close

Вход

Забыли?

вход по аккаунту

?

DESCRIPTION JPH06269083

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH06269083
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone device which can be widely used, for example, a microphone mounted on a camera
integrated type VTR, a microphone for speech / song, etc. It exerts a great effect on the
microphone device.
[0002]
2. Description of the Related Art A microphone converts a change in sound pressure caused by a
sound wave into mechanical vibration of a diaphragm and operates an electroacoustic conversion
system based on the mechanical vibration to obtain an electrical signal. There are many.
Therefore, when mechanical sound is given to the diaphragm due to some factor other than the
desired voice when the desired voice is picked up by the microphone, this becomes noise for the
desired voice. In this case, if the above factor is wind, wind noise (hereinafter referred to as wind
noise) is generated.
[0003]
As a method of reducing wind noise generated in a microphone, (1) use of a windscreen
(windshield) (2) use of an electrical / acoustic high pass filter (3) adoption of a configuration
showing nondirectionality in a low range, etc. Are conventionally used frequently.
10-04-2019
1
[0004]
However, according to the method (1), in general, the wind noise becomes smaller as the outside
dimension of the windscreen is larger and the distance between the microphone element and the
inner wall of the windscreen is larger. So, if you try to reduce wind noise sufficiently, there is a
problem that you have to prepare a big windscreen.
This problem is a major obstacle to downsizing and portability of the device.
[0005]
In addition, since wind noise is mainly noise in the bass region, the method using the fixed
electrical / acoustic high-pass filter described in (2) above is effective, but it is desirable to reduce
wind noise at the same time There is also a drawback that the low frequency range of the sound
source is also reduced and the sound collection quality is reduced.
[0006]
Furthermore, the method (3) is used because the wind noise is lower when the directivity of the
microphone is omnidirectional rather than directional.
However, the wind noise reduction effect by this method is not so large, and in addition, the wind
noise does not reach a sufficiently low level due to the influence of the case when actually
configuring the microphone device.
[0007]
The applicant has previously proposed a method that can sufficiently reduce wind noise while
avoiding the above problems, as Japanese Patent Application No. 3-349274. This method is an
application of an adaptive noise canceller.
[0008]
10-04-2019
2
FIG. 8 is a block diagram showing the configuration of an example of the previously proposed
microphone device, and in the same figure, 10 is an adaptive noise canceller. First, this adaptive
noise canceller will be described.
[0009]
In the adaptive noise canceller 10, 1 is a main input terminal, 2 is a reference input terminal, and
the main input signal input through the main input terminal 1 is supplied to the combining
circuit 4 through the delay circuit 3. Further, the reference input signal input through the
reference input terminal 2 is supplied to the synthesis circuit 4 through the adaptive filter circuit
5 and is subtracted from the signal from the delay circuit 3. The output of the synthesis circuit 4
is fed back to the adaptive filter circuit 5 and is led to the output terminal 6.
[0010]
In this adaptive noise canceller, the main input signal is the sum of the desired signal s and the
noise signal n0 uncorrelated with it. On the other hand, the noise signal n1 is input as the
reference input signal. The noise signal n1 of the reference input is uncorrelated with the desired
signal s, but is correlated with the noise signal n0.
[0011]
The adaptive filter circuit 5 filters the reference input noise signal n1 and outputs a signal y
which approximates the noise signal n0. In this case, the adaptive filter circuit 5 updates the
filtering coefficient of the reference input noise signal n1 by the predetermined adaptive
algorithm so that the subtraction output (residual output) e of the combining circuit 4 is
minimized. Go on.
[0012]
As the output signal y of the adaptive filter circuit 5, it is also possible to obtain a signal having
the same amplitude as that of the noise signal n0. The delay circuit 3 compensates for the time
10-04-2019
3
delay required for the arithmetic processing in the adaptive filter circuit 5, the propagation time
in the adaptive filter, and the like, and is used to time align with the signal to be subtracted.
[0013]
The principle of the adaptive noise canceller will be described below.
