 dB, 13.8 dB, and 13.7 dB, respectively. The reduction amount of the sound pressure level of the sound reduction area 2 has been improved to the same level as the sound reduction areas 1 and 3. On the other hand, the reduction amount of the sound pressure level of the sound reduction areas 1 and 3 seems to have deteriorated, but it can be said that a reduction amount of 15 dB or more is a sufficient effect. Even if the reduction amount of the sound pressure level of the sound reduction areas 1 and 3 deteriorates slightly, the range of application in practical scenes can be expanded by improving the reduction amount of the sound pressure level of the sound reduction area 2 by that amount. In other words, in the second embodiment, the sound reduction area can be adjusted according to such a scene just by switching the phase of the phase shifter.

[0067] As described above, according to the second embodiment, the phase correction is performed on the audio signal, and the sound emitted from the speaker is made into a traveling wave, and sound increase control and sound power minimization control are performed. This makes it possible to reduce excessive sound pressure interference in the sound reduction areas, and to suppress the variation in the amount of reduction in sound pressure level for each sound reduction area.

[0068] 13, the phase shifters 1023L, 1023C, and 1023R are provided in front of the acoustic filters 1022L, 1022C, and 1022R, respectively. In contrast, the phase shifters 1023L, 1023C, and 1023R may be provided in the rear of the acoustic filters 1022L, 1022C, and 1022R, respectively.

[0069] In addition, in the embodiment, since the number of speakers is three, three phase shifters are provided. The number of phase shifters is not limited to three as long as it corresponds to the number of speakers. When the number of speakers is m, the phase correction amount θi of the i-th speaker (i=1, 2, ... m) may be θi=exp(j×2πi / m).

[0070] (Third embodiment) Next, a third embodiment will be described. In the third embodiment, the description that overlaps with the first or second embodiment will be omitted or simplified.

[0071] In the second embodiment, phase correction is performed on the audio signal. However, an effect equivalent to phase correction can be obtained by further reducing the gain of the sound radiated from the speaker farthest from the sound increase control point.

[0072] Fig. 17 is a diagram showing an example of the configuration of an acoustic control device according to a third embodiment. Here, in Fig. 17, explanations of parts overlapping with Fig. 1 are omitted. In the third embodiment, an audio signal processing device 102 has an amplifier 1021a, and amplifiers 1024L, 1024C, and 1024R. Other configurations are the same between the third embodiment and the first embodiment.

[0073] The amplifier 1021a amplifies the audio signal input from the audio signal input unit 101 with a gain G1. The gain G1 is equal to the gain G. In other words, the amplifier 1021a is the same as the amplifier 1021.

[0074] The amplifier 1024L attenuates the audio signal input from the amplifier 1021a to the audio signal input unit 101 with a gain G2L. The amplifier 1024C attenuates the audio signal input from the amplifier 1021a to the audio signal input unit 101 with a gain G2C. The amplifier 1024R attenuates the audio signal input from the amplifier 1021a to the audio signal input unit 101 with a gain G2R. For example, among the gains G2L, G2C, and G2R, the gain of the amplifier corresponding to the speaker farthest from the sound increase control point is smaller than 1, and the gain of the amplifier other than the speaker farthest from the sound increase control point is 1. For example, when the sound increase area and the sound decrease area are set as shown in FIG. 7A, the speaker farthest from the sound increase control point, that is, the sound increase area, is the speaker 104L. Therefore, the gain G2L is a value smaller than 1, for example, 0.6. On the other hand, the gains G2C and G2R are 1.

[0075] Fig. 18A is a diagram showing the calculation results of the relationship between the sound pressure levels of the sound increase area and sound reduction areas 1, 2, and 3 for each frequency when gain correction of the acoustic filter coefficient qL is not taken into consideration. When the sound increase area and sound reduction areas 1, 2, and 3 are set as shown in Fig. 7A, as shown in Fig. 18A, the reduction in sound pressure level in sound reduction areas 1 and 3 is greater than that in sound reduction area 2. Therefore, in order to obtain a sufficient sound pressure level gradient between the sound increase area and the sound reduction area, it is more important to lower the sound pressure level of sound reduction area 2 than to further reduce the sound pressure level of sound reduction areas 1 and 3.

[0076] FIG. 18B is a diagram showing the calculation results of the relationship between the sound pressure levels of the sound increase area and the sound reduction areas 1, 2, and 3 for each frequency when the gain correction of the acoustic filter coefficient qL is taken into consideration. As shown in FIG. 18B, when the acoustic filter coefficient qL becomes smaller than the value shown in the formula (9), the sound pressure level of the sound reduction area 2, for example, in the range of 600 Hz to 800 Hz decreases. On the other hand, the sound pressure levels of the sound reduction areas 1 and 3 in the same band increase. This tendency becomes stronger as the value of the gain G2L becomes smaller. In other words, if the sound pressure level of the sound reduction area 2 is reduced too much, the sound pressure levels of the sound reduction areas 1 and 3 increase by that amount, and as a result, a sufficient sound pressure level gradient cannot be obtained. In the example, when the value of the gain G2L is 0.6 to 0.7, the reduction amounts of the sound pressure levels of the sound reduction areas 1, 2, and 3 are almost equal.

[0077] As described above, according to the third embodiment, the variation in the amount of reduction in sound pressure level for each sound reduction area can be suppressed by using gain correction instead of phase correction.

[0078] Here, the audio signal processing device 102 in the third embodiment does not have the phase shifters 1023L, 1023C, and 1023R. In contrast, the audio signal processing device 102 in the third embodiment may have the phase shifters 1023L, 1023C, and 1023R. That is, phase correction and gain correction may be combined.

