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JP2004328623

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DESCRIPTION JP2004328623
An object of the present invention is to efficiently output only a driver's voice on a vehicle as an
output waveform signal. SOLUTION: A microphone 2 whose phase largely changes depending on
the direction of a sound source, and a microphone 1 closely arranged with a phase different from
that of the microphone 2 depending on the direction of the sound source, and waveform signals
outputted from each other A sound source direction determination device comprising: a phase
comparator (determination means) 3 for determining a direction of a sound source based on a
phase relationship. A microphone device that controls an output level of a waveform signal from
a microphone based on the determination result of the phase comparator 3. [Selected figure]
Figure 11
Microphone device and sound source direction determination device
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone device and a sound source direction determination device that receives a sound
wave output from a sound source and outputs an output waveform signal based on the sound
wave. A microphone device receives a sound wave by a microphone, amplifies a waveform signal
output from the microphone by an amplifier, and outputs the amplified signal. As a microphone,
generally, a nondirectional microphone or a unidirectional microphone is used. The directional
characteristics of the microphone device are basically determined by the directional
characteristics of the microphone used in the device. The nondirectional microphone has a
substantially circular directivity as shown in FIG. In addition, as shown in FIG. 2 (D), the
unidirectional microphone has a substantially cardioid-shaped directional characteristic. In
recent years, car navigation systems and mobile communication systems have begun to be widely
used in vehicles such as automobiles. In such a system, for example, a car navigation system is
operated based on a result of analysis of voice received by a microphone device by a voice
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recognition device, or voice received by a microphone device is transmitted by a mobile
communication system. In a microphone device used in such an application, it is desirable to
have a characteristic that reliably receives the driver's voice and does not receive surrounding
running noise and the like as much as possible. For this reason, it is common to arrange a
unidirectional microphone as close to the driver in the vehicle as possible toward the driver. At
that time, there are also those that change directivity. (See, for example, Patent Document 1).
However, although the use of a unidirectional microphone is an improvement over the use of a
nondirectional microphone, a large amount of ambient running noise and the like will be
received. From the word uni-directionality, imagine the characteristic of high sensitivity only to
the front, but in fact the sensitivity to receive sound from the side is only a few dB lower than the
sensitivity to receive from the front is there. Therefore, the output signal of the microphone
device includes a component based on the driver's voice as well as a component such as
surrounding driving noise. As a result, the recognition rate of the voice recognition device may be
degraded or the call quality of the mobile communication system may be degraded. Therefore, it
is conceivable to use, as the microphone to be used, a microphone in which the sensitivity in the
direction other than the front is suppressed lower than the directivity characteristic of the single
directivity.
Also, noting that there is a difference in the reception level between the driver's voice and the
running noise, when the level of the waveform signal of the microphone exceeds a predetermined
threshold level, this waveform signal is output as an output signal. It is conceivable. [Patent
Document 1] Japanese Patent Application Laid-Open No. 2001-245396 (Page 2-Page 5, FIG. 1).
However, according to these conventional ideas, it is not possible to efficiently output only the
driver's voice in the vehicle as an output waveform signal. With regard to the improvement of the
directional characteristics of the former microphone, there is no microphone that is more
suitable than the single directivity in reality. For example, there is a microphone called
superdirectivity in which the sensitivity from the side is reduced rather than unidirectionality,
and the shape of the directional characteristic is sharpened to the front. However, superdirective
microphones in principle need to have a length equal to or greater than the wavelength of the
sound wave, and even short ones have a length of about 30 cm. For this reason, installing toward
the driver's mouth becomes impractical. In addition, there is a microphone with directional
characteristics of bi-directionality, which has low sensitivity from the side. The bi-directional
microphone has a substantially 8-shaped directivity characteristic as shown in FIG. 2 (B). In the
case of bi-directionality, the side sensitivity is low but the back sensitivity is similar to the front. If
the sound from the back side is a problem, I think that it will be improved if the back of the bidirectional microphone is covered. However, if the back of the bi-directional characteristic is
closed, it will be close to the non-directional characteristic. An omnidirectional microphone is a
microphone that mainly captures changes in air pressure generated by the movement of air
rather than direct movement of air by sound waves. The directional characteristics become
omnidirectional because the change in air pressure is generated similarly for sound waves from
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any direction. When one side of the diaphragm is closed, the movement of the diaphragm is
mainly due to the pressure change. For this reason, the same applies to the case of
unidirectionality, but if the surroundings other than the front of the diaphragm of the
microphone are closed, the directional characteristics of the microphone will be close to
omnidirectional contrary to the intention. It is [0015] In the latter threshold level based
determination technique, a desired level difference is required between the output level of the
audio signal and the output level of the running noise. However, the output level of the voice
signal largely changes depending on the voice and intonation of the speaker, the variation of the
distance between the speaker and the microphone, or the ambient noise level.
Therefore, considering such fluctuations in the output level of the audio signal, it is not possible
to set an appropriate threshold level, which may result in the voice being choppy or running
noise being always output. Do. In order to secure an absolute level difference between the output
level of the audio signal and the output level of the traveling noise, the distance between the
driver and the microphone may be as short as possible. However, it is not realistic to force the
driver to wear a headset with a microphone. As a matter of fact, the distance between the driver
and the driver can be reduced by mounting the microphone near the sun visor. By this, it will be
close to about 30 cm to 40 cm. However, unlike the case of wearing the headset, the output level
of the voice fluctuates because the distance between the speaker and the microphone fluctuates.
