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JPH0564290

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DESCRIPTION JPH0564290
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound collecting apparatus for use in a conference system or the like which is less in
reverberation and noise.
[0002]
2. Description of the Related Art In recent years, electronic conferencing systems are becoming
popular. In these systems, since the microphone is placed on the desk away from the speaker,
noise is likely to be mixed and the S / N is poor. For this reason, means for removing noise with a
voice switch or the like is used.
[0003]
Hereinafter, with reference to the drawings, an example of the sound collection device of the
above-described conventional conference system will be described.
[0004]
FIG. 6 is a block diagram of a microphone installation and a sound collection device of a
conventional conference system.
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[0005]
In FIG. 6, 1 is a microphone, 2 is an attenuator that attenuates the output of the microphone 1
and is output to the outside, 3 is a level detector, and 4 is an attenuation controller.
[0006]
The signal collected by the microphone 1 is level-adjusted by the attenuator 2 and output to the
outside.
The output of the microphone 1 is also input to the level detector 3, and the signal level is
determined by the level detector 3.
The attenuation controller 4 controls the attenuation of the attenuator 2 in accordance with the
signal level.
[0007]
The attenuation controller sets the attenuation of the attenuator 2 large until the signal level
exceeds a preset value, thereby eliminating low-level noise.
When voice enters and the signal level rises and exceeds a preset value, the attenuation amount
of the attenuator 2 is reduced and a signal is output to the outside.
[0008]
Conventionally, such a circuit called a voice switch has been incorporated to suppress noise and
improve S / N.
[0009]
However, although the above configuration can eliminate low-level noises, high-level noises and
reverberant sound in which the speaker's voice is reflected by a wall or ceiling and is incident on
a microphone. It had the problem that it was ineffective for the removal of
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[0010]
The present invention solves the above-mentioned problems, and it is an object of the present
invention to provide a sound pickup device capable of effectively removing loud noise and
reverberation.
[0011]
SUMMARY OF THE INVENTION In order to achieve the above object, the sound pickup apparatus
of the present invention includes a main microphone placed close to a speaker and attenuating
the output of the main microphone and outputting it to the outside. , A plurality of
submicrophones mounted on the ceiling or wall around the room away from the speaker, a
plurality of level detectors provided on each of the main microphone and the submicrophone,
and a plurality of submicrophones from the level of the main microphone The reverberation level
estimation function to estimate the level of the reverberation sound that reaches, and the
attenuation amount controller that controls the attenuation amount of the attenuator from this
estimated reverberation level and the level of the main microphone .
[0012]
In addition, a main microphone placed close to the speaker, an attenuator for attenuating the
output of the main microphone and outputting it to the outside, a plurality of sub microphones
spaced apart from the speaker, and a main microphone and a sub microphone, respectively. A
plurality of level detectors provided in the unit, an average level detector for obtaining the
average level of the sub microphone from the output of the level detector, a distribution width
detection function for finding the distribution width of the sub microphone level from the output
of the level detector, An attenuation controller is provided to control the attenuation of the
attenuator from the level, the distribution width and the level of the main microphone.
[0013]
According to the present invention, with the above-described configuration, the section mainly
composed of direct sound from the speaker and the section mainly composed of noise and
reverberation are accurately discriminated, and the gain of the output is adjusted based on the
discrimination result.
[0014]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A sound pickup apparatus
according to an embodiment of the present invention will be described below with reference to
the drawings.
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[0015]
(Embodiment 1) FIG. 1 shows a layout diagram of microphones and a block diagram of a
processing circuit of a sound pickup apparatus according to a first embodiment of the present
invention.
The embodiment of FIG. 1 is a sound collecting device with excellent dereverberation
performance.
In FIG. 1, 11 is a main microphone, 12 is an attenuator, 13 is a level detector for the main
microphone, 14 is an attenuation controller, 15a to 15e are secondary microphones, and 16a to
16e are level detectors for secondary microphones, 17a to 17e are weighters, and 18 is an adder.
[0016]
The signal collected by the main microphone 11 of FIG. 1 is led to the attenuator 12 and also to
the level detector 13.
The signal level is determined by the level detector 13 and the value is input to the attenuation
controller 14.
The attenuation controller 14 determines that the noise is noise if the level is smaller than a
predetermined threshold value, controls the attenuation of the attenuator 12 to a large extent,
and determines that it is voice if the level is large. Control the amount of attenuation small.
The operation up to this point is exactly the same as the conventional example.
[0017]
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The signals collected by the sub microphones 15a to 15e provided on the wall or ceiling of the
room are leveled by the level detectors 16a to 16e, weighted by the weighting units 17a to 17e,
and then added by the adder 18. .
The weighting values are set to match the attenuation of the reflected sound from the wall or
ceiling on which each sub microphone is attached to the main microphone.