[0014]
Now, assuming that the desired signal s, the noise n0, the noise n1, and the output signal y are
statistically stationary and the average value is 0, the residual output e becomes e = s + n0−y.
The expected value of this squared is E [e2] = E [s2] + E [(n0-y) 2] + 2E [s (n0-y) because the
desired signal s has no correlation with the noise n0 and the output y. ]] = E [s2] + E [(n0-y) 2].
Assuming that the adaptive filter circuit 5 converges, the adaptive filter circuit 5 updates the
adaptive filter coefficients such that E [e2] is minimized. At this time, E [s2] is not affected, so
Emin [e2] = E [s2] + Emin [(n0-y) 2].
[0015]
That is, E [(n0-y) 2] is minimized by minimizing E [e2], and the output y of the adaptive filter
circuit 5 becomes an estimator of the noise signal n0. The expected value of the output from the
combining circuit 4 is only the desired signal s. That is, adjusting the adaptive filter circuit 5 to
minimize the total output power is equal to the subtraction output e being the least squares
estimated value of the desired speech signal s.
[0016]
The adaptive filter circuit 5 can be realized either by an analog signal processing circuit or a
digital signal processing circuit, but in general, a digital processing circuit using a DSP (digital
signal processor) It is made up of
[0017]
10-04-2019
4
In the example of FIG. 8, the microphone device for reducing wind noise using the adaptive noise
canceller 10 described above is realized as follows.
That is, in the microphone device of FIG. 8, two microphone elements 11 and 12 are disposed in
proximity to each other. The microphone elements 11 and 12 have the same characteristics, and
for example, a nondirectional microphone unit is used.
[0018]
Then, the output of one microphone element 11 is converted into a digital signal by the A / D
converter 13, and the digital signal is supplied to the main input terminal 1 of the adaptive noise
canceller 10 as the main input signal. Further, the output of the other microphone element 12 is
converted into a digital signal by the A / D converter 14, and the digital signal is supplied to the
subtraction circuit 15.
[0019]
In the subtraction circuit 15, the difference between the digital signal of the output of the
microphone element 11 from the A / D converter 13 and the digital signal of the output of the
other microphone element 12 is determined, and the difference output is used as a reference
input signal. , And is supplied to the reference input terminal 2 of the adaptive noise canceller
10.
[0020]
Then, the signal obtained at the output terminal 6 of the adaptive noise canceller 10 is converted
back to an analog signal by the D / A converter 16 and is output to the output terminal 17 as the
output signal of the microphone device.
[0021]
The wind noise reduction operation of the microphone device of FIG. 8 will be described.
When sound is collected by the microphone device in an environment where wind noise occurs,
the outputs of the microphone elements 11 and 12 include wind noise in the collected sound
10-04-2019
5
signal.
[0022]
As described above, since the two microphone elements 11 and 12 are arranged close to each
other, the sound is collected by the two microphone elements 11 and 12 in a highly correlated
state.
On the other hand, since the wind noise generated in the microphone element 11 and the
microphone element 12 by the wind is unique to each microphone element, there is no
correlation between the wind noise of both microphone elements.
[0023]
Therefore, when the difference operation of the outputs of the two microphone elements 11 and
12 is performed in the subtractor circuit 15, the audio signal is canceled, and the component of
only wind noise is obtained from the subtractor circuit 15. In the configuration of FIG. 8, the
wind noise component in the output signal of the microphone 11 supplied to the adaptive noise
canceller 10 as the main input and the wind noise component from the subtraction circuit 15
have a correlation, and the wind from the subtraction circuit 15 As the noise component is the
reference input of the adaptive noise canceller 10 as described above, wind noise in the main
input is sufficiently reduced by the adaptive noise canceller 10 at the output terminal 17.
[0024]
As described above, according to the configuration of FIG. 8, wind noise can be reduced as
described above, but the occurrence of distortion on voice input remains as a problem. That is, as
described above, it is premised that the desired input signal in the adaptive noise canceller is
uncorrelated with the unwanted noise signal. However, in practice, the wind noise of the
microphone and the low frequency component of the desired voice are not completely
uncorrelated, and as a result, the desired voice signal is not output without distortion.
