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JPS63144699

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DESCRIPTION JPS63144699
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound collecting apparatus constructed by combining a plurality of pairs of unidirectional
microphones used in an audio communication conference or the like. (Prior Art) A microphone
for a voice communication conference is disposed at the center of the conference console to pick
up the voice of a talker located around the conference console, and its sound collection
characteristic is high in the horizontal direction around the microphone. It is desirable to reduce
the sensitivity in the vertical direction of the microphone as much as possible in order to make it
Q not to be affected by the reflected sound from the ceiling or the conference table as well as the
sensitivity. As a prior art example for realizing a sound collection device having such
characteristics, there is one in which two directional microphones are used and their directional
axes are shifted by 90 degrees and combined. FIG. 2 is a diagram for explaining the configuration
according to the prior art and its operation. First, in FIG. 2A, l is a microphone having bidirectional characteristics and has directional characteristics of sensitivity as indicated by dotted
lines in the drawing. The signs + and-in the figure indicate that a relative phase difference
between the electric signal output and the sound in the front direction of the microphone and the
sound in the back direction is 180 degrees. When one bi-directional microphone 1 is used, B
which is 90 degrees accumulated with respect to the directional axis A-A '. For sound waves
coming from the direction of B ', the sensitivity is zero and the output voltage is zero. The second
bi-directional microphone, whose directivity axis is set in the direction of 90 degrees of the first
microphone whose sensitivity is zero, is arranged by adding the outputs of these two
microphones. It is an explanatory view of a method for obtaining sensitivity also for sound input
in the direction of 90 degrees with respect to the directivity axis of the first microphone, and is a
diagram showing horizontal surface directivity characteristics. That is, when the outputs of the
two bi-directional microphones 1 and 2 are added and the outputs are combined as the output of
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the microphone, the directivity characteristic becomes a pattern of bunches ? 10 sin ? shown
by a solid line, ? = 135 With respect to the sound input from the directions of Y and Y 'of 315
░ and 315 ░, it has directivity characteristics such that the sensitivity becomes zero, except for
the angle which is different as in the case shown in FIG. . (Problems to be Solved by the
Invention) However, even in the method of arranging the two bi-directional microphones at right
angles as described above, since there is a dead angle direction in which the sensitivity becomes
zero, acoustic signals from this direction are collected. There was a problem that it became
impossible to make sound. An object of the present invention is to solve the above-mentioned
problems and to provide a sound collection device capable of performing high sensitivity sound
collection by changing the directivity at all times to the change of the position of the sound
source.
(Means for Solving the Problems) The present invention comprises a plurality of radially
arranged pairs of unidirectional microphones and a plurality of differential amplifiers
corresponding to six pairs of the unidirectional microphones. In the sound device, a phase in
which the output side of one microphone and the output side of the other microphone are
switched for six pairs of unidirectional microphones and alternatively connected to the 10 input
side or the-input side of the differential amplifier The output side of the microphone with the
larger output level is connected to the 10 input side of the differential amplifier based on the
comparison result from the switching device, the output level of both microphones, and the
comparison result from the comparator. And a controller for controlling the phase switch to
connect the output side of the other microphone to the negative input side of the differential
amplifier. (Operation) When a sound is generated from the sound source, each microphone
captures it. Then, the outputs of both microphones are compared by the comparator in six pairs
of microphones, and the controller controls the phase switch based on the comparison result, and
the switch differentials the output side of the microphone with the larger output. While
connecting to the 10 input side of the amplifier, the output side of the other microphone is
connected to the-input side of the differential amplifier. As a result, the phase of the microphone
output of each pair is switched in the direction close to the sound source, so that the synthesis /
turn is formed in the direction closest to the sound source. Also, if the position of the sound
source changes, the phase of each microboss / pair is switched accordingly, and the synthesis /
gating turns in the direction closest to the sound source are also switched. (Embodiment) FIG. 1
is a block diagram of an embodiment of the present invention. In FIG. 1, Ia, lb, 2a and 2b are unidirectional microphones, respectively, which are on the same circumference (... At equal intervals
and whose directivity axis is normal outside with respect to the circumference It is arranged to
face. The arrows of the microphones in the figure indicate the pointing directions. 11.12 is a
comparator, 21.22 is a controller, 31.32 is a phase reversal switch, 41.degree. 42 is a differential
amplifier, 50 is an adder, and 60 is an electrical output terminal of the microphone device. In FIG.
1, first, an operation when a sound pressure is input from the direction of Zl which is the
pointing direction (the direction in which the sensitivity becomes high) of the microphone 1a will
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be described. For sound input from the Z1 direction, the output level of the counter microphone
is compared with the input sound pressure of the microphone 1b paired with the microphone 1a
by the comparator or the monitor, and in this case, the directivity axis is the input sound
pressure. It is determined that the output level of the microphone 1a disposed in the 21 direction
is a dog.
The determination result controls the phase inversion switch 31 by the controller 21. At this
time, the phase inversion switch 3 is set such that the output of the microphone 1a is connected
to the positive side of the differential amplifier 41. The outputs of one of the microphone pairs
2a and 2b have input sound pressure from the same direction with respect to the microphones,
so the output levels from the microphones become equal when compared by the comparator 12.
