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JP2003284185

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DESCRIPTION JP2003284185
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises
first and second nondirectional microphones, and combines first and second audio signals from
the first and second nondirectional microphones, and The present invention relates to a stereo
microphone device adapted to generate a directional stereo sound field signal.
[0002]
2. Description of the Related Art First, with reference to FIG. 1, a conventional stereo microphone
device (see Japanese Patent Laid-Open No. 4-27298 (Japanese Patent No. 2946638)) will be
described. In this stereo microphone device, the sense of stereo is obtained by the cabinet shape
and the distance between a pair of nondirectional microphones on the high frequency side of the
voice band, and the left and right audio signals from the pair of nondirectional microphones are
obtained on the low frequency side. The phase difference of the above is used to obtain stereo
feeling by circuit processing described later. The division on the high band side and the low band
side of the voice band is performed using a low pass filter, and the cutoff frequency of the low
pass filter depends on the distance between a pair of nondirectional microphones, but in general
A few kHz, for example, around 6 kHz. In other words, it can be said that such a stereo
microphone device divides the voice band into two bands and performs stereo sound field
processing of only the low band side using a circuit.
[0003]
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The circuit configuration of this conventional stereo microphone device will be described below
with reference to FIG. The first and second audio signals (right and left audio signals) (Rch and
Lch inputs) from the first and second nondirectional microphones 1 and 2 are respectively
transmitted to the first and second amplifiers (AMP) 3. , 4 are amplified and their respective
amplified outputs are supplied to first and second adders (subtractors) 9 and 10, respectively.
[0004]
The amplified first and second audio signals from the first and second amplifiers 3 and 4
respectively have first and second delay units (low pass filters) 5 and 6 and first and second
attenuations, respectively. Through the first and second delay / attenuation means consisting of
the second and third delay / attenuation means, and the second and second delay-delayed and
band-limited to below the cut-off frequency of the low-pass filter The delay / attenuation output
of 1 is supplied to the first and second adders (subtractors) 9 and 10, respectively, to amplify the
first and second amplified signals from the first and second amplifiers 3 and 4, respectively.
Matrix processing is performed by subtracting each from the audio signal of.
[0005]
Then, the subtraction outputs from the first and second subtractors (adders) 9 and 10 are
respectively supplied to the first and second equalizers 11 and 12 composed of filter circuits to
adjust the frequency characteristics. As a result, directional stereo sound field signals, that is, first
and second output sound signals (Rch and Lch) 13, 14 are output.
[0006]
The distance between the first and second nondirectional microphones 1 and 2 is about 30 mm.
Also, the cut-off frequency of the respective low-pass filters of the first and second delay units 5,
6 each comprising a low-pass filter is approximately 6 kHz.
Of the first and second audio signals from the first and second nondirectional microphones 1 and
2, frequency components of about 6 kHz or less are calculated by the adders (subtractors) 9 and
10, and approximately Frequency components exceeding 6 kHz are spatially calculated in stereo
by the distance between the microphones and the cabinet shape in which the first and second
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nondirectional microphones 1 and 2 are mounted.
[0007]
SUMMARY OF THE INVENTION With the miniaturization of the electronic equipment in which
the first and second omnidirectional microphones 1 and 2 are mounted, that is, with the
miniaturization of the cabinet, the first and second omnidirectional When the distance between
the microphones 1 and 2 is narrowed to, for example, 10 mm, the cutoff frequency of the low
pass filter constituting the first and second delay units 5 and 6 is about 18 kHz, and the entire
voice band is In addition, electrical stereo arithmetic processing by the circuit is required.
[0008]
Also, the first and second voices from the first and second non-directional microphones become
more likely as the voice band is extended to higher frequencies, so that the voice becomes more
susceptible to the shape of the cabinet in which the microphone is mounted. If the frequency
components below the cut-off frequency of the low-pass filter constituting the first and second
delay elements of the signal are subjected to stereo calculation with uniform characteristics, an
optimal stereo sound field can not be realized.
[0009]
For example, video cameras have become smaller and smaller in recent years, and the conditions
for the design of the cabinet and the arrangement of the microphones mounted in the cabinet
have become extremely severe. Due to the spacing between the microphones and the structure of
the cabinet, it is becoming difficult to obtain a stereo sound field on the high side of the voice.
