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DESCRIPTION JPS625800

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DESCRIPTION JPS625800
[0001]
[Summary] When installing an audio conference apparatus of the howling suppressor method,
the reverberation time is measured, and the directivity of the microphone of the local station is
adjusted to be suitable for the reverberation time of the meeting room ak. BACKGROUND OF THE
INVENTION 1. Field of the Invention The present invention relates to a howling suppressor type
audio conferencing apparatus. The audio conference apparatus of the howling-sub-fusa system
will be described with reference to the drawings. 4 is a block diagram of an example of a howling
suppressor type audio conference apparatus, FIG. 5 is a block diagram of a peripheral portion of
the comparator 6 of FIG. 4, and FIG. 6 is a characteristic diagram for explaining the reverberation
of FIG. It is. In the figure, 1 is a microphone, 2.4.5 is an amplifier, 3 is a variable attenuator, 6 is a
comparator, 7 is a speaker, 8 is a capacitor, 10.11 is a diode, and 12 is a resistor. The same
reference numerals denote the same functions throughout the drawings. The A station side and
the B station side are the same device, and both devices are connected to each other by a line
LINE. Taking the station A side as an example, the audio signal is converted to an electrical signal
by the microphone 1 and amplified by the amplifier 2 to obtain a variable attenuator 3. The
signal is sent to the line LINE via the amplifier 4. On the other hand, the received voice signal is
received from station B via the line LINE, amplified by the amplifier 5 and then output as voice
from the speaker 7. In this case, a howling suppressor is used to suppress howling caused by the
acoustic coupling from the speaker 7 to the microphone 1. The outline of this howling
suppressor will be described according to FIG. The transmission signal of the output of the
amplifier 2 is rectified by the diode 10 into a DC voltage 2. On the other hand, the reception
signal of the output of the amplifier 5 is also rectified by the diode 11 to become a direct current
voltage 1. The magnitudes of the voltage values of the DC voltages V1 and 2 are compared by the
comparator 6. When the reception signal is large on the metal plate, the attenuation amount of
the variable attenuator 3 is increased by the output of the comparator 6 to suppress the
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transmission signal, and conversely, the attenuation of the variable attenuator 3 is large when the
transmission signal is large. The amount is reduced to suppress the occurrence of howling.
Assuming that the voice shown in FIG. 6A from station B is input to station A, the voice waveform
is amplified by the amplifier 5 and then rectified by the diode 11 to become a DC voltage 1. In
this case, as shown in FIG. 6 (B), the waveform of the DC voltage {circle over (1)} rises with a
delay of time t2 and charges up with a delay of time t1 because of discharge. The output of the
speaker 7 is inputted to the microphone l by the reflection of the room of the meeting / room on
the A station side.
The output signal of this speaker 7 is as shown in FIG. 6 (A), but due to the influence of
reverberation, as shown in FIG. 6 (C), the sound is output for a time t3 including a portion
indicated by a. Will remain. Since the DC voltage vi has already disappeared and the attenuation
amount of the variable attenuator 3 has become substantially zero at the time of the portion a,
the reverberation signal of the portion a is not attenuated by the variable attenuator 3 Sent to
station B. For this reason, the reception signal becomes stronger than the transmission signal on
the B station side, and the attenuation amount is added to the variable attenuator 3 on the B
station side to suppress the transmission signal. Therefore, if the B station side transmits a
speech within the time period of (t 3-t 1), the voice of the b portion shown in FIG. 6 (A) is
attenuated by the variable attenuator 3 of the B station side and bo As a result, the station A side
will not be reached, resulting in a serious loss of voice fidelity. Therefore, there is a demand to
eliminate this problem by changing the directivity of the microphone as appropriate for the room
due to the reverberation of the room. [Problems to be Solved by the Prior Art and the Invention]
As prior art, in order to eliminate the influence of reverberation, it is conceivable to use a
unidirectional microphone in any room. In this way, it is possible that the sound reflected in the
room does not easily enter the microphone and the problem of reverberation is considerably
reduced. However, this has the problem that human beings have to speak straight to the
microphone and the problem of being very tired occurs in the case of a conference room with
little reverberation. [Means for Solving the Problem] The above problem is that white noise is
transmitted to the speaker of the local station for a predetermined time, the attenuation time of
the reverberation of the white noise received by the microphone of the local station is measured,
and the attenuation time is This problem is solved by the audio conference apparatus according
to the present invention, in which the directivity of the microphone is changed according to the
magnitude of. [Operation] According to the present invention, since the directivity of the niyori
microphone of the attenuation time of the reverberation in the room is changed, the directivity
matches the room, becomes non-directional in a room with a small reverberation, and the human
is a straight microphone There is no need to speak towards, and in this case the problem of
getting very tired is eliminated. FIG. 1 is a block diagram of an embodiment of the present
invention, FIG. 2 is a time chart showing the operation when white noise is inserted in FIG. 1, and
FIG. 3 is a characteristic diagram of a variable directional microphone of one example. It is. In the
figure, 1 'is a variable directional microphone, 14.15 is a condenser microphone, 16.31 is a
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capacitor, 17 to 21 is a resistor, 22 is a transistor, 23 is a power supply, 24 channel controller,
25, 26, 42.43 ° 44 is a switch, 27 is a rectangular waveform oscillator, 28 is a white noise
oscillator, 29 is an amplifier, 30 is a diode, 32.33 is a comparator, 34.35 is a differentiating
circuit, 36 is a flip flop, 37 is an AND circuit, 38 is Clock oscillator 39, 40.41 indicates a counter.
