JP2004064739A - Sound image control system - Google Patents

Abstract

A sound image control system for realizing sound image localization control at the same time by two persons is provided.
The present invention is a sound image control system that controls a sound image localization position by reproducing an audio signal with a plurality of speakers. The sound image control system includes at least four speakers for reproducing an audio signal, and a signal processing unit. The signal processing unit sets four control points corresponding to the positions of both ears of the two listeners as control points, and the two target sound source positions indicating the sound image localization positions felt by the two listeners are determined by the respective listeners. Signal processing is performed for each audio signal input to each speaker so as to be in the same direction. Here, the two target sound source positions are such that the distance from the listener located on the target sound source side to the target sound source position for the listener is greater than the distance from the other listener to the target sound source position for the other listener. Set to be shorter.
[Selection] Fig. 6

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sound image control system, and more particularly, to a sound image control system that controls a sound image localization position by reproducing an audio signal with a plurality of speakers.
[0002]
[Prior art]
2. Description of the Related Art In recent years, multi-channel signal reproduction systems represented by DVDs have become widespread, but in many cases, five or six speakers cannot be installed due to housing conditions or the like. For this reason, a sound image control system using a so-called virtual reproduction method has been developed in which a surround signal is virtually reproduced by two speakers of Lch and Rch.
[0003]
In particular, in a sound image control system for use in car audio, the influence of reflection, reverberation, and standing waves is strong due to the narrow space in the car interior, and the installation position of the speaker is limited. In such a state, it has conventionally been quite difficult to localize the sound image freely. However, there is still a strong demand for localizing vocals and the like included in the music at the front center of the passenger. Therefore, in order to respond to this demand, a sound image control system described below is being developed (for example, see Patent Document 1).
[0004]
Hereinafter, a conventional sound image control system will be described with reference to the drawings. FIG. 47 is a diagram showing a configuration of a conventional sound image control system. In FIG. 47, the sound image control system is installed in an automobile 601, and includes a sound source 61, a signal processing unit 62, an FR speaker 621 installed in a right front door of the automobile 601, and a left front door of the automobile 601. And an FL speaker 622 installed in the device. The signal processing section 62 includes control filters 63 and 64.
[0005]
The operation of the sound image control system shown in FIG. 47 will be described below. The signal from the sound source 61 is signal-processed by the signal processing unit 62 and is reproduced by the FR speaker 621 and the FL speaker 622. The control filter 63 controls an Rch signal from the sound source 61, and the control filter 64 controls an Lch signal from the sound source 61. Here, the signal processing unit 62 performs signal processing such that the FR speaker 621 is localized at the target sound source 631 and the FL speaker 622 is localized at the target sound source 632. Specifically, the control filters 63 and 64 of the signal processing unit 62 are controlled as follows. That is, using the center position of listener a as a control point (marked by x in FIG. 47) as a control point, the transfer characteristic from FR speaker 621 is FR, the transfer characteristic from FL speaker 622 is FL, and the transfer characteristic from target sound source 631 is G1. Assuming that the transfer characteristic from the target sound source 632 is G2, the characteristic HR of the control filter 63 and the characteristic HL of the control filter 64 in the signal processing unit 62 are as follows.
HR = G1 / FR
HL = G2 / FL
By realizing this characteristic, the FR speaker 621 is controlled to be reproduced at the position of the target sound source 631, and the FL speaker 622 is controlled to be reproduced at the position of the target sound source 632. As a result, a center component common to the Lch and Rch is localized between the virtually localized target sound sources 631 and 632. That is, the listener a feels a sound image on the target sound source 635 in front.
[0006]
[Patent Document 1]
JP-A-10-276500
[0007]
[Problems to be solved by the invention]
However, in the conventional system shown in FIG. 47, since the number of control points is one, the difference between the right ear and the left ear, which is a perception mechanism of sound image localization, cannot be controlled, and the sound image localization effect is small. there were. Many sound image control systems currently in general use only perform time correction of the FR speaker 621 and the FL speaker 622, and do not truly realize the virtual target sound sources 631 and 632.
[0008]
In a home sound image control system, sound image control using both ears as control points has been considered. However, in this case, the control points are two points, that is, the two ears of only one listener, and there is no sound image control system that simultaneously controls each ear of the two listeners. .
[0009]
Therefore, an object of the present invention is to provide a sound image control system that simultaneously performs sound image control on each of both ears of at least two listeners.
[0010]
Means for Solving the Problems and Effects of the Invention
In order to achieve the above object, the present invention has the following features. That is, the present invention is a sound image control system that controls a sound image localization position by reproducing an audio signal with a plurality of speakers. The sound image control system includes at least four speakers for reproducing an audio signal, and a signal processing unit. The signal processing unit sets four control points corresponding to the positions of both ears of the two listeners as control points, and the two target sound source positions indicating the sound image localization positions felt by the two listeners are determined by the respective listeners. Signal processing is performed for each audio signal input to each speaker so as to be in the same direction. Here, the two target sound source positions are such that the distance from the listener located on the target sound source side to the target sound source position for the listener is greater than the distance from the other listener to the target sound source position for the other listener. Set to be shorter.
[0011]
According to the above, since a feasible target sound source position can be set, it is possible to control four points corresponding to the positions of both ears of two listeners as control points. That is, a similar sound image localization feeling and sound quality can be given to two listeners.
[0012]
In the above description, the signal processing unit “performs signal processing so that the target sound source position is in the same direction with respect to each of the listeners” means “from the first target sound source to the first listener. The amplitude frequency characteristic in the transfer characteristic to the right ear and the amplitude frequency characteristic in the transfer characteristic from the second target sound source to the second listener right ear are the same, and the first listener from the first target sound source. The signal processing is performed so that the amplitude frequency characteristic in the transfer characteristic to the left ear and the amplitude frequency characteristic in the transfer characteristic from the second target sound source to the second listener's left ear are equal. " Here, the two listeners are referred to as a first and a second listener, respectively, a target sound source position for the first listener is set as a first target sound source position, and a target sound source position for the second listener is set. Is the second target sound source position.
[0013]
In the above description, “a listener located on the target sound source side” refers to a listener located on a side closer to the target sound source position to be set. For example, when two listeners are located side by side and the target sound source position is set to the right (rightward) as viewed from each listener, the “listeners located on the target sound source side” Means the listener located on the right side of the two listeners located side by side (listener a in the example of FIG. 6). Further, for example, when two listeners are located side by side and the target sound source position is set to the front side (forward direction) when viewed from each listener, the “listener located on the target sound source side” is , The listener located on the front side of the two listeners located side by side on the front side. When two listeners are positioned diagonally, similarly to the above-mentioned case (when two listeners are arranged side by side or front and back), the "listener located on the target sound source side" You can judge.
[0014]
In the above description, the direction from the listener to the target sound source position when the front of the listener is 0 ° is θ degrees, the distance between the centers of the listeners is X, the sound speed is P, and Assuming that the transmission time to the control point is T1, T2, T3, and T4 in the order of the control points that are closer to the target sound source position, the two target sound source positions are T1 <T2 ≦ T3 (= T2 + Xsin θ / P) < T4 may be set so as to satisfy a condition.
[0015]
In addition, the signal processing unit is configured to output an audio signal to the two target sound source positions with respect to the center position between the two listeners and the speakers installed in opposite directions in the front-rear direction and the left-right direction. The input may be stopped. The "speakers installed in the opposite directions with respect to the front and rear directions and the left and right directions with respect to the two target sound source positions with respect to the center position between the two listeners" specifically refer to the following speakers. . That is, when the target sound source is set on the right front side with respect to the center position (see FIG. 16), it refers to a speaker installed on the left rear side with respect to the center position. In addition, when the target sound source is set to the left rear side with respect to the center position (see FIG. 18), it refers to a speaker installed on the right front side with respect to the center position.
[0016]
According to the above, the number of speakers required in the sound image control system can be reduced. Further, since the number of signals to be subjected to signal processing is reduced, the amount of calculation in signal processing can be reduced.
[0017]
Further, when the two target sound source positions are set in front of the two listeners, the signal processing unit outputs an audio signal to a speaker installed behind each of the listeners. May be stopped. Also in this case, similarly to the above, the number of speakers required in the sound image control system can be reduced.
[0018]
Further, the signal processing unit may have a configuration including a frequency division unit, a low-band processing unit, and a high-band processing unit. Here, the frequency division unit frequency-divides the audio signal into a low-frequency component and a high-frequency component. The low-frequency processing unit performs signal processing on the low-frequency component signal of the audio signal for each signal input to each speaker, and then inputs the signal to each speaker. The high-frequency processing unit inputs the signal of the high-frequency component of the audio signal from the center position of the two target sound source positions to the most recent speaker so that the signal of the high-frequency component matches the signal input to each speaker by the low-frequency processing unit. .
[0019]
According to the above, signal processing is performed only on low-frequency components for which sound image localization control is effective, so that the amount of calculation in signal processing can be reduced.
[0020]
When the plurality of speakers include a tweeter disposed in front of the center position between two listeners, the following may be performed. That is, when the two target sound source positions are set in front of the two listeners, the high-frequency processing unit may input the high-frequency component of the audio signal to the tweeter.
[0021]
According to the above, a tweeter can be used as a CT speaker (see FIG. 1) disposed in front of the center position between two listeners. Thus, the size of the CT speaker can be reduced. This is particularly effective when a sound image control system is applied to an automobile.
[0022]
Further, the plurality of speakers may be installed in an automobile, and at least one of the plurality of speakers may be installed on a rear seat side. At this time, it is assumed that the two listeners are located in front seats in the car. Further, the signal processing unit is installed in the automobile. When signal processing is performed on audio signals of a plurality of channels, audio signals of all channels are input to a speaker installed on the rear seat side without performing signal processing.
[0023]
According to the above, when the sound image control system is installed in an automobile, good sound quality can be ensured for listeners located in both the front seat and the rear seat.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
(Embodiment 1)
FIG. 1 is a diagram showing a sound image control system according to Embodiment 1 of the present invention. In FIG. 1, 1 is a DVD player as a sound source, 2 is a signal processing unit, 20 is a CT speaker, 21 is an FR speaker, 22 is an FL speaker, 23 is an SR speaker, and 24 is an SL speaker. Reference numeral 31 denotes a target sound source of the listener a, and reference numeral 32 denotes a target sound source of the listener b.
