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JPH04356900

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DESCRIPTION JPH04356900
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound source for recording when recording using a microphone on a recording medium such as
an audio tape used for a cassette deck or a video tape used for a deck video or video movie. More
specifically, the present invention relates to a surround microphone system for recording
surround signals.
[0002]
2. Description of the Related Art FIG. 7 shows a conventional example of a stereo microphone
system.
[0003]
Sound waves W1 and W2 emitted from a sound source 1 to be recorded are collected by a first
microphone 2 separated by a distance D and a second microphone 3 separated by a distance D +
d.
Sounds N1 to N5 and N6 to N10 which are not desired to be recorded are also collected at the
same time to become electric signals S1 and S2, and are recorded by the recording device 4. The
sounds N1 to N5 and N6 to N10 which are not desired to be recorded include surround signals
of the recording sound field.
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[0004]
The prior art will be described in more detail with reference to FIG. In FIG. 8A, the sound source
1 models the time waveform of the sound wave generated at time t1 and expresses it as W0. FIG.
8B is a model of the time waveform of the signal S1 collected by the first microphone 2 of the
sound wave W1 generated by the sound source 1. The time difference t2-t1 corresponds to the
distance difference D between the sound source 1 and the first microphone 2 shown in FIG. FIG.
8C is a model of the time waveform of the signal S2 collected by the second microphone 3 of the
sound wave W2 generated by the sound source 1. The time difference t3-t1 corresponds to the
distance difference D + d between the sound source 1 and the second microphone 3 shown in
FIG. The sounds N1 to N5 and N6 to N10 which are not desired to be recorded are represented
by N as waveforms having no correlation with each other.
[0005]
However, in the configuration of the conventional example described above, first, it is larger than
the sound that the user does not want to record the sound desired to record, that is, the surround
signal, that is, the S / N ratio is good. In order to record, it was realized by increasing the S of the
sound to be recorded, that is, the S / N ratio by bringing the microphone closer to the sound
source in a distance, so under the condition that it can not be easily brought close to the sound
source There is a drawback that the N ratio can not be recorded well.
[0006]
Second, since two-channel recording is used, the surround sound can not be distinguished from
the sound desired to be recorded, and the surround effect can not be obtained.
[0007]
In view of the above problems, the present invention time-delays the auxiliary microphone
output so that the microphone output and the auxiliary microphone output match, and adds the
time-delayed signal to the microphone output, and This invention provides a surround
microphone system with a good S / N ratio which outputs four channels by delaying the addition
output in time and adding and subtracting the outputs.
[0008]
SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the surround
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microphone system of the present invention has a position closer to a sound source that collects
sound waves than a microphone for collecting sound waves in stereo. First microphone, first and
second microphones for picking up sound waves from the sound source in stereo, and third twochannel branching means for branching an output signal of the first microphone into two
channels , First and second time delaying means for delaying the first and second output signals
of the first two-channel branching means, and second one for branching the output signal of the
second microphone into two channels Two-channel branching means, third two-channel
branching means for branching the output signal of the third microphone into two channels, and
the first time delaying means Fourth two-channel branching means for branching an output
signal into two channels, fifth two-channel branching means for branching an output signal of
the second time delay means into two channels, and the second two-channel branching means A
first output signal of the first input terminal, and a first output signal of the fifth two-channel
branching unit input to a second input terminal for subtraction; and The first output signal of the
third two-channel branching unit is input to the first input terminal, and the first output signal of
the fourth two-channel branching unit is input to the second input terminal; The second output
signal of the second subtraction means for subtraction and the second two-channel branching
means is inputted to the first input terminal, and the second output signal of the fifth twochannel branching means is First addition means for adding to the input terminals of 2 and
adding The second output signal of the third two-channel branching unit is input to the first
input terminal, and the second output signal of the fourth two-channel branching unit is input to
the second input terminal; The output signals of the second addition means to be added and the
first and second subtraction means are input, and the delay times of the first and second time
delay means are controlled so that the output signal value becomes minimum. Of the first adding
means, a sixth two-channel branching means for branching the output signal of the first adding
means into two channels, and an output signal of the first adding means Seventh two-channel
branching means for branching into channels, fourth time delay means for delaying the first
output signal of the sixth two-channel branching means, and first of the seventh two-channel
branching means Third time delay means for delaying the output signal; An eighth 2-channel
branching unit for branching an output signal of the time delay unit of 4 into 2 channels; a 9th 2channel branching unit for branching an output signal of the third time delay unit into 2
channels; The first output signal of the eight 2-channel branching means is input to the first
input terminal, and the first output signal of the ninth 2-channel branching means is input to the
second input terminal for subtraction And the second output signal of the eighth two-channel
branching unit to the first input terminal, and the second output signal of the ninth two-channel
branching unit as the second input The delay time of the third and fourth time delaying means is
input so that the output signal of the third adding means input to the terminal and subtracted
and the output signal of the third subtracting means are input and the output signal value
becomes minimum. Calculating means for calculating a signal for controlling the A first output
terminal for outputting a second output signal of the sixth two-channel branching means; a
second output terminal for outputting a second output signal of the seventh two-channel
branching means; And a fourth output terminal for outputting an output signal of the third
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subtracting means.