[0025]
10-04-2019
6
Specifically, non-linear distortion such as modulation distortion appears as a phenomenon such
as being added to the audio signal output or the audio signal level being reduced. This is
particularly noticeable when the audio signal level is relatively large or when the number of taps
of the adaptive filter is small, for example, when the filter is a digital FIR filter.
[0026]
There is a so-called trade-off relationship between the wind noise reduction effect and the
distortion effect on the desired voice, and if the wind noise is to be sufficiently suppressed, the
adaptive noise reduction processing causes large distortion to the desired voice in the main
input. In addition, it is against the purpose of making good sound collection quality. In addition, if
the distortion to the desired voice is to be suppressed, the wind noise reduction effect is reduced,
and it is also difficult to obtain a good sound collection quality.
[0027]
An object of the present invention is to provide a microphone device capable of obtaining good
sound collection quality while sufficiently reducing wind noise by solving the above problems.
[0028]
SUMMARY OF THE INVENTION In order to solve the above problems, the microphone device
according to the present invention basically uses an adaptive noise canceller to reduce wind
noise. In view of the noise of the subject, the adaptive noise canceller is characterized in that it
operates only on the bass region of the main input.
[0029]
That is, in the microphone device according to the present invention, when the reference
numerals of the embodiments to be described later correspond, the outputs of the first and
second microphone elements 11 and 12 arranged in close proximity and the outputs of the first
and second microphone elements Of the first microphone element 11 and adaptive noise
canceller 10 for adaptively reducing noise components contained in the main input signal based
on the reference input signal; The first filter 21 for extracting the component of the
predetermined band higher than the predetermined frequency in the above, and the component
of the predetermined band lower than the predetermined frequency in the output signal of the
first microphone element 11 and extracting the extracted signal component The second filter 22
10-04-2019
7
for supplying the adaptive noise canceller 10 as the main input signal, and the first and second
microphone elements 11 and 12 The third filter 23 which extracts the component of the
predetermined band below the predetermined frequency in the minute output and supplies the
extracted signal component as the reference input signal to the adaptive noise canceller 10, and
the output of the first filter 21 A signal is added to the output of the adaptive noise canceller 10
to provide a device output 24.
[0030]
The first to third filters 21 to 23 are for limiting the adaptive operation to wind noise to some
extent, and can be configured as band pass filters.
Also, the first filter 21 may be a high pass filter for that purpose.
The second and third filters 22 and 23 can be configured as low pass filters for that purpose.
[0031]
The wind noise of the microphone is noise mainly composed of a low frequency band of several
hundred Hz or less.
On the other hand, the audio signal is distributed at about 100 Hz or more. According to the
present invention having the above configuration, the high frequency component of, for example,
several hundred Hz or more is extracted from the audio signal collected by the first microphone
element 11 by the first filter. Due to the nature of wind noise described above, the output of the
first filter contains almost no wind noise component. The output of the first filter 21 is supplied
to the addition means 24 as it is.
[0032]
On the other hand, the low pass component of the voice signal collected by the first microphone
element 11 and the main component of wind noise are obtained from the second filter 22, and
10-04-2019
8
this is the main input of the adaptive noise canceller 10. Similarly, the low pass component of the
difference between the outputs of the first and second microphone elements 11 and 12, ie, the
main component of wind noise, is obtained from the third filter 23, and this is the reference of
the adaptive noise canceller 10. It is considered as an input.
[0033]
In this state, when the adaptive operation is performed, a low frequency component of the
collected voice in which the wind noise component is canceled is obtained as an output signal of
the adaptive noise canceller 10. In the addition means, this low frequency component and the
middle and high frequency components of the collected voice not influenced by the adaptive
processing at all are added. Since this addition output is the device output, wind noise is
sufficiently reduced, and a high quality collected sound signal can be obtained.
[0034]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the microphone
device according to the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a microphone device according to the
present invention, and the parts corresponding to those in the above-mentioned example of FIG.
8 are assigned the same reference numerals.