[0025]
The DVD player 1 outputs, for example, 5-channel audio signals (CT signal, FR signal, FL signal, SR signal, and SL signal). The signal processing unit 2 performs signal processing described later on each signal output from the DVD player. The CT signal is signal-processed by the signal processing unit 2 and input to each of the five speakers. The signal processing unit 2 performs signal processing for each CT signal input to each speaker. Similarly to the CT signal, each of the above signals is input to each of the five speakers, and signal processing is performed for each signal input to each speaker.
[0026]
FIG. 1 shows the positional relationship among the listeners a and b, the speakers 20 to 24, and the target sound sources 31 and 32. As shown in FIG. 1, in the first embodiment, CT speaker 20 is installed in front of the center positions of two listeners a and b. FR speaker 21 and FL speaker 22 are installed on the front right and front left, respectively, from the center position. The FR speaker 21 and the FL speaker 22 are installed symmetrically. The SR speaker 23 and the SL speaker 24 are installed on the rear right side and the rear left side from the center position, respectively. Although five speakers are arranged in Embodiment 1 as described above, in other embodiments, five speakers may be arranged in other positions. Further, in other embodiments, six or more speakers may be arranged.
[0027]
FIG. 2 is a block diagram showing an internal configuration of the signal processing unit 2 shown in FIG. In FIG. 2, 100 to 109 are filters, and 200 to 209 are adders.
[0028]
Hereinafter, the operation of the sound image control system will be described with reference to FIGS. Here, four points (AR, AL, BR, and BL shown in FIG. 1) corresponding to the positions of both ears of the two listeners a and b are set as control points. Further, as an example, a case will be described where target sound sources 31 and 32 are set in order to further expand the sound image localization position of the sound of the FR signal from the position of FR speaker 21 to the right. The positions of the two target sound sources, that is, the positions of the target sound sources 31 and 32, are set to be in the same direction for the two listeners. The signal processing unit 2 processes the FR signal from the DVD player 1 and reproduces the signal from the CT speaker 20, the FR speaker 21, the FL speaker 22, the SR speaker 23, and the SL speaker 24. In this signal processing, if the transfer characteristics GaR and GaL from the target sound source 31 to the control points AR and AL and the transfer characteristics GbR and GbL from the target sound source 32 to the control points BR and BL are reproduced, the listeners a and b Sounds as if the sound of the FR signal is being reproduced at the positions of the target sound sources 31 and 32, respectively.
[0029]
More specifically, in the signal processing unit 2, the FR signal input from the DVD 1 is subjected to signal processing by the filters 105 to 109. The output signals of the filters 105 to 109 are reproduced by the CT speaker 20, the FR speaker 21, the FL speaker 22, the SR speaker 23, and the SL speaker 24. The transfer characteristics of the reproduced sound need only be equal to the transfer characteristics GaR, GaL, GbR, and GbL from the target sound sources 31, 32 at the binaural ears of the listeners a and b. The output signals of the filters 105 to 109 are added to the output signals of the other channels subjected to the signal processing by the adders 200 to 209.
[0030]
Although FIG. 2 shows only the configuration for processing the CT signal and the FR signal, the signal processing unit 2 performs filter signal processing on other signals in the same manner, and adds all the signals of each channel. Output.
[0031]
Here, the transfer characteristics from the FL speaker 22 to the control points AR, AL, BR, and BL are FLaR, FLaL, FLbR, and FLbL, respectively. Similarly, the transfer characteristics from the FR speaker 21 to the control points AR, AL, BR, and BL are FRaR, FRaL, FRbR, and FRbL, respectively, and the transfer characteristics from the SR speaker 23 to the control points AR, AL, BR, and BL. , The transfer characteristics from the SL speaker 24 to each of the control points AR, AL, BR, and BL are SLaR, SLaL, SLbR, and SLbL, respectively. The transfer characteristics to the control points AR, AL, BR, and BL are denoted by CTaR, CTaL, CTbR, and CTbL, respectively. In this case, in order to perform signal processing so that the transfer characteristics from the target sound source to each control point are GaR, GaL, GbR, and GbL, the following equations may be established.
GaR = H5.CTaR + H6.FRaR + H7.FLaR + H8.SRaR + H9.SLaR
GaL = H5 · CTaL + H6 · FRaL + H7 · FLaL + H8 · SRaL + H9 · SLaL
GbR = H5 · CTbR + H6 · FRbR + H7 · FLbR + H8 · SRbR + H9 · SLbR
GbL = H5 · CTbL + H6 · FRbL + H7 · FLbL + H8 · SRbL + H9 · SLbL
Here, H5 to H9 are filter coefficients of the filters 105 to 109 shown in FIG. In the above equation (hereinafter referred to as equation (a)), the number of unknowns (filter coefficients) is larger than the number of equations, but this is not because there is no solution (instead that the equation cannot be solved). , Indefinite (various solutions exist depending on conditions). In fact, the MINT method (for example, in the references “M. Miyoshi and Kaneda,“ Inverse filtering of room acoustics ”), IEEE Trans. Acoustic. It is described that control is performed by the number of control points + 1 speakers. In general, it is known that if there are at least as many speakers as the number of control points, a filter coefficient (that is, a solution) for controlling the speakers is obtained.
[0032]
As described above, the transfer characteristics from the CT speaker 20, the FR speaker 21, the FL speaker 22, the SR speaker 23, and the SL speaker 24 to each control point (each ear of the listeners a and b) are measured, and the target sound source is measured. By measuring the transfer characteristics from 31 and 32 to each control point, the filter coefficients H5 to H9 of the filters 105 to 109 can be calculated using the above equation.
[0033]
In the above description, the FR signal has been described as an example. However, the filter coefficients H0 to H4 of the filters 100 to 104 for performing signal processing on the CT signal can be obtained by the same method as described above. Further, a filter coefficient can be obtained for the FL signal, the SL signal, and the SR signal not shown in FIG. 2 by the same method. Thus, sound image localization control is performed on signals of all channels.
[0034]
By calculating each filter coefficient as described above, it is possible to control the sound image to be localized at the set target sound source position. However, depending on how to set the target sound source position, the solution of the above equation may not be calculated, and in this case, the set target sound source position cannot be realized. Therefore, an appropriate setting method of the target sound source position will be described below.
[0035]
FIG. 3 is a diagram showing a case where transfer characteristics from target sound sources 31 and 32 are given to listeners a and b with the same characteristics. That is, the target sound sources 31 and 32 are set to be in the same direction and at the same distance from the listeners a and b. FIG. 4 is a diagram showing a time characteristic and a frequency characteristic (amplitude) of the transfer characteristic in the case shown in FIG. FIGS. 4A and 4C show the transfer characteristics GR, and FIGS. 4B and 4D show the transfer characteristics GL. Here, T1 shown in FIGS. 3 and 4 indicates a propagation time from the target sound source 31 to the right ear of the listener a. Similarly, T2 indicates a propagation time from the target sound source 31 to the left ear of the listener a, T3 indicates a propagation time from the target sound source 32 to the right ear of the listener b, and T4 indicates a propagation time from the target sound source 32 to the listener b. Shows the propagation time to the left ear. ΔT indicates the difference between the propagation times at the right and left ears of the listener, that is, T2−T1.
[0036]
On the other hand, FIG. 5 is a diagram showing a case where the speaker 30 is actually installed near the positions of the target sound sources 31 and 32. In FIG. 5, gaR, gaL, gbR, and gbL indicate transmission characteristics from the speaker 30 to each of the listeners a and b. Since there is one playback speaker for a certain channel (in this case, FRch), it is as shown in FIG. T1 is the propagation time from the speaker 30 to the right ear of the listener a, T2 is the propagation time from the speaker 30 to the left ear of the listener a, and T3 is the propagation time from the speaker 30 to the right ear of the listener b. , T4 indicate the propagation times from the speaker 30 to the left ear of the listener b. In FIG. 5, the distance from the speaker 30 to the listener is greater for the listener b than for the listener a.
T1 <T2 <T3 <T4 (1)
There is a relationship. Also, if the left ear of the listener a and the right ear of the listener b are adjacent to each other,
T1 <T2 ≦ T3 <T4 (2)
It becomes. That is, the equation (2) indicates a temporal relationship that can be physically allowed (which may be the natural world).
[0037]
Here, considering the case of FIG. 3, setting the same transfer characteristic to the listener a and the listener b means that the listener a and the listener b are at the same position when viewed from the speaker 30. That is, physically impossible. More specifically, in the case of the target sound sources 31 and 32 shown in FIG. 3, T1 to T4 need to satisfy the relationship of Expression (1) or Expression (2). T3 (= T1) <T2 in the ear and the right ear of the listener b, which does not satisfy the equations (1) and (2). In order to realize a target sound source, the signal processing unit 2 performs signal processing on signals input to the five speakers 20 to 24, but the signal processing unit 2 uses causality (the above equation (1) or (2) 3), it is not possible to perform control going back in time as shown in FIG. As described above, when setting the respective target sound sources 31 and 32 for the two listeners a and b, it is necessary to set the target sound source positions in the same direction and equidistant for each listener. Can not. Therefore, it is important to set the target sound sources 31 and 32 that satisfy the causality law.
[0038]
FIG. 6 is a diagram illustrating a method of setting a target sound source according to the present invention. The transfer characteristics GaR and GaL from the target sound source 31 to both ears of the listener a are the same as the transfer characteristics GR and GL in FIG. That is, the time characteristics are shown in FIGS. On the other hand, the target sound source 32 for the listener “b” is set at a position apart from the target sound source 32 shown in FIG. That is, the target sound source 32 is set so that T3 = T1 + t and T4 = T2 + t. By setting in this manner, the time characteristic is a characteristic shifted from the time characteristic shown in FIGS. 4A and 4B by the time t (in the time axis direction). The amplitude frequency characteristics are the same as those in FIGS. 4C and 4D (that is, the direction of the target sound source is the same as in FIG. 3). Therefore, the direction from the listener b to the target sound source 32 can be set so as to satisfy the causality while being the same as in FIG. That is, by setting the target sound source 32 at a distance away from the position shown in FIG. 3 by the time t, Expression (1) or Expression (2) can be satisfied. Thereby, the signal processing unit 2 can control the FR signal, and can obtain a filter coefficient for realizing the target sound source.
[0039]
A method for determining t in more detail will be described below. FIG. 7 is a diagram showing a transmission path from each of the target sound sources 31 and 32 to the center position of the listeners a and b. Here, arrows indicated by dashed lines indicate equal time (distance). Therefore, the transmission path to the listener b takes a longer time (a longer distance) than the transmission path to the listener a by the portion indicated by the dotted arrow. That is, assuming that the direction of the target sound sources 31 and 32 is θ degrees with the front of the listener being 0 degrees and the distance between the listener a and the listener b is X, the transmission path for the listener b is The distance Y = Xsinθ is longer than the transmission path. Therefore, the causality is satisfied if the time for the sound of the FR signal to propagate through the distance Y is considered. That is, if the sound speed is P,
t = Xsin θ / P (3)
And it is sufficient.
