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JP2002095095

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DESCRIPTION JP2002095095
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
volume control apparatus capable of properly controlling the volume of a center speaker in an
audio or video apparatus such as a television receiver having a center speaker in addition to the
left and right speakers. About.
[0002]
2. Description of the Related Art In audio or video equipment such as a television receiver, in
order to enhance the acoustic effect, in addition to the left and right speakers, a center speaker is
disposed to improve the sense of reality etc. ing. Further, as the sound supplied to the center
speaker, (L + R) signal obtained by adding the sound signal of the left (L) and right (R) channels
of the stereo signal is used, and this is used as a signal of the center channel. Hereinafter, the
audio signal of L channel is abbreviated as L signal, the audio signal of R channel is abbreviated
as R signal, and the audio signal of center channel is abbreviated as center signal.
[0003]
In an apparatus having such a center speaker, since the center signal is always supplied to the
center speaker, stereo separation may be impaired. For example, when there is a signal only in
the L channel, the R signal is zero, so the center signal is L + R = L, and when the L channel and
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center channel volumes are equal, the sound is reproduced from the middle position of the left
speaker and the center speaker I feel like I This is equivalent to a state in which the distance
between the left and right speakers is reduced, and the left and right separation feeling is
reduced.
[0004]
One way to improve this is to control the volume of the center speaker. For example, a signal in
the vocal band (about 400 Hz to 4 KHz) is extracted from the center signal component to
generate a signal for controlling the volume of the center signal, and the volume is increased
when the control signal exceeds a certain level. There is something that
[0005]
According to this example, when the center signal is small, the volume of the center is reduced
and stereo separation is improved, and when the center signal is large, clear vocal sound is
reproduced from the center speaker according to the input level. be able to.
[0006]
However, although such an example is an effective method for reproducing vocal sounds, the
vocal band also includes the tonal band of the instrument. Since the volume of the speaker is also
increased, the separation may be deteriorated when the input signal exceeds a certain level.
[0007]
Japanese Patent Laid-Open No. 4-249484 describes an example in which the volume of the
center signal is controlled using the (LR) component.
In the example of this publication, the (LR) signal is converted to DC to control the gain of the
center signal, and the levels of the L and R signals are increased or decreased according to the
output of the gain-controlled center signal. .
[0008]
Then, the difference between the left and right audio signals is detected, and if the difference is
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small, the vocal sound is output from the center speaker to extract the vocal sound from the left
and right speakers. If the difference is large, the sound of the center speaker is reduced. It is
intended to reduce the loss of vocal sound from the left and right speakers.
[0009]
However, in this example, the circuit configuration is complicated, and when the levels of L and R
signals are low, even if there is a difference between L and R signals, the level of (L−R) signal is
close to zero. There was a problem that the volume of the center speaker was not sufficiently
controlled and the SN was deteriorated.
[0010]
As described above, in the conventional volume control circuit for extracting the signal of the
vocal band to control the volume of the center signal, the vocal band includes the tonal band of
the musical instrument. Therefore, when the input signal exceeds a certain level, the separation
may be deteriorated.
[0011]
In the example of controlling the gain of the center signal using the (LR) component and
increasing or decreasing the levels of the L signal and R signal according to the output of the
gain controlled center signal, the circuit configuration is It is complicated, and when the L and R
signal levels are low, there is a problem that the volume of the center speaker is not sufficiently
controlled.
[0012]
The present invention has been made in view of the above problems, and an object of the present
invention is to provide a volume control apparatus capable of properly controlling the volume of
the center channel without impairing the stereo feeling.
[0013]
According to the present invention, there are provided first and second speakers, and a third
speaker disposed between the first and second speakers, and the first and second speakers. A
signal source for outputting the first and second audio signals (L, R) supplied to the second
speaker and the first and second audio signals are added to generate a third audio signal (L + R)
An adder circuit; a volume control circuit to which the third audio signal is input and which is
controlled by a volume control signal to be supplied to the third speaker; and the first and second
audio signals Of the signal obtained by subtracting the (L−R) signal, subtracting the first
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absolute value circuit that outputs the absolute value | L + R | of the signal added by the addition
circuit, and A second absolute value circuit for outputting the absolute value | LR |, the absolute
value of the addition signal, and the decrease A control signal is generated according to the
difference (| L + R |-| LR |) from the absolute value of the signal, and an arithmetic circuit
supplied to the volume control circuit as the volume control signal is provided. It is a volume
control device.