In addition, as the distance between the microphone and the driver decreases, the level of
fluctuation increases. For example, if this distance is 30 cm, the level of the audio signal will
change about twice by moving 5 cm back and forth. Therefore, even if the installation location of
the microphone is devised, it is very difficult to set an appropriate threshold level. Therefore, the
inventor of the present invention has, for example, a bi-directional microphone or a microphone
having directivity characteristics in which the front and back sensitivities of the bi-directionality
are changed differently, depending on the receiving direction of the sound wave. By focusing on
the fact that the phase changes, and utilizing this property, it is thought that the abovementioned problems can be solved well, and the present invention has been completed. That is,
the present invention solves the above problems, and a sound source direction determination
device capable of determining the relative direction of a sound source based on the phase
difference between waveform signals output from a plurality of microphones. The aim is to get
Another aspect of the present invention is a microphone device that determines the relative
direction of a sound source based on the phase difference between waveform signals output from
a plurality of microphones, and controls an output waveform signal based on the determination
result. The aim is to get A sound source direction determining apparatus according to the present
invention comprises: a first microphone in which the phase of a waveform signal outputted is
largely changed according to the direction of a sound source; and a first microphone according to
the direction of a sound source. Microphones that output a waveform signal of a phase different
from that of the microphones, and are output from the respective microphones and the second
microphones disposed close enough to the wavelength of the sound wave, and the respective
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microphones Determining means for determining the direction of the sound source based on the
result of comparing the phases of the waveform signals.
The sound source direction determination device according to the present invention further
includes, as the first microphone whose phase of the waveform signal output is largely changed
depending on the direction of the sound source, the sensitivity on the front side and the
sensitivity on the back side of the bi-directional characteristic. In addition to using a microphone
having directivity characteristics that are changed differently, the direction of the high sensitivity
side of the microphone is installed in the direction opposite to the front of the device. According
to the sound source direction determination apparatus of the present invention, the phases of the
waveform signals to be output are mutually different depending on the direction of the sound
source, and a plurality of microphones disposed close to each other and the waveform signals
output from these microphones Or operation means for adding or subtracting waveform signals
obtained by shifting the phase of the waveform signal output from the microphones, and
waveform signals based on the waveform signals output from each microphone And a
determination unit that determines the direction of the sound source based on the result of
comparing the phase of the waveform signal different from the waveform signal to be output and
the waveform signal output from the calculation unit. According to the sound source direction
determination apparatus of the present invention, the ratio of the waveform signals to be added
or subtracted can be varied in the arithmetic means for adding or subtracting the waveform
signals. In the microphone device according to another invention of the present application, the
phases of the output waveform signals are different from each other depending on the direction
of the sound source, and based on the waveform signals output from a plurality of microphones
disposed close to each other. Determining means for determining the direction of the sound
source by comparing the phases of the plurality of waveform signals generated; and output level
variable means for changing the output level of the waveform signal according to the determined
direction of the sound source; Is provided. The microphone device according to another aspect of
the present invention further includes level detection means for detecting the level of the
waveform signal based on the sound wave, and in the output level variable means for changing
the output level, the detection result by the level detection means Is also intended to change the
output level. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a microphone
device and a sound source direction determination apparatus according to an embodiment of the
present invention will be described based on the drawings. Embodiment 1 FIG. 1 is a circuit
diagram showing a sound source direction determination apparatus according to Embodiment 1
of the present invention. The sound source direction determination device mainly includes the
nondirectional microphone 1 as the second microphone, the bidirectional microphone 2 as the
first microphone, and waveform signals output from the microphones 1 and 2. And a phase
comparator 3 as a determination means for comparing the phases of and outputting a phase
determination signal that changes based on the result of the phase comparison.
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Further, between the nondirectional microphone 1 and the phase comparator 3, and between the
bidirectional microphone 2 and the phase comparator 3, the amplitudes of the waveform signals
output from these microphones 1 and 2, respectively. An amplification amplifier 4 is provided to
amplify the signal. FIG. 2A is a directional characteristic diagram showing the directional
characteristics of the nondirectional microphone 1 shown in FIG. The directional characteristic
curve of the nondirectional characteristic has a substantially circular shape. That is, the
amplitude of the waveform signal output from the nondirectional microphone 1 is constant
regardless of the relative direction as long as the strength of the sound source is constant and the
distance to the sound source is also constant. FIG. 2B is a directional characteristic diagram
showing the directional characteristics of the bi-directional microphone 2 shown in FIG. The
directional characteristic curve of the bi-directional characteristic has a substantially 8-shape like
connecting two circles. That is, the amplitude of the waveform signal output from the
bidirectional microphone 2 changes not only according to the distance between the bidirectional
microphone 2 and the sound source, but also according to the relative direction between the
bidirectional microphone 2 and the sound source . Specifically, when a sound wave is given to
the bi-directional microphone 2 from a direction perpendicular or parallel to the vibration plane
(not shown), the sound wave from a direction perpendicular to the sound wave from the direction
parallel to the vibration plane Can output a waveform signal with a large amplitude. In FIG. 2B,
the vibration plane is disposed on the horizontal axis. In addition, the bidirectional microphone 2
has a sound source located above the horizontal axis in FIG. 2B and a sound source located below
the horizontal axis in FIG. 2B. The phase of the waveform signal output from the bidirectional
microphone 2 is shifted by 180 degrees. In other words, the phase changes by 180 degrees near
the position of the 8-shaped recess in the directivity characteristic diagram of FIG. 2 (B).
