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JPH05191900

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DESCRIPTION JPH05191900
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
three-speaker sound reproducing apparatus, and more particularly to a three-speaker sound
reproducing apparatus in which a method of distributing drive signals of the speakers is
improved.
[0002]
2. Description of the Related Art Many conventional stereo sound reproducing apparatuses adopt
a two-speaker drive system, and the left and right speakers L and R add the left and right
reproduction sound signals EL and ER, so that the sound from each speaker The output is as
shown in FIG. 8, and when the listener is close to the center between the left and right speakers,
a dropout phenomenon occurs.
[0003]
Therefore, as shown in FIG. 9, a third center speaker C is provided between the left and right
speakers L and R, and EC = 1/2 (ER + EL) (1) is added as a drive signal EC of this center speaker
C3. A speaker drive system has been proposed.
As is apparent from the equation (1), the average value of ER and EL is EC, which is the sound
source arrangement of FIG.
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[0004]
However, although the hollow defect phenomenon is eliminated in this method, as shown in FIG.
10A, when the center speaker C is driven by the EC of formula (1) even under the condition of
only EL and ER = 0 originally, FIG. There is a drawback that the sound source arrangement
shown in FIG.
[0005]
As a three-speaker driving method in which this drawback is improved, for example, there is one
disclosed in Japanese Patent Laid-Open No. 3-9700.
In this method, k = | ER-EL | / | ER + EL | (2) (2) is calculated, and driving signals ER ', EL' and EC
'of R, L and C speakers are calculated by 3) Set as shown in the equation. ER '= kEREL' = kEL} (3)
EC '= (1-k) (ER + EL)
[0006]
According to this method, as shown in FIG. 11, when k = 1, for example, only the L side is
acoustic as shown in FIG. 11A and when k = 0, ER = EL. As such, only C is a sound source.
[0007]
However, even in this method, for example, even if there is a vocal sound EV originally supposed
to be at the center and a back sound EB, if the back sound EB is larger than the vocal sound EV,
as shown in FIG. It becomes a sound source distribution as shown.
If EB> EV and EL = EB + EV, ER = EV, then the drive signal of each speaker is as shown in
equation (4), EL ′ = k (EB + EV) ER ′ = k (EV)} (4) EC ′ = (1-k) (EB + 2 EV) EB is small and EV is
large k = there was a vocal sound in C, but at k 1 1, the vocal sound moves to the L side and the
vocal sound peeling phenomenon occurs There is a drawback. Also in this case, it is desirable
that the low-level vocal sound image be close to C, as shown in FIG.
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[0008]
An object of the present invention is to obtain a natural sound image by signal distribution to
each speaker such that the small level sound from the center speaker is not pulled to the position
of the large level sound in the three-speaker sound reproducing apparatus It is to propose a
configuration that can be done.
[0009]
In order to achieve the above object, the three-speaker sound reproducing apparatus according
to the first aspect of the present invention amplitude-detects the left and right signals EL and ER
of the sound signal and detects the left and right signals. Amplitude detection means for
obtaining eL and eR, comparison means for comparing the difference signal eR-eL of the left and
right side detection signals with a predetermined reference signal and obtaining a comparison
result, and different in polarity based on the comparison result Control signal output means for
outputting left and right control signals, difference component signal extraction means for
extracting two different difference component signals EL-ER and ER-EL from the left and right
signals, and the difference component signal ER-EL. Right component signal generation means
for generating a right component signal ER ′ by amplitude control with the right control signal,
and amplitude control of the difference component signal EL-ER with the left control signal to
generate a left component signal EL ′ Left component signal generation means And central
component signal generating means for amplitude-controlling the left and right side signals EL
and ER with the left and right side control signals and combining the amplitude-controlled
signals to generate a central component signal EC '; The left and right speakers for reproducing
and outputting the component signals EL ′ and ER ′, and the central speaker for reproducing
and outputting the central component signal EC ′ are provided between the left and right
speakers.
