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JPH0690500

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH0690500
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound image localization control apparatus used in a three-speaker system for outputting twochannel stereo sound.
[0002]
2. Description of the Related Art In general, a two-speaker system consisting of two speakers, one
for R channel signals and one for L channel signals, is often used for reproducing stereo signals.
[0003]
According to this two-speaker system, it is considered ideal that the listener listens at a position
where the listener and the two speakers form an equilateral triangle as shown in FIG.
[0004]
However, the listener can not always listen in an ideal position, and as shown in FIG. 6A, when
the angle between the listener and the two speakers is expanded, the sound is originally localized
between the two speakers. The sound image you want may be blurred.
Also, in the case of in-vehicle use, as shown in FIG. 6 (B), the listener will listen at a position not
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equidistant with the two speakers, and the sound image will be localized to a speaker close to the
listener. That happened.
[0005]
Then, in order to solve the above-mentioned fault, a three-speaker system is proposed.
The three-speaker system is provided with a central speaker at an intermediate position between
the R and L speakers. FIG. 7 is a block diagram showing an outline of a conventional sound image
localization control apparatus used in the three-speaker system. The R speaker, L speaker and
center speaker are not shown.
[0006]
In FIG. 7, the sound image localization control device comprises a coefficient unit 10 for
multiplying the input signal, a coefficient unit 11 for multiplying the input signal by the
multiplication coefficient of the same value as the coefficient unit 10, and each input signal It has
an adder 12 for combining and sending out a combined signal, and a coefficient unit 13 for
multiplying the combined signal.
[0007]
Next, the operation of the conventional sound image localization control apparatus will be
described.
[0008]
In FIG. 7, the R channel input signal RE 1 is branched and supplied to the coefficient unit 10 and
the adder 12.
The coefficient unit 10 multiplies RE1 by a coefficient x and supplies an output signal x · RE1 to
the R speaker.
The L channel input signal LE1 is branched and supplied to the coefficient unit 11 and the adder
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12. The coefficient unit 11 multiplies LE1 by the coefficient x and supplies the output signal x ·
LE1 to the L speaker. The adder 12 combines the LE 1 and RE 1 and supplies a composite signal
CE 1 (CE 1 = RE 1 + LE 1) to the coefficient unit 13. The coefficient unit 13 multiplies the CE1 by
a coefficient y and supplies a composite output signal y · CE1 to the center speaker.
[0009]
According to the above-described conventional sound image localization control device, it is
possible to somewhat improve the blurring of the sound image when the distance between the
two speakers is wide and the bias of the sound image localization when the two speakers and the
listener are not equidistant.
[0010]
However, since the sounds of RE1 and LE1 are simultaneously output from the center speaker,
there is a drawback that the sense of stereo is lost.
[0011]
Moreover, what was recorded on the recording medium as follows so that a sound image may be
localized between speakers at the time of reproduction | regeneration is considered.
[0012]
In general, a stereo recording medium, such as a CD, a tape or the like, is recorded such that a
sound image is localized between speakers that respectively output an L channel and an R
channel when listening in an ideal listening environment.
As described above, as a method of providing localization in stereo reproduction, it is realized by
adding a level difference (amplitude difference) or a time difference to each channel and
recording a sound (instrument sound, voice, etc.).
[0013]
For example, FIG. 8 is an explanatory view showing a relationship between each signal of L
channel and R channel of a recording medium recorded by adding a level difference and sound
image localization.
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[0014]
In FIG. 8A, when the L channel and the R channel have the same phase and the same amplitude,
the sound image is localized at the center of the two speakers.
However, when there is a signal only in the R channel in FIG. 8B, the sound image is localized to
the R speaker, and when there is a signal only in the L channel in FIG. 8C, the sound image is
localized to the L speaker.
[0015]
Next, in the L channel and the R channel recorded in advance on the recording medium at the
time of recording, there is a central component signal 0.5C which is correlated with each other.
The operation in the case of being supplied to the sound image localization apparatus of FIG. 7
will be described in consideration of the central component signal.
In this case, L- and R-channel signals are represented by L and R, respectively.