Therefore, it has become necessary to perform stereo sound field correction using a circuit over
the entire audio band, but in that case, it is difficult to be affected by the high frequency side
susceptible to the influence of a cabinet etc. On the low frequency side, it is necessary to optimize
by changing the method of stereo sound field processing by the circuit.
[0010]
Also, the stereo operation circuit of the above-mentioned conventional stereo microphone device
[Japanese Patent Laid-Open No. 4-27298 (Patent No. 2946638)] is almost all uncorrelated in
order to emphasize the decorrelation of the left and right audio signals. There is a defect that
noise is enhanced by passing the wind noise, which is the sexing component, through the stereo
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operation circuit, but the defect is reduced by weakening the sense of stereo in the wind noise
band of several tens Hz to several hundreds Hz. It can be improved.
[0011]
In view of the above, according to the present invention, even if the sound field is disturbed in
the audio frequency band due to the difference between the cabinets in which the first and
second nondirectional microphones are mounted, the entire voice band is performed regardless
of the sound field disturbance. It is intended to propose a stereo microphone device that can
realize good stereo sound field characteristics.
[0012]
A first invention comprises first and second omnidirectional microphones, and first and second
audio signals from the first and second omnidirectional microphones. In the stereo microphone
device configured to generate a directional stereo sound field signal by combining, the first and
second voice bands of the first and second voice signals are respectively divided into a plurality
of voice bands. A plurality of first and second band-division audio signals respectively from the
first and second band-division means, and delaying and changing levels of the plurality of first
and second band-division speech signals respectively; Delay and attenuation means, and first and
second addition means for respectively adding the plurality of first and second delay and
attenuation outputs from the plurality of first and second delay and attenuation means
respectively; Second addition And a second subtraction means for subtracting the addition output
from the first addition means from the second sound signal. A stereo microphone device which
obtains a directional stereo sound field signal from the first and second subtraction means.
[0013]
A second invention has a first and a second nondirectional microphone, combines the first and
second audio signals from the first and the second nondirectional microphone, and produces a
directional stereo. In the stereo microphone device configured to generate a sound field signal,
second and first band dividing means for dividing the voice band of each of the first and second
voice signals into a plurality of voice bands, and the second A plurality of second and first delay /
attenuation means respectively delaying and changing levels of the plurality of second and first
band-divided speech signals respectively from the first and second band-dividing means; The
plurality of second and first band-division speech signals from the first band division means, and
the plurality of first and second delays respectively from the plurality of first and second delay
and attenuation means・ Attenuation output Controlling respective levels of a plurality of first
and second subtraction outputs respectively from the plurality of first and second subtraction
means and the plurality of first and second subtraction means respectively subtracting A
plurality of first and second level control means, and a plurality of first and second level
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controlled outputs respectively from the plurality of first and second level control means
respectively; It is a stereo microphone apparatus which has a second addition means and is
adapted to obtain a directional stereo sound field signal from the first and second addition
means.
[0014]
According to the first aspect of the present invention, the first and second band dividing means
divide the voice bands of the first and second voice signals into a plurality of voice bands,
respectively. Delay and attenuation means respectively delay the plurality of first and second
band-divided speech signals from the first and second band-dividing means and change the level,
and the first and second addition means , Adding the plurality of first and second delay /
attenuation outputs respectively from the plurality of first and second delay / attenuation means,
and adding from the second addition means by the first subtraction means The output is
subtracted from the first speech signal, and the second subtraction means subtracts the addition
output from the first addition means from the second speech signal, and the first and second
subtraction means direct the directed signal. You get sex stereo sound field signal To.
[0015]
According to the second invention, the voice bands of the first and second voice signals are
respectively divided into a plurality of voice bands by the second and first band dividing means,
and the plurality of second and first voice bands are respectively divided. Delay and attenuation
means for respectively delaying and changing the levels of the plurality of second and first banddivided speech signals from the second and first band-dividing means, respectively; A plurality of
second and first band-division speech signals from the second and first band-division means by
the subtraction means, and a plurality of each from the plurality of first and second delayattenuation means The first and second delay / attenuation outputs are respectively subtracted,
and the plurality of first and second level control means respectively cause the plurality of first
and second plurality of first and second subtraction means respectively. 2 The level of each of
the subtraction outputs is controlled, and the plurality of first and second level-controlled
outputs respectively from the plurality of first and second level control means are respectively
added by the first and second addition means. The directional stereo sound field signal is
obtained from the first and second addition means.