[0010]
The three-speaker sound reproducing apparatus according to the second aspect of the present
invention is a left and right signal obtained by performing correlation calculation processing on
the left and right signals EL and ER of the sound component signal to improve the correlation
between the two signals. Correlation calculation means for outputting EL 'and ER', detection
means for detecting amplitudes of the left and right side signals EL 'and ER' and outputting left
and right side detection signals eL 'and eR', and said left and right side detection signal eL ',
Comparison means for comparing eR ′ and outputting left and right control signals based on
the comparison result, and difference component signal extraction for extracting two different
difference component signals EL-ER, ER-EL from the left and right signals EL, ER Means, right
component signal generating means for amplitude controlling the difference component signal
ER-EL with the right control signal to generate a right component signal ER ′, and the difference
component signal EL-ER by the left control signal Amplitude control to generate left component
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signal EL ' Left component signal generating means, and central component signal generating
means for combining both signals obtained by controlling the amplitudes of the left and right
side signals EL and ER respectively with the left and right side control signals to generate a
central component signal EC ' Providing left and right side speakers for reproducing and
outputting the left and right side component signals EL ′ and ER ′, and a center speaker
provided between the left and right side speakers for reproducing and outputting the center
component signal EC ′ It features.
[0011]
In the apparatus according to the second aspect of the present invention, the correlation
operation means includes at least two variable coefficient units, and the EL of the left and right
side component signals is ER via another variable coefficient unit, and ER is other variable. Each
may be added to EL via a coefficient unit.
Furthermore, in the apparatus of the second invention or the apparatus, the detection means may
include means for roughening the value of the detection signal of the amplitude detection.
[0012]
In the device according to the first aspect of the invention, the left and right side signals EL and
ER are amplitude-detected to obtain the left and right side detection signals eL and eR, and the
difference signal is compared with the reference signal.
Based on the comparison result, the left and right control signals are obtained, and the difference
component signal ER-EL is amplitude-controlled by the right control signal to generate the right
component signal ER '.
The left component signal EL 'is generated by amplitude-controlling the difference component
signal EL-ER by the left control signal.
[0013]
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Signals obtained by amplitude control of the left and right side signals EL and ER by the left and
right side control signals are synthesized to generate a central component signal EC. The left and
right side speakers reproduce and output the left and right side component signals EL 'and ER',
respectively, and the center speaker reproduces and outputs the center component signal EC '.
[0014]
Thus, in the device according to the first aspect of the present invention, the smaller amplitude of
the left and right side signals EL and ER is reproduced by the center speaker, and the right
component signal ER 'is reproduced by the right speaker when the left signal EL is smaller. When
the right signal ER has a small amplitude, the left component signal EL 'is reproduced by the left
speaker.
[0015]
Next, in the device according to the second aspect of the invention, the left and right side signals
EL, ER are subjected to correlation processing to obtain the left and right side signals EL ', ER'.
The signals eL 'and eR' are obtained.
The left and right control signals are output based on the comparison result of finding the
difference component between the two signals eL 'and eR'. The subsequent operation is similar to
that of the device of the first invention.
[0016]
The calculation process is, for example, a process of multiplying EL and ER respectively by
predetermined coefficients and adding ER and EL. Furthermore, in the amplitude detection for
obtaining eL 'and eR', for example, the calculation accuracy of the detection is made coarse.
[0017]
Embodiments of the present invention shown in the drawings will be described below. FIG. 1
shows an embodiment of a three-speaker sound reproducing apparatus according to the first
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invention. In the figure, 1 and 2 are input terminals of left and right side signals ER and EL of an
acoustic signal, and 3 and 4 are amplitude detectors, which correspond to the amplitude
detection means. 5 is a subtraction circuit, 6 is a comparison circuit, and constitutes the
comparison means. 7 is a reference voltage, 8 is a polarity inverting circuit, 9 and 10 are control
waveform generating circuits, and these circuits constitute the control signal generating means.
Reference numerals 11 and 12 denote differential amplifiers, which correspond to the difference
component extraction means. 13 to 16 are gain control circuits, 17 is an addition circuit, gain
control circuits 13 and 14 correspond to the right and left component signal generating means,
respectively, and gain control circuits 15 and 16 and addition circuit 17 generate the central
component signal Configure the means. 18 is a right component signal (ER ') output terminal, 19
is a center component signal (EC') output terminal, 20 is a left component signal (EL ') output
terminal, 21 is a right speaker, 22 is a center speaker, and 23 is a left speaker It is. The left and
right side speakers 21 and 23 are provided in front of the listener position, and the center
speaker 22 is provided between the left and right side speakers 21 and 23.
[0018]
In the circuit of FIG. 1 configured as described above, the left and right side signals ER and EL are
amplitude-detected in addition to the amplitude detectors 3 and 4, respectively, and the left and
right side detection signals eR (= | ER |) and eL (= | EL |) And each signal is applied to the
subtraction circuit 5 to obtain the difference signal eR-eL.
[0019]
FIG. 2 shows signal waveforms of respective parts of the circuit of FIG.
When the figures (a) and (b) show the ER and EL, the solid line in the figure (c) shows the eR and
the broken line shows the eL. The same figure (d) represents eR-eL.