[0040]
As described above, the target sound source can be realized by setting the position so as to satisfy the above equation (1) or (2). In addition, it is desirable that at least one of the actual speakers 20 to 24 is installed at a position that satisfies the relationship of the transmission time at each control point corresponding to the target sound source position. Explaining in the above example, the transmission times T1, T2, T3, and T4 corresponding to the target sound source positions at the control points AR, AL, BR, and BL have a relationship of T1 <T2 <T3 <T4. If there is a speaker installed at a position that satisfies this relationship, a target sound source can be easily realized. Specifically, in the first embodiment, FR speaker 21 exists at a position that satisfies the relationship of T1 <T2 <T3 <T4. Therefore, the target sound source can be easily realized by the sound image control system according to the first embodiment. The reason why the target sound source shown in FIG. 3 cannot be set can also be considered as follows. That is, there is no speaker position that satisfies the relationship of T1 = T3 <T2 = T4, as shown in FIG. 3, so that it is impossible to set the target sound source shown in FIG. it can.
[0041]
Note that the filter coefficient for realizing the target sound source set as described above may be calculated by a computer using the above equation (a), or by using an adaptive filter as shown in FIG. 8 described below. May be calculated.
[0042]
FIG. 8 is a diagram illustrating a method for calculating a filter coefficient using an adaptive filter in the first embodiment. 8, reference numerals 105 to 109 denote adaptive filters, 300 denotes a measurement signal generator, 151 denotes a target characteristic device in which a target characteristic GaR is set, 152 denotes a target characteristic device in which a target characteristic GaL is set, and 153 denotes a target characteristic GbR. The set target characteristic device, 154 is a target characteristic device in which the target characteristic GbL is set, 41 is a microphone installed at the right ear position of the listener a, 42 is a microphone installed at the left ear position of the listener a, Reference numeral 43 denotes a microphone provided at the position of the right ear of the listener b, reference numeral 44 denotes a microphone provided at the position of the left ear of the listener b, and reference numerals 181 to 184 denote subtracters.
[0043]
The measurement signal output from the measurement signal generator 300 is input to the target characteristic units 151 to 154, and is given the transfer characteristics of the target sound source shown in FIG. On the other hand, the measurement signal is input as a reference signal to adaptive filters 105 to 109 (the same reference numerals are assigned to correspond to FIG. 2), and outputs of adaptive filters 105 to 109 are reproduced by speakers 20 to 24, respectively. The reproduced sound is detected by the microphones 41 to 44 and input to the subtracters 181 to 184. The subtracters 181 to 184 subtract output signals of the target characteristic units 151 to 154 from output signals of the microphones 41 to 44, respectively. The residual signals output from the subtracters 181 to 184 are input to the adaptive filters 105 to 109 as error signals.
[0044]
In the adaptive filters 105 to 109, the MEFX method (for example, the reference document “S.J. Elliott, et al.,” “A multiple error LMS algorithm and application to the active control of the emission control. 35, No. 10, 1423-1434 (1987) ”), so that each error signal is minimized (close to 0). Accordingly, the target transfer characteristics GaR, GaL, GbR, and GbL are realized at the positions of both ears of the listeners a and b by sufficiently converging the coefficients H5 to H9 of the adaptive filters 105 to 109. . As described above, when the filter coefficient is obtained in the time domain, the coefficient cannot be obtained unless the causality described in FIG. 5 is satisfied. Therefore, the target sound source position must be set as described in FIG. 6 and FIG. No.
[0045]
As described above, in the present invention, the transmission characteristics from the speaker 30 to the listeners a and b take into account the original natural principle that sound waves arrive sequentially from the ones having shortest transmission paths (see FIG. 5). As shown in FIG. 6, target sound sources 31 and 32 satisfying causality are set. As a result, sound image localization control using the two ears of the two listeners a and b as control points becomes possible. Therefore, the listeners a and b feel that the target sound sources 31 and 32, which do not actually exist, actually exist at the place. That is, it is felt that the FR speaker 21 is further expanded rightward.
[0046]
In the above description, the FR signal has been described, but the FL signal is also set in the same manner as the target sound source, except that the direction is left. Therefore, by the same method as described above, sound image localization control using FL listeners as control points for both ears of two listeners a and b becomes possible.
[0047]
Next, a case where sound image localization control is performed on a CT signal will be described. FIG. 9 is a diagram illustrating a case where the CT signals are simultaneously localized in front of the listeners a and b. Here, an actual target characteristic is considered. FIG. 10 is a diagram illustrating a case where the speaker 30 is actually located in front of the listener a (or b). As is apparent from FIG. 10, the transfer characteristics gaR, gaL, gbR, and gbL are all approximately equal, and their transmission times T are approximately equal. Therefore, when setting the target sound source in front of the listener, it is not necessary to consider special causality. For example, by setting the transfer characteristics gaR, gaL, gbR, and gbL that are all (or almost equal) to the target characteristic units 151 to 154 in FIG. 8, a filter coefficient for realizing the transfer characteristics is obtained. Thus, the listeners a and b feel as if the target sound sources 31 and 32 that do not actually exist actually exist at that location, that is, the CT speakers 20 are in front of the listeners a and b.
[0048]
Next, a case where sound image localization control is performed on the SL signal will be described. FIG. 11 is a diagram illustrating a case where sound image localization control is performed so that the SL speaker 24 is further enlarged to the left. FIG. 12 is a diagram illustrating a case where the speaker 30 is actually installed near the positions of the target sound sources 31 and 32. In FIG. 12, gaR, gaL, gbR, and gbL indicate transmission characteristics from the speaker 30 to each of the listeners a and b. Also, T4 'is the propagation time from the speaker 30 to the right ear of the listener a, T3' is the propagation time from the speaker 30 to the left ear of the listener a, and T2 'is the right ear of the listener b from the speaker 30. T1 ′ indicates the propagation time from the speaker 30 to the left ear of the listener b. In FIG. 12, the distance from the speaker 30 to the listener is greater for the listener a than for the listener b.
T1 ′ <T2 ′ <T3 ′ <T4 ′ (4)
There is a relationship. Also, if the left ear of the listener a and the right ear of the listener b are adjacent to each other,
T1 ′ <T2 ′ ≦ T3 ′ <T4 ′ (5)
It becomes. In other words, this equation (5) indicates a temporal relationship physically allowed (which may be the natural world).
[0049]
Therefore, target sound sources 31 and 32 are set as shown in FIG. 13 in order to satisfy the relationship of the above equation (4) or (5). The relationship between the transfer characteristic GaR from the target sound source 31 to the right ear of the listener a and the transfer characteristic GbR from the target sound source 32 to the right ear of the listener b is the same in amplitude frequency characteristics (that is, the direction is the same). However, the relationship is such that the target sound source 31 is set apart by the time t. Similarly, the relationship between the transfer characteristic GaL from the target sound source 31 to the left ear of the listener a and the transfer characteristic GbL from the target sound source 32 to the left ear of the listener b is the same in the amplitude frequency characteristic (that is, the direction is the same). ), The target sound source 31 is placed at a distance of time t. By setting the target characteristics in this way, the causality can be satisfied. Thus, the signal processing unit 2 can control the SL signal, and can also obtain a filter coefficient for realizing the target sound source.
[0050]
For the SR signal, by setting the target sound source position in the same manner as the SL signal, sound image localization control using the control points of both ears of the two listeners a and b becomes possible.
[0051]
As described above, all five channel signals (the WF signal is not specifically described here, but the low-frequency signal has little sense of direction, and the necessity of sound image localization control is lower than that of other channel signals. However, it is not impossible, and control may be performed by the same concept if necessary.), The method of setting the target sound source position and the sound image localization control using the same have been described. FIG. 14 is a diagram showing a case where all five signals are combined. In FIG. 14, the target sound sources 31FR, 31CT, 31FL, 31SR, and 31SL for the listener a are indicated by dotted speakers. The target sound sources 32FR, 32CT, 32FL, 32SR, and 32SL for the listener b are indicated by hatched speakers.
[0052]
FIG. 14 shows solid arrows connecting the center position of the listener a and actual speakers (CT speaker 20, FR speaker 21, FL speaker 22, SR speaker 23, and SL speaker 24). As is clear from the solid arrows, the balance relationship between the listener a and each of the existing speakers, such as the distance and angle, is unbalanced. On the other hand, dotted arrows connecting the center position of the listener a and the target sound sources (target sound sources 31FR, 31CT, 31FL, 31SR, and 31SL) are shown. As is clear from the dotted arrows, by performing the sound image localization control as in the present embodiment, the balance relationship such as the distance and angle between the listener a and each target sound source is improved to a good balance. . As can be seen from FIG. 14, the listener b has the same improvement effect as the listener a.
[0053]
Note that, as in the first embodiment, by expanding the set position of the target sound source to the left and right of the actual speaker installation position, the actual speaker cannot be installed at a sufficiently wide angle due to a small room or the like. In this case, or even when the FR speaker 21, the FL speaker 22, and the CT speaker 20 are incorporated in a television, the user can listen to the sound with a wider sound.
[0054]
In the first embodiment, the target sound source is set in front of each of the listeners a and b for the CT signal. However, if there is a screen such as a television, the target sound source is set at the screen position. It may be.
[0055]
FIG. 15 is a diagram illustrating a method of setting a target sound source at a position common to listeners a and b. For example, assuming that the television is installed at the front center of the listeners a and b, the speaker 30 is installed there. In this case, the transfer characteristic gaL from the speaker 30 to the left ear of the listener a is substantially equal to the transfer characteristic gbR from the listener b to the right ear. Similarly, the transfer characteristic gaR from the speaker 30 to the right ear of the listener a is substantially equal to the transfer characteristic gbL of the listener b to the left ear. Therefore, as described in FIGS. 9 and 10, by setting the transfer characteristics in the case shown in FIG. 15 in the target characteristic units 151 to 154 in FIG. 8 as they are, the filter coefficient can be calculated.
[0056]
As described above, in the sound image localization control of the CT signal, when the target sound source is set in front of each of the listeners a and b, or the target sound source is set at a position symmetrical to the listeners a and b (for example, a front center position). In such a case, there is no particular need to devise a method for satisfying the causality law, such as the FR signal. That is, the target sound source can be set in the same direction and at the same distance with respect to the two listeners a and b.