[0014]
According to the present invention, by using the difference value of the absolute values (| L + R || LR |) as the volume control signal of the center signal, the first audio signal (L) and the second
audio signal (L) can be used. The level of the third audio signal (L + R) can be controlled
according to the level of the audio signal (L), and the volume of the third audio signal can be
properly controlled without impairing the separation of the stereo.
[0015]
DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings.
[0016]
FIG. 1 is a block diagram showing an example in which an embodiment of the present invention
is applied to a television receiver, and 11 is an audio signal source.
As this signal source 11, a television sound multiplex signal processing circuit, a digital sound
processor or the like can be considered, and it is possible to output L signal and R signal
respectively.
[0017]
The arrangement of speakers in a television receiver is schematically shown. The receiver 12 is
provided with a left speaker 13 and a right speaker 14 and a center speaker 15, and the L signal
from the signal source 11 and the L signal from the signal source 11 are The R signal is supplied
to the left speaker 13 and the right speaker 14 respectively.
[0018]
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The L signal and the R signal are added by an adder circuit 16 to generate an (L + R) signal,
which is output as a center signal.
The center signal is supplied to the center speaker 15 via the volume control circuit 17.
[0019]
The process of generating the center signal has been described above, but in the present
invention, the volume of the center signal is controlled by the method described below.
That is, the output of the addition circuit 16 is supplied to a band pass filter (BPF) 18, which
extracts a signal (mainly vocal sound) around 400 Hz to 4 KHz and further supplies it to a DC
conversion circuit 19.
[0020]
Further, the L signal and the R signal are subtracted by a subtraction circuit 20 to generate an (LR) signal, and the output of the subtraction circuit 20 is supplied to a high pass filter (HPF) 21. A
signal of about 4 KHz or more is extracted by the HPF 21 and is further supplied to the DC
conversion circuit 22.
[0021]
The DC conversion circuits 19 and 22 are circuits for extracting absolute values of the (L + R)
signal and the (L-R) signal, and output | L + R | and | L-R |.
Further, these DC signals are supplied to the non-inverted input terminal (+) and the inverted
input terminal (-) of the operational amplifier 25 through the weighting circuit 23 composed of
the resistors R1 and R2 and the weighting circuit 24 composed of the resistors R3 and R4. The
circuit 26 including the operational amplifier 25 constitutes a volume control signal generation
circuit.
09-05-2019
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[0022]
The operational amplifier 25 forms an arithmetic circuit for generating a control voltage for
controlling the volume of the center signal, extracts the control voltage for volume control from
the output of the operational amplifier 25, and supplies the control voltage to the volume control
circuit 17. It is like that.
Therefore, the volume of the center signal is controlled in accordance with the difference
between the (L + R) component and the (L-R) component.
[0023]
The center signal may be obtained from the output of the BPF 18.
[0024]
Next, the operation of the volume control of the center speaker will be described.
The volume control circuit 17 of the present invention performs gain control of the center
channel signal as shown in FIG.
That is, the gain of the center channel is controlled by the level difference between the DC
control signals | L + R | and | LR |, and in the case of | L + R | >> | LR |, the center channel signal
is amplified and | It is attenuated in the case of L + R |> | LR |, and is not amplified (gain 0) in the
case of | L + R | = | LR |.
[0025]
This situation will be specifically described.
For example, in the state where the L signal and the R signal are substantially equal, | L + R | と
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な り 2L, and | L−R | = 0.
As a result, the state becomes | L + R | >> | LR | state A, the control voltage from the operational
amplifier 25 rises in the positive direction, the center signal is amplified and the volume rises,
and the center signal (for example, vocal sound) can be heard clearly it can.
[0026]
On the other hand, when there is a signal only in the left channel, | L + R | = L, and | L−R | = L.
As a result, the state B of | L + R | = | LR | is obtained, and the difference between the (+) and (−)
input voltages of the operational amplifier 25 becomes 0, so the center signal is not amplified.
The volume can be prevented from rising and the stereo effect will not be reduced.
[0027]
Similarly, in the state where there is a signal only in the right channel, L + R = R, and L−R = −R.
However, since the DC conversion circuits 19 and 22 take an absolute value, | L + R | = In the
state B of | LR |, the difference between the (+) and (−) input voltages of the operational
amplifier 25 becomes 0, and the center signal is not amplified.