[0016]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The circuit configuration of an
example of a stereo microphone device according to an embodiment of the present invention will
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be described in detail with reference to FIG. 2 as follows. Will be described with the same
reference numerals.
The stereo microphone device of this example has first and second nondirectional microphones 1
and 2, and the first and second audio signals from the first and second nondirectional
microphones 1 and 2 are detected. It is a stereo microphone device that is synthesized to
generate a directional stereo sound field signal.
[0017]
The first and second audio signals (right and left audio signals) (Rch and Lch inputs) from the
first and second nondirectional microphones 1 and 2 are input to the first and second amplifiers
3 and 4, respectively. The input is amplified and its amplified output is supplied to the first and
second adders 9, 10 respectively.
[0018]
The respective amplified outputs input to and amplified by the first and second amplifiers 3 and
4 respectively have a plurality of voice bands of the first and second voice signals respectively,
here, for example, four voice bands. It supplies to the 1st and 2nd band division means to divide.
The first band division means comprises first to fourth band division units 30 to 33 connected in
parallel to each other.
The second band division means is composed of first to fourth band division units 34 to 37
connected in parallel to each other.
[0019]
When each of the first to fourth band division units 30 to 33 and 34 to 37 is configured by a
band pass filter (BPF), each filter bank is configured as shown by B1 to B4 in FIG. The low pass to
high pass sequentially, and adjacent pass bands partially overlap each other.
[0020]
When the first to fourth band division units 30 to 33 and 34 to 37 are respectively configured by
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low pass filters (LPFs), the respective filter banks are cut as shown by B1 to B4 in FIG. 4. In the
low pass filter characteristics LPF1 to LPF4 in which the off frequency sequentially changes from
low to high, a band B4 obtained by subtracting the band of the low pass filter characteristic LPF3
from the band of the low pass filter characteristic LPF4 and a band from the low pass filter
characteristic LPF3 to the low pass filter characteristic LPF2 A band B3 obtained by subtracting,
a band B2 obtained by subtracting the band of the low pass filter characteristic LPF1 from the
band of the low pass filter characteristic LPF2, and a band B1 formed by the low pass filter
characteristic LPF1 become a pass band, and the low band side of the pass band partially
overlaps .
[0021]
In this case, the pass bands of the first band division units 30 and 34 are the same.
Similarly, the passbands of the second band division units 31 and 35 are the same.
The pass bands of the third band division units 32 and 36 are the same.
The pass bands of the fourth band division units 33 and 37 are the same.
[0022]
The band division outputs from the first to fourth band division units 30 to 33 are the first to
fourth of the first to fourth delay units 40 to 43 and the first to fourth attenuation units 50 to 53,
respectively. The first adder (addition means) 20 is supplied and added through the cascade
means, and the addition output is supplied to a second adder (subtractor) [addition means
(subtraction means)] 10 to Is subtracted from the amplified left audio signal from the amplifier 4
of FIG.
[0023]
The band division outputs from the first to fourth band division units 34 to 37 are respectively
the first to fourth of the first to fourth delay means 44 to 47 and the first to fourth attenuation
means 54 to 57. The cascaded means is supplied to the second adder (addition means) 21 for
addition, and the addition output is supplied to a first adder (subtractor) [addition means
(subtraction means)] 9 to Is subtracted from the amplified right audio signal from the amplifier 3,
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i.e., a matrix operation process is performed.
[0024]
The respective subtraction outputs from the first and second subtractors (adders) 9 and 10 are
respectively supplied to first and second equalizers 11 and 12 composed of filter circuits, and the
frequency characteristics are adjusted. Thereafter, directional stereo sound field signals, that is,
first and second output sound signals (Rch and Lch) 13 and 14 are output.
