Acoustic control device, acoustic control system, program product and method

Abstract

An acoustic control device, an acoustic control system, a program product, and a method are provided. An acoustic control device according to one embodiment is provided with an acoustic filter coefficient calculation unit. An acoustic filter coefficient calculation unit calculates a first relational expression between acoustic filter coefficients on the basis of a multiplication rate of sound pressure at a sound increasing control point that is increased by sound played from a main sound source and two or more additional sound sources, and a transfer function between the main sound source and the additional sound sources and the sound increasing control point. The sound filter coefficient is applied to a sound signal including information of the played sound, and is determined to be equal to the volume velocity of the sound played from the main sound source and each of the additional sound sources. A second relational expression between the acoustic filter coefficients of the main sound source and the additional sound sources is calculated on the basis of the first relational expression and the second relational expression, where the sum of the volume velocity of the sound played from the additional sound sources and the volume velocity of the sound played from the main sound source is not zero, and each acoustic filter coefficient is calculated on the basis of the first relational expression and the second relational expression.

Description

Technical Field

[0001] Embodiments generally relate to acoustic control systems, program products, and methods. Background Art

[0002] Services using various sounds, such as voice guidance in public spaces, car navigation systems, and voice conversations using online conferencing systems, are widely used. While the sounds in these services are useful for those who need guidance or wish to converse, they can become mere noise for those who do not need guidance or do not wish to converse. Specifically, the desired and undesirable areas for sound transmission vary depending on the location and time of day. Therefore, there is a need for sound field control technologies that facilitate the transmission of sound only in specific directions.

[0003] The embodiments provide a sound control device, a sound control system, a program product, and a method that facilitate transmitting sound only in a specific direction. Summary of the Invention

[0004] The acoustic control device of the embodiment includes an acoustic filter coefficient calculation unit. The acoustic filter coefficient calculation unit calculates a first relational expression between acoustic filter coefficients applied to a sound signal including information about the sound being played and determined to be equal to the volume velocity of the sound played from the main sound source and each of the additional sound sources, based on a multiplication rate of sound pressure at a sound-addition control point where sound is added by sound played from a main sound source and two or more additional sound sources, and a transfer function between the main sound source and the additional sound sources and the sound-addition control point. The acoustic filter coefficients are determined to be equal to the volume velocity of the sound played from the main sound source and each of the additional sound sources, and a second relational expression between the acoustic filter coefficients of the main sound source and each of the additional sound sources, conditional on the sum of the volume velocity of the sound played from each of the additional sound sources and the sum of the volume velocity of the sound played from the main sound source being non-zero. The acoustic filter coefficients are calculated based on the first and second relational expressions. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 It is a diagram showing an example of the configuration of the sound control device according to the embodiment.

[0006] Figure 2 This is an external view showing an example of the structure of a speaker.

[0007] Figure 3 This is a block diagram showing elements included in the control device.

[0008] Figure 4 This is a conceptual diagram of the acoustic power control rule for explaining the condition of equation (2).

[0009] Figure 5This is a diagram showing an example of the sound-increasing section set when the conditions of the acoustic power minimization control rule are satisfied.

[0010] Figure 6 : is a diagram showing a sound pressure node formed when the conditions of the acoustic power reduction control rule are satisfied.

[0011] Figure 7 This is a diagram showing an example of the sound-increasing section set when the conditions of the acoustic power reduction control rule are satisfied.

[0012] Figure 8 It is shown in Figure 4 In the example, let α i =-β i =-1 and set to α r +β r =1, the acoustic filter coefficient q obtained according to formula (1) L ,q C ,q R Graph of the gain characteristics.

[0013] Figure 9 It is shown in Figure 4 In the example, let α i =-β i =-1 and set to α r +β r =1, the acoustic filter coefficient q obtained according to formula (1) L ,q C ,q R Phase characteristics of the diagram.

[0014] Figure 10 It shows that the radiation Figure 8 as well as Figure 9 This graph shows the sound pressure level around the speaker when the sound is convoluted by the acoustic filter characteristics.

[0015] Figure 11 It is shown in Figure 12 as well as Figure 13 Graph of evaluation points in the calculation results described in .

[0016] Figure 12 1 is a diagram showing calculation results of the frequency characteristics of the sound pressure at evaluation points A and B.

[0017] Figure 13 1 is a diagram showing the frequency characteristics of the sound pressure difference between evaluation points A and B before and after the combined control of the sound increase control and the acoustic power reduction control is performed.

[0018] Figure 14 This is a graph showing changes in sound pressure distribution when the frequency of the audio signal and the distance between speakers are variously changed.

[0019] Figure 15 4 is a graph showing experimental results using noise in the 400 Hz to 1250 Hz band as an applied frequency band.

[0020] Figure 16 Graphs showing experimental results under noise up to 20,000 Hz, including frequency bands other than the applied frequency band.

[0021] Figure 17 It is shown in Figure 15 as well as Figure 16 Graph of evaluation points in the experimental results described in .

[0022] Figure 18 1 is a diagram showing the result of sound reinforcement in the left direction using a noise source in the 400 Hz-1250 Hz band as an applied frequency band.

[0023] Figure 19 This is a conceptual diagram when the sound control device according to the embodiment is used in a sound guidance system.

[0024] Figure 20 This is a conceptual diagram of a voice guidance system as an application example of the acoustic control system according to the embodiment.

[0025] Figure 21 This is a conceptual diagram when the sound control system according to the embodiment is used in a digital signage system.

[0026] Figure 22 This is a conceptual diagram when the sound control system according to the embodiment is used in a digital signage system.

[0027] Figure 23 The diagram shows the relationship between the main sound source C and the additional sound sources S1, ..., S i A diagram showing an example of a sound control device that is not arranged in a horizontal arrangement.

[0028] Figure 24 This is a diagram showing the positional relationship between the sound source and the sound-intensification control point that enables a sufficient sound pressure gradient to be obtained.

[0029] Figure 25 This is a diagram showing an example of the hardware configuration of the sound control device.