As the variable directional microphone, one having a circuit configuration shown in 1 'of FIG. 1 is
currently used. This arrangement is such that the directivity can be varied by arranging the
condenser microphones 14.15 in opposition to each other and varying the voltage to this. For
example, if the voltage on one side of the capacitor microphone 15 is set to a point, the
directivity becomes non-directional as shown in FIG. 3A, and if the voltage is set to a point, the
directivity becomes as shown in FIG. If it makes a point, it will become middle directivity as
shown to (B). The case of FIG. 1 is an example in the case of using this variable directional
microphone 1 '. When the measurer operates the controller 24, the switch 25 is closed and the
switch 26 is closed for a predetermined time during which one rectangular waveform shown in
FIG. 2 (A) passes. By closing the switch 26, a rectangular waveform as shown in FIG. 2 (A) in
which the outputs of the rectangular waveform oscillator 27 and the white noise oscillator 28 are
superimposed is sent out to the room from the speaker 7. Also, by closing the switch 25, the
measuring circuit is connected. The rectangular waveform signal sent out to the room for the
predetermined time is input to the microphone 1 ° including the reverberation. This signal is
switch 25. Through the amplifier 29, the diode 30. It is rectified and smoothed by the capacitor
31 and becomes a direct current voltage as shown in FIG. 2 (B). This voltage is referred to as Vr.
The voltage Vr attenuates with time as shown in FIG. 2 (B), and is input to the comparator 32.33.
The reference voltage of the comparator 32 is {circle around (3)} shown in FIG. 2 (C), and the
reference voltage of the comparator 33 is {circle around (4)} shown in FIG. 2 (C). The comparator
32 outputs an output when the input voltage Vr becomes the reference voltage 3. The output is
differentiated by the differentiating circuit 34 and becomes a waveform as shown in FIG. 2D, and
the SR type la flip flop 36 is turned on. Do. The comparator 33 similarly outputs an output when
the input voltage Vr becomes the reference voltage 4. This output is differentiated by the
differentiating circuit 35 to form a waveform as shown in FIG. Switch 36 off. As shown in FIG. 2
(F), the AND circuit 37 is open while the flip flop 36 is on, and the output of the clock oscillator
38 shown in FIG. 2 (G) is a counter as shown in FIG. 2 (H). It is sent to 39, 40.41. First, the
counter 39 counts output pulses and is taken to overflow, and then the counter 40 counts output
pulses and is reset when it overflows, and then the counter 41 starts to count output pulses.
Accordingly, when the flip-flop 36 is on for a short time, the switch 42 is closed by the output of
the counter 39 and when the flip-flop 36 is long, the switch 44 is closed by the output of the
switch 41. Close 43 Therefore, the directivity of the variable directional microphone 1 is nondirectional in a room with a short reverberation, is unidirectional in a room with a long
reverberation, and is intermediate directivity in an intermediate room. As described above, since
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the directivity of the microphones can be changed by the length of the reverberation time of the
room, the microphones become omnidirectional in a room with little reverberation, and it is not
necessary for the human to face straight and not to be tired. Of course, in this case as well, in a
reverberant room, the microphones become directional, and the effects of the reverberation are
eliminated, but the human needs to face the microphones straight. Since the reverberation time
of the room does not change, it is sufficient to hold the switch after setting the switch. Effect of
the Invention] As described above in detail, according to the present invention, since the
directivity of the microphone can be varied by the length of the reverberation time of the room,
the microphone becomes non-directional in a room with little reverberation, and human faces
straight There is an effect that you do not need to get tired.
[0002]
Brief description of the drawings
[0003]
1 is a block diagram of an embodiment of the present invention, FIG. 2 is a time chart showing
the operation at the time of white noise insertion of FIG. 1, FIG. 3 is a characteristic diagram of
one example of the variable directivity microphone, The figure is a block diagram of an example
of a howling suppressor type audio conference apparatus, FIG. 5 is a block diagram of the
peripheral portion of the comparator 6 of FIG. 4, and FIG. 6 is a characteristic diagram for
explaining the reverberation of FIG. is there.
In the figure, 1 is a microphone, 1 is a variable directional microphone, 2.4.5.29 is an amplifier, 3
is a variable attenuator, 6.32.33 is a comparator, 7 is a speaker, 8.9, 16. 31 is a capacitor,
10.11.30 is a diode, 12.13.17 to 21 is a resistor, 14.15 is a capacitor microphone, 23 is a power
supply, 24 is a controller, 25.26, 42, 43. 44 is a switch, 27 indicates a rectangular waveform
oscillator, 28 indicates a white noise oscillator, 34.35 indicates a differentiating circuit, 36
indicates a flip flop, 37 indicates an AND circuit, and 38 indicates a clock oscillator 39 to 41
indicates a counter. ; = 竿 1 eye dormitory 1 J J cotton wight ny rice insertion), 菫 'A' FCE 13 タ
イ ム タ イ ム time knowledge-To fida · If) branch hand effect Fl, 1 す 佇 佇 U シ 9 9 J ^ principal
bond ^ The
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