[0025]
The delay time of the first to fourth delay means 40 to 43 and the attenuation of the first to
fourth attenuation means 50 to 53 for each of the band division outputs from the first to fourth
band division units 30 to 33 Amount, and delay time of the first to fourth delay means 44 to 47
and attenuation of the first to fourth attenuation means 54 to 57 for each of the band division
outputs from the first to fourth band division units 34 to 37 By optimizing the quantities
individually, good stereo sound field characteristics can be obtained over the entire audio band.
[0026]
In the conventional stereo microphone device described with reference to FIG. 1, since the first
and second delay devices 5 and 6 also serve as a band limiting function, they are usually
configured with a low pass filter (LPF). In this case, in order to simultaneously satisfy the two
parameters of the delay amount and the cut-off frequency, it is necessary to optimize the filter to
be used, and it is difficult to fit it. In this case, since the band division means and the delay means
are independent, optimization of the two parameters of the pass band and the delay amount is
much easier.
[0027]
Although the circuit configuration of another example of the stereo microphone device according
to the embodiment of the present invention will be described in detail with reference to FIG. 5
below, the portions corresponding to FIGS. 1 and 2 in FIG. The description will be given with the
same reference numerals.
The stereo microphone device of this example has the first and second non-directional
microphones 1 and 2 as in FIG. 2, and the first and second non-directional microphones 1 and 2
from the first and second non-directional microphones 1 and 2, respectively. It is a stereo
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microphone apparatus which synthesize | combined the audio | voice signal of 2, and was made
to produce | generate a directional stereo sound field signal.
[0028]
The first and second audio signals (right and left audio signals) (Rch and Lch inputs) from the
first and second nondirectional microphones 1 and 2 are input to the first and second amplifiers
3 and 4, respectively. It is input and amplified.
[0029]
The respective amplified outputs input to and amplified by the first and second amplifiers 3 and
4 respectively have a plurality of voice bands of the first and second voice signals respectively,
here, for example, four voice bands. It supplies to the 2nd and 1st band division means to divide.
The first band division means comprises first to fourth band division units 30 to 33 connected in
parallel to each other.
The second band division means is composed of first to fourth band division units 34 to 37
connected in parallel to each other.
[0030]
When each of the first to fourth band division units 30 to 33 and 34 to 37 is configured by a
band pass filter (BPF), each filter bank is configured as shown by B1 to B4 in FIG. The low pass to
high pass sequentially, and adjacent pass bands partially overlap each other.
[0031]
When the first to fourth band division units 30 to 33 and 34 to 37 are respectively configured by
low pass filters (LPFs), the respective filter banks are cut as shown by B1 to B4 in FIG. 4. In the
low pass filter characteristics LPF1 to LPF4 in which the off frequency sequentially changes from
low to high, a band B4 obtained by subtracting the band of the low pass filter characteristic LPF3
from the band of the low pass filter characteristic LPF4 A band B3 obtained by subtracting, a
band B2 obtained by subtracting the band of the low pass filter characteristic LPF1 from the
band of the low pass filter characteristic LPF2, and a band B1 formed by the low pass filter
characteristic LPF1 become a pass band, .
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[0032]
In this case, the pass bands of the first band division units 30 and 34 are the same.
Similarly, the passbands of the second band division units 31 and 35 are the same.
The pass bands of the third band division units 32 and 36 are the same.
The pass bands of the fourth band division units 33 and 37 are the same.
[0033]
The band division outputs from the first to fourth band division units 30 to 33 are respectively
supplied to first to fourth adders (subtractors) [addition means (subtraction means)] 64-67.
The band division outputs from the first to fourth band division units 34 to 37 are respectively
supplied to first to fourth adders (subtractors) [adding means (subtracting means)] 60 to 63.
[0034]
The band division outputs from the first to fourth band division units 30 to 33 are the first to
fourth of the first to fourth delay units 40 to 43 and the first to fourth attenuation units 50 to 53,
respectively. First to fourth adders (subtractors) [adding means (subtracting means)] 60 to 63
through the cascade means, and the band division outputs from the first to fourth band division
units 34 to 37, respectively Are respectively subtracted from
[0035]
The band division outputs from the first to fourth band division units 34 to 37 are respectively
the first to fourth of the first to fourth delay means 44 to 47 and the first to fourth attenuation
means 54 to 57. The first to fourth adders (subtractors) [adding means (subtracting means)] 64
to 67 are supplied to the first to fourth band dividers 30 to 33 respectively through the cascade
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means. Each is subtracted from the output.