[0009]
The present invention uses the principle of synchronous addition in that when adding a plurality
of signals according to the above configuration, the correlated signals are voltage added and the
uncorrelated signals are energy added. Yes, the conventional example is further equipped with
one auxiliary microphone, and the output signal is temporally processed to pick up the sound
source to be recorded with a good S / N ratio when it is separated from the sound limit, It has the
advantage that it is possible to distinguish and pick up surround signals.
[0010]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A microphone system according to
an embodiment of the present invention will be described below with reference to the drawings.
[0011]
FIG. 1 is a block diagram of a surround microphone system according to an embodiment of the
present invention.
[0012]
In FIG. 1, the sound wave emitted from the sound source 1 at a distance is first transmitted to the
stereo microphone in the conventional example, that is, the first microphone 5 closer to the
sound source 1 than the second microphone 2 and the third microphone 3. The sound waves W0
are collected as sound waves W0 and converted into signals S1. Next, the sound waves W1 and
W2 are collected by the second and third microphones 2 and 3 and converted into signals S2 and
S3.
Also, as described above, sound waves N1 and N2 which are not desired to be recorded are
simultaneously converted.
[0013]
Now, the signal S1 picked up by the microphone 5 is branched into two channels by the first twochannel branching means 6, and the first output signal is inputted to the first time delay unit 7, A
delayed signal S4 is output, the second output signal of which is input to the second time delay 8
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to output an independently time delayed signal S5.
[0014]
The signal S2 picked up by the second microphone 2 is branched into two channels by the
second two-channel branching means 12, and the first output signal thereof is the first input
terminal of the first subtractor 30. And the second output signal is input to the first input
terminal of the first adder 17.
On the other hand, the signal S3 picked up by the third microphone 3 is branched into two
channels by the third two-channel branching means 10, and the first output signal thereof is
supplied to the first input terminal of the second subtractor 11. The second output signal is input
to the first input terminal of the second adder 16.
[0015]
The output signal S4 of the first time delay unit 7 is branched into two channels by the fourth
two-channel branching means 9, the first output signal of which is applied to the second input
terminal of the second subtractor 11. The second signal is input to the second input terminal of
the second adder 16 to output the signal S7.
On the other hand, the output signal S5 of the second time delay unit 8 is branched into two
channels by the fifth two-channel branching means 13, and the first output signal is inputted to
the second input terminal of the first subtractor 30. The second signal is input to the second
input terminal of the first adder 17 to output the signal S9.
[0016]
The signal S6 is input to the first BPF (band pass filter) 14 and the signal S8 is input to the
second BPF 15, resulting in signals S10 and S11 limited to bands around 100 Hz to 3 KHz, It is
input to the first arithmetic means 28 configured by a microcomputer or the like.
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Then, as already described, each of the output signal S2 of the second microphone 2 and the
output signal S3 of the third microphone 3 is independently operated, and the first time delay
unit 7 and the first time delay device 7 are The delay time of the second time delay unit 8 is
controlled independently.
[0017]
The output signal S9 of the first adder 17 is branched into two channels by the sixth two-channel
branching means 19, and the first output signal thereof is input to the fourth time delay unit 21
to produce the signal S13. The second output signal is output to the output terminal 32 to
become the first signal SL of four channels to be obtained.