[0016]
In FIG. 7, the input signal R1 (R1 = R + 0.5C) is branched and supplied to the coefficient unit 10
and the adder 12. The coefficient unit 10 multiplies R1 by a coefficient x and supplies an output
signal x.R1 to the R speaker. Further, the input signal L1 (L1 = L + 0.5C) is branched and supplied
to the coefficient unit 11 and the adder 12. The coefficient unit 11 multiplies the coefficient x
and outputs the output signal x · L1 to the L speaker. Supply. The adder 12 combines the R1 and
L1 and supplies a composite signal C0 (C0 = L + R + C) to the coefficient unit 13. Then, the
coefficient unit 13 performs multiplication processing of the coefficient y to supply the
synthesized output signal y · C 0 to the central speaker.
[0017]
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According to the above-described conventional sound image localization control device, since the
synthesized output signal y · (L + R + C) is output to the central speaker, it is possible to prevent
the sound image from being localized unevenly.
[0018]
However, according to the three-speaker system using the conventional sound image localization
control apparatus, the sound of the central component signal is transmitted from the left and
right speakers, and not only the central component signal is transmitted from the central
speaker. Since the signals for the left and right speakers are combined and output, there is a
problem that a sufficient stereo feeling can not be obtained.
[0019]
The present invention has been made in view of the above problems, and an object thereof is to
provide a sound image localization control device capable of obtaining a sufficient stereo feeling
while preventing localized localization of a sound image. It is to provide.
[0020]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
processes L and R speakers disposed apart from each other by processing first and second input
signals. A sound image localization control device for supplying to a central speaker disposed in
the middle, the means for supplying to the L speaker a signal having no correlation with the
second input signal among the first input signals, and Means for supplying a signal having no
correlation with the first input signal to the R speaker among the second input signals, and
signals having correlation among the first and second input signals And means for combining
and supplying to the central speaker.
[0021]
According to this configuration, only the voices of the signals for the L and R speakers are output
from the L and R speakers, and the central speaker is a signal having correlation among the first
and second input signals. Since only the sound of the central component signal synthesized is
output, the listener can obtain sufficient stereo feeling while preventing the localized localization
of the sound image.
[0022]
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An embodiment of a three-speaker system using a sound image localization control apparatus
according to the present invention will be described below with reference to the drawings.
The sound image localization control apparatus of this embodiment uses an adaptive filter for
estimating a target signal.
[0023]
The adaptive filter here can be realized by digital signal processing, and there are many
algorithms for realizing the adaptive filter, but in this system, it can be realized by the LMS
algorithm that finds the minimum value of the mean square error, and the adaptive filter is an
FIR filter When configured, an effect can be obtained with several tens of taps.
[0024]
Next, the above-mentioned adaptive filter composed of an FIR filter will be described along with
the principle.
FIG. 1 is a block diagram for explaining the principle of an adaptive filter composed of an FIR
filter.
[0025]
In FIG. 1, the adaptive filter filters the input signal x while changing the filter coefficients and
outputs the target signal d so as to approximate the output signal y.
That is, the purpose of the adaptive filter is to subtract the output signal y from the target signal
d to minimize the mean square of the error signal e.
Therefore, the root mean square error, which is the root mean square value of the error signal e,
is denoted as E [e2].
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[0026]
The sound image localization control apparatus of the present invention will be described based
on this principle.
[0027]
The sound image localization control apparatus according to the present invention processes the
first and second input signals and supplies sound images to the L and R speakers disposed apart
from each other and the central speaker disposed between the two speakers. A localization
control device, which is a unit for supplying a signal having no correlation with the second input
signal to the L speaker among the first input signals, and the first of the second input signals;
Means for supplying a signal having no correlation with the input signal to the R speaker, and
means for combining the signals having correlation with each other among the first and second
input signals to supply the central speaker Is provided.
[0028]
FIG. 2 is a more detailed block diagram of the above configuration.
The sound image localization control apparatus shown in FIG. 2 combines the two input signals
L1 and R1 to generate a combined signal C0, and adds the coefficients L1 and R1 based on
predetermined control signals. Adaptive filters 2a and 2b, which are adaptive processing means
for controlling and adaptively processing to generate two estimated signals L1 'and R1', and two
error signals R0 and L0 by subtracting L1 'and R1' from C0 respectively. And subtractors 3a and
3b, which are subtraction means for obtaining R.sub.0, and coefficient control means 6a and 6b
for giving predetermined control signals to the adaptive filters 2a and 2b according to the
R.sub.0 and L.sub.0. Calculating means comprising: a subtractor 4a for obtaining R.sub.1; a
subtractor 4b for obtaining the difference between R.sub.1 and R.sub.0; and an adder 5 for
combining the output signals of the subtractors 4a and 4b to generate a combined output signal
C.sub.1; Is equipped.