[0030] (Explanation of Symbols)

[0031] 100: Sound control device; 101: Sound signal input unit; 102: Sound signal processing device; 103: Control device; 104L, 104C, 104L: Speaker; 205: Communication interface; 206: Input unit; 207: Output device; 208: External interface; 209: Control unit; 210: Storage unit; 211: Power supply unit; 212: Timing device; 1021: Amplifier; 1022L, 1022C, 1022R: Sound filter; 1031: Acquisition unit; 1032: Sound filter coefficient calculation unit; 1033: Sound filter coefficient storage unit; 1034: Sound filter setting unit. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments will be described with reference to the drawings. Figure 1 1 is a diagram showing an example of the structure of a sound control device according to an embodiment. The sound control device 100 includes a sound signal input unit 101, a sound signal processing device 102, a control device 103, and speakers 104L, 104C, and 104R. In the embodiment, the speakers 104L, 104C, and 104R are, for example, Figure 2 As shown, they are arranged horizontally in a horizontally long frame. Figure 2 , the arrangement of the speakers 104L, 104C, and 104R as viewed from the front is shown. The speaker 104C is located between the speakers 104L and 104R. Figure 2 In the figure, an example is shown in which the speakers 104L, 104C, and 104R are integrated in a straight line. The angle formed by the two directions from the speaker 104C toward the speakers 104L and 104R is preferably greater than 150 degrees and less than 180 degrees, and more preferably greater than 170 degrees and less than 180 degrees. The angle formed by the front direction of the speaker 104C and the direction from the speaker 104C toward the speaker 104L, and the angle formed by the front direction of the speaker 104C and the direction from the speaker 104C toward the speaker 104R are, for example, greater than 85 degrees and less than 95 degrees. Figure 2 , an example is shown in which the front directions of the speakers 104L, 104C, and 104R are parallel to each other. The front directions of the speakers 104L, 104C, and 104R are parallel to each other or form an angle of less than 5 degrees with each other. The positional relationship of the speakers can be based on the center of the front of the speaker, for example. The longitudinal and depth directions are directions along the front direction of the speaker 104C. The transverse direction refers to a direction perpendicular to the front direction of the speaker 104C. In the following, unless otherwise specified, a straight line refers to a straight line passing through the speakers 104L and 104R.

[0033] The sound control device 100 utilizes a combination of sound amplification control and sound power reduction control for multiple speakers, making it easier to transmit sound only to the area in front of the horizontally arranged speakers. Sound amplification control increases the sound pressure in a specific direction by controlling the amplitude of the sound emitted from the multiple speakers. On the other hand, sound power reduction control reduces the sound power of the multiple speakers, as if they were a single speaker, by controlling the amplitude and phase of the sound emitted from the multiple speakers, without minimizing the sound power.

[0034] The sound signal input unit 101 inputs a sound signal to the sound signal processing unit 102. Alternatively, the sound signal input unit 101 may input the sound signal to the control unit 103. A sound signal is a signal containing sound information. For example, the sound signal is prepared in advance for playback. The sound signal may be generated sequentially for each playback, or may be input by a user or the control unit 103.

[0035] The audio signal processing device 102 performs signal processing on the audio signal and includes an amplifier 1021 and acoustic filters 1022L, 1022C, and 1022R.

[0036] 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 .

[0037] The acoustic filter 1022L is configured according to the acoustic filter coefficient q specified by the control device 103. L , filters the audio signal output from the amplifier 1021. Then, the acoustic filter 1022L outputs the filtered audio signal to the speaker 104L. In addition, the acoustic filter 1022C is configured to filter the audio signal according to the acoustic filter coefficient q specified by the control device 103. C , filters the audio signal output from the amplifier 1021. Then, the acoustic filter 1022C outputs the filtered audio signal to the speaker 104C. In addition, the acoustic filter 1022R is configured to filter the audio signal according to the acoustic filter coefficient q specified by the control device 103. R , filtering the audio signal output from the amplifier 1021. Then, the acoustic filter 1022R outputs the filtered audio signal to the speaker 104R. These acoustic filters are devices for passing only the sound of a specific frequency band of the audio signal. The acoustic filter coefficient q can be L ,q C ,q R Set equal to the complex volume velocity of the speakers 104L, 104C, and 104R.

[0038] The control device 103 is used to obtain the acoustic filter coefficients q to be provided to the acoustic filters 1022L, 1022C, and 1022R based on the frequency of the sound signal and the intervals between the speakers 104L, 104C, and 104R. L ,q C ,q R In addition, the control device 103 can also set the gain G. The control device 103 will be described in detail later.

[0039] Speakers 104L, 104C, and 104R are sound sources that emit sound corresponding to the filtered sound signals output from the corresponding acoustic filters. For example, when viewed from the front of speaker 104C, speaker 104L operates as a left speaker, speaker 104C operates as a center speaker, and speaker 104R operates as a right speaker. The functions and structures of speakers 104L and 104R are interchangeable. Speaker 104C is the main sound source. Speakers 104L and 104R, which are arranged symmetrically with respect to speaker 104C, are additional sound sources. Figure 2 In the structure, the intervals between the speakers 104L, 104C, and 104R are fixed. Here, the speakers 104L, 104C, and 104R do not necessarily need to be integrally formed. On the other hand, in order to perform sound power reduction control and sound enhancement control, it is best to arrange the speakers 104L, 104C, and 104R close to each other to a certain extent. In addition, Figure 2 The illustrated housing also houses a sound signal input unit 101, a sound signal processing device 102, and a control device 103. The spacing d between speakers 104L, 104C, and 104R is determined based on the frequency band in which the sound pressure gradient is generated by the sound enhancement control and the acoustic power reduction control. For example, the spacing d is 0.05 m to 2 m.

[0040] Next, the control device 103 will be described. Figure 3 103 is a block diagram showing elements included in the control device 103. The control device 103 includes 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.

[0041] The acquisition unit 1031 acquires various information necessary for calculating the acoustic filter coefficient and inputs the acquired information to the acoustic filter coefficient calculation unit 1032. The information acquired by the acquisition unit 1031 includes, for example, frequency, speaker spacing, and transfer function information.