[0018]
The output signal S7 of the second adder 16 is branched into two channels by the seventh twochannel branching means 18, and the first output signal thereof is inputted to the third time
delay unit 20 and the signal S12 is obtained. The second output signal is output to the output
terminal 31 to be the four channels of the second signal SR to be obtained.
[0019]
On the other hand, the output signal S13 is branched into two channels by the eighth twochannel branching means 23, the first output signal of which is inputted to the first input
terminal of the third subtractor 25, and the second signal The output signal is input to the first
input terminal of the third adder 24.
[0020]
Further, the output signal S12 is branched into two channels by the ninth two-channel branching
means 22, and the first output signal is inputted to the second input terminal of the third
subtractor 25 and the signal S15 is obtained. The second output signal is output to the second
input terminal of the third adder 24 to output the signal 14.
The output signal S14 is output to the output terminal 33, and becomes a third channel SC signal
to be obtained.
[0021]
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Further, the output signal S15 is branched into two channels by the tenth two-channel branching
means 23, and the first output signal is outputted to the output terminal 34 to become the fourth
channel signal SS to be obtained, The second output signal is input to the third BPF 27 and
becomes a signal S16 limited to a band up to around 100 Hz to 3 KHz, and is input to the second
calculation means 29 configured by a microcomputer or the like.
[0022]
Hereinafter, the present embodiment will be described in more detail with reference to FIGS.
The signal S1 is externally input to a first time delay 7 and a second time delay 8 which can
control its delay time.
The first time delay unit 7 may generate a delay time corresponding to the distance difference
D1 between the first and second microphones 1 and 2 or the first and third microphones 1 and
3. Although depending on the direction angle of 1, the maximum value Tm of the delay time
satisfies the following equation (1).
C is the velocity of sound.
[0023]
Tm = D1 / C [sec] (1) Now, this delay time changes as shown in FIG. 3 according to the direction
angle X of the sound source, and the sound source or the microphone moves, or If each moves at
the same time, it must be automatically changed to an optimal value.
[0024]
Next, the method of automation will be described with reference to FIGS. 1 and 4.
However, since the two-channel automatic calculation composed of the first time delay unit 7 and
the second time delay unit 8 is performed independently, only one channel will be described.
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[0025]
The output signal S5 of the second time delay unit 8 is branched into two channels by the fifth
two-channel branching means 13, and the first output signal thereof is applied to the first input
terminal of the first subtractor 30. input.
On the other hand, the output signal S2 of the second microphone 2 is branched into two
channels by the second two-channel branching means 12, and the first output signal is inputted
to the second input terminal of the first subtractor 30, An output signal S8 is obtained.
[0026]
The output signal S8 indicates the correction error of the delay time caused by the distance
between the first and second microphones 5 and 2 and the direction angle X of the sound source.
That is, it is realized by changing the delay time value of the second time delay unit 8 so as to
always minimize the output signal S8 of the first subtractor 30.
[0027]
The output signal S8 is input to the second BPF 15 to obtain a signal S11.
The second BPF 15 has a frequency band of 100 Hz to 3 kHz for a sound source such as voice to
be normally recorded, and has a function of excluding a malfunction at other frequencies.
However, this second BPF 15 is not necessary when this automatic operation works, for example,
because the sound source to be recorded is limited.
[0028]
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The output signal S11 of the second BPF 15 is input to the input terminal of the first arithmetic
means 28, which executes the arithmetic operation described below, and outputs the delay time
control signal S13 of the second time delay unit 8. .
[0029]
FIG. 4 is a program flow of the first arithmetic means 28. As shown in FIG.
In FIG. 4, first, at step 50, the delay time of the second time delay unit 8 is initialized to zero. At
step 51, the delay time value is increased for each unit. In step 52, subtraction is performed by
the first subtractor 30 to obtain a signal S8. In step 53, if the value is the minimum, the next step
54 is performed, otherwise step 51 is performed. In step 54, if the function is to be stopped, the
progress of the program is ended, otherwise step 50 is executed.
[0030]
FIG. 2 shows a time waveform model of each signal at the moment when the signal S8 or the
signal S11 is the minimum value at step 53 in FIG.
[0031]
The sound waves W1 to W3 emitted from the sound source 1 at a distance are first collected by
the first microphone 5 close to the sound source 1 and converted into the signal S 1, and then
collected by the second microphone 2 And converted into a signal S2, collected by the third
microphone 3, and converted into a signal S3.