[0057]
As described above, according to the first embodiment, it is possible to simultaneously perform sound image localization control for two listeners, and a similar sound image localization effect can be obtained for each listener.
[0058]
(Embodiment 2)
Hereinafter, a sound image control system according to Embodiment 2 will be described. FIG. 16 is a diagram illustrating a sound image control system when performing sound image localization control on an FR signal in the second embodiment. The configuration of the sound image control system shown in FIG. 16 is the same as the configuration shown in FIG. 1 except that sound image localization control of the FR signal is performed without using the SL speaker 24. In the second embodiment, the purpose of realizing the target sound sources 31 and 32 for the FR signal (the same applies to other channel signals) is the same as in the first embodiment, but the number of speakers used is different. . Specifically, in the first embodiment, four control points are controlled by five speakers 20 to 24, but in the second embodiment, four control points are controlled by four speakers 20 to 23. In the second embodiment, since the number of control points and the number of control speakers are the same, the characteristic of the control filter in the signal processing unit 2 is uniquely obtained (the solution of equation (a) is obtained).
[0059]
Here, the reason why the SL speaker 24 is not used is that the SL speaker is located at a position substantially opposite to the target sound source of the FR signal. Since the SL speaker 24 is located at the exact opposite position to the target sound sources 31 and 32, the sound transmitted from the SL speaker 24 naturally reaches the control point in the opposite direction to the sound transmitted from the target sound sources 31 and 32. . In this case, although there is no problem at the control point, the more the control point is deviated, the more the characteristic (particularly the phase) between the sound transmitted from the target sound sources 31 and 32 and the sound transmitted from the SL speaker 24 is shifted ( The target characteristics do not match the wavefront). Therefore, it may be preferable not to use (do not input a signal) a speaker located in a direction opposite to the target sound source position.
[0060]
In general, if the number of control speakers is reduced, there is a high possibility that the sound image localization effect will be degraded. However, the present sound image control system has the SR speaker 23 positioned opposite to the position of the target sound sources 31 and 32 in the front-rear direction but the same direction in the left-right direction, and the SR speaker 23 opposite to the position of the target sound sources 31 and 32 in the left-right direction. FL speakers 22 are located in the same direction in the front-back direction. Accordingly, when sound image localization control is performed on the FR signal using the same number of speakers as the control points, by using speakers 20 to 23 other than the SL speaker 24 at positions exactly opposite to the positions of the target sound sources 31 and 32 in the front, rear, left and right directions. , The control filter coefficient of the signal processing unit 2 can be calculated. Although the number of control filters is smaller than that of the first embodiment, the localization effect is secured to the same degree as that of the first embodiment (using a speaker whose wavefront relatively matches the target characteristic). Because). The method for setting the target characteristics is the same as in the first embodiment, and a description thereof will be omitted.
[0061]
Although the above description has been given of the FR signal, the number of speakers can be similarly reduced for the FL signal. Specifically, when the target sound sources 31FL and 32FL shown in FIG. 14 are to be realized for the FL signal, a configuration without using the SR speaker 23 can be adopted.
[0062]
Next, a case where sound image localization control is performed on a CT signal will be described. FIG. 17 is a diagram illustrating a sound image control system when performing sound image localization control on a CT signal in the second embodiment. Compared to the first embodiment (FIG. 9), the second embodiment is different from the first embodiment in that the SR speaker 23 and the SL speaker 24 are not used as control speakers. The reason why the SR speaker 23 and the SL speaker 24 located at positions opposite to the target sound sources 31 and 32 are not used is the same as in the case of the FR signal.
[0063]
Here, in the case of FIG. 17, since the number of control speakers (speakers 20 to 22) is smaller than the control point, the characteristics of the control filter of the signal processing unit 2 are not obtained (there is no solution of the equation (a)). ). However, since the speakers 20 to 22 in the same direction as the target sound sources 31 and 32 are used (a speaker whose wavefront is relatively matched to the target characteristic is used), the characteristics are reduced because the number of speakers is one less. There is no need not to ask. In particular, since the localization effect by the phase control is greater as the frequency is lower (about 2 kHz or less), if the sound image localization control is performed only for the low-frequency component of the signal, sufficient control can be performed even if the number of speakers is one. Characteristics can be determined. More specifically, if the phase difference between both ears is within λ / 4, it is generally considered that the listener perceives the same phase. Assuming that the distance between human ears is 17 cm, if the wavelength λ is a frequency such that λ / 4 = 0.17, that is, λ = 0.68, the center between the listener's ears is obtained. The vicinity (one point (marked by X in FIG. 17)) can be set as a control point. That is, when the frequency is equal to or lower than f = v / λ = 340 / 0.68 = 500 (Hz) (v is the speed of sound), one control point can be set. In this case, the number of control points for the two listeners is two, which is smaller than the number of speakers, so that a solution of the filter coefficient can be obtained. As described above, in the configuration shown in FIG. 17, although the number of control filters is smaller than that in the first embodiment, the same localization effect as that of the first embodiment is ensured. The method for setting the target characteristics is the same as in the first embodiment, and a description thereof will be omitted.
[0064]
Next, a case where sound image localization control is performed on the SL signal will be described. FIG. 18 shows a control method of the SL signal. FIG. 18 is a diagram illustrating a sound image control system when performing sound image localization control on an SL signal in the second embodiment. Compared with Embodiment 1 (FIG. 11), Embodiment 2 is different in that the configuration is such that FR speaker 21 is not used as a control speaker. The reason why the FR speaker 21 located at a position substantially opposite to the target sound sources 31 and 32 is not used is the same as in the case of the FR signal. As described above, in the configuration shown in FIG. 18, although the number of control filters is smaller than that of the first embodiment, the same localization effect as that of the first embodiment is ensured. The method for setting the target characteristics is the same as in the first embodiment, and a description thereof will be omitted.
[0065]
Although the description has been given of the SL signal, the number of speakers can be similarly reduced for the SR signal. Specifically, when the target sound sources 31SR and 32SR shown in FIG. 14 are to be realized with respect to the SR signal, a configuration without using the FL speaker 22 can be adopted.
[0066]
As described above, when the number of speakers to be used is reduced and each channel signal is combined, the overall configuration of the sound image control system is the same as in FIG. 14, but the internal configuration of the signal processing unit 2 is different from that of the first embodiment. . Specifically, as described above, two control filters of control filters 103 and 104 in FIG. 2 are reduced in the CT signal, and one control filter of control filter 109 in FIG. 2 is reduced in the FR signal. . Similarly, in the FL signal, one control filter is reduced. Further, one control filter is reduced for each of the SR signal and the SL signal. As described above, six control filters are reduced in the entire system, so that the total operation amount of the signal processing unit 2 can be reduced, or the number of control filter taps can be increased in order to equalize the operation amount. , There is an advantage.
[0067]
As for the CT signal, a configuration using only the FR speaker 21 and the FL speaker 22 as shown in FIG. 19 is also conceivable. In this case, the number of control filters can be further reduced by one.
[0068]
In the first and second embodiments, the case where the number of listeners is two has been described, but the number of listeners is not limited to this. That is, even when there are three or more listeners, control may be performed in the same way as described above. However, it should be noted that if the number of listeners is three or more, the number of control points increases as compared with the case of the first embodiment, so that it is necessary to use more speakers accordingly.
[0069]
In addition, although the speaker system and the listening room have not been mentioned at all, the present invention can be applied not only to general systems and rooms, but also to applications to car audio and the like.
[0070]
(Embodiment 3)
Hereinafter, a sound image control system according to Embodiment 3 will be described. FIG. 20 is a diagram illustrating a sound image control system according to Embodiment 3. 20, 1 is a DVD player as a sound source, 2 is a signal processing unit, 20 is a CT speaker, 21 is an FR speaker, 22 is an FL speaker, 23 is an SR speaker, 24 is an SL speaker, and 31 is a target of the listener a. A sound source, 32 is a target sound source of the listener b, 500 is a display, and 501 is a car. FIG. 20 shows a configuration in which the sound image control system (FIG. 1) according to Embodiment 1 is applied to an automobile. Also in the third embodiment, the purpose of realizing the target sound sources 31 and 32 for the FR signal (the same applies to other channel signals) is the same as that of the first embodiment. In FIG. 20, speakers 21 and 22 are installed at (or near) the front door, CT speaker 20 is installed near the center of the front console, and speakers 23 and 24 are installed at the rear tray. In the third embodiment, in addition to the audio signal, a video signal is output from the DVD player. The video signal is reproduced by the display 500.
[0071]
The interior of a car has complex acoustic characteristics such as standing waves that are likely to be generated or strong reverberation due to the fact that it is a closed small space or that there is a reflector such as glass. . Therefore, under the conditions where the number of speakers and the cost performance of the signal processor are limited, sound image localization control is performed for a plurality of (here, four) control points in the entire frequency band from the low band to the high band. That involves considerable difficulty.
[0072]
Therefore, in the third embodiment, the signal is divided into bands, and the sound image localization control is performed on a low frequency band where control is relatively easy. Regarding the crossover frequency to be divided, for example, it is conceivable to perform sound image localization control at a frequency of about 2 kHz or less at which phase characteristics are important. If an acoustic characteristic that is difficult to control exists at 2 kHz or less, the frequency may be divided near that frequency. Hereinafter, the operation of the sound image control system according to Embodiment 3 will be described.
[0073]
FIG. 21 is a diagram illustrating an internal configuration of the signal processing unit 2 according to the third embodiment. The configuration shown in FIG. 21 is configured to divide each input signal (only the CT signal and the FR signal are shown in FIG. 21) into a low band and a high band. The description of the same parts as those in FIG. 2 will be omitted.
[0074]
21, 310 and 311 are low-pass filters (hereinafter referred to as LPFs), 320 and 321 are high-pass filters (hereinafter referred to as HPFs), 330 to 333 are delay units (delayed in the figure as "Delay"), and 340 to 345. Denotes level adjusters (in the figure, denoted as “G1” to “G6”, respectively). The input FR signal is appropriately level-adjusted by level adjusters 344 and 345, and is input to LPF 311 and HPF 321. The LPF 311 extracts a low-frequency component of the FR signal, and the extracted signals are subjected to signal processing by filters 105 to 109. The operation of the filters 105 to 109 is the same as that of FIG. 2 except that the signal being handled is a low-frequency component.