Hereinafter, a point at which the phase is largely changed in such a hollow portion of the
directivity characteristic diagram will also be described as a phase singularity. In FIG. 2B, the
portion A is the phase singularity. The phase hardly changes in portions other than the phase
singular point A in FIG. 2 (B). That is, waveform signals with almost the same phase can be
obtained in any direction if it is above the horizontal axis in FIG. 2 (B). Moreover, if it is the lower
side than the horizontal axis of FIG. 2 (B), although the phase is 180 degree | times and an upper
side, a waveform signal of the substantially same phase is obtained even if it is 180 degree shift.
Therefore, for example, when a sound wave of positive phase is input from the sound source on
the upper side of the horizontal axis in FIG. 2B and a waveform signal of positive phase is output
from the bidirectional microphone 2, When sound waves of positive phase are input from the
sound source on the lower side of the horizontal axis, the bidirectional microphone 2 outputs
waveform signals of negative phase.
Hereinafter, based on the positive phase of the sound wave, the direction in which the waveform
signal of positive phase is output from the bidirectional microphone 2 will be referred to as the
front direction of the bidirectional microphone 2. Further, based on the positive phase of the
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sound source, the direction in which the waveform signal of negative phase is output from the
bidirectional microphone 2 is referred to as the back direction of the bidirectional microphone 2.
Further, the direction of the horizontal axis in FIG. 2B is referred to as the side direction of the bidirectional microphone 2. In the nondirectional microphone 1, unlike the bidirectional
microphone 2, there is no phase singularity A whose phase largely changes before and after that,
and the relative direction of the sound source is in any direction. , Output the waveform signal of
the same phase. Incidentally, as the nondirectional microphone 1, there is a pressure type
microphone. The pressure microphone is realized by, for example, a dynamic microphone, a
condenser microphone, an electret condenser microphone, or the like. This pressure type
microphone basically has a structure in which the front side of the diaphragm is open and the
rear side is sealed by the housing. There are two types of principles by which the movement of
air by sound waves moves the diaphragm. One is a movement that receives air movement
directly and follows air movement. The second is the movement in which the diaphragm is
moved by the change in air pressure generated by the movement of air. In addition, these two
types of movement are overwhelmingly larger in the latter case due to barometric pressure. In
the case of a pressure type microphone, since the back side is sealed, the air pressure on the
back side of the diaphragm is constant, and the diaphragm is moved by the change in air
pressure on the front side. Since the movement due to the change in air pressure is dominant, the
pressure microphone outputs a waveform signal according to the change in air pressure at the
location of the microphone. Since the pressure change around the microphone does not depend
on the relative direction of the sound source, the pressure type microphone has a constant
sensitivity regardless of the relative position of the sound source, and the phase does not change
depending on the direction of the sound source. On the other hand, the bidirectional microphone
2 moves differently. The bidirectional microphone 2 is a velocity microphone, and is realized by,
for example, a ribbon microphone. The velocity microphone has a structure in which the
periphery of the diaphragm is open. When the periphery of the diaphragm is opened, if the size
of the diaphragm is sufficiently smaller than the wavelength of the sound wave, the air pressure
on the front side of the diaphragm and the air pressure on the back side become exactly the
same.
When this happens, the diaphragm will not be moved by changes in barometric pressure, but will
move according to the direct movement of air. In the velocity type microphone, the vibration
direction of the diaphragm is opposite between the case where the sound wave comes from the
front side of the diaphragm and the case where the sound wave comes from the back side of the
diaphragm. For example, it is assumed that a certain sound source is disposed on the front side of
the diaphragm, and at a certain timing, the movement of air by the sound wave is in the direction
toward the microphone. For air movement coming from the front, the diaphragm moves to the
back. When the same sound source is disposed on the back side of the diaphragm at the same
distance and viewed at the same timing, the movement of air by the sound wave toward the
microphone is the same as when the sound source is on the front side. However, in this case,
04-05-2019
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since the air comes from the back side of the diaphragm, the diaphragm moves toward the front
side. This movement is the reverse when the sound source is on the front side. Since the
waveform signal output of the microphone follows the movement of the diaphragm, in the
velocity type microphone, the waveform signal output from the microphone is different between
when the relative direction of the sound source is the front side and when it is the back side. The
phase is reversed. If the pressure microphone and the velocity microphone are disposed
sufficiently close to the wavelength of the sound wave and there is a sound source on the front
side of the velocity microphone, the pressure microphone A waveform signal having substantially
the same phase is output to the waveform signal output from the. In FIG. 3, a sound wave coming
from a sound source emitting a sine wave of a single frequency is received by a pressure
microphone as the nondirectional microphone 1 and a velocity microphone as the bidirectional
microphone 2. , Indicates waveform signals output from these microphones. In this figure, let B
be a waveform signal output from the pressure type microphone. When the sound source is on
the front side of the velocity microphone, the output waveform of the velocity microphone is a
waveform signal A having substantially the same phase as the waveform B. In addition, since the
waveform signal output of the velocity type microphone when the sound source is on the back
side is in opposite phase to that when the sound source is on the front, the waveform signal
output is C in reverse phase to A. Therefore, when the waveform signal output of the velocity
microphone as the bidirectional microphone 2 is viewed on the basis of the waveform signal
output B of the pressure microphone as the nondirectional microphone 1, as shown in FIG. If in
phase, it can be said that the sound source is on the front side.