Although not shown in FIG. 2, the error signals R0 and L0 and the combined output signal C1 are
subjected to signal processing such as conversion / amplification, and the R speaker, L speaker,
and the two speakers disposed separately are provided. And an output means (not shown) for
supplying a central speaker disposed in the middle.
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[0029]
Next, the operation of the sound image localization control apparatus of the present invention
configured as described above will be described.
[0030]
In FIG. 2, an input signal L1 (L1 = L + 0.5C) and an input signal R1 (R1 = R + 0.5C) are supplied
as two input signals.
[0031]
L1 branches respectively and is supplied to the adder 1, the adaptive filter 2a and the subtractor
4a.
Similarly, R1 is also supplied to the adder 1, the adaptive filter 2b and the subtractor 4b.
[0032]
The adder 1 adds the L1 and R1 and supplies a combined signal C0 (C0 = L + R + C) to the
subtractors 3a and 3b.
[0033]
The adaptive filter 2a filters L1 based on a control signal to be described later and supplies an
estimated signal L1 '(L1' = (L + 0.5C) ') to the subtractor 3a.
Then, the subtractor 3a subtracts L1 'from the C0 and supplies an error signal R0 to the R
speaker via the subtractor 4b and the output means (not shown).
Further, the control signal of the adaptive filter 2a is generated by the coefficient control means
6a based on R0 which has been subjected to the subtraction process by the subtractor 3a.
[0034]
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Then, the subtractor 4b subtracts R0 from R1 (R1 = R + 0.5C) and supplies the difference 0.5C to
the adder 5.
[0035]
The adder 5 adds the difference processed by the subtractor 4b and the difference processed by
the subtracter 4a, and outputs a combined output signal C1 (C1 = 0.5C + 0.5C = C) through the
output means. Supply to the center speaker.
[0036]
Therefore, the error signal R0, the error signal L0, and the combined output signal C1 are
supplied to the R speaker and L speaker which are disposed apart from each other and the
central speaker disposed between the two speakers.
[0037]
FIG. 3 applies the principle of the above-mentioned adaptive filter to the L channel side of the
present system, and the R channel side is also the same configuration, and the description
thereof is omitted.
[0038]
In FIG. 3, the input signal L1 (L1 = L + 0.5C) and the input signal R1 (R1 = R + 0.5C) are recorded
with the central component signal 0.5C in the same phase and the same amplitude, respectively,
L, R, It is assumed that C has no correlation.
[0039]
The relationship of FIG.
The estimated signal L1 '(L1' = (L + 0.5C) ') is obtained by filtering the L1 with the adaptive filter
2a so as to minimize the mean square value of the error signal R0.
[0040]
Then, this root mean square error becomes as shown in Equation 2.
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[0041]
Then, since L, R, and C are uncorrelated, the second term on the right side shown in Equation 2
becomes 0, and becomes the equation shown in Equation 3.
[0042]
Here, since E [R2] does not depend on the filter coefficients, the adaptive filter 2a minimizing E
[R0 2] is minimizing the second term of the right side of Eq. 3 as shown in Eq. .
Therefore, the equation 3 becomes as shown in the equation 5.
[0044]
As is apparent from the equation (5), according to the sound image localization control apparatus
of this embodiment, L and R speakers L and R are obtained by eliminating the central component
signal 0.5C from the input signals L1 and R1. It will be done.
[0045]
According to the three-speaker system using the sound image localization control apparatus of
the present invention configured as described above, the voices of the signal L and the signal R
are output to the L speaker and the R speaker as shown in FIG. At the same time, the voices of
the central output signal C1, which is correlated with each other in the input signals L1 and R1,
are output to the central speaker.
[0046]
Therefore, the listener can obtain sufficient stereo feeling while preventing the localized
localization of the sound image.
[0047]
According to the sound image localization control apparatus of the present invention configured
as described above, the first and second input signals are processed to separate L and R speakers,
and the two speakers. Means for supplying a sound image localization control device to a central
speaker disposed in the middle of the first and second input signals, among the first input
signals, to the L speaker. Means for supplying a signal having no correlation with the first input
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signal to the R speaker among the second input signals, and signals having correlation among the
first and second input signals The L and R speakers output the L signal and R signal voices
respectively from the L and R speakers, and the center speaker correlates with each other. Sex By
the sound of the center component signal only is output, while preventing uneven localization of
the sound image, it noted and may listener obtain sufficient stereo.
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