[0036]
The first to fourth subtraction outputs from the first to fourth subtractors 60 to 63 are supplied
to first to fourth gain control means 70 to 73, respectively, and the levels are controlled,
respectively. The signal is supplied to an adder (addition means) 80 of 1 and added.
[0037]
The first to fourth subtraction outputs from the first to fourth subtractors 64 to 67 are
respectively supplied to first to fourth gain control means 74 to 77, and the levels thereof are
controlled, respectively. It is supplied to the two adders (addition means) 81 and added.
[0038]
Then, directional stereo sound field signals from the first and second adders 80 and 81, that is,
first and second output sound signals (Rch and Lch) 13, 14 are output.
[0039]
In the stereo microphone device according to the embodiment of the present invention shown in
FIGS. 2 and 5, the first and second non-directional signals are divided for each of the bands
divided by the first and second band dividing means of the voice band. Parameters such as stereo
sensitivity characteristics and frequency level characteristics can be optimally set in
consideration of the effect of the sound field due to the mounting distance of the microphone to
the cabinet and the shape of the surrounding cabinet.
[0040]
The stereo microphone device according to the embodiment of the present invention shown in
FIG. 2 and FIG. 5 can be configured with an analog circuit or a digital circuit, and can be
implemented by software operating on a digital signal processor (DSP) or computer. Can also be
realized.
[0041]
According to the first invention, the first and second nondirectional microphones are combined,
and the first and second audio signals from the first and second nondirectional microphones are
combined. In the stereo microphone device configured to generate a directional stereo sound
field signal, first and second bands respectively dividing the voice bands of the first and second
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voice signals into a plurality of voice bands. A plurality of first and second delay / attenuation
means for respectively delaying and changing the levels of the plurality of first and second banddivision audio signals from the division means and the first and second band-division means,
respectively; Means, and first and second addition means for respectively adding the plurality of
first and second delay and attenuation outputs from the plurality of first and second plurality of
delay and attenuation means, and Addition from the addition means A first subtracting means for
subtracting the output from the first audio signal; and a second subtracting means for
subtracting the addition output from the first adding means from the second audio signal; And
since the stereo sound field signal of directivity is obtained from the second subtraction means,
the optimum stereo feeling in the low frequency which is easily influenced by wind noise and the
high frequency which is easily influenced by cabinet shape And a frequency characteristic is
obtained, and it is possible to obtain a stereo microphone device capable of obtaining a stereo
operation effect over the entire audio band.
[0042]
According to the second invention, the first and second nondirectional microphones are
combined, and the first and second audio signals from the first and second nondirectional
microphones are combined to obtain directivity. And second band dividing means for dividing the
voice band of each of the first and second voice signals into a plurality of voice bands, and a
stereo microphone apparatus configured to generate a stereo sound field signal of A plurality of
second and first delay / attenuation means for respectively delaying and changing levels of the
plurality of second and first band-divided speech signals from the second and first band-dividing
means; From the plurality of second and first band-division speech signals from the plurality of
first and second band-dividing means, and respectively from the plurality of first and second
band-dividing speech signals and respectively from the plurality of first and second delayattenuation means Delayed and attenuated output Controlling the levels of the plurality of first
and second subtraction outputs respectively from the plurality of first and second subtraction
means and the plurality of first and second subtraction means respectively subtracting First and
second level control means respectively adding a plurality of first and second level controlled
outputs respectively from the plurality of first and second level control means Because the
directional stereo sound field signal is obtained from the first and second addition means, the
low-pass frequency susceptible to the influence of wind noise, and the influence of the cabinet
shape It is possible to obtain optimal stereo feeling and frequency characteristics at high
frequencies that are easily received, obtain stereo processing effects over the entire audio band,
and adjust each of the divided audio bands to a desired level Can achieve levels equalizer
function, moreover, does not use a high-order filter of the equalizer circuit, it is possible to obtain
a stereo microphone apparatus capable of improving the conventional phase characteristics and
S / N.
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