[0075]
On the other hand, the HPF 321 extracts a high-frequency component of the input signal, and the extracted signal is time-adjusted by the delay unit 333. The delay unit 333 adjusts the time mainly for the purpose of adjusting the time of the low-frequency component signal processed by the filter 106 to the time. The output signal of the delay unit 333 is added to the output signal of the filter 106 via the adder 206 by the adder 210 and input to the FR speaker 21 (in FIG. 21, simply referred to as “FR”. The same applies to the drawings.). As described above, the low-frequency component of the input signal is controlled by filters 105 to 109 so as to be located at the positions of target sound sources 31 and 32, and the high-frequency component of the input signal is controlled by FR speaker 21 in a direction close to the target sound source. Will be played. As a result, even in a vehicle cabin having complicated acoustic characteristics, it is possible to control the listeners a and b so that the FR signals are reproduced from the target sound sources 31 and 32, respectively.
[0076]
Here, when the input signal (here, FR signal) is subjected to signal processing by dividing it into a high-frequency component and a low-frequency component as described above, depending on the installation location of the FR speaker 21, the high frequency reproduced from the FR speaker 21 may be used. There is a possibility that the sound image localization feeling is pulled by the sound of the band component and the sound image of the entire FR signal is heard at a position shifted from the target sound sources 31 and 32. Since the amplitude (sound pressure) characteristic of the high-frequency component of the signal is more effective in localization perception than the phase characteristic, intensity control of sound image localization can be performed by sorting and reproducing with other speakers. is there. Hereinafter, a specific example will be described.
[0077]
FIG. 22 is a diagram illustrating an internal configuration of the signal processing unit 2 in the case where intensity control is performed on a high-frequency component of an input signal in the third embodiment. The configuration shown in FIG. 22 is a configuration in which the high frequency component of the FR signal is distributed to the FR speaker 21 and the SR speaker 23, and the intensity control is performed by the level adjusters 345 and 346.
[0078]
The FL signal is the same as the FR signal except that the left and right are different. That is, the high frequency component of the FL signal can be reproduced only from the FL speaker 22, or the intensity control between the FL speaker 22 and the SL speaker 24 can be performed.
[0079]
Next, the CT signal will be described. FIG. 23 is a diagram illustrating a sound image control system when performing sound image localization control on a CT signal in the third embodiment. In FIG. 23, target sound sources 31 and 32 are set in front of listeners a and b, respectively. The configuration of the sound image control system (including the configuration of the signal processing unit 2) is the same as that in FIG.
[0080]
In FIG. 21, the LPF 310 extracts a low-frequency component of a CT signal, and performs signal processing on the extracted signal by filters 100 to 104. The operation of the filters 100 to 104 is the same as that of FIG. 2 except that the signal being handled is a low-frequency component.
[0081]
On the other hand, the high frequency component of the CT signal is extracted by the HPF 320. The level of the extracted signal is appropriately adjusted by the level adjusters 341 to 343 so as to perform intensity control so as to be located in front of the listeners a and b. The level-adjusted signals are time-adjusted by delay units 330 to 332, added to the outputs of filters 100 to 104 by adders 200 to 204, and input to the CT speaker. In the delay units 330 to 332, for example, adjustment is performed so that the low-frequency components from the filters 100 to 104 coincide with the time at the ears of the listeners a and b. As described above, the low-frequency component of the CT signal is sound image localized by the filters 100 to 104, and the high-frequency component of the CT signal is intensity-controlled. As a result, it is possible to give the listeners a and b a feeling that the CT signal is being reproduced from the positions of the target sound sources 31 to 32 shown in FIG.
[0082]
FIG. 24 is a diagram illustrating a sound image control system when performing sound image localization control on a CT signal in the third embodiment. FIG. 24 differs from FIG. 23 in that the target sound source 31 of the CT signal (here, the target sound source 31 is the target sound source for both the listeners a and b) is set at the position of the display 500. ing. In this case, it is effective to set a target sound source position on the display 500 when not only audio reproduction but also video reproduction is involved. This is because it is natural that the dialogue of the movie, the voice of the singer, and the like can be heard from the position corresponding to the image, that is, from the position of the display 500. Note that the method of setting the target sound source 31 shown in FIG. 24 may be the same method as in the case of FIG.
[0083]
When the target sound source 31 is set as shown in FIG. 24, the signal processing unit 2 is configured as shown in FIG. 22, for example. 22, a low-frequency component of a CT signal is extracted by an LPF 310, and the extracted signal is subjected to signal processing by filters 100 to 104. On the other hand, the high frequency component of the CT signal is extracted by the HPF 320, and the extracted signal is time-adjusted by the delay unit 330. Further, the time-adjusted signal is added to the output of the filter 100 by the adder 200 and input to the CT speaker 20. The delay unit 330 adjusts the time so that, for example, the low-frequency components from the filters 100 to 104 coincide with the ears of the listeners a and b. Note that the sound pressure levels to be added by the adder 200 may be adjusted by the level adjusters 340 and 341. As described above, the low frequency component of the CT signal is sound image localization controlled by the filters 100 to 104, and the high frequency component of the CT signal is reproduced from the CT speaker 20 close to the display 500. Thereby, it is possible to give each listener a and b a sense as if the CT signal is being reproduced from the display 500 in FIG.
[0084]
Next, the SL signal will be described. FIG. 25 is a diagram illustrating a sound image control system when performing sound image localization control on an SL signal in the third embodiment. In FIG. 25, target sound sources 31 and 32 are set to the left rear of the listeners a and b, respectively.
[0085]
FIG. 26 is a diagram illustrating an internal configuration of the signal processing unit 2 according to the third embodiment. In FIG. 26, the low-frequency component of the SL signal is extracted by the LPF 312 and then subjected to signal processing by the filters 110 to 114. On the other hand, the high frequency component of the SL signal is extracted by the HPF 322 and time-adjusted by the delay units 335 and 336. For example, the delay units 335 and 336 adjust the time so that the low-frequency components from the filters 110 to 114 are in time at the ears of the listeners a and b. The level of the time-adjusted signal is appropriately adjusted by level adjusters 348 and 349 so as to perform intensity control so that the sound image is localized at the positions of the target sound sources 31 and 32 shown in FIG. The signals whose levels have been adjusted are added to the outputs of filters 112 and 114 and adders 212 and 213, respectively, and input to SL speaker 24 and FL speaker 22. As described above, the low frequency components of the SL signal are sound image localization controlled by the filters 110 to 114, and the high frequency components of the SL signal are intensity controlled. Thereby, it is possible to give each listener a and b a sense that the SL signal is being reproduced from the positions of the target sound sources 31 and 32 shown in FIG.
[0086]
Note that the SR signal is the same as the SL signal except that the left and right are different. That is, the high frequency component of the SR signal can be reproduced only from the SR speaker 23, or the intensity control between the SR speaker 23 and the FR speaker 21 can be performed.
[0087]
Note that, even when the positions of the speakers are different, the same control as described above can be performed. FIG. 27 is a diagram illustrating a sound image control system when performing sound image localization control on the SL signal when the positions of the speakers are different. In FIG. 27, the SR speaker 23 and the SL speaker 24 are installed at the right rear door and the left rear door of the automobile, respectively.
[0088]
In FIG. 27, since the target sound sources 31 and 32 of the SL signal are almost at the same position as the SL speaker 24, the high frequency component of the SL signal may be reproduced from the SL speaker 24. Further, since the target sound sources 31 and 32 of the SL signal are almost at the same position as the SL speaker 24, the sound signal localization control is not performed for the entire band of the SL signal, and the entire band of the SL signal is reproduced from the SL speaker 24. Is also good. In this case, the delay unit 335 shown in FIG. 26 is used for time adjustment with other channel signals. As described above, when the target sound source position is almost the same as the position of the speaker, the filters 110 to 114, the LPF 312, and the HPF 322 can be reduced.
[0089]
As described above, in the case where the sound image control system is applied to the inside of the vehicle, the control method of each of the signals of each of the 5 channels has been described. Therefore, if all the signals are combined as described with reference to FIG. 14, the sound image localization control can be simultaneously performed on each of the 5ch signals.
[0090]
In the third embodiment, the four control points have been described as the positions of both ears of the listener of the front seat of the car. However, the positions of the control points are not limited to this, and the positions of the control points of the rear seat are not limited thereto. The position of the listener may be used as the control point.
[0091]
(Embodiment 4)
Hereinafter, a sound image control system according to Embodiment 4 will be described. The sound image control system according to the fourth embodiment is an application example to an automobile as in the third embodiment, and a case where the number of control speakers is equal to or less than the number of control points as in the second embodiment will be described. Regarding the FR signal, the FL signal, the SR signal, and the SL signal, the method of reducing the number of control speakers is the same as that of the second embodiment, and the processing of the high frequency component is the same as that of the third embodiment. On the other hand, regarding the CT signal, the method of reducing the number of control speakers may be the same as that in the second embodiment, or may be a method described below.
[0092]
In the fourth embodiment, sound image localization control is performed using two FR speakers 21 and FL speakers 22 for low-frequency components of CT signals, and CT speakers are used for high-frequency components of CT signals. That is, since the wavelength of the low-frequency component of the CT signal is long, four control points are controlled by the two speakers 21 and 22. Then, for the high frequency component of the CT signal, intensity control is performed by the three speakers 20 to 22. FIG. 28 is a diagram illustrating a sound image control system when performing sound image localization control on a CT signal in the fourth embodiment. As is clear from FIG. 28, regarding the control of the CT signal, no CT signal is input to the SR speaker 23 and the SL speaker 24. FIG. 29 is a diagram illustrating an internal configuration of the signal processing unit 2 according to the fourth embodiment. The operation of the signal processing unit 2 illustrated in FIG. 29 is the same as the operation related to the CT signal illustrated in FIG. 21 except that the number of filters is small, and thus detailed description is omitted.
[0093]
In FIG. 29, of the components of the CT signal, only the high frequency component is input to the CT speaker 20. That is, since the CT speaker 20 only needs to be able to reproduce only the high frequency component, the CT speaker can be realized by a small speaker such as a tweeter. In general, the space for installing the CT speaker 20 (especially in a car) is not large, so that it is often difficult to install the CT speaker 20. Therefore, the above problem can be solved by implementing the CT speaker 20 with a small speaker as in the fourth embodiment. Furthermore, if the CT speaker 20 can be incorporated into the display 500, the space merit will be very large.
[0094]
In the fourth embodiment, the target sound source position of the CT signal may be set to the position of display 500. FIG. 30 is a diagram showing a state where the target sound source position of the CT signal is set to the position of display 500 in the third embodiment. As shown in FIG. 30, the target sound source 31 of the CT signal (here, the target sound source 31 is the target sound source for both the listeners a and b) is the position of the display 500. At this time, the configuration of the signal processing unit 2 is, for example, as shown in FIG. FIG. 31 is a diagram showing an internal configuration of the signal processing unit 2 for realizing the target sound source position shown in FIG. The configuration shown in FIG. 31 is the same as the configuration shown in FIG. 29 except that the high frequency component of the CT signal is input only to the CT speaker 20, and thus the detailed description of the configuration shown in FIG. 31 is omitted. Here, it is assumed that the CT speaker is incorporated in the display 500 or is installed near the display 500.