Also, conversely, as shown in FIG. 3C, it can be seen that the sound source is on the back side if
the phases are substantially in opposite phase. The phase comparator 3 in FIG. 1 makes this
determination. Based on the waveform signal from the nondirectional microphone 1, the phase
comparator 3 determines whether the phase of the waveform signal from the bidirectional
microphone 2 is approximately the same phase or the opposite phase. Then, for example, a high
level phase determination signal is output if the phase is approximately the same, and a low level
phase determination signal is output if the phase is approximately the opposite phase. Looking at
this phase determination signal, if the level is high, the sound source is on the front side, and if it
is low, the sound source is on the back side. As described above, in the sound source direction
determination apparatus according to the first embodiment, the phase relationship between the
waveform signal output from the nondirectional microphone 1 and the waveform signal output
from the bidirectional microphone 2 is used. , The relative direction of the sound source can be
determined. Therefore, as shown in FIG. 4 by overlapping the directivity characteristics in the
installation state of the two microphones 1 and 2, by using the sound source direction
determination device according to the first embodiment, the sound source is a sound source
direction determination device It can be determined whether it is on the front side A or on the
back side B. And based on this judgment result, on-off control of switches, such as illumination,
can be carried out. In addition, based on the determination result, when there is no sound from
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the front, the level of the ambient noise can be reduced by narrowing the amplitude of the
waveform signal output. Second Embodiment FIG. 5 is a circuit diagram showing a sound source
direction determining apparatus according to Embodiment 2 of the present invention. The sound
source direction determination apparatus mainly has a nondirectional microphone 1 as a second
microphone, and a directivity characteristic in which the sensitivity on the front side and the
sensitivity on the back side of the bidirectivity are changed differently. A phase as determination
means for comparing the phases of the waveform signals output from the microphone 5 as one
microphone and these microphones 1 and 5 and outputting a phase determination signal that
changes based on the result of the phase comparison And a comparator 3. Further, between the
nondirectional microphone 1 and the phase comparator 3 and between the microphone 5 and
the phase comparator 3, the amplitudes of the waveform signals output from the microphones 1
and 5 are amplified, respectively. An amplification amplifier 4 is provided. The microphone 5
having directivity characteristics in which the sensitivity on the front side and the sensitivity on
the back side of the bi-directionality are changed as described above is realized, for example, by
substantially covering the back side of the bi-directional microphone 2 can do.
In this case, for example, directivity characteristics as shown in FIG. 2 (C) are obtained. When air
is vibrated by voice or the like when the back side of the diaphragm of the bidirectional
microphone 2 is incompletely closed, the movement of air on the back side of the diaphragm is
suppressed from the front side. The air pressure on the front side and the back side of the
diaphragm does not match. Therefore, the movement of the diaphragm is a mixture of elements
of air pressure as well as direct movement of air. As a result, as shown in FIG. 2C, the sensitivity
of the back side of the bi-directional microphone 2 becomes lower than that of the front side, and
the two phase singular points A are also shifted to the back side. It becomes a directional
characteristic of the shape. Hereinafter, this directivity characteristic is referred to as a
hypercardioid characteristic. The hypercardioid property in the narrow sense is a combination of
elements of air pressure at a specific ratio, but here, all hypercardioid properties have two phase
singularities A and the front side and back side have different sensitivities I will write. Further,
the larger one of the upper eight-shaped shape in FIG. 2C is the high sensitivity side, and the
smaller one is the low sensitivity side. The microphone 5 is described as a hypercardioid
microphone 5. If the degree of sealing on the back side of the hypercardioid microphone 5 is
further increased, the sensitivity on the back side further decreases, and eventually the phase
singularity A becomes one and the rise in sensitivity on the back side disappears Then, the
characteristics are as shown in FIG. 2 (D). A characteristic like this figure is called a cardioid
characteristic. A unidirectional microphone is basically a cardioid characteristic. The constituent
elements other than the high parkar geoid microphone 5 are the same as the elements having the
same names in the first embodiment, and the same reference numerals are given and the
description is omitted. The second embodiment is characterized in the installation method of the
microphone in addition to the component. The arrangement of the two microphones sufficiently
close to each other is the same as in the first embodiment, but in the second embodiment, in
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particular, the low sensitivity side of the hypercardioid microphone 5 is placed toward the front
of the device. That is, the direction of the high sensitivity side of the hypercardioid microphone 5
is installed in the direction opposite to the front of the device. The high parkar geoid property
can have many properties depending on the shape of the blocking side. Not only the position of
the phase singular point A, but also the phases on the high sensitivity side and the low sensitivity
side change depending on the shape. Nevertheless, the hypercardioid microphone 5 in the
second embodiment can be handled in the same manner as the bi-directional microphone 2 in
the first embodiment.
