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DESCRIPTION JPS6318797

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DESCRIPTION JPS6318797
[0001]
Industrial Application The present invention relates to a microphone (hereinafter referred to as a
microphone). In a loudspeaker system consisting of an amplifier and speakers. The present
invention relates to a howling suppressor capable of suppressing howling that occurs. (Prior Art)
FIG. 2 shows the structure of a conventional howling suppressor. In FIG. 2, 6 is a microphone, 4
is an amplifier, 5 is a speaker, 7 is a voice signal of the speaker, 9 is a feedback signal from the
speaker to the microphone, 2 is an impulse response estimation circuit, 8 is a white noise output
circuit , 11 is a changeover switch. Next, the operation of the conventional example will be
described. In FIG. 2, before starting to use this loudspeaker, the positions of the speaker and the
microphone are fixed first, the changeover switch 11 is turned to the white noise output circuit 8
side, and the white noise is output from the speaker 5 through the amplifier 4 The signal is
received by micro. At this time, it is necessary to prevent other sounds from entering the micro.
Next, zero or more preparations to estimate the impulse response between the speaker 5 and the
micro using the output of the white noise circuit 8 and the microphone output by the impulse
response estimation circuit 2 using the learning adjustment method are completed, and the next
When using it as a loudspeaker, by turning the switch to the output side of the impulse response
estimation circuit 2, the impulse response estimated in preparation and the convolution
operation of the amplifier input are performed, and the feedback signal from the speaker to the
microphone The feedback was suppressed by artificially creating the microphone output and
subtracting it from the microphone output. (Problems to be Solved by the Invention) However, in
the above-mentioned conventional howling suppressor, for estimation of the impulse response
between the speaker 5 and the micro, the white noise is output from the speaker 5 before
starting to use the loudspeaker. In addition to the need for preparation, since the estimation of
the impulse response is performed only once, there is a problem that it is not possible to follow
the change in the impulse response due to the temperature around the loudspeaker, the variation
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of the position of the micro and the speaker 5, and the like. The present invention solves such
conventional problems, and it is not necessary to prepare for outputting loud white noise from
the speaker 5 for estimation of the impulse response, and estimation of the impulse response
may be re-performed from time to time. It is an object of the present invention to provide an
excellent howling suppressor capable of following changes in the impulse response of a
loudspeaker system. (Means for Solving the Problems) In order to solve the above problems, the
present invention calculates the power of the microphone output and detects the time when the
power becomes almost zero, and the time T from the present time A buffer means for
accumulating the output of the impulse response estimation means up to a point just before, and
storing contents read out in response to the detection of the zero point of the power calculation
means; In response to the detection, based on the output of the buffer means and the
microphone output, the impulse response between the speaker and the microphone is estimated
using a learning identification method, and the convolution operation of the impulse response
and the output of the buffer means is Feedback signal from the speaker to the microphone.
Simulated feedback. Howling is reduced by subtracting the simulated signal from the microphone
output. Characterized by comprising applying a impulse response estimation means.
(Operation) The point at which the power of the microphone output becomes almost zero is
detected, and a signal with a certain amount of power input to the amplifier is output again from
the buffer storage means a short time T before that point. Make it output from the speaker
through the amplifier and create a time when the input to the microphone is only the feedback
signal from the speaker. By using the output of the buffer storage means and the microphone
output during that time, the impulse response between the speaker and the microphone is reestimated as needed by the impulse response estimation means using the learning identification
method. Therefore, according to the present invention, the power calculation means detects the
time when the power of the microphone output becomes almost zero, and the output start to the
buffer means starts, and the impulse response estimation means learns the identification method
of the impulse response between the speaker and the microphone The impulse response
estimation means provides an impulse response between the speaker and the microphone using
the output of the buffer means and the microphone output when it is output from the speaker
and returned to the microphone. Is estimated, and feedback signal from the speaker to the
microphone is simulated using the impulse response estimated here until the next start timing is
given from the power calculation means, and howling is suppressed by subtraction from the
microphone output. be able to. (Embodiment) FIG. 1 shows the construction of an embodiment of
the present invention. In FIG. 1, 6 is a microphone, 4 is an amplifier, 5 is a speaker, 7 is voice
from a speaker, 9 is a feedback signal from the speaker to the microphone, 1 is a buffer circuit,
and the output of the impulse response estimation circuit 2 is always It stores data from the
current time until time T, and starts outputting the contents of buffer circuit 1 at the timing given
from power calculation circuit 3. Impulse response estimation circuit 2 receives the timing from
power calculation circuit 3 and estimates the impulse response between speaker 5 and the micro
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using the learning identification method from the output of buffer circuit 1 and the micro output,
and the estimation ends After that, the convolution operation of the impulse response and the
output of the buffer circuit 1 is performed to artificially generate the feedback signal 9, and this
is subtracted from the output of the micro, and this is used as the output. The power calculation
circuit 3 always calculates the power of the micro output, detects when the power becomes zero,
and outputs the buffer content output start and the impulse response estimation start signal 10
to the buffer circuit 1 and the impulse response estimation circuit 2 Do. According to the above
embodiment, whenever the input signal to the microphone is interrupted, the impulse response
between the speaker and the microphone at that time can be estimated, and a stable feedback
suppression effect can be obtained at all times.
(Effects of the Invention) The present invention has the following effects, as is apparent from the
above embodiments. (1) Since the signal immediately before the input signal to the microphone
is interrupted is used as the signal output from the speaker at the time of impulse response
estimation, the listener is less likely to hear white noise than in the conventional example. It does
not make a loud noise. (2) Since the impulse response is re-estimated each time the input signal
to the microphone breaks, it has a stable howling suppression effect.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a schematic block diagram of a howling suppression apparatus according to an
embodiment of the present invention, and FIG. 2 is a schematic block diagram of a conventional
howling suppression apparatus.
DESCRIPTION OF SYMBOLS 1 ... Buffer circuit, 2 ... Impulse response estimation circuit, 3 ...
Power calculation circuit, 4 ... Amplifier, 5 ... Speaker, 6 ... Microphone, 7 ... Speaker's voice Signal
9: Feedback signal from speaker to microphone 10: Buffer content output start and impulse
response estimation start signal.
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