[0035]
By the way, as described above, the wind noise of the microphone is a noise whose main
component is several hundred Hz or less. On the other hand, the audio signal is distributed at
about 100 Hz or more. FIG. 2 shows an example of wind noise and an average power spectrum of
an audio signal. In FIG. 2, the solid line 31 is the power spectrum of wind noise when the wind
speed is 2 m / sec, the solid line 32 is the power spectrum of wind noise when the wind speed is
4 m / sec, and the solid line 33 is the power spectrum of male speech.
[0036]
It can be understood from FIG. 2 that wind noise reduction may be performed for several
hundred Hz or less, and frequency components of several hundred Hz or more may be output
10-04-2019
9
without being subjected to any processing.
[0037]
For this reason, in the example of FIG. 1, after the output of one microphone element 11 of the
pair of microphone elements 11 and 12 disposed close to each other is converted into a digital
signal by the A / D converter 13, It is supplied to the high pass filter 21.
The high-pass filter 21 has a cutoff frequency of, for example, 700 Hz, and extracts an
intermediate and high frequency component of the output signal of the microphone element 11
that hardly includes wind noise.
[0038]
The output signal of the high pass filter 21 is supplied to an adder circuit 24 provided between
the output terminal 6 of the adaptive noise canceller 10 and the D / A converter 16. Note that,
instead of the high pass filter 21, a band pass filter that does not use a frequency band higher
than the required voice band as a pass band may be used.
[0039]
The output signal of the A / D converter 13 is also supplied to a band pass filter 22. The band
pass filter 22 has, for example, 100 Hz to 700 Hz as a pass band, and passes the low frequency
component of the microphone element 11 and the main component of wind noise. The upper
frequency of the pass band of the band pass filter 22 may not necessarily coincide with the
cutoff frequency of the high pass filter 21. An output signal of the band pass filter 22 is supplied
to a main input terminal 1 of the adaptive noise canceller 10 as a main input.
[0040]
Also, the digital signal of the difference signal between the microphone element 11 and the
microphone element 12 from the subtraction circuit 15 is supplied to the band pass filter 23
having the same characteristics as the band pass filter 22 and only the wind noise component is
extracted. The noise is input to the reference input terminal 2 of the adaptive noise canceller 10.
10-04-2019
10
[0041]
The adaptive filter circuit 5 of the adaptive noise canceller 10 comprises an FIR filter type
adaptive linear combiner 100 and a filter coefficient calculation circuit 110, as also shown in FIG.
The adaptive filter circuit 5 can be configured as software by a DSP on which a microcomputer is
mounted. The algorithm for updating the filter coefficients uses, in this example, the LMS (least
mean square) method which is frequently used because the amount of calculation is small and
practical.
[0042]
The LMS method will be described with reference to FIG. As shown in FIG. 3, the adaptive linear
coupler 100 includes a plurality of delay circuits DL1, DL2,..., DLm (m is a positive integer) each
having a delay time Z-1 of unit sampling time, and input noise n1 and weighting circuits MX0,
MX1, MX2,... MXm for multiplying the output signals of delay circuits DL1, DL2,... DLm by
weighting factors (filter coefficients), and the outputs of weighting circuits MX0 to MXm The
adder circuit 101 is provided. The output of the adder circuit 101 is the signal y described in the
example of FIG.
[0043]
The weighting coefficients supplied to the weighting circuits MX0 to MXm are formed by the
filter coefficient calculation circuit 110 based on the residual signal e from the synthesis circuit 4
and the reference input n1 by the LMS algorithm. The algorithm executed by the filter coefficient
calculation circuit 110 is as follows.
[0044]
Now, let the input vector Xk at time k be Xk = [x0k x1k x2k ... xmk] T, as also shown in FIG.
Assuming that m), the input / output relationship is as shown in the following equation 1:
10-04-2019
11
[0046]
Then, if the weight vector Wk at time k is defined as Wk = [w0kw1kw2k... Wmk] T, the input /
output relation is given by yk = XkT.Wk.