[0079] In the example described in the third embodiment, only the gain of the amplifier 1024L is reduced, but this is not limiting. Gain correction may be performed using the gains of the amplifiers 1024C and 1024R as well. For example, the values ​​of the gains G2L, G2C, and G2R may be adjusted according to the distance from the volume increase control point.

[0080] (Other variations) In the above-mentioned embodiments, the number of speakers is three. However, the number of speakers may be two or more. In particular, when the number of speakers is three or more, the number of volume increase control points can be two or more. Specifically, when the number of speakers is m, the number of volume increase control points can be (m-1). FIG. 19 is a diagram showing an example of setting volume increase control points when the number of speakers is four. In FIG. 19, four speakers 104L, 104C, 104R, and 104D are arranged in four directions, up and down and left and right. And, two volume increase control points P1 and P2 are arranged at the upper right and lower right when viewed from the right speaker 104R.

[0081] Even in such a case, the acoustic filter coefficients qL, qC, qR, qD for the speakers 104L, 104C, 104R, 104D can be calculated from the speaker spacings dCL, dRC, dDR, dLD between the respective speakers, the frequency of the audio signal, and the transfer functions DL1, DC1, DR1, DD1 between the speakers 104L, 104C, 104R, 104D and the increase control point P1, and the transfer functions DL2, DC2, DR2, DD2 between the speakers 104L, 104C, 104R, 104D and the increase control point P2.

[0082] Here, when there are two or more volume increase control points, the two or more volume increase control points may be in one volume increase area or in separate volume increase areas. When there are two or more volume increase control points in one volume increase area, the two or more volume increase control points may be increased by a common volume increase factor as described in the first embodiment, or may be increased by different volume increase factors. For example, when there are three volume increase control points, a first volume increase control point with a volume increase factor of 2 may be placed in one volume increase area, a second volume increase control point with a volume increase factor of 1 may be placed behind the first volume increase control point, and a third volume increase control point with a volume increase factor of 0.1 may be placed behind the second volume increase control point. In this case, a sound pressure level gradient may occur even in one volume increase area. Note that when multiple volume increase control points are increased by different volume increase factors, the formulas (2) and (3) may be calculated for each volume increase control point.

[0083] 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. 20. Fig. 20 is a diagram showing an example of the hardware configuration of the acoustic control device 100.

[0084] As shown in FIG. 20, 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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]

[0093] 100 Acoustic control device, 101 Audio signal input unit, 102 Audio signal processing device, 103 Control device, 104L, 104C, 104R, 104D Speaker, 205 Communication interface (I / F), 206 Input unit, 207 Output device, 208 External interface (I / F), 209 Control unit, 210 Memory unit, 211 Power supply unit, 212 Timer, 1021, 1021a Amplifier, 1022L, 1022C, 1022R Acoustic filter, 1023L, 1023C, 1023R Phase shifter, 1024L, 1024C, 1024R Amplifier, 1031 Acquisition unit, 1032 Acoustic filter coefficient calculation unit, 1033 Acoustic filter coefficient memory unit, 1034 Acoustic filter setting unit.

Claims

1. Calculating a first relational expression between acoustic filter coefficients of an acoustic filter to be applied to an audio signal including information of sounds reproduced by each of the two or more sound sources, based on a multiplication factor at a sound increase control point for sounds reproduced by two or more sound sources and a transfer function between each of the two or more sound sources and the sound increase control point; Calculating a second relationship between the acoustic filter coefficients based on information about the frequency of the audio signal and an interval between the two or more sound sources; calculating respective acoustic filter coefficients based on the first relational expression and the second relational expression; An acoustic control device comprising an acoustic filter coefficient calculation unit.

2. The acoustic control device according to claim 1 , wherein the acoustic filter coefficient calculation section calculates the second relational expression so that acoustic power due to the two or more sound sources is minimized.

3. 3. The acoustic control device according to claim 2, wherein the value at which the acoustic power is minimized is determined based on a theoretical limit value of an amount of reduction in acoustic power that is determined by the frequency and the interval.

4. 4. The acoustic control device according to claim 3, wherein when the frequency of the audio signal is predetermined, the interval is determined based on the predetermined frequency of the audio signal and the theoretical limit value.

5. 4. The acoustic control device according to claim 3, wherein when the interval between the audio signals is predetermined, the frequency is determined based on the predetermined interval between the two or more sound sources and the theoretical limit value.

6. 2. The acoustic control device according to claim 1, further comprising a phase shifter provided for each of the two or more sound sources, which corrects the phase of each audio signal containing information of the sound reproduced by each of the two or more sound sources so that the sound reproduced by the two or more sound sources becomes a traveling wave.

7. 2. The acoustic control device according to claim 1, further comprising an amplifier provided for each of the two or more sound sources, which attenuates each audio signal containing information about a sound reproduced by each of the two or more sound sources with a gain corresponding to a distance from the volume increase control point among the two or more sound sources.

8. A program for causing a computer to function as each unit of the acoustic control device according to claim 1.

9. Calculating a first relational expression between acoustic filter coefficients of an acoustic filter to be applied to an audio signal including information of sounds reproduced by each of the two or more sound sources, based on a multiplication factor at a sound increase control point for sounds reproduced by two or more sound sources and a transfer function between each of the two or more sound sources and the sound increase control point; Calculating a second relationship between the acoustic filter coefficients based on information about the frequency of the audio signal and an interval between the two or more sound sources; calculating respective acoustic filter coefficients based on the first relational expression and the second relational expression; An acoustic control method comprising:

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