[0095]
In the fourth embodiment, the four control points have been described as the positions of both ears of the listener in the front seat of the car. However, the positions of the control points are not limited to this, and The position of the listener may be used as the control point.
[0096]
In the fourth embodiment, the case where the sound image control system is applied to an automobile has been described. However, as another embodiment, for example, a sound image control system is applied using a television and an audio system in a home. Things are conceivable. Specifically, when the CT speaker 20 can be used for high-frequency sound reproduction as in the fourth embodiment, the CT speaker 20 is realized by a built-in speaker of a television, and the other speakers are realized by audio speakers. It becomes possible.
[0097]
(Embodiment 5)
Hereinafter, the sound image control system according to Embodiment 5 will be described. FIG. 32 is a diagram illustrating an outline of the sound image control system according to the fifth embodiment. Embodiment 5 is an example in which a listener at the back seat of an automobile is taken into consideration. That is, in the fifth embodiment, a case will be described in which the number of listeners is four, that is, listeners a to d, as shown in FIG.
[0098]
FIG. 33 is a diagram illustrating a configuration of the signal processing unit 2 according to the fifth embodiment. The signal processing unit 2 shown in FIG. 33 performs sound image localization control for two listeners a and b located in the front seat, and performs signal localization control for two listeners c and d located in the rear seat. Reproduces the signals of all channels by rear speakers 23 and 24 (these reference numbers are assigned to the above-mentioned SR speakers 23 and SL speakers 24 because they correspond to the above-mentioned SR speakers 23 and SL speakers 24). As a result, deterioration and omission of information to the listener in the rear seat are prevented. Here, it is assumed that the CT signal is localized at the position of the display 500. However, the target sound source position of the CT signal is not limited to this, and may be located in front of each of the listeners a and b as described above. Hereinafter, the operation of the signal processing unit 2 will be specifically described.
[0099]
From the CT signal, a low-frequency component is extracted by the LPF 310, and the extracted signal is subjected to signal processing for sound image localization control by the filters 100 to 102. On the other hand, the high frequency component of the CT signal extracted by the HPF 320 is given an appropriate delay by the delay unit 330, and is added by the adder 200 to the output of the filter 100. The output signals from the filters 100 to 102 and the high frequency component of the CT signal are input to the speakers 20 to 22 and reproduced. Thus, the sound of the CT signal can be sound image localized at the position of the display 500.
[0100]
Although FIG. 33 shows a configuration in which the rear speakers 23 and 24 are not used, the present invention is not limited to this and may be used. However, the sound image or sound quality of the rear seat must be considered. According to the configuration of FIG. 33, the influence of the rear seats of the sound image localization control by the filters 100 to 102 can be suppressed, and only the target front speakers 20 to 22 are used for the front seats. And a good sound image localization effect can be obtained.
[0101]
The low frequency component is extracted from the FR signal by the LPF 311, and the filters 105 to 108 perform signal processing for sound image localization control. On the other hand, the high frequency component of the FR signal extracted by the HPF 321 is given an appropriate delay by the delay unit 331, and is added by the adder 210 to the output of the filter 106. Then, by reproducing the outputs of the filters 105 to 108 and the high frequency components by the speakers 20 to 23, the sound image localization control of the FR signal can be performed. The output signals from the filters 105 to 108 and the high frequency component of the FR signal are input to the speakers 20 to 23 and are reproduced. Thus, sound image localization control of the sound of the FR signal can be performed.
[0102]
Although FIG. 33 shows a configuration in which the rear speaker (SL speaker) 24 is not used, the present invention is not limited to this and may be used. Further, the configuration shown in FIG. 33 is a configuration in which the high frequency component of the FR signal is reproduced only by the FR speaker 21. However, the present invention is not limited to this, and the intensity control by a plurality of speakers as in the third embodiment is performed. May be performed. However, the sound image or sound quality of the rear seat must be considered. According to the configuration of FIG. 33, it is possible to suppress the influence of the rear seats of the sound image localization control by the filters 105 to 108, and to obtain a good sound image localization effect also for the front seats.
[0103]
The same processing as the FR signal is performed on the FL signal. That is, the low-frequency component of the FL signal is extracted by the LPF 312, and the filters 115 to 118 perform signal processing for sound image localization control. On the other hand, the high frequency component of the FL signal extracted by the HPF 322 is given an appropriate delay by the delay unit 332, and is added by the adder 211 to the output of the filter 117. Then, by reproducing the outputs of the filters 115 to 118 and the high-frequency components by the speakers 20 to 22, 24, the sound signal localization control of the FL signal can be performed.
[0104]
Although FIG. 33 shows a configuration in which the rear speaker (SR speaker) 23 is not used, the present invention is not limited to this and may be used. Further, the configuration shown in FIG. 33 is a configuration in which the high frequency component of the FL signal is reproduced only by the FL speaker 21. However, the present invention is not limited to this, and intensity control using a plurality of speakers is performed as in the third embodiment. May be performed. However, the sound image or sound quality of the rear seat must be considered. According to the configuration of FIG. 33, it is possible to suppress the influence of the rear seats of the sound image localization control by the filters 115 to 118, and to obtain a good sound image localization effect also for the front seats.
[0105]
After the SR signal is appropriately adjusted in level by the level adjuster 347, the SR signal is appropriately delayed in the delay unit 334 and reproduced from the SR speaker 23. That is, in the fifth embodiment, the sound image localization control by the filter is not performed on the SR signal. This is for the listeners c and d of the rear seats in addition to the listeners a and b of the front seats. When the sound image localization control for the front seats is performed also for the SR signal, the rear speakers 23 and This is because the listeners c and d close to 24 are strongly affected by the rear speakers 23 and 24, and there is a high possibility that the sound quality and the like for the listeners c and d will be adversely affected. In addition, as shown in FIG. 27, when the rear speakers 23 and 24 are installed on the rear door, the surround sound effect can be easily obtained without performing the sound image localization control because the target sound source position is relatively close to the installation position. Therefore, in this case, it can be said that the necessity of performing sound image localization control using a filter on the SR signal is small. The sound image localization control by the filter is not performed on the SL signal for the same reason as the SR signal. This is the end of the description of the sound image localization control of each channel signal for the listeners a and b in the front seat in FIG.
[0106]
Next, the rear seat will be described. In the configuration for only the front seat as in the above-described first to fourth embodiments, the sound image and the sound quality for the listener in the rear seat are not considered, and the best effect can be obtained in the front seat. It is adjusted to. In this case, in the rear seat, the sound from the rear speakers 23 and 24 is large, and the sound from the front speakers (CT speaker, FR speaker and FL speaker) 20 to 22 is small due to the relationship between the listener and the distance between the speakers. The balance between the sound coming from the front and the sound coming from the rear becomes very bad. Therefore, when audio services are also provided to the listeners c and d in the rear seat as shown in FIG. 32, it is necessary to solve the imbalance in the reproduction sound levels of the front speakers and the rear speakers.
[0107]
Therefore, in the fifth embodiment, a configuration for solving the above imbalance is adopted. Further, at this time, the sound image localization effect for the listeners a and b in the front seat is not affected. In order to achieve this compatibility, in FIG. 33, sound image localization control is performed on the front seat as described above while suppressing the influence of the rear seat. On the other hand, the rear seat is configured to improve only the imbalance between the CT, FR, and FL signals, and the SR and SL signals without performing sound image localization control. Hereinafter, FIG. 33 will be described in detail.
[0108]
The CT signal is adjusted in level by a level adjuster 348, delayed by a delay unit 335, and then applied to adders 214 and 215. The level of the FR signal is adjusted by a level adjuster 349, delayed by a delay unit 336, and then applied to an adder 215. The level of the FL signal is adjusted by the level adjuster 350, delayed by the delay unit 337, and then applied to the adder 214. Further, the output signals of adders 214 and 215 are applied to adders 212 and 213, respectively. As a result, a signal obtained by adding the CT signal and the FR signal to the SR signal is reproduced by the rear speaker 24. Further, a signal obtained by adding the CT signal and the FL signal to the SL signal is reproduced by the rear speaker 23.
[0109]
As described above, in the fifth embodiment, in addition to the SR signal and the SL signal, the CT signal, the FR signal, and the FL signal are reproduced from the rear speakers 23 and 24. Thereby, the problem of the imbalance felt by the listener in the rear seat can be improved. The mutual influence between the front seat and the rear seat is suppressed by adjusting the overall level balance by the level adjusters 340 to 347 for the front seat and the level adjusters 348 to 350 for the rear seat. Can be. As a result, good sound quality can be obtained in both the front seat and the rear seat.
[0110]
(Embodiment 6)
Hereinafter, the sound image control system according to Embodiment 6 will be described. FIG. 34 is a diagram showing an outline of the sound image control system according to the sixth embodiment. The sound image control system according to the sixth embodiment controls a woofer signal (WF signal) included in a 5.1-channel audio signal. Here, FIG. 34 shows a case where only the front seat is controlled, and the signal processing unit 2 at this time is configured as shown in FIG. 35, for example.
[0111]
FIG. 35 is a diagram illustrating a configuration of the signal processing unit 2 according to the sixth embodiment. The control for the listener in the front seat is the same as in FIG. 33 except for the WF signal. The WF signal may be adjusted only for the front seat, and since the frequency band in which the WF signal is reproduced is an extremely low frequency band (for example, about 100 Hz or less), it is considered that the sound pressure is substantially the same for the listeners a and b. As described above, in FIG. 35, the WF signal is subjected to level adjustment and delay adjustment, and is reproduced by the WF speaker 25.
[0112]
It should be noted that if the control is performed only for the front seat listener, the configuration of FIG. 35 is not a problem, but if the rear seat listener is also to be controlled (see FIG. 36), the WF signal Is set for the listener in the front seat, so that the rear seat has an excessively high playback level. In order to solve this, the following method may be adopted. Hereinafter, a sound image control system according to Embodiment 6 in which a listener at the rear seat is considered will be described.