The phase relationship between the waveform signal output of the nondirectional microphone 1
and the waveform signal output of the hypercardioid microphone 5 is the relationship between B
and A, C in FIG. Alternatively, they are generally in antiphase relation. Therefore, as in the first
embodiment, the phase comparator 3 also determines whether the phase of the waveform signal
output of the nondirectional microphone 1 is approximately the same phase or the opposite
phase. It can be judged whether it is on the front side or the back side. As described above, the
sound source direction determination apparatus according to the second embodiment is based on
the relationship between the waveform signal output from the nondirectional microphone 1 and
the phase of the waveform signal output from the hypercardioid microphone 5. , The relative
direction of the sound source can be determined. Therefore, by using the sound source direction
determining apparatus according to the second embodiment, as shown in FIG. 6 by overlapping
the directivity characteristics in the installation state of the two microphones 1 and 5, the sound
source can It can be determined whether it is on the front side A or in the surrounding direction
B. And based on this judgment result, on-off control of switches, such as illumination, can be
carried out. In addition, based on the determination result, when there is no sound from the front,
the level of the ambient noise can be reduced by narrowing the amplitude of the waveform signal
output. In particular, by setting the low sensitivity side of the hypercardioid microphone 5 to the
front side of the sound source direction determination device as in the second embodiment, the
angle is narrower than in the case where the bidirectional microphone 2 is used. It can be
determined whether there is a sound source in the range. When the bi-directional microphone 2
is used, this range is fixed at 180 degrees, but the use of the hypercardioid microphone 5 can
narrow this angular range. Further, by changing the structure of the hypercardioid microphone
5, it is possible to freely change the angle range of the position determination of the sound
source to some extent. As a result, for example, by installing the sound source direction
determination device on a sun visor of a car or a ceiling in the vicinity thereof, it is possible to
narrow down the driver's attention to determine whether or not the user is speaking. Third
Embodiment FIG. 7 is a circuit diagram showing a sound source direction determination
apparatus according to the third embodiment of the present invention. The sound source
direction determination device mainly includes the nondirectional microphone 1 as one
microphone among the plurality of microphones, the bidirectional microphone 2 as one
microphone among the plurality of microphones, and the nondirectional A phase inverter 6 for
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inverting the phase of the waveform signal output of the dynamic microphone 1, an adder 7 as
arithmetic means for adding the output of the phase inverter 6 and the waveform signal output
of the bidirectional microphone 2 at a specific ratio A phase comparator 3 as a determination
unit that compares the phase of the output of the adder 7 with the waveform output of the
nondirectional microphone 1 and outputs a phase determination signal that changes based on
the result of the phase comparison; Equipped with
In addition, between the nondirectional microphone 1 and the phase comparator 3 and between
the bidirectional microphone 2 and the adder 7, the amplitudes of the waveform signals output
from these microphones 1 and 2 are respectively An amplification amplifier 4 for amplifying is
provided. In the third embodiment, instead of using the hypercardioid microphone 5 in the
second embodiment, a signal obtained by inverting the phase of the waveform signal output of
the nondirectional microphone 1 by the phase inverter 6 and bi-directional The waveform signal
output of the differential microphone 2 is added by the adder 7 to be used. When the sound
wave comes from the front side, the phases of the nondirectional microphone 1 and the
bidirectional microphone 2 are approximately the same phase, so the phases of the output of the
phase inverter 6 are approximately opposite to each other. Assuming that the amplitudes of the
output of the nondirectional microphone 1 and the output of the bidirectional microphone 2 are
the same when the sound source is in front of the output signal of the phase inverter 6, for
example, the amplitude is halved, Suppose that the adder 7 adds. When the sound source is on
the front, the output of the bidirectional microphone 2 and the output signal of the phase
inverter 6 are in antiphase, so the amplitude after addition is half of the output of the
bidirectional microphone 2. At this time, the phase after addition does not change. When the
sound source is on the back side, the phase is the same, so the amplitude is 1.5 times and the
phase is not changed. Furthermore, when the sound source is in the side direction, the amplitude
of the output of the bi-directional microphone 2 is small, so that the amplitude and phase after
addition become approximately equal to the output signal of the phase inverter 6. Since the
signals after addition in the adder 7 are opposite in phase to the front and back as in the
bidirectional microphone 2, there should be a phase singular point A where the phase is inverted
somewhere along the way However, the phase singular point A disappears on the side where the
phase singular point A exists in the bidirectional microphone 2. In this case, the phase singular
point A of the signal after addition in the adder 7 is a point at which the output of the
bidirectional microphone 2 has the same phase as that on the front side and half the amplitude.
Since the sensitivity of the bi-directional microphone 2 is roughly proportional to the cosine of
the angle from the front, that point, that is, the phase singularity A is approximately around +/−
60 degrees from the front. The signal after addition in the adder 7 and the waveform signal from
the nondirectional microphone 1 are shown in an overlapping manner in FIG. The microphones
used are the non-directional microphone 1 and the bi-directional microphone 2, but using the
phase inverter 6 and the adder 7 to generate a signal corresponding to the hypercardioid
microphone 5 it can.
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The other components are the same as the respective components of the same names in the first
embodiment except that the signal corresponding to the high parkar geoid microphone 5 is
generated by the adder 7 and the same reference numerals are given and described. Omit. The
phase of the signal entering the phase comparator 3 is also identical to that of the first
embodiment. Therefore, as in the first embodiment, if the phase comparator 3 determines
whether the phase is approximately the same phase or the opposite phase with respect to the
waveform signal output of the nondirectional microphone 1, the sound source is the front of FIG.
It can be determined whether it is on the side A or on the back side B. As described above, the
sound source direction determination apparatus according to the third embodiment uses the
non-directional microphone 1 and the bi-directional microphone 2 and has a narrow angle range
as in the case of using the hypercardioid microphone 5. The relative direction of the sound
source of can be determined. Therefore, the same thing as Embodiment 2 can be said, such as
advantages in application. In the case of the high parkar geoid microphone 5, the location of the
phase singularity A is determined by the structure of the microphone, so the location can not be
changed unless the microphone is changed. However, in the case of the third embodiment, the
location of the phase singularity A can be changed only by changing the input level of the adder
7. In addition, it is also advantageous to be able to be configured by a microphone that is more
general than the hypercardioid microphone 5. In FIG. 7, the bi-directional microphone 2 is
installed so as to output a signal having the same phase as the non-directional microphone 1 to
the sound source on the front side, but it should be installed in the opposite direction You can
also. In this case, the outputs of the nondirectional microphone 1 and the bidirectional
microphone 2 become waveform signals of substantially opposite phase with respect to the
sound source on the front side, so the phase inverter 6 is omitted and the adder 7 is used as it is.