[0042] Frequency refers to the frequency of the sound signal input from the sound signal input unit 101. The acquisition unit 1031 acquires frequency information from the sound signal input unit 101, for example. Furthermore, if the speed of sound c is known, the frequency can be converted into wave numbers. The acquisition unit 1031 can also acquire wave number information from the sound signal input unit 101. Furthermore, if the frequency of the sound signal is a fixed value, the acquisition unit 1031 can input pre-stored fixed frequency information to the acoustic filter coefficient calculation unit 1032.

[0043] Speaker spacing refers to the spacing between multiple speakers. Acquisition unit 1031 acquires the speaker spacing based on, for example, user input. The speaker spacings can be equal or different. Furthermore, if the speakers are fixed, the speaker spacing can be set to a fixed value. In this case, acquisition unit 1031 can input pre-stored fixed speaker spacing information to acoustic filter coefficient calculation unit 1032.

[0044] The transfer function is a function that represents the sound transfer characteristics between each of the speakers 104L, 104C, and 104R and the sound reinforcement control point. It is determined by the positional relationship between the speakers 104L, 104C, and 104R and the sound reinforcement control point. The sound reinforcement control point is the control target position of the sound reinforcement control. The transfer function is used to calculate the spatial transfer characteristics C of the sound transmitted from the speaker 104L to the sound reinforcement control point. L , the spatial transfer characteristic C of the sound transmitted from the speaker 104C to the sound reinforcement control point C , the spatial transfer characteristic C of the sound transmitted from the speaker 104R to the sound reinforcement control point R Matrix representation of the elements. In an anechoic room or an audio-visual room with little sound reflection, sounds based on random signals or TSP (Time Stretched Pulse) signals are radiated from the speakers 104L, 104C, and 104R. The sounds are collected by microphones located at the sound reinforcement control points. Based on the microphone acquisition signals obtained by the collected sounds, the transfer characteristics of each space can be measured. The acquisition unit 1031 acquires the transfer function measured in this way. In addition, when the positions of the speakers 104L, 104C, and 104R and the positions of the sound reinforcement control points are fixed, the transfer function can be processed as a fixed transfer function. In this case, the acquisition unit 1031 can input the pre-stored fixed transfer function to the acoustic filter coefficient calculation unit 1032.

[0045] The acoustic filter coefficient calculation unit 1032 receives various information from the acquisition unit 1031 and the acoustic filter coefficient for at least one speaker from the acoustic filter coefficient storage unit 1033, and calculates the 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.

[0046] The acoustic filter coefficient storage unit 1033 stores the acoustic filter coefficient q for the speaker 104C. C .

[0047] The acoustic filter setting unit 1034 sets the acoustic filter coefficient q for the acoustic filter 1022L. L , set the acoustic filter coefficient q for the acoustic filter 1021C C , set the acoustic filter coefficient q for the acoustic filter 1022R R .

[0048] The following describes the acoustic filter coefficients used in the embodiment. The acoustic filter coefficients are calculated based on the first and second equations obtained from the sound increase control rule and the acoustic power control rule, respectively. The first equation obtained from the sound increase control rule when there are M sound increase control points and N sound sources is expressed by the following equation (1), and the second equation obtained from the sound power control rule is expressed by the following equation (2). Here, one of the N sound sources is the main sound source, and the remaining are additional sound sources.

[0049]

[0050] q in formula (1) S1 The complex volume velocity of the sound radiated from the first additional sound source among the N sound sources, i.e., the acoustic filter coefficient. The first additional sound source is, for example, the speaker 104L. S1j is the transfer function between the jth sound enhancement control point and the first sound source. S(N-1)j is the transfer function between the jth sound enhancement control point and the (N-1)th sound source. n in formula (1) is the multiplication rate of the sound pressure energy under the sound enhancement control. q in formula (2) C The complex volume velocity of the sound radiated from the main sound source, i.e., the acoustic filter coefficient. C is stored in advance in the acoustic filter coefficient storage unit 1033. In addition, q in equation (2) si α is the complex volume velocity of the sound radiated from the i-th additional sound source among the (N-1) additional sound sources, that is, the acoustic filter coefficient. siis a complex function determined by equation (1). * indicates the case of complex conjugation. The acoustic filter coefficient that satisfies both equations (1) and (2) is a combination of the sound enhancement control rule and the acoustic power control rule. As described later, in the embodiment, the conditions of equation (2) are determined to be a combination that reduces the acoustic power without achieving the minimum. Equation (2) with this condition added is the second relational equation based on the acoustic power reduction control rule.

[0051] The conditions of formula (2) are described below. Figure 4 This is a conceptual diagram for explaining the acoustic power control rule of the condition of equation (2). Figure 4 , the sound power control rule using three speakers 104L, 104C, and 104R arranged in a horizontal arrangement is shown. For simplicity of explanation, the intervals between speakers 104L and 104C, and the intervals between speakers 104C and 104R are assumed to be equal.

[0052] exist Figure 4 In the example, the acoustic power W when the speakers 104L, 104C, and 104R are regarded as one speaker is expressed by the following equation (3).

[0053]

[0054] Here, q in formula (3) C is the complex volume velocity of the sound radiated from the speaker 104C which is the main sound source. R is the complex volume velocity of the sound radiated from the speaker 104R. L is the complex volume velocity of the sound emitted from speaker 104L. c is the speed of sound. ω is the angular vibration number, and ρ is the density of the medium, such as air. k is the wave number. * indicates the complex conjugate. As described above, the complex volume velocity can be correlated with the acoustic filter coefficient.

[0055] Here, in formula (3), let q L =α·q C ,q R =β·q C α, β are the same as α in formula (2) si The corresponding complex function. At this time, Equation (3) is as shown in Equation (4).

[0056]

[0057] As shown in Equation (4), the acoustic power W is a function of the product of the wave number and the speaker spacing, kd. Therefore, the amount of reduction in acoustic power W is determined by the value of kd. When the value of kd, i.e., the frequency of the sound emitted from the speaker and the speaker spacing, are appropriately determined, the values ​​of sinc(kd) and sinc(2kd) in Equation (4) can both be approximated to 1. In this case, Equation (4) is approximated as shown in Equation (5). To minimize the acoustic power W in Equation (5), either the first or second term within the brackets of Equation (5) can be zero.