[0113]
FIG. 36 is a diagram illustrating an overview of the sound image control system according to Embodiment 6 in the case where a listener is also present at the rear seat. As shown in FIG. 36, using the speakers 21 to 25 except the CT speaker 20, control is performed so that the WF signal reproduction level becomes approximately the same sound pressure at the four control points α, β, γ, and θ. Here, the CT speaker 20 is not used for control, but may be used. However, it is considered that the CT speaker 20 is unlikely to be used because it is generally difficult to reproduce an extremely low frequency. In addition, the reason why the listener has one point in the vicinity instead of each ear is that the target frequency is considered to be sufficient because the wavelength of the target frequency is a low frequency.
[0114]
FIG. 37 is a diagram illustrating a method of calculating a filter coefficient using an adaptive filter in the sixth embodiment. In FIG. 37, target characteristics at control points α, β, γ, and θ (that is, microphones 41 to 44) are set in target characteristic units 155 to 158. Here, the transfer characteristic from the WF speaker 25 to the control point α is P1, the transfer characteristic from the control point β is P2, the transfer characteristic to the control point γ is P3, and the transfer characteristic to the control point θ is P4. Further, P1 is set in the target characteristic unit 155, P2 is set in the target characteristic unit 156, P3 'is set in the target characteristic unit 157, and P4' is set in the target characteristic unit 157. Here, P3 'is the characteristic of P3 adjusted so that the level is approximately equal to P1 or P2, and the time characteristic is approximately equal to P3. P4 'is a characteristic of P4 adjusted so that the level is approximately equal to P1 or P2, and the time characteristic is approximately equal to P4.
[0115]
In FIG. 37, the sounds reproduced from the speakers 21 to 25 are controlled by the adaptive filters 120 to 124 so as to be equal to the target characteristics of the target characteristic units 155 to 158 at the positions of the microphones 41 to 44. Then, the filter coefficient that minimizes the error signal from the subtracters 185 to 188 is determined. The filter coefficients thus obtained are set in the filters 120 to 124 in FIG. The levels of target characteristic units 157 and 158 may be adjusted by adjusting the levels of target characteristic units 157 and 158, or conversely, the levels of target characteristic units 157 and 158 may be adjusted.
[0116]
FIG. 38 is a diagram illustrating a configuration of the signal processing unit 2 in a case where a listener in a rear seat is considered. As shown in FIG. 38, the WF signal is appropriately delayed by the delay unit 351 and then subjected to signal processing by the filters 120 to 124, input to each speaker except the CT speaker 20, and reproduced. Thus, the listeners a to d can hear the reproduced sound of the WF signal of the same level. In the above, the case where the reproduction levels of the WF signals to the listeners a to d are set to the same level has been described. However, the present invention is not limited to this, and the reproduction level sets a desired target characteristic. It can be freely changed by the following. Further, the configuration in which four control points are controlled by five speakers has been described. However, for example, when the WF speaker 25 is not provided, the configuration may be such that the other four speakers 21 to 24 are controlled.
[0117]
FIG. 39 is a diagram illustrating an overview of a sound image control system according to Embodiment 6 when the number of control points for a WF signal is two. As shown in FIG. 39, regarding the control of the WF signal, since the target frequency is low, the control point α near the middle between the listeners a and b and the control point β near the middle between the listeners c and d Two points may be controlled by three speakers (SR speaker, SL speaker, and WF speaker) 23 to 25 (or by three speakers of FR speaker 21, FL speaker 22, and WF speaker 25). FIG. 40 shows an example of the configuration of the signal processing unit 2 in this case. Since there are two control points, a configuration using an SR speaker 23 and an SL speaker 24 as the control speakers may be used. Thus, the number of WF speakers 25 can be reduced.
[0118]
In the above description, the transfer characteristic (the above-described P1 to P6) from the WF speaker 25 to each control point is used as the target characteristic device of the WF signal, but the relationship between the time and the level of P1 to P6 is followed. If possible, a device having an arbitrary frequency characteristic such as a BPF may be used. In this case, the target characteristic units 155 to 158 can be configured by the level adjuster, the delay unit, and the BPF.
[0119]
As described above, even when there are listeners a to d in the front and rear seats, the WF signal reproduction level can be optimally adjusted for each listener.
[0120]
In the sixth embodiment, the control method in the car interior has been described. However, the present invention is not limited to this. The sound image control system according to the sixth embodiment may be applied to a general room such as a home listening room or an audio system. May be applied.
[0121]
(Embodiment 7)
Hereinafter, the sound image control system according to Embodiment 7 will be described. In the first to sixth embodiments, multi-channel signals have been described. In the seventh embodiment, sound image localization control of two-channel signals will be described. FIG. 41 is a diagram illustrating a configuration of a sound image control system according to Embodiment 7. As shown in FIG. 41, the sound image control system differs from the first embodiment in that the sound source is changed from the DVD player 1 to the CD player 4 and that the multi-channeling circuit 3 is provided. In the seventh embodiment, the WF speaker 25 is provided. Other points are the same as those of the above-described first embodiment.
[0122]
The 2ch signal (FL signal and FR signal) output from the CD player 4 is converted to 5.1ch by the multi-channeling circuit 3. FIG. 42 is a diagram illustrating an example of the configuration of the multi-channeling circuit 3. The input FR signal and FL signal are directly used as the FL signal and the FR signal of the signal processing unit 2. In addition, CT, SL, and SR signals in the 5.1ch signal are obtained in the following manner.
[0123]
In FIG. 41, the FL signal and the FR signal are added by an adder 240, whereby a CT signal is generated. Normally, the signal to be localized in the center is included in the FL signal and the FR signal in the same phase as in the case of vocals. Therefore, when added, the in-phase component is level-emphasized. The WF signal is generated by limiting the generated CT signal to a WF signal band by a band-pass filter (hereinafter, BPF) 260. This processing is based on the fact that the low-frequency component is normally included in the FL signal and the FR signal in the same phase as the signal to be localized in the center.
[0124]
On the other hand, the subtracter 250 extracts a difference component between the FL signal and the FR signal by subtracting the FR signal from the FL signal. This means that only the components included independently of the FL signal and the FR signal are extracted. In other words, the in-phase component localized at the center is reduced. As a result, an SL signal is generated. Similarly, the subtractor 251 subtracts the FL signal from the FR signal to generate an SR signal. Then, the generated SL signal and SR signal are given an appropriate delay by the delay units 270 and 271, respectively, to enhance the sense of surround. In the delay units 270 and 271, for example, a delay time that is relatively longer than the FL signal, the FR signal, and the CT signal, and that is different between the SL signal and the SR signal is set. In addition, a setting that simulates a reflected sound may be used. As described above, in the seventh embodiment, the 5.1ch signal is generated from the 2ch signal. However, the method is not limited to the method shown in FIG. 42 and is generally known as a so-called Dolby Pro Logic. The technique used may be used.
[0125]
The 5.1ch signal thus generated is subjected to sound image localization control by the signal processing unit 2 in the same manner as in the first to sixth embodiments. FIG. 43 is a diagram illustrating an example of a configuration of the signal processing unit 2 according to the seventh embodiment. The operation of the signal processing unit 2 shown in FIG. 43 is the same as the operation described in FIG. 21, FIG. 35, and the like, and thus detailed description will be omitted.
[0126]
As described above, it is possible to improve the sense of reality by converting the sound source of the 2ch signal into 5.1ch, and to control the sound image localization. In particular, it is possible to localize the CT signal in front of each of the listeners a and b, which was impossible in the conventional 2ch reproduction. With this configuration, it is possible to provide a new audio service of a 2-channel sound source that has not been available.
[0127]
(Embodiment 8)
Hereinafter, a sound image control system according to Embodiment 8 will be described. The eighth embodiment differs from the other embodiments in the method of setting the target characteristics. FIG. 44 shows the same target characteristics as in FIG. When the sound image localization control by the filter signal processing is performed on the low-frequency component of the signal, it can be approximated to a substantially constant level flat characteristic as shown by the dotted lines in FIGS. 44 (c) and (d). In the eighth embodiment, times T1 and T2 and levels approximated by delay characteristics shown in FIG. 45 are set as target characteristics in target characteristic units 151 to 154 shown in FIG. Here, in FIG. 45, the characteristics other than the low range are flat, but the LPF characteristics limited to the target frequency range may be multiplied. Further, instead of the flat characteristic, a simple approximate characteristic closer to the target characteristic as shown by a dashed line in FIG.
[0128]
FIG. 46 is a diagram showing a control effect when the target characteristics shown in FIG. 45 are set. FIG. 46 shows an example in which the CT signal is localized at the display position. Here, FIGS. 46A and 46B show the amplitude frequency characteristics at the driver's seat. FIGS. 46C and 46D show the amplitude frequency characteristics at the passenger seat. FIG. 46 (e) shows the phase difference characteristics at both ears of the passenger seat. FIG. 46F shows a phase difference characteristic between both ears of the driver's seat. In FIG. 46, the dotted line indicates the case where the control is OFF, and the solid line indicates the case where the control is ON.
[0129]
As can be seen from FIG. 46, the amplitude frequency characteristics of both the driver's seat and the passenger's seat are flattened. Thus, the sound quality is improved by preventing the unique peaks and valleys in the amplitude characteristics. Further, it can be seen that the phase characteristic is also improved to a characteristic close to a straight line. In particular, in FIG. 46 (f), the part where the phase is out of phase at 200 to 300 Hz is improved, and the feeling of anti-phase and the feeling of unlocalization are improved. The reason why the phase characteristics change as the frequency becomes higher is that the target characteristics are different between the left and right ears of the listeners a and b. Since the listener a (driver's seat) measures FIG. 46 (f) with reference to the left ear, the listener b (passenger seat) measures FIG. 46 (e) with reference to the right ear. The phase is changing. As described above, by replacing the target characteristic with a simple delay or level adjustment, it is possible to obtain a sound image localization effect and a sound quality improvement effect.
[0130]
Although a case has been described above where a target characteristic approximating the actual transfer characteristic is set, it is possible to set the amplitude frequency characteristic to some extent arbitrarily after approximating the phase characteristic (time characteristic). As a result, it is possible to perform sound quality adjustment such as sharpness and weight while performing sound image control.
[0131]
As described above, according to the sound image control system according to the present invention, it is possible to simultaneously perform sound image control on four points near each ear of two listeners. Furthermore, by disposing the speaker in a direction symmetrical with respect to the target sound source position in the front-rear, left-right and front-rear directions, it is possible to reduce the circuit configuration and the amount of calculation without affecting the sound image control effect.
[0132]
Further, the input signal is frequency-divided into a low-frequency component and a high-frequency component, and the sound image localization control is performed on the low-frequency component so as to be equal to the target characteristic at the control point, and the sound image localization control is not performed on the high-frequency component. With this configuration, the amount of calculation required for signal processing can be reduced.