The output of this adder is the estimated level of the reverberant sound input to the main
microphone 11. The estimated reverberation level thus obtained is input to the attenuation
controller 14. The attenuation controller 14 compares this estimated reverberation level with the
main microphone level output from the level detector 13 for the main microphone, and when
both are almost equal, the signal incident on the main microphone is mainly reverberation. The
amount of attenuation of the attenuator 12 is increased, and when the level of the main
microphone is large, it is determined that the direct sound from the speaker is the main factor,
and the amount of attenuation is controlled to be small.
[0018]
As a result of the above processing, an audio signal with a high sound quality in which the
reverberation signal is suppressed can be obtained as the output of the attenuator 12.
[0019]
As described above, according to the present embodiment, the sub microphones 15a to 15e, the
level detectors 16a to 16e for the sub microphones, the weighting devices 17a to 17e, and the
adder 18 are provided. Since the amount of attenuation of the unit 12 is controlled, reverberation
mixed in the main microphone 11 can be effectively suppressed.
[0020]
(Embodiments 2 and 3) FIGS. 2 and 3 show a layout of microphones and a block diagram of a
processing circuit of a sound pickup apparatus according to the second and third embodiments
of the present invention.
Both of the embodiments shown in FIGS. 2 and 3 are sound collecting devices with excellent
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reverberation removing performance.
In FIG. 2, reference numeral 21 denotes a delay unit, and the other components are the same as
those in the configuration of FIG. In the embodiment of FIG. 1, the dereverberation operation
works before the reflected sound comes back, which causes a slight distortion of the voice.
However, in the embodiment of FIG. The delay time of 21 can be chosen equal to eliminate such
drawbacks.
[0021]
In FIG. 3, reference numerals 31 a to 31 e denote delay units, and the others are similar to the
configuration of FIG. 1. In the embodiment of FIG. 3, the time until the reflected sound is
returned can be individually set by each of the delay units 31a to 31b for each sub microphone,
and the reverberation sound level can be estimated more accurately. Degradation can be reduced.
[0022]
Embodiment 4 Next, the fourth embodiment of the present invention will be described with
reference to the drawings. FIG. 4 shows a layout diagram of microphones and a block diagram of
a processing circuit of a sound collection system according to a fourth embodiment of the
present invention. The embodiment shown in FIG. 4 is a sound collecting device excellent in the
noise removal performance from outside the room. In FIG. 4, 41 is an average level calculator, 42
is a maximum value detector, 43 is a minimum value detector, 44 is a subtractor, 45 is an
attenuation amount controller, and the others are similar to the configuration of FIG.
[0023]
The values of the secondary microphone level output from the level detectors 16 a to 16 e are
input to the average level detector 41, the maximum value detector delay 42, and the minimum
value detector 43. The average level detector calculates this average level and inputs it to the
attenuation controller 45. The maximum value detector 42 and the minimum value detector 43
obtain the maximum level and the minimum level, respectively, and input them to the subtractor
44, where the distribution width of the level is obtained and sent to the attenuation controller 45.
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The attenuation controller 45 determines whether the sound source is present indoors or
outdoors based on the average level and the distribution width. When the distribution width is
smaller than the average level, the sound source is considered to be in the room, the attenuation
amount of the attenuator 12 is increased, and when the distribution width is larger than the
average level, the sound source is judged to be in the room. Reduce the amount of attenuation.
[0024]
As described above, according to this embodiment, the sub microphones 15a to 15e, the level
detectors 16a to 16e for the sub microphones, the average level detector 41, the maximum value
detector 42, and the minimum value detector 43 , Subtractor 44 and damping amount controller
45 are provided to measure the average value and distribution width of the sound pressure level
in the room and control the amount of attenuation of the attenuator 12 with this value. Can be
effectively suppressed.
[0025]
(Fifth Embodiment) FIG. 5 shows a layout diagram of microphones and a block diagram of a
processing circuit of a sound collection system according to a fifth embodiment of the present
invention.
The embodiment shown in FIG. 5 is also a sound collecting device excellent in noise removal
performance from the outside. In FIG. 5, 51a to 51e are subtractors, 52a to 52e are absolute
value converters, 53 is an adder, and others are similar to the configuration of FIG. In the
example of FIG. 4, when relatively high level noise is input to a specific microphone from an air
conditioner or the like, the distribution width tends to be measured large, so the noise detection
accuracy is reduced. is there. In the embodiment of FIG. 5, since the sum of the absolute value of
the difference from the average level is used as the distribution width, such an influence can be
reduced.
[0026]
As is apparent from the above embodiments, according to the present invention, a main
microphone, an attenuator, a plurality of sub microphones, a plurality of level detectors, a
reverberation level estimation function, and an attenuation control The reverberation signal can
be effectively suppressed, and even in a sound collection situation where the distance between
the main microphone and the speaker is relatively long, easy-to-hear voice signals with little
reverberation can be collected, and further Since the main microphone, attenuator, sub
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microphone, multiple level detectors, average level detector, distribution width detection
function, and attenuation controller are provided, noise signal is effectively suppressed Thus, it is
possible to provide a sound collection device capable of collecting easy-to-hear audio signals with
little noise mixing even in a sound collection situation where the distance between the main
microphone and the speaker is relatively long.
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