[0058]

[0059] As mentioned above, α and β are both complex functions. Therefore, when α = α r +jα i ,β=β r +jβ i When the real part and the imaginary part are separated and the brackets of formula (5) are arranged, the brackets of formula (5) are as shown in formula (6).

[0060] {(α r +β r )+1} 2 +(α i +β i ) 2 (6)

[0061] According to equation (6), the approximate solution to minimize the acoustic power W satisfies α r +β r =-1, and α i +β i = 0. Here, if Figure 4 As shown in the figure, when the speakers 104L and 104R as two additional sound sources are arranged symmetrically with respect to the speaker 104C as the main sound source, and the front point is set as the sound reinforcement control point, q L =q R , that is, α=β(α r =β r , and, α i =β i ) holds true. At this time, from formula (6), we can see that if we set α i =β i =0, and α r =β r =-1 / 2, then W is minimized. Finally, according to equations (1) and (2), the acoustic filter coefficient q L ,q C ,q R can be determined as q L =-1 / 2,q C =1,q R=-1 / 2. Figure 4 The acoustic filter coefficients q applied to each speaker are shown in L ,q C ,q R When sound is emitted from the speakers 104L, 104C, and 104R using such acoustic filter coefficients, a sound pressure gradient is generated around the speakers 104L, 104C, and 104R, and the sound can be made to reach only the vicinity of the sound-increasing control point.

[0062] Here, the speakers 104L and 104R are located symmetrically with respect to the speaker 104C. Therefore, when the acoustic filter coefficient is set to q L =-1 / 2,q C =1,q R = -1 / 2 and sound is emitted from speakers 104L, 104C, and 104R, Figure 5 The area A to the right of speaker 104R shown in the figure becomes a sound-boosting section where the sound pressure increases. Although not shown, the same applies to the area to the left of speaker 104L. Meanwhile, in front of speaker 104C, the sound from speaker 104L and the sound from speaker 104R, which are sounds with opposite phases, interfere with each other, creating a sound pressure node n. Consequently, the sound-boosting effect in the area in front of speaker 104C is reduced.

[0063] Thus, when the sound from speaker 104L and the sound from speaker 104R are in anti-phase at the front of speaker C, acoustic power W is minimized, but the sound reinforcement effect in front of speaker 104C is also reduced. If speakers 104L, 104C, and 104R are arranged vertically in the depth direction, such that area A to the right of speaker 104R is the front, sufficient sound reinforcement effect in the front direction can be expected. However, arranging speakers 104L, 104C, and 104R vertically means an increase in the depth dimension. Depending on the application of the sound control device, arranging the speakers in the depth direction may be difficult.

[0064] The sound pressure node forms in front of speaker 104C because the sound radiated from speakers 104L and 104R, which serve as additional sound sources and are positioned symmetrically with respect to speaker 104C, the main sound source, is in anti-phase with respect to speaker 104C. Therefore, if the sound radiated from speakers 104L and 104R, which are positioned symmetrically with respect to speaker 104C, is not in anti-phase with respect to speaker 104C, the sound power W will not be minimized, but the sound in the direction in front of speaker 104C will be amplified.

[0065] Therefore, in the embodiment, in formula (6), α is not set i =β i =0 and set it to α i =-β i , and set it as α r +β r =X(X≠-1). For example, when X is set to 1, α=α r +jα i ,β=β r +jβ i , so the following condition of formula (7) is obtained.

[0066] α+β=1 (7)

[0067] According to equations (2) and (7), the acoustic filter coefficient q L ,q C ,q R can be determined as q L =α,q C =1,q R =(1-α). Based on this formula and formula (1), the final acoustic filter coefficient q is determined L ,q C ,q R .exist Figure 6 The acoustic filter coefficients q applied to each speaker are shown in L ,q C ,q R Here, the value of X can be any value other than -1. From the perspective of reducing acoustic power W, the value of X is close to -1. However, the closer the value of X is to -1, the less the sound reinforcement effect in the direction of the speaker's front is. Therefore, the value of X is best determined by considering both the effect of reducing acoustic power W and the sound reinforcement effect in the direction of the speaker's front. Furthermore, in the applicant's experiments, it was confirmed that when X was set to 0, 1, and 2, both the effect of reducing acoustic power W and the sound reinforcement effect in the direction of the speaker's front were achieved.

[0068] For example, in q L =1,q C =1,q R = -1, the sound pressure node n is as follows Figure 6 As shown in FIG. 1 , the speaker 104R is biased toward one side. Therefore, the reduction in the sound reinforcement effect is suppressed with respect to the front of the speaker 104C. Figure 7 As shown, the area A in front of the speaker 104C can become a sound-increasing section.

[0069] The acoustic filter coefficients calculated above are for an example where the sound source consists of a main sound source and two additional sound sources arranged symmetrically with respect to the main sound source. Generally speaking, when the sound source consists of N additional sound sources, the acoustic filter coefficients can be determined so as to satisfy the conditions shown in the following equation (8). Specifically, the sum of the complex volume velocities of the main sound source and the complex volume velocities of the additional sound sources must not be zero. In this case, the sounds radiated from at least two of the additional sound sources are in opposite phases.

[0070]

[0071] Figure 8 as well as Figure 9 Shown respectively in Figure 4 In the example, let α i =-β i =-1 and set to α r +β r =1 and the acoustic filter coefficient q obtained according to formula (1) L ,q C ,q R The gain characteristic and phase characteristic of the sound signal are calculated by performing an inverse Fourier transform on the product of the gain characteristic and the phase characteristic to convolve the sound signal into an FIR (finite impulse response) filter.

[0072] like Figure 8 As shown, the acoustic filter coefficient q C The convolved sound signal and the acoustic filter coefficient q L The gain of the convolved sound signal is roughly the same in the range of 500Hz-3000Hz. Figure 9 As shown, the acoustic filter coefficient q C The convolved sound signal and the acoustic filter coefficient q L The phase of the convolved sound signal is also roughly the same in the range of 500Hz-3000Hz. On the other hand, the acoustic filter coefficient q in the range of 500Hz-3000Hz is R The gain of the convolved sound signal is greater than the acoustic filter coefficient q C Convolved sound signal and acoustic filter q L The gain of the convolved sound signal is reduced. In addition, the acoustic filter coefficient q R The sign of the phase of the convolved sound signal relative to the acoustic filter coefficient q L The sign of the phase of the convolved sound signal is reversed. On the other hand, the acoustic filter coefficient q R The convolved sound signal and the acoustic filter coefficient q L The convolved sound signals are not in an anti-phase relationship.

