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JP2011193330

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DESCRIPTION JP2011193330
An object of the present invention is to realize a microphone device capable of further
suppressing wind noise even in a strong wind, without impairing the sound quality of an audio
signal to be picked up as much as possible. A microphone device according to the present
invention includes a microphone for acquiring voice, wind extraction means for extracting a
component based on wind among voices acquired by the microphone, and a voice of high
frequency component from the voice acquired by the microphone. A high frequency extraction
means for extracting, a mixing means for mixing the voice acquired by the microphone and the
voice extracted by the high frequency extraction means, the mixing means being based on the
component based on the wind extracted by the wind extraction means Thus, the mixing ratio
between the voice acquired by the microphone and the voice extracted by the high frequency
extracting means is adjusted. [Selected figure] Figure 1
Microphone device
[0001]
The present invention relates to a microphone device capable of wind noise reduction processing
by forming a sound pressure gradient type directional microphone by combining a plurality of
microphone units.
[0002]
The configuration of a conventional microphone device capable of wind noise reduction
processing will be described with reference to FIG.
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The output of the first microphone unit 1 is input to the A / D conversion means 11, and the
output of the second microphone unit 2 is input to the A / D conversion means 21. The A / D
conversion means 11 and 21 are means for converting an analog signal into a digital signal in
order to process the acoustic signal in a digital signal by the directivity synthesis means 100 and
the frequency characteristic correction means 200.
[0003]
The output signals of the first and second microphone units 1 and 2 are also input to the wind
noise detection means 300. The directivity synthesis means 100 comprises a first signal delay
means 22, a first signal amplification means 23, and a signal subtraction means 51. The first
signal delay means 22 delays the output signal of the A / D conversion means 21 by time τ1.
The first signal amplification means 23 variably amplifies the output signal of the first signal
delay means 22 based on the parameter α set according to the wind noise level output from the
wind noise detection means 300. The parameter α is an amplification factor that changes in 0 ≦
α ≦ 1. It is 1 when there is no wind and 0 when it is the strongest. The signal subtraction means
51 is a means for subtracting the output signal of the signal amplification means 23 from the
output signal of the A / D conversion means 11.
[0004]
The frequency characteristic correction means 200 is composed of a signal addition means 61, a
second signal delay means 62, and a second signal amplification means 63. The signal addition
means 61 adds the output signal of the signal subtraction means 51 and the frequency
characteristic correction signal output from the signal delay means 62. The second signal delay
means 62 delays the output signal of the signal addition means 61 by time τ2. The second
signal amplification means 63 variably amplifies the output signal of the second signal delay
means 62 in accordance with the parameter α corresponding to the level of wind noise output
from the wind noise detection means 300.
[0005]
The wind noise detection means 300 receives the signals from the first and second microphone
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2
units 1 and 2 and detects wind noise. The wind noise detection method compares the low-pass
and high-pass components to calculate the cross-correlation of the output signals of the two
microphone units 1 and 2 in order to use the frequency spectrum, and compares the wind signal
with the voice signal. Noise utilizes the fact that the correlation value of the signal is low. More
specifically, there is a method shown in Patent Document 2 and the like.
[0006]
With this configuration, the sound wave from the lower side of the drawing is canceled by the
signal delay means 22 and the signal subtractor 51, and when there is no wind, the directivity
synthesis means 100 emphasizes the high region by 6 dB / oct. An audio signal coming from
above in the drawing is output. Since the frequency characteristic correction means 200 operates
as a normal integrator when there is no wind, it has a characteristic that the high region is
attenuated at 6 dB / oct, which is the inverse characteristic of the frequency characteristic
correction means 200. Therefore, an audio signal having flat frequency characteristics can be
obtained from the frequency characteristic correction means 200.
[0007]
When the wind blows, the value of the parameter α decreases. Therefore, the point at which the
high frequency band is emphasized by the frequency characteristic from flat to 6 dB / oct at the
same time when the signal subtraction means 51 and the signal delay means 22 decrease the
cancellation effect of the sound wave from the lower direction Will rise. That is, the drop of the
signal in the low band is suppressed. On the other hand, in the frequency characteristic
correction means 200, since the frequency characteristic becomes flat in the low band part due
to the decrease of the parameter α, the overall frequency characteristic becomes flat together
with the change of the frequency characteristic in the frequency characteristic correction means
200.
