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JPH09149490

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DESCRIPTION JPH09149490
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone device capable of exhibiting directivity, and more particularly to a microphone
device capable of reducing the output of sound other than the direction of the speaker and
reducing the collection of ambient noise. .
[0002]
2. Description of the Related Art Heretofore, as this type of microphone device, there has been
one as disclosed in Japanese Utility Model Application Laid-Open No. 2-21997. It places two
omnidirectional microphones in a straight extension direction of a straight line extending in its
longitudinal direction. Then, when the linear direction extending in the longitudinal direction of
the two nondirectional microphones is set as the speaker direction, the voices having different
delays due to the time difference of the sound propagation caused by the difference in distance
to the respective nondirectional microphones Is input. The respective nondirectional
microphones to which voices with different delays are input output voice signals having phase
differences due to differences in delay and are given to common output means. In the output
means, the difference in amplitude due to the phase difference between the outputs of the two
nondirectional microphones is calculated, and the difference signal is output to the speaker
device.
[0003]
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1
The configuration of the above-mentioned conventional microphone device will be further
described in detail with reference to FIG. FIG. 2 is a diagram showing the configuration of a
microphone apparatus in which two nondirectional microphones are arranged in a straight line
in the longitudinal direction to give directivity. In FIG. 2, M1 and M2 are omnidirectional
microphones, 102 is a housing accommodating omnidirectional microphones M1 and M2 in a
straight line in the longitudinal direction, and 101 is an axis passing through the omnidirectional
microphones M1 and M2 arranged in the longitudinal direction The operational amplifier 103
calculates the difference in amplitude due to the phase difference between the outputs of the two
microphones M1 and M2 and outputs it. The buffer amplifier 104 amplifies the output of the
operational amplifier. P1, an output terminal for outputting the output of the buffer amplifier
104 to a speaker device (not shown).
[0004]
Next, with reference to FIG. 2, the operation of the conventional microphone device will be
described in detail. First, when the talker 105 utters, the voice is first captured by the
nondirectional microphone M2, and then captured by the nondirectional microphone M1. At that
time, the sound captured by the nondirectional microphone M2 is captured slightly earlier than
the sound captured by the nondirectional microphone M1. The outputs of the nondirectional
microphones M1 and M2 output with a phase difference corresponding to the delay difference
due to the propagation of voice are respectively connected to the input of the operational
amplifier 103, and the operational amplifier 103 calculates the difference between the two audio
inputs. . The difference of the voice input is amplified by the buffer amplifier 104 and output to
the speaker device through the output terminal P1.
[0005]
As described above, the difference between the two voice inputs is mainly due to the difference
in distance from the talker 105 to the two omnidirectional microphones M1 and M2 arranged in
a straight line in the longitudinal direction along the directional axis. It is caused by the arrival or
propagation time difference (phase difference). Therefore, the sounds emitted from directions
other than the transmitter 105 in the directional axis direction and arriving at the nondirectional
microphones M1 and M2 respectively are input substantially simultaneously (without a phase
difference), and are therefore eliminated in the operational amplifier 103 As a result of the
output being reduced, it is possible to reduce the collected sound volume such as noise generated
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from the lateral direction.
[0006]
SUMMARY OF THE INVENTION However, in the above-mentioned conventional microphone
device, two nondirectionality for highly random ambient noise such as wind noise which is not
directional and whose source can not be determined Not only the noise output from the
operational amplifier does not decrease but also the noise output is greatly expanded compared
to the case where the sound is collected by any one of the nondirectional microphones because a
large difference occurs in the outputs of the microphones. Was a problem.
[0007]
The present invention has been made to solve the above-mentioned conventional problems, and
in the case where ambient noise with high randomness such as wind noise is high, the increase of
the collected sound volume is prevented, while the sound from the talker direction It is an object
of the present invention to provide a microphone device capable of exhibiting strong directivity
by reducing the output of sound emitted from directions other than the direction of the speaker.
[0008]
SUMMARY OF THE INVENTION A microphone device according to the present invention uses
two omnidirectional microphones arranged in a straight line with the longitudinal direction
directed to the talker, and the output of one omnidirectional microphone is used. The low
frequency component is extracted from the signal and the sound pressure level is determined,
and when it is higher than a predetermined level, only the output signal of the one nondirectional
microphone is output, and when lower than the predetermined level, the one non It is used by
switching so as to output a signal obtained by adding the output signal of the directional
microphone and the reverse phase signal obtained by inverting the output signal of the other
nondirectional microphone.
[0009]
According to the present invention, when the highly random ambient noise is high, only the
output signal of one of the nondirectional microphones is output to prevent an increase in the
volume of the ambient noise, while the highly random ambient noise When it is low, only the
sound from the direction of the transmitter can be picked up, and the output of the sound
emitted from the direction other than the direction of the transmitter can be reduced to exhibit a
strong directivity.