[0073] Figure 10 Shows radiation Figure 8 as well as Figure 9 The sound pressure level around the speaker when the sound is convoluted by the acoustic filter with the characteristics of the speaker. Figure 10 The example shows that the distance between the speakers is 0.1m and the frequency of the sound emitted is 1500Hz. Figure 10 The x-axis and y-axis of are, for example, distances from the origin when the position of the speaker 104C is set as the origin. Figure 10 The vertical axis is the sound pressure level. That is, Figure 10 The distribution of the sound pressure level in the area in the front direction of the loudspeaker 104C is shown.

[0074] Figure 10 This is a diagram showing calculation results regarding the relationship between the frequency and the sound pressure level during radiation. Figure 10 The horizontal axis is the frequency of the sound signal. Figure 10 The vertical axis is the sound pressure level. Figure 8 as well as Figure 9 As shown, the acoustic filter coefficient q L The convolved sound signal and the acoustic filter coefficient q R The convolved sound signal is not in phase opposition. Figure 10 As shown, no sound pressure node that causes a decrease in the sound pressure level is generated in the front direction of the speaker 104C. In addition, a sound pressure gradient is generated in the front left direction.

[0075] Hereinafter, the combined control of the sound-increasing control and the acoustic power reduction control in the case of three speakers will be further described. Figure 11 It is shown in Figure 12 as well as Figure 13 Graph of evaluation points in the calculation results described in . Figure 11 Points L, C, and R represent the positions of speakers 104L, 104C, and 104R, respectively. That is, speaker 104C is located at the origin. The distance between speakers 104L and 104C, and the distance between speakers 104C and 104R, is d. The sound-increasing control point P is located at (-dL, -R). Figure 12 as well as Figure 13 These are the results when d = 0.1 m, L = 0.2 m, R = 0.5 m, and U = 0.2 m.

[0076] Furthermore, based on equations (1), (2), and (8), the acoustic filter coefficients q for convolution of the sound signals input to speakers 104L, 104C, and 104R are calculated as shown in the following equation (9): L ,q C ,q RHere, n in equation (9) is the multiplication rate of the sound pressure energy at the sound reinforcement control point P. C is the transfer function between the sound reinforcement control point P and the loudspeaker 104C. L is the transfer function between the sound reinforcement control point P and the loudspeaker 104L. R is the transfer function between the sound reinforcement control point P and the loudspeaker 104R.

[0077] q c =1

[0078]

[0079] In this setting, the evaluation point A is set at (-d, -U) and the evaluation point B is set at (+d, -U). Figure 10 As shown, the evaluation point A is a point where a greater increase in sound is expected than the evaluation point B.

[0080] Figure 12 : is a graph showing the calculation results of the frequency characteristics of the sound pressure at the evaluation points A and B. Figure 12 As shown, up to a frequency of approximately 3000 Hz, which is the frequency of the sound signal, the sound pressure at evaluation point A is higher than that at evaluation point B. The difference between the sound pressure at evaluation point A and the sound pressure at evaluation point B is approximately 10dB-12dB. Thus, for sound signals up to 3000 Hz, evaluation points A and B ensure a sufficient sound pressure gradient, meaning that the sound becomes difficult to hear at evaluation point B and easy to hear at evaluation point A. On the other hand, above 3000 Hz, the difference between the sound pressure at evaluation point A and evaluation point B begins to disappear, and thereafter the sound pressure at evaluation point B becomes higher than that at evaluation point A. This is due to the influence of side lobes generated by the high frequency.

[0081] Figure 13 1 is a diagram showing the frequency characteristics of the sound pressure difference between evaluation points A and B before and after the combined control of the sound increase control and the acoustic power reduction control is performed. Figure 13 OFF:AB represents the calculation result of the frequency characteristic of the sound pressure difference between the evaluation points A and B before the implementation of the combined control. Before the implementation of the combined control, the sound is emitted only from the speaker 104C as the main sound source. On the other hand, Figure 13 ON:AB represents the frequency characteristics of the sound pressure difference between the evaluation points A and B after the combined control is implemented. After the combined control is implemented, the sound is emitted from the speaker 104C as the main sound source and from the speakers 104L and 104R as the additional sound sources. Figure 13As shown, before the combined control is implemented, there is no sound pressure difference between evaluation points A and B. In other words, the sound is equally audible at both evaluation points A and B. On the other hand, after the combined control is implemented, a sound pressure difference is generated between evaluation points A and B.

[0082] Figure 14 Graph 1 is a graph showing changes in sound pressure distribution when the frequency of the sound signal and the distance between the speakers are varied. Figure 14 As shown, if the frequency (i.e., the product of the wave number and the speaker spacing, kd) is the same, the sound pressure distribution is consistent. Furthermore, it can be seen that, at the same speaker spacing, the lower the frequency, the narrower the speaker spacing, and the more sidelobes are suppressed. Based on this relationship between frequency and speaker spacing, the control effect of the designed acoustic filter coefficient can be inferred. For example, if the frequency of the sound signal being played is known, the appropriate speaker spacing can be determined accordingly. Conversely, if the speaker spacing is fixed, the applicable frequency band that produces a sufficient sound pressure gradient can be determined accordingly.