[0008]
As described above, the reduction of the frequency characteristic in the low band is suppressed
and the correction amount is reduced, thereby suppressing the enhancement of the wind noise
component much in the low band.
[0009]
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JP 10-126878 JP 10 JP 10-23 590
[0010]
However, in the above configuration, the wind noise can not be suppressed more than when the
value of the parameter α which is the output of the wind noise detection means 300 becomes
zero.
The reason is that in this case, the sound captured by the microphone unit 1 is only output as it
is, and there is a problem that if the wind noise is captured by the microphone unit 1, it is output
as it is.
[0011]
The present invention has been made in view of such conventional problems, and realizes a
microphone device capable of further suppressing wind noise even in a strong wind without
deteriorating sound quality of an audio signal to be picked up as much as possible. The purpose
is to
[0012]
In order to solve the above problems, a microphone device according to the present invention
includes a microphone for acquiring voice, a wind extraction unit for extracting a component
based on wind among voices acquired by the microphone, and a high frequency from the voice
acquired by the microphone A high frequency extraction unit for extracting the component
sound, and a mixing unit for mixing the sound acquired by the microphone with the sound
extracted by the high frequency extraction unit, and the mixing unit uses the wind extracted by
the wind extraction unit The mixing ratio of the sound acquired by the microphone to the sound
extracted by the high frequency extraction means is adjusted based on the component based on.
[0013]
As described above, according to the microphone device of the present invention, the wind noise
can be suppressed without deteriorating the sound quality by changing the directivity to the nondirectivity as usual to the wind noise of the normal level. By suppressing the low-pass component
further during rapid wind change, for example, gust wind, it is possible to suppress wind noise
that could not be suppressed conventionally.
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[0014]
The block diagram showing the configuration of the microphone device according to the first
embodiment. The flowchart showing the operation of the microphone device according to the
first embodiment. The schematic diagram showing the characteristic of the audio output of the
microphone device according to the first embodiment. A schematic diagram for explaining the
features of such a microphone device A block diagram showing a configuration of a conventional
microphone device
[0015]
〔1.
Embodiment 1] [1-1.
Configuration] A microphone device according to a first embodiment of the present invention will
be described with reference to FIG.
FIG. 1 is a block diagram showing the basic configuration of the microphone device of the
present embodiment.
In this figure, blocks having the same functions as in FIG. 5 are assigned the same reference
numerals and detailed explanations thereof will be omitted.
[0016]
The output signals of the first and second microphone units 1 and 2 are both input to the
directivity synthesis means 100 and then to the frequency characteristic correction means 200,
and are output as directivity-synthesized speech signals.
Further, the output signals of the microphone units 1 and 2 are also input to the wind noise
detection means 300, and the wind noise level α is detected. Here, windless, that is, when there
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is no wind noise, α = 1 is output, and as wind noise increases, it is reduced to α = 0.
[0017]
The variation detection means 3 detects the variation of the wind noise detection means 300
output α. It is configured by a differentiating circuit, and here, a value of 0 to 1 is output as A
according to the decrease width of the input value. The filter 4 is an audio signal as an input, is a
high pass filter with a cutoff frequency of 200 Hz, and cuts low frequency components of the
audio signal. A value obtained by subtracting the output A of the change amount detection means
3 from 1 is obtained by the subtractor 5, and the output of the filter 4 and the input of the filter
4 are combined with the multipliers 6, 7 and the adder 8. A weighted addition output with a
certain audio signal can be obtained. That is, low-pass cutting is performed according to the
change amount A of the audio signal. As shown in FIG. 3, when the change amount A is 0, no lowpass cut is performed as shown in (A). As the value of the change amount A increases, the lowerpass components are cut deeper as (B) and (C).
[0018]
〔1−2. Operation] The operation of the thus configured microphone device will be described
with reference to FIG. When the recording mode is set in step S100 and the operation is started,
the sound acquisition by the microphone units 1 and 2 is started in step S110, and the voice
signal synthesized with directivity by the directivity synthesizing unit 100 and the frequency
characteristic correcting unit 200 is It is output.