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[0010]
According to a first aspect of the present invention, there is provided a first and a second nondirectional microphones, wherein the first and second non-directional microphones are arranged
in a straight line with the longitudinal direction directed to the talker; Judgment means for
judging the sound pressure level of the low frequency component of the output signal collected
by the nondirectional microphone and outputting the judgment result, the output signal of the
first nondirectional microphone, and the second nondirectional Difference signal output means
for calculating the phase difference with the output signal of the microphone and outputting the
difference signal, and selecting and outputting only the output signal of the first nondirectional
microphone based on the determination result of the determination means Switching means for
switching whether to select or output a difference signal of the output signals of the first and
second nondirectional microphones, and based on the determination result of the determination
means, the first no Directional microphone output Automatically selects whether to output only
the output signal or to output the difference signal between the output signals of the first and
second nondirectional microphones, and the ambient noise with high randomness such as wind
noise This prevents the increase of the sound collection volume, and reduces the output of the
sound emitted from the direction other than the direction of the transmitter to exert a strong
directivity.
[0011]
The invention according to claim 2 of the present invention is a low-pass filter for extracting a
low frequency component from an output signal collected by the first nondirectional microphone
by the determination means, and a low pass filter for the extracted low frequency component. A
sound pressure level calculator for calculating a sound pressure level, and the first
nondirectionality with respect to the switching means when the sound pressure level is higher
comparing the calculated sound pressure level with a predetermined level Judgment result to
instruct to output only the output signal of the microphone, and to output the difference signal
by the phase difference of the output signals of the first and second nondirectional microphones
when the sound pressure level is lower To determine the magnitude of the sound pressure level
of the low-frequency component including a large amount of random ambient noise with large
wind noise from the output signal of the omnidirectional microphone. Around Or prevent an
increase in current volume of the sound, an effect that can effectively determine whether to
emphasize the directivity.
[0012]
The invention according to claim 3 of the present invention is a phase inverter in which the
difference signal output means inverts the phase of the output signal collected by the second
nondirectional microphone and outputs a reverse phase signal; A difference signal due to the
phase difference between the collected output signals of the first and second nondirectional
03-05-2019
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microphones by adding the collected output signal of the first nondirectional microphone and the
reverse-phase signal whose phase is inverted And adding means for outputting the difference
signal to output a difference signal consisting of the phase difference of the output signals
collected by the first and second nondirectional microphones to exhibit strong directivity. It has
the effect of being able to
[0013]
Hereinafter, an embodiment of the present invention will be described in detail with reference to
the attached drawings and FIG.
FIG. 1 is a view showing the configuration of a microphone device in which two nondirectional
microphones according to an embodiment of the present invention are arranged in a straight line
in the longitudinal direction to give directivity.
[0014]
First, the configuration of the microphone device in the present embodiment will be described
with reference to FIG.
In FIG. 1, 21 and 22 are arranged on a straight line in the longitudinal direction, and the
extension direction of the straight line is directed to the talker's direction so that directivity is
given, and the received air vibration is an electroacoustic signal. The first and second
(interchangeable) nondirectional microphones 23 (hereinafter also referred to as output signals
of the nondirectional microphones 21 and 22) and output the same; 23 is a collection input from
the nondirectional microphone 21; It is a branching unit that divides the sound signal into only
two lines and outputs it.
[0015]
Also, 24 is a low pass filter that extracts only the low frequency component where the power of
ambient noise such as wind noise is excellent and the collected sound signal input from one
output of the splitter 23 is input from the low pass filter 25 Sound pressure level calculator for
calculating the sound pressure level of the low frequency component of the signal input from the
nondirectional microphone 21; 31 is a predetermined predetermined level for the sound
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pressure level of ambient noise from the sound pressure level calculator 25; In contrast to this, it
is a determination unit that determines whether it is larger or smaller than that and outputs the
determination result to the switch 33.
[0016]
Reference numeral 26 denotes a second branch which further divides the signal input from the
other output of the branch 23 into two systems and outputs the signal. 27 denotes an
omnidirectional microphone 21 input from one output of the second branch 26. Is an amplifier
for amplifying the signal from the input and output to the switch 33, and 28 is an amplifier for
amplifying the signal from the nondirectional microphone 21 input from the other output of the
second branch 26 and for outputting to the adder 32. is there.
[0017]
Further, 29 is a phase inverter that outputs an inverted phase signal of the phase of the input
signal from the nondirectional microphone 22, 30 is an amplifier that amplifies the opposite
phase signal from the phase inverter 29, and 32 is no signal from the amplifier 28. An adder as
addition means for adding the output of the directional microphone 21 and the negative phase
signal of the nondirectional microphone 22 from the amplifier 30 and outputting a difference
signal indicating the difference between the two input signals to the switch 33; Only the output
signal of the nondirectional microphone 21 from the amplifier 27 is controlled according to the
determination result of the determination unit 31, or the output signal of the nondirectional
microphone 21 from the adder 32 and the output of the nondirectional microphone 22 It is a
switch as a switching means which switches whether the difference signal which consists of a
difference component of a signal is output.