[0083] Figure 15 The experimental results under noise in the 400Hz-1250Hz band are shown as the applied frequency band. As mentioned above, the applied frequency band is a frequency band of the sound signal that is expected to obtain a sufficient sound pressure gradient, which is determined by the speaker spacing. Figure 15 In the example, the speaker spacing d is 0.1m. Figure 16 The experimental results under noise up to 20000 Hz including frequencies outside the application frequency band are shown. Figure 17 As shown, the experiment was conducted by arranging three speakers 104L, 104C, and 104R in a horizontal arrangement and measuring the sound pressure at evaluation points A, B, C, D, and E in the front direction of the speaker 104C. Evaluation point B is a position separated by an interval R in the front direction of the speaker 104L. Evaluation point C is a position separated by an interval R in the front direction of the speaker 104C. Evaluation point D is a position separated by an interval R in the front direction of the speaker 104R. Evaluation point A is a position separated by an interval L to the left from evaluation point B. Evaluation point E is a position separated by an interval L to the right from evaluation point D. L is 0.2m. In addition, the interval R in the front direction up to evaluation points A, B, C, D, and E is 0.25m. In addition, Figure 15 as well as Figure 16 The horizontal axis is the center frequency of the 1 / 3 octave band. Figure 15 as well as Figure 16 The vertical axis is the 1 / 3 octave band level.

[0084] like Figure 15As shown, when the acoustic filter coefficient obtained according to formula (8) is used, a sound pressure gradient of about 12 dB is achieved at any of the evaluation points AE in the front direction of the speaker 104C in the application frequency band of 400 Hz to 1250 Hz. Figure 16 As shown, when the acoustic filter coefficients obtained according to equation (8) are used, a sound pressure gradient of approximately 12 dB is achieved at all evaluation points AE in frequency bands higher than the application frequency band. This is because the acoustic filter coefficients are designed to prevent a sound pressure node from occurring in the direction in front of the speaker.

[0085] Figure 18 The result of sound reinforcement in the left direction using a noise source in the 400Hz-1250Hz band as the applied frequency band is shown. Figure 18 The speaker spacing d is 0.1m when the result is obtained. That is, when the position of speaker 104C is set as the origin, speaker 104L is at (-0.1, 0) and speaker 104R is at (0.1, 0). In addition, the sound reinforcement control point is at (-0.3, -1). The spacing R up to the evaluation point is 0.25m from the position of the speaker. Figure 18 In the example, the sound pressure drops sharply when the evaluation point changes from the front of speaker 104L to the front of speaker 104R, that is, when the evaluation point changes from (-0.1, 0.25) to (0.1, 0.25). Thus, in the embodiment, a sharp sound pressure gradient can be formed by changing the distance over a short interval of 0.2 m.

[0086] Figure 19 This is a conceptual diagram of the case where the sound control device according to the embodiment is used in a sound guidance system. Figure 19 , the distribution of sound pressure in the vicinity of a user who is listening to the voice guidance of the voice guidance system is schematically shown. Figure 19 The sound pressure distribution G1 is the distribution of the sound pressure generated by the sound emitted from the sound control device, and the sound pressure distribution G2 is the distribution of the sound pressure outside the control target of the sound control device, that is, under natural attenuation.

[0087] By radiating sound according to the acoustic filter coefficients described in the embodiment, Figure 19 As shown in FIG. 1 , the speakers 104L, 104C, and 104R can be arranged in a horizontal arrangement while the front direction of the speaker 104C is set as the sound-increasing section A. Figure 19As shown in the sound pressure distribution G1, the sound pressure is high in the sound-augmented section A, while the sound pressure drops sharply outside the sound-augmented section A. Furthermore, as shown in the sound pressure distribution G2, the sound pressure also drops due to natural attenuation corresponding to the distance from the sound control device. Therefore, user u1 in the sound-augmented section A can hear the guidance sound emitted from the sound control device. On the other hand, user u2 outside the sound-augmented section A has difficulty hearing the guidance sound emitted from the sound control device. In particular, dark noise is indispensable in public spaces. Therefore, in the section where user u2 is located, the sound pressure of the guidance sound emitted from the sound control device drops sharply, and the sound is further drowned out by the dark noise. Therefore, in public spaces, it can be expected that user u2 will have even greater difficulty hearing the guidance sound. Therefore, the technology of the embodiment is also suitable when using sound guidance in public spaces.

[0088] Furthermore, by utilizing the characteristic of the rapid attenuation of sound pressure within a relatively narrow range described in the embodiment, the technology of the embodiment can also be applied to a sound control system having a plurality of sound control devices arranged in a straight line. Figure 20 : is a conceptual diagram of a voice guidance system as an application example of the sound control system involved in the embodiment. Figure 20 In the embodiment, a first sound control device composed of speakers 104L1, 104C1, and 104R1 arranged in a horizontal arrangement and a second sound control device composed of speakers 104L2, 104C2, and 104R2 arranged in a horizontal arrangement are arranged in a straight line. Figure 20 , the distribution of sound pressure in the vicinity of the user who is listening to the voice guidance of the voice guidance system is also schematically shown. Figure 20 The sound pressure distribution G1 is the distribution of the sound pressure generated by the sound emitted from the first sound control device, and the sound pressure distribution G2 is the distribution of the sound pressure outside the control target of the first sound control device, that is, under natural attenuation. Figure 20 The sound pressure distribution G3 is the distribution of the sound pressure generated by the sound radiated from the second sound control device, and the sound pressure distribution G4 is the distribution of the sound pressure outside the control target of the second sound control device, that is, under natural attenuation.

[0089] In this configuration, the first sound control device on the left side sets a sound increase control point on the front left side of speaker 104C1, thereby defining a sound increase section A1 on the front left side of speaker 104C1. Meanwhile, the second sound control device on the right side sets a sound increase control point on the front right side of speaker 104C2, thereby defining a sound increase section A2 on the front right side of speaker 104C2.

[0090] Therefore, if Figure 20As shown in the sound pressure distribution G1, the sound pressure is high in the sound-augmented section A1, while the sound pressure drops sharply outside the sound-augmented section A1. Furthermore, as shown in the sound pressure distribution G2, the sound pressure also drops due to natural attenuation corresponding to the distance from the first sound control device. Therefore, the user u1 in the sound-augmented section A1 can hear the guidance sound emitted from the first sound control device. On the other hand, the user u2 outside the sound-augmented section A1 has difficulty hearing the guidance sound emitted from the first sound control device. In addition, as shown in the Figure 20 As shown in sound pressure distribution G3, the sound pressure is high within the sound-amplified section A2, while the sound pressure drops sharply outside of the sound-amplified section A2. Furthermore, as shown in sound pressure distribution G4, the sound pressure also drops due to natural attenuation corresponding to the distance from the second sound control device. Therefore, user u2 within the sound-amplified section A2 can hear the guidance sound emitted from the second sound control device. Meanwhile, user u1 outside of the sound-amplified section A1 has difficulty hearing the guidance sound emitted from the second sound control device.