Here, assuming that the desired response is dk, the residual ek is expressed as follows. In the ek =
dk-yk = dk-XkT.WkLMS method, updating of the weight vector is sequentially performed
according to the equation (1) such as Wk + 1 = Wk + 2. Here, μ is a gain factor (step gain) that
determines the speed and stability of adaptation.
[0047]
In the configuration of FIG. 1 as described above, in the adaptive noise canceller 10, the
microphones which are the main input only for the bass region including the main component of
the wind noise among the sounds collected by the microphone element 11 An adaptive process is
performed to cancel the wind noise in the output of the element 11. As a result, at the output
terminal 6 of the adaptive noise canceller 10, a low frequency component of the output of the
microphone element 11 from which wind noise has been reduced and removed can be obtained.
[0048]
Then, the adder circuit 24 adds the output signal of the adaptive noise canceller 10 and the midhigh frequency component of the output of the microphone element 11 which hardly contains a
wind noise component, so the wind noise component is added to the output terminal 17. A sound
pickup voice signal of the reduced microphone element 11 is obtained.
[0049]
Even in the case of the example of FIG. 1, distortion may occur depending on the sound level and
the setting of the adaptation operation, but the middle and high frequency components of the
signal of the microphone element 11 are not affected by the adaptation processing at all, As
output through the filter 21, the improvement of the speech quality as a whole is sufficiently
achieved.
[0050]
10-04-2019
12
Further, in the example of FIG. 1, although components of 100 Hz or less are mostly contained in
wind noise but hardly contained in an audio signal, frequency components of 100 Hz or less are
extracted using band pass filters 22 and 23. do not do.
However, it goes without saying that the low-pass filter may be used instead of the band pass
filters 22 and 23, and the noise reduction processing may be performed by the adaptive noise
canceller 10 even for frequency components of 100 Hz or less.
[0051]
FIG. 4 is a block diagram showing another embodiment of the microphone device according to
the present invention.
In this example, since the reference input of the adaptive noise canceller 10 represents the
magnitude of wind noise at that time, the adaptive processing operation of the adaptive noise
canceller 10 is performed by detecting the magnitude of the reference input signal level. It is to
control.
[0052]
That is, in the example of FIG. 4, the output signal of the band pass filter 23 is supplied to the
adaptive noise canceller 10 as the reference input and to the level detection circuit 25, and the
signal level is detected. Then, the level detection output of the level detection circuit 25 is
supplied to the filter coefficient calculation circuit 110 of the adaptive filter circuit 5 of the
adaptive noise canceller 10 as a control signal for updating the coefficient. Others are similar to
the example of FIG.
[0053]
The filter coefficient calculation circuit 110 receives the output of the level detection circuit 25
and calculates the magnitude of the step gain μ of the above-described filter coefficient update
10-04-2019
13
equation (1) according to the level of the reference input signal (that is, wind noise). Control. In
other words, when the wind noise is large, it is necessary to set the step gain μ large to increase
the noise reduction effect of the adaptive noise canceller 10, and when the wind noise is small,
the noise reduction effect of the adaptive noise canceller 10 needs to be large enough. Because
there is not, step gain μ is set smaller. In this way, it is possible to cope with the sound signal so
as not to be difficult to hear by wind noise.
[0054]
FIG. 5 is a block diagram showing another embodiment of the microphone device according to
the present invention. In the example of FIG. 1, since the wind noise is hardly included in the
output of the high pass filter 21, it can be said that this output is mainly composed of the middle
and high frequency components of the audio signal. Therefore, the magnitude of the level of the
output signal of the high-pass filter 21 can be interpreted as indirectly representing the
magnitude of the audio signal. In the example of FIG. 5, the operation of the adaptive noise
canceller is controlled in the same manner as the example of FIG. 4 in accordance with the level
of the output signal of the high pass filter 21 in consideration of the above points.
[0055]
That is, in the example of FIG. 5, the output signal of the high pass filter 21 is supplied to the
addition circuit 24 and to the level detection circuit 26, and the signal level is detected. Then, the
level detection output of the level detection circuit 26 is supplied to the filter coefficient
calculation circuit 110 of the adaptive filter circuit 5 of the adaptive noise canceller 10 as a
control signal for updating the coefficient. Others are similar to the example of FIG.