A phase inverter 29 and an adder 32 are included to constitute a difference signal output means.
[0018]
Next, with reference to FIG. 1, the operation of the microphone device in the present embodiment
will be described in detail.
First, the output signal (sound collection signal) from the nondirectional microphone 21 is
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branched into two directions or two systems by the branching device 23, and one output signal is
output to the low pass filter 24.
The low pass filter 24 extracts only low frequency components from which the power of ambient
noise such as wind noise having high randomness is excellent from the input signal and outputs
the low frequency component to the sound pressure level calculator 25.
The sound pressure level calculator 25 calculates the sound pressure level of the low frequency
component and outputs the sound pressure level to the determiner 31, where the magnitude of
the sound pressure level is determined, and the determination result is output to the switch 33.
[0019]
The output signal from the nondirectional microphone 21 branched in the other direction in the
branching device 23 is input to the second branching device 26, where it is branched again into
two systems, one of which is amplified by the amplifier 27 and switched. It is output to one of the
33 input terminals.
The output signal from the other nondirectional microphone 21 branched by the second branch
26 is inputted to one input terminal of the adder 32 through the amplifier 28.
[0020]
Also, assuming that the sound source is on the non-directional microphone 21 side on a straight
line passing through the non-directional microphones 21 and 22, the non-directional microphone
21 has a delay converted from air vibration in the non-directional microphone 22. The electric
acoustic signal (sound collection signal) slightly delayed in phase from the sound collection
signal of を 通 し て is inverted through the phase inverter 29, amplified by the amplifier 30 as a
reverse phase signal in reverse phase to the output of the amplifier 28, and added to the adder
32. It is input to the other input terminal.
The adder 32 outputs the outputs of the two amplifiers 28 and 30, that is, the sound collection
signal of the nondirectional microphone 21 and the antiphase signal of the sound collection
03-05-2019
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signal of the nondirectional microphone 22 slightly delayed in phase from the nondirectional
microphone 21. Are added to calculate the difference, and the difference signal due to the phase
difference between the two signals is output to the switch 33.
[0021]
The switch 33 receives the determination result from the determination unit 31, selects one of
the output signal from the amplifier 27 and the output signal from the adder 32 according to the
determination result, and outputs it to the speaker device.
That is, when it is determined that the ambient noise such as wind noise having high randomness
is high (large) in the determination unit 31, the switch 33 selects the output signal of the
nondirectional microphone 21 from the amplifier 27 When the ambient noise such as wind noise
is determined to be low (small) due to high randomness, the switch 33 outputs the nondirectional signal from the adder 32. Directivity on the directional axis passing through the
nondirectional microphones 21 and 22 mounted on the directional microphone device by
outputting a signal consisting of the difference between the output signal of the directional
microphone 21 and the output signal of the nondirectional microphone 22 Can be realized.
[0022]
In the present embodiment described above, a phase inverter and an adder are used as the
difference signal output means, and one of the signals collected by the two nondirectional
microphones is made into a reverse phase, and then the other nondirectional is obtained. The
difference between the two collected signals is output by adding it to the microphone's collected
signal, but without using a phase inverter and an adder, instead using two differential amplifiers
using a differential amplifier The difference between the sound collection signals of the
microphones may be output.
[0023]
Further, in the embodiment of the present invention described above, the case of using two
nondirectional microphones has been described, but three or more nondirectional microphones
can also be used.
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In three cases, a combination of the first and second omnidirectional microphones and a
combination of the first and second omnidirectional microphones may be used to realize a
microphone with lower noise and stronger directivity. it can.
[0024]
The microphone device according to the present invention is configured as described above, and
in particular, determines the magnitude of the ambient noise amount in the low frequency band
where wind noise with high randomness is predominant, and determines that it is small. Then,
according to the judgment result, one of the signals collected by the two nondirectional
microphones is reversed in phase, and then switching is made to add both collected signals and
output, thereby reducing the ambient noise 2 Strong directivity can be exhibited on a straight
line passing through two nondirectional microphones, and when it is determined that wind noise
with high randomness is high, only one of the collected signals of two nondirectional
microphones is adopted. By automatically switching so as to be output, it is possible to prevent in
advance the increase of the sound collection volume of the ambient noise when the wind noise
with high randomness is large.
[0025]
Brief description of the drawings
[0026]
1 is a diagram showing the configuration of a microphone device configured by two nondirectional microphones according to an embodiment of the present invention
[0027]
Fig. 2 is a diagram showing the configuration of a microphone device configured by two
conventional omnidirectional microphones.
[0028]
Explanation of sign
[0029]
21 omnidirectional microphone 22 omnidirectional microphone 23 splitter 24 low pass filter 25
sound pressure level calculator 26 second splitter 27 amplifier 28 amplifier 29 phase inverter 30
amplifier 31 determiner 32 adder 33 switch 33 Omnidirectional microphone M2
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Omnidirectional microphone 101 Directed axis 102 Housing 103 Differential amplifier 104
Buffer amplifier 105 Speaker
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