[0091] In this way, even in a sound guidance system where multiple sound control devices are arranged in a straight line, the user can be prevented from hearing the sound from a sound control device adjacent to the sound control device from which the guidance is actually being heard. This can also protect the user's privacy. In the past, the mainstream method was to use ultrasonic speakers to produce such directional sounds. However, sometimes, because ultrasonic speakers have too good a straight-line performance, the sound is reflected from the wall or ground behind them, causing the sound to be heard secondary. According to the technology of the embodiment, there is no need to use ultrasonic speakers, so such secondary sounds will not be heard.

[0092] Here, in Figure 20 In the embodiment, the first sound control device and the second sound control device set the sound enhancement control points in different directions. Figure 20 The natural attenuation of sound pressure corresponding to the distance from the sound control device shown in the sound pressure distribution G2 and G4 is shown. Therefore, if there is a certain degree of spacing between the first sound control device and the second sound control device, the sound amplification control points of the first sound control device and the second sound control device do not necessarily need to be set in different directions.

[0093] Figure 21 as well as Figure 22 This is a conceptual diagram when the sound control system according to the embodiment is used in a digital signage system. Figure 21 as well as Figure 22 This is a diagram of the digital signage system viewed from above. Figure 21In the digital signage system, the first sound control device composed of the speakers 104L1, 104C1, and 104R1 arranged in a horizontal arrangement is arranged facing the front, and the second sound control device composed of the speakers 104L2, 104C2, and 104R2 arranged in a horizontal arrangement is arranged facing the rear. Figure 22 In the digital signage system, the first sound control device composed of the speakers 104L1, 104C1, and 104R1 arranged horizontally is arranged to face the front, the second sound control device composed of the speakers 104L2, 104C2, and 104R2 arranged horizontally is arranged to face the rear, the third sound control device composed of the speakers 104L3, 104C3, and 104R3 arranged horizontally is arranged to face the right, and the fourth sound control device composed of the speakers 104L4, 104C4, and 104R4 arranged horizontally is arranged to face the left.

[0094] Even in the Figure 21 as well as Figure 22 When sound control devices are deployed as shown, similar to the sound guidance system, the sound pressure is high only within the sound-amplified section of each sound control device, while the sound pressure drops sharply outside of the sound-amplified section. Therefore, users within each sound-amplified section hear only the sound radiated from the corresponding sound control device.

[0095] As described above, according to the embodiments, the acoustic filter coefficients are designed to reduce the acoustic power when treating multiple sound sources as a single source while not minimizing the acoustic power. By implementing this acoustic control, which combines acoustic power reduction control with sound amplification control, the position of the sound pressure node is offset from the frontal direction of the main sound source. This allows the sound sources to be arranged horizontally while simultaneously amplifying the sound in the direction in front of the main sound source.

[0096] (Variation)

[0097] In the above embodiment, the combination control of the sound enhancement control and the sound power reduction control using three sound sources arranged in a horizontal arrangement is mainly described. As shown in equations (2) and (8), the technology of the embodiment can be applied even if the number of sound sources is four or more. Here, one of the sound sources is the main sound source, and the remaining sound sources are additional sound sources. Furthermore, as Figure 23 As shown, even if the main sound source C and the additional sound sources S1, ..., S i The technology of the implementation method can also be applied if the various sound sources are arranged horizontally.

[0098] For example, Figure 23 The additional sound source S when the sound enhancement control point P is 1 i The acoustic filter coefficient q siThe first and second equations of the equations are expressed as equations (10) and (11) according to the sound reinforcement control rule and the sound power control rule. On this basis, α in equation (11) si The conditions of formula (12) need to be satisfied.

[0099]

[0100] q in formula (10) S1 is the complex volume velocity of the sound radiated from the first additional sound source, i.e., the acoustic filter coefficient. S1 It is the transfer function between the sound enhancement control point P and the first sound source. S(N-1) It is the transfer function between the sound reinforcement control point P and the (N-1)th sound source. C It is the transfer function between the main sound source C and the sound enhancement control point P. si is the additional sound source S i The transfer function between the control point P and the sound reinforcement point is shown in Figure 1. * indicates the case of complex conjugate. In addition, α in formula (11) si is a complex function determined by formula (10).

[0101] Furthermore, in the embodiments, the sound-increasing control point P can be set at any position in the direction directly in front of the sound source. On the other hand, as described above, the longer the distance between the sound sources, the more likely the sound pressure at locations farther from the sound source will decrease due to the influence of side lobes. Furthermore, the farther away from the sound source, the greater the drop in sound pressure due to natural attenuation. Therefore, to achieve a sufficient sound pressure gradient at the sound-increasing control point P, it is best to set the sound-increasing control point P within a certain range from the sound source. Figure 24 : is a diagram showing the positional relationship between the sound source and the sound reinforcement control point P that can obtain a sufficient sound pressure gradient. Figure 24 In FIG, a main sound source C and two additional sound sources S arranged symmetrically with respect to the main sound source C are shown. The distance between the main sound source C and the additional sound source S is d. The applicant's experiments have confirmed that: if Figure 24 In the arrangement shown, the sound reinforcement control points P are arranged within the range of -3d≦x≦3d with respect to the x direction that coincides with the direction of the straight line on which the sound sources are arranged. A sufficient sound pressure gradient is obtained at the sound reinforcement control points P.

[0102] Next, use Figure 25 An example of the hardware configuration of the sound control device 100 described in each of the above embodiments will be described. Figure 25 1 is a diagram showing an example of the hardware configuration of the sound control device 100 .

[0103] like Figure 25As shown, the sound control device includes a computer to which a control unit 209, a storage 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.