The addition results in the same phase characteristics as above. However, since the waveform
signal from the adder 7 to the phase comparator 3 is also in reverse phase, the determination in
the phase comparator 3 must be reversed. Fourth Embodiment FIG. 9 is a circuit diagram
showing a sound source direction determining apparatus according to the fourth embodiment of
the present invention. The sound source direction determination device mainly includes the
nondirectional microphone 1 as one microphone among the plurality of microphones, the
bidirectional microphone 2 as one microphone among the plurality of microphones, and the
nondirectional Phase inverter 6 that inverts the phase of the waveform signal output of the
differential microphone 1, a voltage control amplifier 8 that changes the output level of the
phase inverter 6, the output of the voltage control amplifier 8 and the waveform signal output of
the bidirectional microphone 2 And the phase of the output of the adder 7 and the waveform
signal output of the omnidirectional microphone 1 are compared with each other, and the phase
determination signal changing based on the result of the phase comparison is And a phase
comparator 3 as judging means for outputting.
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In addition, between the nondirectional microphone 1 and the phase comparator 3 and between
the bidirectional microphone 2 and the adder 7, the amplitudes of the waveform signals output
from these microphones 1 and 2 are An amplification amplifier 4 for amplifying is provided. In
the third embodiment, the phase singular point A is moved by adding the output from the
nondirectional microphone 1 whose phase is inverted to the output of the bidirectional
microphone 2 in the adder 7. ing. In the fourth embodiment, the voltage control amplifier 8 is
added so that the amount of addition can be varied, that is, the movement of the phase singular
point A can be controlled. In FIG. 8, the ratio of addition of the waveform signal from the
bidirectional microphone 2 and the signal obtained by inverting the signal of the nondirectional
microphone 1 in the adder 7 is 2: 1. This ratio is set to 2: 比率 3 as shown in FIG. The voltage
control amplifier 8 can control the change of the ratio from the outside. In the fourth
embodiment, the voltage control amplifier 8 is added, and the other components are the same as
the respective elements having the same names in the third embodiment except that the adding
ratio in the adder 7 is variable. The same reference numerals are given and the description is
omitted. The phase of the signal entering the phase comparator 3 is also identical to that of the
first embodiment. Therefore, as in the first embodiment, when the phase comparator 3
determines whether the waveform signal output of the nondirectional microphone 1 is
approximately the same phase or the opposite phase, the sound source is the front side A of FIG.
It can be judged whether it is on the back side B or on the back side. Further, as in the third
embodiment, the bidirectional microphone 2 can be installed in the reverse direction and the
phase inverter 6 can be omitted. As described above, the sound source direction determination
apparatus according to the fourth embodiment uses the non-directional microphone 1 and the bidirectional microphone 2 and has a narrow range such as that using the hypercardioid
microphone 5. The relative direction of the sound source can be determined. Also, the position of
the phase singular point A can be controlled from the outside. Therefore, the advantages of the
application side, etc. are basically the same as in Embodiment 3, and further, as a microphone of
a video camera with a zoom function, is there any sound source in the zoom range in conjunction
with the zoom? Applications such as determining whether or not it is possible are also possible.
Embodiment 5 FIG. 11 is a circuit diagram showing a microphone device according to
Embodiment 5 of the present invention.
The microphone device mainly includes a non-directional microphone 1 as one microphone
among a plurality of microphones, a bi-directional microphone 2 as one microphone among a
plurality of microphones, and these microphones 1 , 2 compare the phases of the waveform
signals output from each other, and output a phase determination signal that changes based on
the result of the phase comparison. A phase comparator 3 as a determination means and a
waveform signal from the bidirectional microphone 2 A voltage control amplifier 8 as output
level variable means for receiving an output and a phase determination signal from the phase
comparator 3 and amplifying a waveform signal from the bidirectional microphone 2 at an
amplification factor according to the level of the phase determination signal; Equipped with The
04-05-2019
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signal amplified by the voltage control amplifier 8 is output as an output waveform signal.
Further, the amplitudes of the waveform signals outputted from these microphones 1 and 2
between the nondirectional microphone 1 and the phase comparator 3 and between the
bidirectional microphone 2 and the phase comparator 3 respectively. An amplification amplifier
4 is provided to amplify the signal. The voltage control amplifier 8 amplifies the waveform signal
from the bidirectional microphone 2 at an amplification factor corresponding to the level of the
phase determination signal, and outputs this as an output waveform signal. Specifically, when the
level of the phase determination signal is high, the waveform signal from the bidirectional
microphone 2 is amplified at a high amplification factor and at a low amplification factor. The
low amplification factor may be 0%. The other components are the same as the components of
the same names in the first embodiment, and the same reference numerals are given and the
description is omitted. When the sound source is arranged on the front side of the microphone
device, the phase of the waveform signal from the nondirectional microphone 1 and the
waveform signal from the bidirectional microphone 2 are almost the same in phase, so the phase
comparator 3 Output the phase determination signal of level. Then, since the phase
determination signal of high level is output from the phase comparator 3, the voltage control
amplifier 8 amplifies the waveform signal from the bidirectional microphone 2 with a
predetermined high amplification factor. The signal amplified by the voltage control amplifier 8
is output as an output waveform signal. Conversely, when the sound source is disposed on the
back side of the microphone device, the waveform signal from the nondirectional microphone 1
and the waveform signal from the bidirectional microphone 2 have substantially opposite phases,
so the phase comparator 3 A low level phase determination signal is output. Then, since a low
level phase determination signal is output from the phase comparator 3, the voltage control
amplifier 8 amplifies the waveform signal from the bidirectional microphone 2 at a
predetermined low amplification factor.