[0020]
Assuming that the difference signal eR-eL is applied to one input of the comparison circuit 6 and
the reference voltage 7 applied to the other is 0, the output becomes a solid line in FIG.
Represents the output of 8. The output of the comparison circuit 6 is a binary 1 or 0 regardless
of the output level of the subtraction circuit 5, and the control waveform generation circuits 9
and 10 respectively control the left and right side control signals shown by a solid line and a
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broken line in FIG. Although generated, each waveform has a slope of time τ. This slope is to
prevent the output of the gain control of the gain control circuits 13-16 from clicking.
[0021]
Next, the differential amplifiers 11 and 12 generate their difference component signals ER-EL
and EL-ER from the left and right side signals ER and EL, and output them to the gain control
circuits 13 and 14, respectively. The gain control circuits 13 and 14 control the amplitudes of
the respective difference component signals with the left and right side control signals to
generate the right component signal ER 'and the left component signal EL' shown in FIGS. 3 (h)
and 3 (j). .
[0022]
FIG. 3 (g) shows the difference component signal ER-EL. On the other hand, the left and right side
signals ER and EL are amplitude-controlled by the left and right side control signals in the gain
control circuits 15 and 16, respectively, and both signals are combined in the addition circuit 17
to obtain the central component signal EC shown in FIG. Generate '.
[0023]
When the signals ER ', EC' and EL 'are supplied to three speakers, a sound source distribution as
shown in FIG. 4 is obtained. That is, when the left and right side signals ER and EL are as shown
in FIGS. 2A and 2B, EL is supplied to the center speaker C and ER-EL is supplied to the right
speaker R as shown in FIG. 4A at t <t1. , T> t1, the central speaker C is supplied with ER and the
left speaker L is supplied with EL-ER.
[0024]
In ER = EL, only the sound source of the center speaker C is the same as in FIG. 11B, and in ER =
0, it is the sound source of only the left speaker L in FIG. Furthermore, under the conditions
shown in FIG. 12, that is, EL = EB + EV, ER = EV (EL> EV), EV is supplied to the center speaker C
and EB is supplied to the left speaker L.
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[0025]
If the above-described effects of the present invention are excessive, α EL and α ER (α <1) may
be added to the left and right side speakers L and R, or α1 / 2 (ER + EC) may be added to the
center speaker C. .
[0026]
FIG. 5 shows an embodiment of a three-speaker sound reproducing apparatus according to the
second invention, which achieves clear localization of the sound image of the central speaker and
clear localization of the sound image of the L and R speakers alone as in the embodiment
described above. Not only that, unnecessary movement of sound image localization is
suppressed, and a more natural three-speaker reproduction sound field can be obtained.
In FIG. 5, the same reference numerals as in FIG. 1 denote the same or similar circuits, and an
arithmetic circuit 30 corresponds to the correlation arithmetic means. Reference numerals 31
and 32 denote detection circuits, and reference numerals 33 and 34 denote lower bit truncation
circuits, which constitute the detection means. Reference numeral 35 denotes a comparison
circuit, which corresponds to the comparison means.
[0027]
FIG. 6 shows an example of the configuration of the arithmetic circuit 30, in which 31a and 31b
are coefficient (1 / x) multipliers, and 31c and 31d are adders.
[0028]
FIG. 7 shows an example of the configuration of the lower bit discarding circuit, wherein A is a
shift down circuit (1/2 m arithmetic unit) and B is a shift up circuit (2 n arithmetic unit).
[0029]
In the embodiment of FIG. 5, the left and right side signals EL and ER are input to the arithmetic
circuit 30, and the following correlation arithmetic processing is performed.
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That is, ER and EL are multiplied by coefficient 1 / x by coefficient multipliers 31a and 31b,
respectively, and the multiplication outputs are added to EL and ER by adders 31c and 31d and
converted into left and right side signals ER 'and EL'. Ru.
ER '= ER + EL / xEL' = EL + ER / x (5)
[0030]
The purpose of the correlation calculation processing is to increase the correlation of the left and
right channel signals by adding 1 / x and multiplying the signal of the opposite channel to each
of the left and right side signals EL and ER. The magnitude of the correlation between the left and
right channels can be changed by the value of the coefficient 1 / x. When 1 / x = 1, the left and
right channels are completely identical, the correlation is the highest, and the correlation
between the left and right channels is lower as 1 / x is smaller. The value of 1 / x can be
arbitrarily varied in the range of 0 <1 / x <1 according to the situation of reproduction so as to
obtain a natural reproduction sound of localization aimed by the present invention.