[0104] The control unit 209 includes a CPU (Central Processing Unit), RAM (Random Access Memory), and / or ROM (Read Only Memory), and controls each component in accordance with information processing. The control unit 209 can function as the sound signal input unit 101, the sound signal processing device 102, and the control device 103. The control unit 209 can call an execution program stored in the storage unit 210 to execute processing.

[0105] The storage unit 210 is a medium that stores information such as programs in a manner readable by computers and machines. Furthermore, the storage unit 210 can store information about the distance between speakers, the frequency of sound signals, and transfer functions. For example, the storage unit 210 can be an auxiliary storage device such as a hard disk drive or a solid-state drive. Furthermore, the storage unit 210 can also include a drive. A drive is a device for reading data stored in other auxiliary storage devices and recording media, and includes, for example, semiconductor memory drives (flash memory drives), CD (Compact Disk) drives, and DVD (Digital Versatile Disk) drives. The type of drive can be appropriately selected depending on the type of storage medium.

[0106] The power supply unit 211 supplies power to each component of the sound control device 100. Furthermore, the power supply unit 211 may also supply power to each component of a device including the sound control device 100. The power supply unit 211 may include, for example, a secondary battery or an AC power supply.

[0107] The timer 212 is a device for measuring time. For example, the timer 212 may be a clock including a calendar, and may send information about the current year, month, and / or date and time to the control unit 209. The timer 212 may also be used to add the date and time to the played audio signal.

[0108] The communication interface 205 is, for example, a short-range wireless communication (e.g., a Bluetooth (registered trademark)) module, a wired LAN (Local Area Network) module, a wireless LAN module, etc., and is an interface for wired or wireless communication via a network. Communication via the network can be either wireless or wired. In addition, the network can be an interconnected network including the Internet, or other types of networks such as a LAN within a company. Furthermore, the communication interface 205 can also perform one-to-one communication using a USB (Universal Serial Bus) cable, etc. Furthermore, the communication interface 205 can also include a micro USB connector. The communication interface 205 is an interface for connecting the sound control device to external devices such as cars, trains, household electrical appliances, and various communication devices. The communication interface 205 is controlled by the control unit 209 and receives various information from external devices via the network, etc. The various information includes, for example, information set in the external device, information on the distance between speakers, information on the frequency of the sound signal, and information on the transfer function.

[0109] The input unit 206 is a device that receives input, and may be, for example, a touch panel, physical buttons, a mouse, or a keyboard. The output device 207 is a device that outputs information, such as a display or speaker, by displaying or sounding. Information about the distance between speakers, the frequency of audio signals, and transfer function information may also be input via the input unit 206.

[0110] The external interface 208 is a component that serves as a medium between the main body of the sound control device and an external device. Examples of the external device include a printer, a memory, and a communication device.

[0111] While several embodiments of the present invention have been described above, these embodiments are merely illustrative and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their variations are intended to be within the scope and spirit of the invention, and are also intended to be within the scope of the invention described in the claims and their equivalents.

Claims

1. A sound control device comprising a sound filter coefficient calculation unit, wherein the sound filter coefficient calculation unit: A first relational expression is calculated between acoustic filter coefficients based on a multiplication rate of sound pressure at a sound-increasing control point where sound is increased by sound reproduced from a main sound source and two or more additional sound sources, a transfer function between the main sound source and the sound-increasing control point, and a transfer function between each of the additional sound sources and the sound-increasing control point. The acoustic filter coefficients are applied to a sound signal including information about the reproduced sound and are determined to be equal to the volume velocity of the sound reproduced from the main sound source and each of the additional sound sources. calculating a second relational expression between the acoustic filter coefficients of the main sound source and each of the additional sound sources, under the condition that the sum of the volume velocities of the sounds emitted from each of the additional sound sources and the sum of the volume velocities of the sounds emitted from the main sound source is not zero; The acoustic filter coefficients are calculated based on the first relational expression and the second relational expression.

2. The sound control device according to claim 1, wherein: The main sound source and each of the additional sound sources are arranged in a straight line. The sound-increasing control point is set within a range three times the distance between the main sound source and the additional sound source in a direction along the straight line.

3. The sound control device according to claim 1, wherein: The main sound source and each of the additional sound sources are arranged in a direction intersecting the front direction of the main sound source. The main sound source is located between at least two of the additional sound sources.

4. A sound control system, wherein: A plurality of the sound control devices according to any one of claims 1 to 3 are provided, and positions of the sound-increase control points of the respective sound control devices are different.

5. A sound control program product, configured to cause a computer to execute: calculating a first relational expression for acoustic filter coefficients based on a multiplication rate of sound pressure at a sound-increasing control point where sound is increased by sound reproduced from a main sound source and two or more additional sound sources, a transfer function between the main sound source and the sound-increasing control point, and a transfer function between each of the additional sound sources and the sound-increasing control point, the acoustic filter coefficients being applied to a sound signal including information about the reproduced sound and being determined to be equal to the volume velocity of the sound reproduced from the main sound source and each of the additional sound sources; calculating a second relational expression between the acoustic filter coefficients of the main sound source and each of the additional sound sources, conditioned on the sum of the volume velocities of the sounds broadcast from each of the additional sound sources and the sum of the volume velocities of the sounds broadcast from the main sound source being non-zero; and The acoustic filter coefficients are calculated based on the first relational expression and the second relational expression.

6. A sound control method comprising: calculating a first relational expression for acoustic filter coefficients based on a multiplication rate of sound pressure at a sound-increasing control point where sound is increased by sound reproduced from a main sound source and two or more additional sound sources, a transfer function between the main sound source and the sound-increasing control point, and a transfer function between each of the additional sound sources and the sound-increasing control point, the acoustic filter coefficients being applied to a sound signal including information about the reproduced sound and being determined to be equal to the volume velocity of the sound reproduced from the main sound source and each of the additional sound sources; calculating a second relational expression between the acoustic filter coefficients of the main sound source and each of the additional sound sources, conditioned on the sum of the volume velocities of the sounds broadcast from each of the additional sound sources and the sum of the volume velocities of the sounds broadcast from the main sound source being non-zero; and The acoustic filter coefficients are calculated based on the first relational expression and the second relational expression.

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