[0133]
Also, by performing signal processing on the woofer signal using a plurality of speakers so as to have approximately the same sound pressure at a plurality of control points, the reproduction level of the woofer signal can be made uniform at the plurality of points. Also, by approximating the target characteristics from the target sound source to the control point with respect to delay and level, sound quality can be improved and arbitrary characteristics can be given.
[0134]
In addition, the signal processing unit controls the sound image of the front two seats in the vehicle interior, and reproduces all the input signals from the sound source without controlling the sound image by the rear speakers in the rear seats. While maintaining the control effect, the balance of the signal levels of the respective channels in the rear seat can be improved, and the clarity and the like can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a sound image control system according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing an internal configuration of a signal processing unit 2 shown in FIG.
FIG. 3 is a diagram showing a case where transfer characteristics from target sound sources 31 and 32 are given to listeners a and b with the same characteristics.
FIG. 4A is a diagram illustrating a time characteristic (impulse response) of a transfer characteristic GR according to the first embodiment of the present invention.
FIG. 3B is a diagram illustrating a time characteristic (impulse response) of the transfer characteristic GL according to the first embodiment of the present invention.
(C) A diagram showing an amplitude frequency characteristic (transfer function) of the transfer characteristic GR according to the first embodiment of the present invention.
(D) is a diagram illustrating an amplitude frequency characteristic (transfer function) of the transfer characteristic GL according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a case where a speaker 30 is actually installed near the positions of target sound sources 31 and 32.
FIG. 6 is a diagram showing a method of setting a target sound source in the present invention.
FIG. 7 is a diagram showing a transmission path from each of the target sound sources 31 and 32 to the center position of the listeners a and b.
FIG. 8 is a diagram illustrating a method for calculating a filter coefficient using an adaptive filter in the first embodiment.
FIG. 9 is a diagram showing a case where a CT signal is simultaneously localized in front of listeners a and b in a sound image.
FIG. 10 is a diagram showing a case where a speaker 30 is actually located in front of a listener a (or b).
FIG. 11 is a diagram showing a case where sound image localization control is performed so that the SL speaker 24 is further enlarged to the left.
FIG. 12 is a diagram showing a case where a speaker 30 is actually installed near the positions of target sound sources 31 and 32.
FIG. 13 is a diagram illustrating a target characteristic setting method in consideration of causality according to the first embodiment of the present invention.
FIG. 14 is a diagram showing a case where all five signals are combined.
FIG. 15 is a diagram illustrating a method of setting a target sound source at a position common to listeners a and b.
FIG. 16 is a diagram showing a sound image control system when performing sound image localization control on an FR signal in the second embodiment.
FIG. 17 is a diagram illustrating a sound image control system when performing sound image localization control on a CT signal in the second embodiment.
FIG. 18 is a diagram illustrating a sound image control system when performing sound image localization control on an SL signal in the second embodiment.
FIG. 19 is a diagram illustrating an overall configuration of a sound image control system using a CT signal as an example according to Embodiment 2 of the present invention;
FIG. 20 is a diagram showing a sound image control system according to a third embodiment.
FIG. 21 is a diagram showing an internal configuration of a signal processing unit 2 according to the third embodiment.
FIG. 22 is a diagram illustrating an internal configuration of the signal processing unit 2 in the case where intensity control is performed on a high-frequency component of an input signal in the third embodiment.
FIG. 23 is a diagram illustrating a sound image control system when performing sound image localization control on a CT signal in the third embodiment.
FIG. 24 is a diagram illustrating a sound image control system when performing sound image localization control on a CT signal in the third embodiment.
FIG. 25 is a diagram illustrating a sound image control system when performing sound image localization control on an SL signal in the third embodiment.
FIG. 26 is a diagram showing an internal configuration of a signal processing unit 2 according to the third embodiment.
FIG. 27 is a diagram showing a sound image control system when sound image localization control is performed on an SL signal when the positions of speakers are different.
FIG. 28 is a diagram illustrating a sound image control system when performing sound image localization control on a CT signal in the fourth embodiment.
FIG. 29 is a diagram illustrating an internal configuration of a signal processing unit 2 according to the fourth embodiment.
FIG. 30 is a diagram showing a state where a target sound source position of a CT signal is set at a position of a display 500 in the third embodiment.
FIG. 31 is a diagram showing an internal configuration of a signal processing unit 2 for realizing the target sound source position shown in FIG.
FIG. 32 is a diagram illustrating an outline of a sound image control system according to a fifth embodiment.
FIG. 33 is a diagram illustrating a configuration of a signal processing unit 2 according to the fifth embodiment.
FIG. 34 is a diagram showing an outline of a sound image control system according to a sixth embodiment.
FIG. 35 is a diagram illustrating a configuration of a signal processing unit 2 according to the sixth embodiment.
FIG. 36 is a diagram showing an outline of a sound image control system according to Embodiment 6 when a listener is also present at the rear seat.
FIG. 37 is a diagram illustrating a method of calculating a filter coefficient using an adaptive filter in the sixth embodiment.
FIG. 38 is a diagram illustrating a configuration of the signal processing unit 2 in a case where a listener in a rear seat is considered.
FIG. 39 is a diagram illustrating an overview of a sound image control system according to a sixth embodiment when the number of control points for a WF signal is two.
FIG. 40 is a diagram illustrating another configuration of the signal processing unit 2 according to the sixth embodiment of the present invention.
FIG. 41 is a diagram showing a configuration of a sound image control system according to a seventh embodiment.
42 is a diagram illustrating an example of a configuration of a multi-channeling circuit 3. FIG.
FIG. 43 is a diagram illustrating an example of a configuration of a signal processing unit 2 according to Embodiment 7.
FIG. 44 (a) is a diagram illustrating a time characteristic (impulse response) of a transfer characteristic GR according to the eighth embodiment of the present invention.
(B) It is a figure which shows the time characteristic (impulse response) of the transfer characteristic GL in Embodiment 8 of this invention.
(C) A diagram showing an amplitude frequency characteristic (transfer function) of a transfer characteristic GR according to the eighth embodiment of the present invention.
(D) is a diagram illustrating an amplitude frequency characteristic (transfer function) of a transfer characteristic GL according to the eighth embodiment of the present invention.
FIG. 45 (a) is a diagram illustrating a time characteristic (impulse response) of a transfer characteristic GR according to the eighth embodiment of the present invention.
(B) It is a figure which shows the time characteristic (impulse response) of the transfer characteristic GL in Embodiment 8 of this invention.
(C) A diagram showing an amplitude frequency characteristic (transfer function) of a transfer characteristic GR according to the eighth embodiment of the present invention.
(D) is a diagram illustrating an amplitude frequency characteristic (transfer function) of a transfer characteristic GL according to the eighth embodiment of the present invention.
FIG. 46 (a) is a diagram illustrating a sound image control effect (amplitude characteristic) at the left ear of the driver's seat according to Embodiment 8 of the present invention.
(B) It is a figure which shows the sound image control effect (amplitude characteristic) in the driver's seat right ear in Embodiment 8 of this invention.
(C) A diagram showing a sound image control effect (amplitude characteristic) in the left ear of the passenger's seat according to Embodiment 8 of the present invention.
(D) A diagram illustrating a sound image control effect (amplitude characteristic) in the right ear of the passenger's seat according to Embodiment 8 of the present invention.
(E) is a diagram illustrating a sound image control effect (a phase difference characteristic between left and right ears) in a passenger seat according to Embodiment 8 of the present invention.
(F) It is a figure showing a sound image control effect (right and left ear phase difference characteristic) in a driver's seat in Embodiment 8 of the present invention.
FIG. 47 is a diagram showing the overall configuration of a conventional sound image control system.
[Explanation of symbols]
1 DVD player
2 Signal processing unit
3 Multi-channel circuit
20 CT speaker
21 FR speaker
22 FL speaker
23 SR speaker
24 SL speaker
25 WF speaker
31, 32 target sound source
500 display
501 car

Claims (7)

A sound image control system that controls a sound image localization position by reproducing an audio signal with a plurality of speakers,
At least four speakers for reproducing audio signals;
Four control points correspond to the positions of both ears of the two listeners, and two target sound source positions indicating sound image localization positions felt by the two listeners are in the same direction with respect to the respective listeners. And a signal processing unit that performs signal processing for each audio signal input to each of the speakers,
In the two target sound source positions, the distance from the listener located on the target sound source side to the target sound source position for the listener is shorter than the distance from the other listener to the target sound source position for the other listener. Sound image control system set as follows. When the front of the listener is 0 degree, the direction from the listener to the target sound source position is θ degrees, the distance between the centers of the listeners is X, the sound speed is P, and the transmission from the target sound source position to each control point is performed. Assuming that the time is T1, T2, T3, and T4 in the order of control points that are closer to the target sound source position, the two target sound source positions satisfy the condition that T1 <T2 ≦ T3 (= T2 + Xsin θ / P) <T4. The sound image control system according to claim 1, wherein the sound image control system is set to satisfy. The signal processing unit is configured to output a sound to a speaker installed in a direction opposite to the two target sound source positions with respect to a center position between the two listeners in the front-rear direction and the left-right direction. The sound image control system according to claim 1, wherein input of a signal is stopped. In the case where the two target sound source positions are set in front of the two listeners, the signal processing unit may include, for each of the speakers, a speaker installed behind the listener. The sound image control system according to claim 1, wherein input of the audio signal is stopped. The signal processing unit,
A frequency dividing unit that frequency-divides the audio signal into a low-frequency component and a high-frequency component,
For a signal of a low-frequency component of the audio signal, after performing the signal processing for each signal input to each of the speakers, a low-frequency processing unit to input to each of the speakers,
A high-frequency signal input to a recent speaker from a center position of the two target sound source positions so that a signal of a high-frequency component of the audio signal is in phase with a signal input to each of the speakers by the low-frequency processing unit. The sound image control system according to claim 1, further comprising a processing unit. The plurality of speakers include a tweeter disposed in front of a center position between the two listeners,
The sound image according to claim 5, wherein the high-frequency processing unit inputs a high-frequency component of the audio signal to the tweeter when the two target sound source positions are set in front of the two listeners. Control system. The plurality of speakers are installed in an automobile, and at least one of the plurality of speakers is installed on a rear seat side,
The two listeners are located in front seats in a car,
The signal processing unit is installed in the car, and performs signal processing on audio signals of a plurality of channels, and performs signal processing on audio signals of all channels for a speaker installed on the rear seat side. The sound image control system according to claim 1, wherein the input is performed without input.

Images