[0056]
The filter coefficient calculation circuit 110 receives the output of the level detection circuit 26,
and the step gain of the equation (1) for updating the filter coefficient according to the output
signal level (that is, the audio signal level) of the high pass filter 21. Control the size of μ. That is,
for example, when the voice level is large, it is not necessary to increase the noise reduction
effect of the adaptive noise canceller 10 so much that the step gain μ is set small, and when the
voice level is small, the step gain μ is set large. Control. Thus, also in this example, distortion
applied to the audio signal can be appropriately reduced, and good sound collection quality can
10-04-2019
14
be obtained.
[0057]
FIG. 6 is a block diagram showing still another embodiment of the microphone device according
to the present invention. This example utilizes that comparing the reference input of the adaptive
noise canceller 10 and the level of the output signal of the high pass filter 21 will (indirectly)
monitor the signal to noise ratio at that time. .
[0058]
That is, if the speech signal level is relatively sufficiently higher than the wind noise level, it is not
necessary to increase the noise reduction effect of the adaptive noise canceller 10 so much,
rather it is preferable to prioritize keeping the speech quality good. Conversely, if the wind noise
level is relatively large, it is better to increase the noise reduction effect of the adaptive noise
canceller 10 and improve the signal-to-noise ratio even if the voice quality is sacrificed a little.
Therefore, in the example of FIG. 6, the adaptive operation of the adaptive noise canceller 10 is
controlled in accordance with the signal-to-noise ratio at that time.
[0059]
In order to realize this, in the example of FIG. 6, the output signal of the high pass filter 21 and
the output signal of the band pass filter 23 are supplied to the level ratio detection circuit 27,
and in the level ratio detection circuit 27, both signals are Level ratio is detected. Then, the level
ratio of both signals detected by the level ratio detection circuit 27 is supplied to the filter
coefficient calculation circuit 110 of the adaptive filter circuit 5 of the adaptive noise canceller
10 as a control signal for updating the coefficient. Others are similar to the example of FIG.
[0060]
The filter coefficient calculation circuit 110 controls the step gain μ in the filter coefficient
update equation (1) according to the level ratio. For example, when the signal-to-noise ratio is
large, the step gain μ is set smaller, and conversely, when the signal-to-noise ratio is small, the
10-04-2019
15
step gain μ is larger. Thus, good sound collecting quality can be obtained.
[0061]
FIG. 7 is a block diagram of still another embodiment of the present invention. This example is an
example in which a bass region in which wind noise is present is divided in a plurality of ways,
and processing using an adaptive noise canceller is performed for each divided band. According
to this example, since wind noise is adaptively reduced for each divided band, it is possible to
reduce wind noise more effectively.
[0062]
The example of FIG. 7 is an example of the case where the bass region where wind noise is
present is divided into two. That is, instead of the band pass filters 22 and 23 in the example of
FIG. 1, the band of 100 Hz to 500 Hz is divided into two, and the band pass filters 221 and 231
having the upper divided band as the pass band, and the lower side thereof. Band pass filters 222
and 232 are provided which use divided bands as pass bands. Then, the output signal of the A /
D converter 13 is supplied to the band pass filters 221 and 222, and the output signal of the
subtraction circuit 15 is supplied to the band pass filters 231 and 232.
[0063]
Also, adaptive noise cancellers 51 and 52 are provided according to the number of divided
bands. The outputs of the band pass filters 221 and 222 are supplied to the main input terminal
1 of the adaptive noise cancellers 51 and 52, respectively, and the outputs of the band pass
filters 231 and 232 are input to the reference input terminals 2 of the adaptive noise cancelers
51 and 52, respectively. Supply to
[0064]
In the case of this example, the magnitude of the step gain μ in the updating of the filter
coefficient in the adaptive filter circuit 5 of the adaptive noise canceller 51 and 52 for each band
is set to an appropriate value for each band. However, as in the examples of FIGS. 4 to 6
10-04-2019
16
described above, the step gain may be adaptively controlled according to the level of the
reference input or the level of the main input, and further, the level ratio of the two.