Also, as described above, sound waves N1 and N2 which are not desired to be recorded are
simultaneously converted. However, the sound waves N1 and N2 which are not desired to be
recorded are expressed as sound waves N because their energy is added as background noise.
[0032]
First, FIG. 2A shows the sound wave W1 from the sound source 1 and the sound wave N not to
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be recorded by expressing the time waveforms of the signal S1 and the signal N collected by the
microphone 2 by modeling. is there. At time t1, the sound wave signal W0 of the sound source 1
is input, and a signal N that the user does not want to record is also input. FIG. 2B shows a time
waveform of a signal S2 collected from the sound wave W1 from the sound source 1 and the
sound wave N not to be recorded by the second microphone 2 separated from the first
microphone 1 by D1. At time t2 delayed from time t1 by time T2, the sound wave signal W1 of
the sound source 1 is input, and the signal N is also input.
[0033]
FIG. 2 (f) shows the time waveform of the signal S3 collected from the sound wave W2 from the
sound source 1 and the sound wave N not to be recorded by the third microphone 3 separated
by D1 from the first microphone 1. is there. At time t3 delayed from time t1 by time T3, the
sound wave signal W2 of the sound source 1 is input, and the signal N is also input.
[0034]
FIG. 2C shows the time waveform of the output signal S5 of the second time delay unit 8 which is
optimally controlled by the control signal S13 output by the calculation function of the first
calculation means 28. That is, the sound wave waveform W0 shown in FIG. 2A is delayed by time
T1 to form a waveform W3.
[0035]
FIG. 2G shows the time waveform of the output signal S4 of the first time delay unit 7 optimally
controlled by the control signal S12 output by the calculation function of the first calculation
means 28. That is, the sound wave waveform W0 shown in FIG. 2A is delayed by time T2 to be a
waveform W4.
[0036]
FIG. 2D shows the time waveform of the output signal S8 of the first subtractor 30 or the output
signal S11 of the second BPF 15. As described above, when the waveform W1 shown in FIG. 2B
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matches the waveform W3 shown in FIG. 2C, the signal desired to be recorded is 0, and only the
sound wave N which is not desired to be recorded.
[0037]
Similarly, FIG. 2 (h) shows a time waveform of the output signal S6 of the second subtractor 11
or the output signal S10 of the first BPF 14, and the waveform W2 shown in FIG. If the waveform
W4 shown in 2 (g) matches, the signal desired to be recorded is 0, and only the sound wave N
which is not desired to be recorded.
[0038]
FIG. 2E shows the time waveform of the output signal S9 of the first adder 17. As shown in FIG.
That is, ideally speaking, the voltage level is increased by 6 dB by adding the signals of the same
homology level, that is, the signals with strong correlation. On the other hand, the uncorrelated
signal is energy-added and rises by 3 dB, so the S / N ratio is improved by 3 dB of the difference.
[0039]
Similarly, FIG. 2I shows a time waveform of the output signal S7 of the second adder 16, and the
S / N ratio is improved by 3 dB.
[0040]
That is, the output signal S9 of the first adder 17 is branched into two channels by the sixth twochannel branching means 19, and the second output signal becomes the first signal SL of four
channels to be obtained. The / N ratio is improved and output to the output terminal 32.
[0041]
Similarly, the output signal S7 of the second adder 16 is branched into two channels by the
seventh two-channel branching means 18, and the second output signal becomes the four
channel second signal SR to be determined. , S / N ratio is improved and output to the output
terminal 31.
[0042]
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FIG. 6 is a program flow of the second arithmetic means 29. In FIG.
In FIG. 6, first, at step 55, the delay time of the third time delay unit 20 is set to an initial value
Tm which is obtained by the equation (1).
At step 56, the delay time value is increased on a unit basis.
In step 57, the third subtracter 25 performs subtraction to obtain a signal S15. In step 58, the
next step 59 is performed if the value is the minimum, otherwise step 56 is performed. In step
59, if the function is to be stopped, the program is ended, otherwise step 55 is executed.
[0043]
FIG. 5 shows a time waveform model of each signal at the moment when the signal S15 or the
signal S16 is the minimum value at step 58 in FIG.