At this time, the control signal from the controller 22 to the phase inversion switch 32 is set to
maintain the previous state, but when the outputs of the microphones are input to the differential
amplifier 42, the amplitude is constant and the phase is constant. Are added 180 degrees
differently, so the electrical output from the differential amplifier 42 is in principle zero. When
noise sources exist vertically in the vertical direction with respect to the plane in which the
microphones are arranged, including the microphone pairs 1a and 1b for the same reason as the
operation of the microphone pairs 2a and 2b. The electric outputs from the six pairs of
microphones are 180 ░ out of phase and added by the differential amplifiers 41 and 42 and the
outputs are zero. Therefore, only the electrical output corresponding to the acoustic signal from
the Z1 direction output from the differential amplifier 41.42 is input to the adder 50, and the
electrical output signal of the microphone 1a is input to the output terminal 60 of the adder 5?.
It is taken out. Next, consider the case where an acoustic signal is input from the Z2 direction. In
this case, since the arrangement of the microphone pairs 1a and 1b and 2a and 2b described
above is equivalent to the case of shifting by 90 degrees, the above operation is applied as it is.
Finally, the operation when an acoustic signal is input from the central direction z3 of the
microphones 1a and 2a will be described. Also in this case, the magnitudes of the output levels of
the microphone pairs 1a and 1b and 2a and 2b are compared by the comparators 1 and 12,
which is the same as the operation described above. That is, for the sound input from the z3
direction, it is determined that the outputs of the microphones 1a and 2a are dogs, and the
outputs of the microphones 1a and 2a are input to the plus side of the differential amplifier / f41
and. As a result, the value of (sum of output levels of microphones 1a and 2a)-(sum of output
levels of microphones 71b and 2b) is taken out of the adder 50 as the output of the microphone
for sound input from the Z3 direction. It becomes. This operation is the same whether the
acoustic input direction is in any direction of the microphone periphery, so there is no blind spot
for the acoustic input direction.
Next, the comparators 11 and 12 and the phase reversal switches 31,. In order to clarify the
effectiveness of the existence of 32. the operation in the absence of the comparator and the
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phase reversal switch 31. 32 will be described. In this case, for the input sound pressure from the
z3 direction, the output of the microphone 1a is read on the plus side of the differential amplifier
4 and the output of the microphone 2a is read on the minus side of the differential amplifier 42,
In addition, considering the case where the input sound pressure levels to the microphones 1a
and 2a are the same for simplicity, the electric signal having the same amplitude but 180 degrees
out of phase is input to the adder 50. The output is zero, and the desired normal operation is not
performed for the acoustic input from the z3 direction. This operation state corresponds to the
case of the input sound pressure condition from the Y direction shown in FIG. 2 of the
conventional example. From the above operation reasons, it is understood that the comparator,
the phase reversal switch, and the controller for controlling these are device functions that are
indispensable to configure the present microphone and to achieve the desired characteristics. In
the embodiment of the present invention, the case where two pairs of microphones are combined
is described, but in the case of using a microphone having a sharp directional characteristic, the
number of microphones is increased to cover the entire circumferential direction. In this case, the
same number of comparators, controllers, phase inversion switches, and differential amplifiers as
the number of microphones may be prepared. Again, the principles and procedures of operation
are the same as described above. Next, FIG. 3 shows the results of determination of level change
characteristics due to angle change in the horizontal direction with respect to a-next gradient
type unidirectional microphone. From this figure, it can be seen that in the case of four, the
reduction amount is 6 dB by 3 dB at 90 degree intervals, and the reduction amount is 60 tt 1.2
dB, 8 tt, 45 u Q, 5 d 13 tt. As a result, by selecting the number of unidirectional microphones to
be used according to the number of persons in the talker, etc., it is possible to collect the emitted
sound from the horizontal direction of the arranged surface with less level change. It is possible
to provide a donut-oriented microphone capable of reducing the output level against room noise
from the vertical direction of the microphone surface, while arranging the sound receiving
speaker in the vertical direction of the microphone surface. Has an advantage that it is possible
to provide a sound collecting device capable of reducing the occurrence of howling.
Although the microphones are arranged on the circumference in the present embodiment, it is
possible to take an arbitrary array such as an oval or a quadrangle depending on the
arrangement of the conference callers. The functional effects of the sound collection device are
not lost. (Effects of the Invention) As described above, according to the present invention, in each
pair of microphones, the outputs of both microphones are compared, and each microphone is
connected by connecting the one with the larger output to the ten inputs of the differential
amplifier. It is possible to form an output synthesizing / tuffing in the direction closest to the
sound source, and switch the direction as the position of the sound source changes. Therefore,
for a sound source whose input direction is not constant, there is an effect that the directivity can
be changed and sound can be collected with high sensitivity.
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[0002]
Brief description of the drawings
[0003]
Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2a is a horizontal
directional pattern of a conventional bi-directional microphone, and Fig. 2 is a combination of
two bi-directional microphones arranged at right angles. FIG. 3 is a directional characteristic
diagram and FIG. 3 is a characteristic diagram of the number of microphones according to the
present invention and the level change in the horizontal direction.
1.2 ... bi-directional microphone, l'l, lb, 22! L, 2b иии Unidirectional microphone, 11.12 и и и
Comparator, 21.22 и и и и и и и и и и и и и и Phase reversal switch, 41.42 и и и differential amplifier, 50 и и и и
и и Adder, 60 ... output terminal. Fig.1 Fig.2 Fig.2 Fig.2 a composite directional pattern of two
biphasic microphone cophones arranged at right angles Fig.2 Fig.2 The number of microphones
according to the present invention and the horizontal direction Level change characteristic figure
3
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