The signal amplified by the voltage control amplifier 8 is output as an output waveform signal. If
the amplification factor is 0%, the component based on the waveform signal from the sound
source is not included in the output waveform signal. As described above, in the microphone
device according to the fifth embodiment, the sound source is based on the relationship between
the waveform signal output from the nondirectional microphone 1 and the phase of the
waveform signal output from the bidirectional microphone 2. The relative direction is
determined, and the amplification factor of the waveform signal based on the sound wave is
switched based on the determination result. Therefore, by using the microphone device
according to the fifth embodiment, when there is a sound source on the front side of the
microphone device, the waveform signal based on the sound wave from the sound source is
amplified, and this is output waveform signal Can be output as Also, when there is no sound
source on the front side of the microphone device, the amplification factor of the waveform
signal is lowered. As a result, in a pseudo manner, the sound of the sound source on the front
side of the microphone device can be efficiently converted into an output waveform signal, and
04-05-2019
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directivity characteristics that do not convert the sound of the sound source on the back side into
an output waveform signal can be obtained. it can. Instead of the voltage control amplifier 8, a
switch which is on / off controlled according to the level of the phase determination signal may
be used. In this case, the amplification factor is switched to 100% and 0%. The same effect as that
of the fifth embodiment can be obtained by performing on control when the phase determination
signal is high level and performing off control when the phase determination signal is low level.
In the fifth embodiment, the voltage control amplifier 8 is added to the first embodiment. Since
the phase determination signal has the same operation as that of the first embodiment, the
directivity characteristic is also in the same range as the determination of the sound source
direction in the first embodiment. In addition to the first embodiment, the second embodiment,
the third embodiment or the fourth embodiment may be used to obtain the phase determination
signal. In this case, the directivity characteristic can be limited to a narrower range or the range
can be changed. Embodiment 6 FIG. 12 is a circuit diagram showing a microphone device
according to Embodiment 6 of the present invention. The microphone device mainly includes a
non-directional microphone 1 as one microphone among a plurality of microphones, a bidirectional microphone 2 as one microphone among a plurality of microphones, and these
microphones 1 , 2 compare the phases of the waveform signals output from each other, and
output a phase determination signal that changes based on the result of the phase comparison. A
phase comparator 3 as a determination means and a waveform signal from the bidirectional
microphone 2 A level detector 9 as level detection means for detecting the level of the output
and outputting a gain control signal according to the level, and multiplying the gain control
signal by the phase determination signal output from the phase comparator 3 The multiplier 10
that outputs the multiplication signal and the waveform signal from the bidirectional microphone
2 are input, and the multiplication signal level from the multiplier 10 is input. And a voltage
control amplifier 8 as an output level variable unit that increases the amplification factor as the
loop voltage is higher.
The signal amplified by the voltage control amplifier 8 is output as an output waveform signal.
Further, between the nondirectional microphone 1 and the phase comparator 3 and between the
bidirectional microphone 2 and the phase comparator 3 respectively, the amplitudes of the
waveform signals outputted from these microphones 1 and 2 An amplification amplifier 4 is
provided to amplify the signal. The level detector 9 detects the level of the waveform signal
output from the bidirectional microphone 2 and outputs a gain control signal according to the
level. FIG. 13 shows an input / output characteristic diagram showing the relationship between
the input signal level of the level detector 9 and the level of the gain control signal output from
the level detector 9. The solid line is the input / output characteristic line of the level detector 9.
The broken line is the input / output characteristic line of the linear amplifier. Then, as shown in
FIG. 13, when the input level is lower than a predetermined first level, this level detector 9
outputs a gain control signal of a level proportional to the input level. Also, when the input level
is higher than the predetermined first level, the control signal of the substantially constant level
04-05-2019
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is output. When the microphone device according to the sixth embodiment is disposed above the
driver's seat of a car, for example, the first level corresponds to the amount of voice of a person
sitting in the driver's seat in the normal car. Based on the input volume level based on the voice
volume, it may be set to a level slightly smaller than that. The other components are the same as
the components of the same names in the fifth embodiment, and the same reference numerals
are given and the description is omitted. When the sound source is arranged on the front side of
the microphone device, since the waveform signal from the nondirectional microphone 1 and the
waveform signal from the bidirectional microphone 2 are substantially in phase, the phase
comparator 3 outputs a high level signal. Output a phase determination signal. The level detector
9 outputs a gain control signal according to the level of the waveform signal from the
bidirectional microphone 2. The multiplier 10 multiplies this gain control signal by the high level
phase determination signal, and outputs this as a multiplication signal. Then, the voltage control
amplifier 8 amplifies the waveform signal from the bidirectional microphone 2 at a
predetermined high amplification factor according to the level of the multiplication signal. The
signal amplified by the voltage control amplifier 8 is output as an output waveform signal.
Conversely, when the sound source is arranged on the back side of the microphone device, the
waveform signal from the nondirectional microphone 1 and the waveform signal from the
bidirectional microphone 2 have substantially opposite phases, so the phase comparator 3 A low
level phase determination signal is output.