[0044]
Next, the operation of the third and fourth time delay units 20 and 21 and the third adder 24 and
the third subtracter 25 and the second arithmetic means 29 will be described with reference to
FIG.
[0045]
First, FIG. 5 (a) shows the time waveform of the input signal S9 of the fourth time delay unit 21
by modeling.
At time t2 delayed by time T2 from time t1, the signal W3 is input, and a signal that the user
does not want to record, that is, the surround signal N is also input.
[0046]
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FIG. 5 (b) shows the time waveform of the input signal S7 of the third time delay unit 20 as a
model.
At time t3, the signal W4 is input, and a signal that the user does not want to record, that is, the
surround signal N is also input.
[0047]
FIG. 5C shows the time waveform of the output signal S13 of the fourth time delay unit 21
optimally controlled by the control signal S18 outputted by the arithmetic function of the second
arithmetic means 29. That is, the sound wave waveform W3 shown in FIG. 5A is delayed by time
T2 to be a waveform W5.
[0048]
FIG. 5D shows the time waveform of the output signal S14 of the third adder 24. As shown in
FIG. That is, ideally speaking, the voltage level is increased by 6 dB by adding the signals of the
same homology level, that is, the signals with strong correlation. On the other hand, the
uncorrelated signal is energy-added and rises by 3 dB, so the S / N ratio is improved by 3 dB of
the difference. This signal S14 is output to the output terminal 33 to become the desired four
channel third signal SC.
[0049]
FIG. 5E shows the time waveform of the output signal S15 of the third subtractor 25 or the
output signal S16 of the third BPF 27. As described above, when the waveform W4 shown in FIG.
5B matches the waveform W5 shown in FIG. 5C, the signal desired to be recorded is 0, and only
the sound wave which is not desired to be recorded, ie, the surround signal N. This signal S15 is
output to the output terminal 34 to become the fourth channel SS signal to be obtained.
[0050]
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The signals SL, SR, SC and SS outputted to the first to fourth output terminals 31, 32, 33 and 34
described above are generally known Dolby surround reproduction signals SL, SR, SC and It
corresponds to SS. That is, although the output signal has four channels, it goes without saying
that two-channel recording can be performed on a two-channel recording medium by Dolby
encoding.
[0051]
As described above, according to the present invention, the auxiliary microphone is provided at a
position closer to the sound source than the position of the conventional stereo microphone, and
the signal collected by the auxiliary microphone is appropriately delayed in time, and the stereo
Independently added to the microphone signal to synthesize a new stereo signal SL, SR of 4channel surround, or a signal obtained by appropriately delaying a signal collected by the
auxiliary microphone and adding it to the stereo microphone, respectively It is possible to
provide a four-channel surround microphone system with a good S / N ratio by appropriately
delaying time and adding or subtracting four-channel surround new center signal SC and
surround signal SS.
[0052]
Brief description of the drawings
[0053]
1 is a block diagram showing the configuration of a microphone system according to an
embodiment of the present invention
[0054]
2 shows a waveform diagram of each part in the same embodiment, (a) is a model time waveform
diagram of the signal collected by the microphone 5
[0055]
Fig. 3 Characteristic diagram showing the relationship between the sound source direction angle
and the delay time in the same embodiment
[0056]
4 is a program flow chart showing the operation of the first arithmetic means 28 in the same
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embodiment.
[0057]
5 is a waveform diagram of each part in the same embodiment, (a) is a model time waveform
diagram of the input signal of the third time delay unit 20
[0058]
6 is a program flow chart showing the operation of the second arithmetic means 29 in the same
embodiment.
[0059]
Fig. 7 is a block diagram showing the configuration of the conventional stereo microphone
system
[0060]
Fig. 8 shows a waveform chart of each part in the conventional example, and (a) shows a model
time waveform chart of a sound wave emitted from the sound source 1 (b) shows a model time
waveform chart of a signal collected by the first microphone
[0061]
Explanation of sign
[0062]
1 sound source 2, 3, 5 microphone 6, 9, 10, 12, 13, 18, 19, 22, 23, 26 2-channel branching
means 7, 8, 20, 21 time delay unit 11, 25, 30 subtractor 14, 15, 27 BPFs 16, 17, 24 Adders 28,
29 Operating means 31 to 34 Output terminals
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