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DESCRIPTION JPH03206799

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DESCRIPTION JPH03206799
[0001]
[Industrial field of application] The present invention eliminates sound mixing when noise can
not be prevented from being generated from acoustic noise sources, and collects sound for
selectively collecting sound from a target sound source. It relates to an apparatus. 2. Description
of the Related Art In recent years, with the miniaturization of sound recording devices, it has
become more common to closely attach a sound collection device composed of a microphone and
a microphone amplifier to a recording medium device such as a tape deck. In performing such
close attachment, there arises a problem that noise generated by the recording medium device is
recorded as an acoustic signal via the sound collection device. FIG. 4 is a block diagram showing
an example of a conventional sound collection device designed to reduce such noise. In FIG. 4,
the signal detected by the microphone 21 is frequency limited by a filter 22 having a
characteristic of blocking a band in which noise components are mainly present, and a signal
with reduced noise can be obtained at an output terminal 23. However, in the conventional
sound collecting apparatus as described above, the signal in the same band as the noise is
removed by the filter 22. Therefore, there is a disadvantage that the frequency characteristic of
the obtained sound quality is deteriorated. The present invention has been made in view of the
problems of such a conventional sound collection device, and it is possible to use a filter for
mixed noise (it is possible to selectively collect a sound from a target sound source by excluding
it) To be a technical issue. [Means for Solving the Problems] The invention of claim 1 comprises a
first microphone for recording a target acoustic signal, a second microphone for detecting noise,
and a transfer characteristic for the noise to reach the first microphone. It is characterized in that
it has a simulated flower container and a subtractor for subtracting the output of the flower
container from the output of the first microphone. Also, the invention of claim 2 relates to an A /
D converter for converting an analog signal obtained from the first microphone recording a
target acoustic signal, the second microphone detecting noise, and the second microphone into a
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digital signal. A digital isomorphic device that simulates the transfer characteristic that the
output signal of the A / D converter is given and the noise reaches the first microphone, and a D
/ A converter that converts the signal of the digital equalizer to an analog signal And a subtractor
for subtracting the output of the D / A converter from the output of the first microphone.
[Operation] According to the present invention having such a feature, the noise generated by the
noise source is detected by the microphone, and the noise is further detected in the first
microphone recording the target acoustic signal by the equal flower device or the digital
equalizer. By simulating the arriving transfer characteristic and subtracting the recording signal
from the simulated noise signal, the noise generated from the recording medium device is
canceled.
The first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of the sound collection device in the first embodiment of the
present invention, and FIG. 2 is an explanatory view showing how signals are processed in the
first embodiment of the present invention. As shown in FIG. 1, this sound collection device has a
first microphone 1 for recording a target acoustic signal and a second microphone 2 for
detecting noise, and the output of the microphone 2 is It is given to an isochore 3 which
simulates the transfer characteristic that noise reaches the first microphone l. Also, the output of
the equalizer 3 is given to the subtracter 4. The subtracter 4 subtracts the output of the equal
flower device 3 from the output of the first microphone 1, and the output is given to the output
terminal 5. Now, in FIG. 2, assuming that n (t) is noise from a noise source and X (t) is a transfer
characteristic from the recording medium to the second microphone 2 represented by an
impulse response, the second microphone 2 The noise y (t) detected by can be expressed as y (t)
= n (t) * x (t)---(1) (* is a convolution integral). On the other hand, assuming that a target acoustic
signal collected by the first microphone 1 is m (t) and a transfer characteristic from the noise
source to the first microphone 1 is v (t), the first microphone 1 detects The signal w (t) is Fouriertransformed by the following equation (% formula%) Hungmu (1): Y (jω) = N (jω) X (jω)-----(3)
Therefore, N (jω) -Y (jω) / X (jω)-----44) is obtained. Now, when Equation (2) is subjected to
Fourier transform, W (jω) = M (jω) + N (jω) V (jω) −−−−− (5), so M (jω) −W (jω) −Y (Jω)
H (′ ′ ω) H (jω) = V (jω) / X (jω) −−−− (6) is obtained. That is, if the noise detected by the
second microphone 2 is processed by the equal flower device 3 having the transfer characteristic
of equation (6) and the output of the equal flower device 3 is calculated by the subtracter 4 from
the signal of the first microphone 1 Only the target acoustic signal M (jω) is obtained at the
output terminal 5, and the noise generated by the noise source is canceled. Note that in order to
perform signal processing based on the above idea, it is necessary to prevent the target acoustic
signal m (t) from mixing into the second microphone 2. For this reason, the second microphone 2
is placed acoustically close to the noise source. Next, a second embodiment of the present
invention will be described with reference to the drawings.