[0065]
The output signals of the adaptive noise cancellers 51 and 52 are supplied to the addition circuit
24 and added to the mid-high band component of the sound collection output signal of the
microphone element 11 from the high pass filter 21 and supplied to the D / A converter 16 to
obtain an analog signal. To the output terminal 17.
[0066]
Although the example of FIG. 7 is an example in which the bass range is divided into two, it may
be of course divided into three or more.
[0067]
According to the microphone device described above, wind noise can be reduced by preparing
two normal microphone elements without preparing a special sensor or the like.
In this case, the two microphone elements are disposed close to each other, which can contribute
to downsizing of the device.
[0068]
In addition, since two microphone elements can be allocated to the left and right channels, even
when configuring a stereo microphone, it can be realized without increasing the number of
microphone elements.
[0069]
According to the examples of FIGS. 4 to 6, the wind noise reduction effect of the adaptive noise
canceller can be appropriately controlled according to the wind noise level and the magnitude of
the voice signal level, so that good sound collection quality and wind noise suppression effect can
be obtained simultaneously. Can.
[0070]
10-04-2019
17
Furthermore, since the wind noise reduction operation is automatic, the user can concentrate on
monitoring of monitor images during shooting with another operation, for example, a camera
integrated VTR.
[0071]
In the above-mentioned example, although two microphone elements 11 and 12 used a
nondirectional microphone, these microphone elements may have any directivity.
However, use of an omnidirectional microphone is easy to handle and inexpensive, so its
practical effect is large.
[0072]
In addition, it is easy to combine two microphone elements to obtain other directivity.
Furthermore, it is also easy to be almost omnidirectional in the low band and unidirectional in
the middle and high bands.
Of course, three or more microphone elements can be used to obtain a signal in accordance with
the subject matter of the present invention.
[0073]
In the above example, the cutoff frequency of the high pass filter 21 and the band pass filters 22,
23, 221, 222, 231 and 232 is fixed, but as shown in FIG. In view of the frequency change
according to the wind speed, these filters can be configured to be variable in the low-off
frequency and controlled to have an appropriate cutoff frequency according to the wind speed.
The cutoff frequency variable filter can be realized, for example, by using an IIR digital filter and
changing its weighting factor.
10-04-2019
18
[0074]
The change of the cut-off frequency may be performed manually or may be performed
automatically by providing a means for measuring the wind speed.
[0075]
Further, the A / D converters 13 and 14 may be connected to the output side of the band pass
filters 22 and 23 without being directly connected to the microphone elements 11 and 12.
In that case, the high pass filter 21 and the band pass filters 22 and 23 are configured by analog
circuits. Also, the D / A converter 16 is to be inserted at the output of the adaptive noise
canceller 10.
[0076]
Further, a band pass filter having the same frequency characteristics as the band pass filters 22
and 23 may be inserted into the output of the adaptive noise canceller.
[0077]
As described above, according to the present invention, in view of the fact that wind noise is
mainly present in the low tone range, the voice collected by the microphone is mostly low-pass
component and wind noise component. An adaptive noise canceller is applied to the lowfrequency component to reduce and remove wind noise, and the low-frequency component and
high-frequency component from which the wind noise is removed are added to the output signal.
As a result, the middle to high frequency components of the picked up voice are not affected by
the adaptive noise canceler at all, and a good quality picked up voice output voice signal with
sufficiently suppressed wind noise can be obtained.
[0078]
Also, in the present invention, the wind noise reduction effect of the adaptive noise canceller is
appropriately controlled according to the wind noise level and the level of the audio signal level,
so that good sound collection quality and sufficient wind noise suppression effect can be
simultaneously obtained. be able to.
10-04-2019
19
10-04-2019
20
Документ
Категория
Без категории
Просмотров
0
Размер файла
31 Кб
Теги
description, jph06269083
1/--страниц
Пожаловаться на содержимое документа