[0031]
In the processing of the arithmetic circuit 30, an unnatural movement of the sound image
localization can be suppressed by increasing the value of 1 / x, but conversely, the information
on the localization (stereo feeling) originally possessed by the input left and right side signals
decreases. The stereo feeling is lost. Therefore, the value of 1 / x is large for 1 / x for sources in
which the sense of localization movement is not emphasized due to the information on the
localization of the input audio source, and 1 / x for sources in which the sense of stereo is
emphasized. Adjust x to be as small as possible.
[0032]
The amplitude detection of the left and right side signals EL ′ and ER ′ with high correlation
between the left and right channels output from the arithmetic circuit 30 is performed by the
detection circuits 31 and 32, respectively, and the left and right side detection signals eL ′ (= |
EL ′ |, eR ′ ( ) Is input to the comparison circuit 35 via the lower bit truncation circuits 33 and
34.
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[0033]
Although the comparison circuit 35 outputs the left and right side control signals based on the
comparison result of eL 'and eR', they are obtained from highly correlated EL 'and ER', so eL '=
eR', that is, three speakers To 1 / x, the lower bit truncation circuits 33 and 34 are used to ensure
this point.
That is, the frequency of occurrence in the case of eL '= eR' is increased by roughening the values
of the left and right side detection signals eL ', eR' by passing through this circuit.
[0034]
For example, when the detection circuits 31 and 32 perform signal processing with digital data,
as shown in FIG. 7, assuming that the output of the detection circuit is 101101001111, shift
down circuit A of the lower bit discarding circuit shifts by 6 bits It is downed to 000000101101,
and is shifted up by 6 bits in the shift-up circuit B and truncated to 6 bits or less to be
101101000000. The value of the truncation bit position m can be arbitrarily varied in
accordance with the situation of reproduction so that the object of the present invention can be
sufficiently achieved.
[0035]
In the processing of the lower bit truncation circuit, if the value of m is reduced, the unnatural
movement of the sound image localization can be suppressed, but conversely, the information
regarding the localization (stereo feeling) originally possessed by the sound reproduction signal
is lost. You will feel less. Therefore, the value of m is small for sources in which the sense of
movement of localization is not so important due to the information on the localization of the
input sound source, and conversely m does not appear unnatural for sources in which the sense
of stereo is important Adjust to make it a little bigger.
[0036]
By thus increasing the occurrence frequency of | EL '| = | ER' |, it is possible to increase the
frequency of simultaneous reproduction from three speakers.
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[0037]
As described above, according to the present invention, the following effects can be obtained in a
three-speaker sound reproducing apparatus.
(I) It does not become a sound field of hollow. (Ii) A single sound field by the left and right signals
also becomes clear. (Iii) Even in the case of a background sound that is offset to a small level
central sound, the small level central sound can be localized by the central speaker. (IV) A natural
three-speaker reproduction sound field can be obtained by suppressing unnatural movement of
sound image localization without impairing the above effects.
[0038]
Brief description of the drawings
[0039]
1 is a block diagram showing an embodiment of the first invention of the present application.
[0040]
2 is a waveform diagram of each signal processing in the above embodiment.
[0041]
3 is a waveform diagram of each signal processing in the above embodiment.
[0042]
4 is a diagram showing the sound field distribution in the embodiment of FIG.
[0043]
5 is a block diagram showing an embodiment of the second invention of the present application.
[0044]
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6 is a block diagram showing a configuration example of the arithmetic circuit of the
embodiment of FIG.
[0045]
7 is a block diagram showing a configuration example of a lower bit truncation circuit of the
embodiment of FIG.
[0046]
8 is a diagram showing the sound source position of the conventional two-speaker drive system.
[0047]
9 is a diagram showing the sound source position of the conventional three-speaker drive
system.
[0048]
10 is a diagram showing the sound source position in the case of only EL in the conventional
three speaker drive system.
[0049]
FIG. 11 is a diagram showing a sound source position of the three-speaker driving method
disclosed in Japanese Patent Application Laid-Open No. 3-9700.
[0050]
12 is a diagram showing a sound source distribution when there is a large back sound on the left
side in FIG.
[0051]
133 is a diagram showing the position of a desirable sound source of the speaker driving
method.
[0052]
Explanation of sign
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[0053]
3, 4 amplitude detector 5 subtraction circuit 6 comparison circuit 9, 10 control waveform
generation circuit 11, 12 differential amplifier 13-16 gain control circuit 17 addition circuit 30
arithmetic circuit
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