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FIG. 3 shows the configuration of a sound collection device according to a second embodiment of
the present invention. 11. A first microphone for detecting an acoustic signal of interest also in
this embodiment. A second microphone 12 for detecting noise is provided, the output of which is
given to an A / D converter 13. The A / D converter 13 converts a human power signal into a
digital signal, and the output thereof is given to the digital container 14. The digital equalizer 14
simulates, by digital signal processing, the transfer characteristic in which noise reaches the first
microphone 11 for recording an acoustic signal. Then, the output of the digital equalizer 14 is
converted to an analog signal through the D / A converter 15, subtracted by the subtracter 16,
and output from the output terminal 17. Now, the operation of the sound collection device
configured as described above will be described. The noise generated by the noise source is n (t),
the transfer characteristic from the noise source to the second microphone 12 is x (t), and the
transfer characteristic from the noise source to the first microphone 11 is v (t) Do. Then, in the
same manner as in the first embodiment, the digital equalizer 14 is an isometric device having
the characteristic H (jω) -V (jω) / X (jω)----47, By processing the noise detected by the
microphone 12 and subtracting the output of the equal flower device from the signal of the first
microphone 11 by the subtractor 16, only the target acoustic signal M (jω) is obtained, and The
noise generated is canceled. In the second embodiment, the output of the second microphone 12
is quantized by the A / D converter 13 and input to the digital equalizer 14. The digital equalizer
14 is realized by a digital filter, and its output is converted to an analog signal by the D / A
converter 15 and input to the subtractor 16. As described above, using the digital equalizer 14
makes it easy to change the characteristics, and for example, if a digital signal processor is used
for the digital equalizer 14, it is possible to cope with different sound collecting media with the
same device. it can. The output of the first microphone 11 may also be subjected to A / Di
conversion and digitally subtracted with the output of the digital equalizer 14 to improve
calculation accuracy. The equalizer does not necessarily have to be disposed only at the rear
stage of the second microphone, and may be provided at the rear stage of the first microphone to
cancel noise. In this case, assuming that the transfer characteristic of the isometric device at the
rear stage of the first microphone is H1 (jω), the transfer characteristic H2 (jω) of the isometric
device at the rear stage of the second microphone is H2 (jω) = (X (jω) / It becomes V [jω))
H1lω).
Also, the microphone is not limited to a particular system, and may be selected appropriately
according to the nature of the signal to be collected. As described above in detail, according to
the present invention, the first microphone for detecting the target acoustic signal, the second
microphone for detecting the noise generated by the noise source, and the second microphone
Only the noise component can be removed by providing an isophone to which the microphones
of the above are connected and a subtractor for subtracting the output of the isola from the
output of the second microphone.
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[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram of a sound pickup apparatus according to a first embodiment of the
present invention, FIG. 2 is a block diagram for explaining a state of signal processing in the first
embodiment of the present invention, and FIG. FIG. 4 is a block diagram of a sound collection
device according to a second embodiment of the present invention, and FIG. 4 is a block diagram
of a conventional sound collection device.
1 2 11 12------Microphone 3 equalizer 4-16-1-Subtractor 13-A / D converter converter
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