Therefore, the volume of the center signal can be prevented from rising, and the stereo effect will
not be reduced.
[0028]
When the sound image is slightly to the left, the state C is | L + R |> | LR |, and the volume of the
center signal is attenuated compared to the state A, so that the sound image is pulled closer to
the center There is no loss of the separation feeling of the Stella.
[0029]
Also, even when the sound image is slightly to the right, since the volume of the center signal is
attenuated since | L + R |> | LR |, the sound image is not pulled closer to the center, and There is
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no loss of separation.
[0030]
As described above, according to the present invention, since the center signal is properly
controlled in accordance with the levels of | L + R | and | LR−, volume control can be performed
without losing the sense of stereo.
[0031]
The present invention is also characterized in that the HPF 21 is disposed on the output side of
the subtraction circuit 20.
That is, when a surround component (mainly around 4 KHz to 10 KHz) is included in the (L-R)
component, this surround component can also be taken in as a control signal.
In addition, since the volume is unnaturally controlled due to level fluctuation when a lowpitched component with less directionality is introduced, only the high-frequency component is
extracted by the HPF 21.
As a result, while suppressing the fluctuation of the reproduction level of the bass, the volume
control of the center speaker is performed using the directivity high-pitched band component,
and the separation of the stereo signal can be improved.
[0032]
In the process of generating the volume control signal, when the operation of (| L + R |-| LR |) is
performed by the operational amplifier 25, the amount of energy is different due to the
difference between the frequency bands of the BPF 18 and the HPF 21. Weighting is performed
by the circuits (R1 and R2) and the resistor circuits (R3 and R4), and adjustment is performed so
as to be α | L + R | -β | LR.
Since the values of α and β also depend on the controlled volume variable range of the center
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signal, they need to be adjusted in accordance with the characteristics of the equipment device to
be used.
[0033]
Next, a second embodiment of the present invention will be described with reference to FIG. The
same parts as in FIG. 1 are indicated by the same reference numerals and the detailed description
is omitted.
[0034]
In the example of FIG. 3, BPFs 181 and 182 are respectively disposed in the L signal and R signal
paths in the previous stage of the adding circuit 16, and HPFs 211 and 212 are provided in the L
signal and R signal paths in the preceding stage of the subtracting circuit 20. Each one is
arranged. The BPFs 181 and 182 extract an audio signal centered on a vocal sound as in the BPF
18 shown in FIG. 1, and from the adder circuit 16, frequency components in a predetermined
band can be obtained. The HPFs 211 and 212 also extract high-frequency tones in the same
manner as the HPF 21 in FIG. 1, and high-frequency components can be obtained from the
subtraction circuit 20.
[0035]
As described above, according to the present invention, the (L + R) signal and the (L-R) signal are
DC-converted through the BPF 18 and the HPF 21, respectively, and their absolute values | L + R
| and | LR | By using as the volume control voltage of the center signal, when there is a signal
only in the L channel or R channel, the volume control of the center channel is not performed
and the sense of stereo is not impaired, and the center signal (L + R) is present In this case, the
volume of the center speaker can be properly controlled, and the center sound can be heard
clearly.
[0036]
Further, in the present invention, even when the levels of the L signal and the R signal are low,
the difference value between the absolute values | L + R | and | LR | , SN can be improved.
[0037]
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Although the above description has dealt with the case where the present invention is applied to
a television receiver, it is needless to say that the present invention is applicable not only to this
but also to general stereo reproduction equipment.
[0038]
As described above, according to the present invention, the difference between the absolute
values | L + R | and | LR | is used to control the volume of the center signal, thereby impairing
the separation of the stereo. Thus, it is possible to provide a volume control apparatus in which
the localization of the center sound is clear.
[0039]
Brief description of the drawings
[0040]
1 is a block diagram showing a volume control device according to an embodiment of the present
invention.
[0041]
2 is an explanatory diagram for explaining the operation of the present invention.
[0042]
3 is a block diagram showing a volume control apparatus according to another embodiment of
the present invention.
[0043]
Explanation of sign
[0044]
11 Signal source 13 Left (L) speaker 14 Right (R) speaker 15 Center speaker 16 Addition (L + R)
circuit 17 Volume control circuit 18 Band-pass filter (BPF) 20 Subtraction (LR) Circuit 21 Highpass filter (HPF) 19, 22 DC conversion circuit 23, 24 Weighting circuit 25 Arithmetic circuit (opamp)
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