The level detector 9 outputs a gain control signal according to the level of the waveform signal
from the bidirectional microphone 2. The multiplier 10 multiplies this gain control signal by the
low level phase determination signal, and outputs this as a multiplication signal. Since the
multiplication signal at this time is multiplication with the low level, it always becomes the low
level. Then, the voltage control amplifier 8 amplifies the waveform signal from the bidirectional
microphone 2 at a predetermined low amplification factor according to the level of the
multiplication signal. The signal amplified by the voltage control amplifier 8 is output as an
output waveform signal. If the amplification factor is 0%, the component based on the waveform
signal from the sound source is not included in the output waveform signal. FIG. 14 shows input
/ output characteristics of the microphone device according to the sixth embodiment. When
there is a sound source on the back side of the microphone device, a low level phase
determination signal is output from the phase comparator 3, so that the output waveform signal
is as shown in the input / output characteristic curve B of FIG. The output level is always low
regardless of the sound wave input level based on the sound source. When there is a sound
source on the front side of the microphone device, a high level phase determination signal is
output from the phase comparator 3, so that the output waveform signal is as shown in the input
/ output characteristic curve A of FIG. The output level corresponds to the input level of the
sound wave input to the bidirectional microphone 2. Specifically, for example, when the first level
in the level detector 9 is set equal to or less than the volume of the person sitting in the driver's
seat in the normal car, the range of (a) of FIG. As shown in relation to the range of b) (portion
04-05-2019
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corresponding to the range of the input level (a) of the input / output characteristic curve A in
FIG. 14), the voice of the person sitting in the driver's seat is output at a substantially constant
level can do. The range of (c) in FIG. 14 is an output level range when a linear amplifier is used.
As apparent from FIG. 14, the range of the output level shown in (b) of FIG. 14 is narrower than
the ranges shown in (c) and (a) of FIG. In other words, it can be said that this is level stable. When
the volume level is lower than the first level, the output waveform signal changes linearly with
the input level at a level lower than the predetermined level. As described above, in the
microphone device according to the sixth embodiment, the sound source is based on the
relationship between the waveform signal output from the nondirectional microphone 1 and the
phase of the waveform signal output from the bidirectional microphone 2. Based on the
determination result, it is possible to output an output waveform signal based on a sound wave
from the sound source only when the sound source is on the front side.
That is, when there is a sound source on the front side, the sound up to a predetermined size can
be output linearly, and the sound with a higher volume can be output at a substantially constant
level. On the other hand, if there is a sound source on the back side, it can be made to have a
very low level or not output at all. In particular, when the volume is higher than the first level, the
output level is substantially constant. For example, even if the position of the head moves, the
voice level of the person sitting in the driver's seat changes. , It can be output as an audible signal
of a certain level easy to hear. Further, it can also be suitably used as a voice input signal of a
voice recognition device. In the sixth embodiment, since the phase determination signal has the
same configuration as that of the first embodiment, the directivity characteristic is also in the
same range as the determination of the sound source direction in the first embodiment. In
addition to the first embodiment, the second embodiment, the third embodiment or the fourth
embodiment may be used to obtain the phase determination signal. In this case, the directivity
characteristic can be limited to a narrower range or the range can be changed. According to the
sound source direction determination apparatus of the present invention, the relative direction of
the sound source can be determined based on the phase relationship between the waveform
signals output from the plurality of microphones. Further, in the microphone device according to
another invention of the present application, the relative direction of the sound source is
determined based on the phase relationship between the waveform signals output from the
plurality of microphones, and the output waveform signal is determined based on the
determination result. Can be controlled. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a
circuit diagram showing a sound source direction determining apparatus according to a first
embodiment of the present invention. FIG. 2 is a directivity characteristic diagram showing
directivity characteristics of various types of microphones alone. (A) is the directivity of a
nondirectional microphone, (B) is the directivity of a bidirectional microphone, (C) is the
directivity of a hypercardioid microphone, and (D) is the directivity of a unidirectional
microphone . FIG. 3 is a waveform diagram showing waveform signals output from a sound
source that outputs a single-frequency sinusoidal sound wave when received by a velocity
04-05-2019
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microphone and a pressure microphone. . 4 is a diagram showing directivity characteristics in the
installation state of two microphones used in the sound source direction determination apparatus
of FIG. 1; FIG. 5 is a circuit diagram showing a sound source direction determination device
according to a second embodiment of the present invention. 6 is a diagram showing directivity
characteristics in an installation state of two microphones used in the sound source direction
determination apparatus of FIG. 5;
FIG. 7 is a circuit diagram showing a sound source direction determination device according to a
third embodiment of the present invention. 8 is a diagram showing directional characteristics of
the nondirectional microphone used in FIG. 7 and a waveform signal generated by an adder. FIG.
9 is a circuit diagram showing a sound source direction determining apparatus according to a
fourth embodiment of the present invention. FIG. 10 is a diagram showing signal characteristics
of the nondirectional microphone used in FIG. 9 and a waveform signal generated by an adder.
FIG. 11 is a circuit diagram showing a microphone device according to Embodiment 5 of the
present invention. FIG. 12 is a circuit diagram showing a microphone device according to
Embodiment 6 of the present invention. FIG. 13 is a characteristic diagram showing input /
output characteristics of the level detector in FIG. 12; FIG. 14 is a characteristic diagram showing
input / output characteristics of the microphone device of FIG. 12; [Description of the code] 1
omnidirectional microphone 2 bidirectional microphone 3 phase comparator (judgment means) 4
amplification amplifier 5 high-parking geoid microphone 6 phase inverter 7 adder 8 voltage
control amplifier 9 level detector 10 multiplier
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