[0019]
Next, in step S120, wind noise (wind noise) is extracted by the wind noise detection means 300,
and a wind noise level α is output. When there is no wind, the wind noise level does not
fluctuate at α = 1, but when the wind blows, the value of the wind noise level α decreases from
1 to 0, and when the wind continues blowing, the value according to the wind intensity It
changes finely in the vicinity.
[0020]
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Next, in step S130, the change amount detection means 3 calculates the change amount A of the
wind noise level α. Since there is no fluctuation at wind noise level α = 1 when there is no wind,
change amount A = 0. When the wind starts blowing, the wind noise level α decreases, so a
value corresponding to the air volume is output. When a strong wind starts blowing suddenly, a
value close to 1 is output, and when a weak wind starts blowing, a small value close to 0 is
output. Further, even when the wind continues blowing, for example, when the wind suddenly
becomes strong, the value of the wind noise level α sharply decreases, so a large value close to 1
is output. The amount of change A is given to the multiplier 7 via the subtracter 5 and the one
directly to the multiplier 6.
[0021]
Based on the amount of change A, the audio signal whose low band has been cut in step S140
and the audio signal whose low band has not been cut are mixed. Since the change amount A is 0
when there is no wind, as described above, the characteristic shown in FIG. 3A is obtained, and
the audio signal is output as it is without being cut in the low band.
[0022]
Here, when a strong wind suddenly starts to be blown, a value close to 1 is output as the amount
of change A. Therefore, the output of the filter 4, that is, the mixing ratio of the large low-pass cut
audio signal increases. As a result, the characteristic of (C) in FIG. 3 is obtained. Subsequently,
when the wind continues blowing, the amount of change A becomes a small value as described
above. Therefore, the output that has passed through the filter 4, that is, the mixing ratio of the
large low-pass cut audio signal is reduced. As a result, the characteristics shown in FIG. 3 (B) are
obtained.
[0023]
Thus, the microphone device according to the present embodiment cuts the low band portion
where the wind noise component is large according to the amount of change of the wind noise,
so that the wind noise is particularly easy to catch on the ear. Also, wind noise can be reduced
during sudden changes in wind power. Moreover, when the change in wind noise is small, the
amount of cut in the low band is small, so that the change in sound quality can be kept small. 〔
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2. Other Embodiments] As described above, Embodiment 1 has been described as an
embodiment of the present invention. However, the present invention is not limited to these.
Therefore, other embodiments of the present invention will be collectively described in this
section.
[0024]
Although the differential value of the wind noise level α is simply detected as the change
amount detection means 3, for example, as shown in FIG. 4, a certain threshold is provided and
the wind noise level α falls below a certain level The value of the change amount A may be
larger than zero. In this way, for example, the low-pass cut by the filter 4 is not performed when
the wind is weak or the change of the wind is weak, and the low-pass is always cut when the
strong wind of a certain level or more is blowing. can do. In the conventional method, wind noise
can not be removed when a strong wind blows, but the wind noise can be removed also in this
case in this embodiment. In this case, although the sound quality is changed, the wind noise
which is originally unnecessary is eliminated, and the problem can be minimized.
[0025]
Further, as the change amount detection means 3, a conversion table for the change of the input
wind noise level α or the wind noise level α is prepared in advance, and the filter coefficient of
the filter 4 is directly controlled (changed). Also good. In this case, the value of the change
amount A in FIG. 1 is fixed at 1. By configuring in this way, it is possible to freely change the
characteristics of the filter 4 according to the intensity of the wind noise level α or according to
the degree of change of the wind noise level α. For example, when the wind noise level α is 1,
the cut-off frequency of the filter 4 is lowered to 20 Hz, and the wind noise level α becomes
smaller, that is, the cut-off frequency of the filter 4 gradually approaches 300 Hz as the wind
becomes stronger. When set to, there is an effect that there is almost no change in the sound
quality when the wind is weak, and the wind noise can be further suppressed by cutting low
frequency components of a wider band when the wind is strong.
[0026]
The present invention is applicable to imaging devices such as digital video cameras and digital
still cameras.
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[0027]
Reference Signs List 1 microphone unit 2 microphone unit 3 change amount detection means 4
filter 5 subtractor 6 multiplier 7 multiplier 8 adder 100 directivity synthesis means 200
frequency characteristic correction means 300 wind noise detection means
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