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DESCRIPTION JPS59194597

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DESCRIPTION JPS59194597
[0001]
(A) Technical Field of the Invention The present invention relates to an improvement of a howling
prevention method for preventing howling caused by sound embedded in a microphone from a
speaker in a voice teleconferencing system using a microphone and a speaker in the same
conference room. is there. (B) Background of technology With a voice teleconferencing system, a
conference room located at a remote location is connected by a communication line, and each
conference room has a microphone and a speaker, and the other conference room is in front of
the speaker by the microphone of one conference room. People who are in a remote conference
room listen to the speaker at the conference and hold a conference. In such an audio
teleconferencing system, a howling prevention method is required to prevent howling that occurs
frequently when sound from a speaker enters the microphone. (C) Prior Art and Problems
Hereinafter, an embodiment of the conventional howling prevention method will be described.
FIG. 1 is a block diagram showing the circuit configuration of the main part of a conventional
voice teleconferencing device. In the figure, 1.2 represents a microphone representing n
microphones. 3 is a microphone coupling amplifier, 4.5 is an automatic loss regulator, 6 and 7 is
an amplifier, 8 and 9 is a rectifier, 10.11 is a voltage detector, 12 is a subtractor, and 13.14 is a
speaker The audio signal of n / a microphones represented by 7 and microphones 1 and 2 is
amplified by the microphone coupling amplifier 3 and does not cause disconnection at the
beginning and end of conversation. Linear variable element (F'ET? through an automatic loss
adjuster 4, and amplified by an amplifier 6 and sent to the other side via a transmission line, and
increased through an automatic loss adjuster 5 on the other side by an amplifier 7. The speaker
13, 14 outputs an audio signal. In this case, it is necessary that the sound from the speaker 13.14
sink into the microphone 1.2 and thereby prevent howling. For this reason, the output level and
reception level of the microphone coupling circuit 3 are respectively rectified by the rectifier 8.9
to be DC voltages V 1 and V 2 and subtracted by the subtractor 12 and when v 2 is larger than vl
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(reception side When vl is greater than v2 (when a human is feeling to the microphone), the
voltage detector 11 detects each of the automatic loss regulators 4, 5 Automatic loss adjusters
that do not increase losses properly but do not increase losses prevent howling). However, the
loss of the automatic loss adjuster can not be infinite in order to prevent talk-end-to-speak.
Therefore, the sound of the speaker 13.14 is reflected by the wall of the room, etc., and it feels to
be inserted into all the n microphones installed, and it is amplified and amplified by the
microphone coupling amplifier 3 and rectified by the rectifier 10. The direct current voltage v1
may be equal to the direct current voltage v2 obtained by rectifying the audio signal on the
receiving side by the rectifier 9.
As soon as it becomes equal, the voltage detector 10.11 does not detect the voltage, and the loss
of the automatic loss regulator 4.degree. The conditions for causing such howling change
according to environmental changes such as the size of the room, the number of the
microphones and the speakers, the number of the microphones and the speakers, and the volume
of the speakers. Therefore, these environmental conditions may be set to conditions that do not
cause howling, but this can not be done easily. Therefore, the voice teleconferencing device using
the conventional automatic loss adjuster has a drawback that howling may occur as described
above. (D) Object of the invention In view of the above-mentioned drawbacks, the object of the
present invention is to provide a howling prevention method capable of easily preventing
howling without changing the environmental conditions when the amount of sound from the
speaker enters the microphone a large amount. It is in. (E) Configuration of the Invention In order
to achieve the above object, the present invention is acoustically coupled to a speaker
microphone, and in an initial state where howling occurs, audio teleconferencing is performed by
a frequency component having a large amount of acoustic coupling. Focusing on the fact that the
system loop of the system is in an oscillating state, a plurality of frequency components with
large coupling amount acoustically coupled to the speaker and the di-microphone are detected in
the voice teleconferencing device using the conventional automatic loss adjuster or the like.
Means for suppressing the plurality of frequency components detected by the means on the
audio signal transmitting side of the microphone to prevent howling. (F) Embodiments of the
Invention An embodiment of the present invention will be described with reference to the
drawings. FIG. 2 is a block diagram showing the circuit configuration of the main part of the
voice teleconference device of the embodiment of the present invention. In the figure, the same
functions as in FIG. 1 are indicated by the same symbols. Reference numeral 15 is a variable
frequency rejector, 16 is a variable frequency band pass r wave device, 17 is a built-in
component detector, 18 is a control circuit, 19 is an automatic frequency switching oscillator for
voice frequency band, 20 is a noise generator, SWI, SW2 Indicates a switch. Sound is generated,
and this noise is output from the speakers 13 and 14 and is embedded in the microphones 1 and
2. The frequency component of the noise amplified by the microphone coupling circuit 3 can be
switched to the frequency to which the frequency automatic switching oscillator 19 is switched (
For example, the frequency of the pass band of the variable frequency band pass P wave device
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16 that changes the frequency of the pass band in synchronization with 10 different frequencies)
is changed, for example, by 10 and passed, and input to the embedded component detector 17
The noise component detector 17 digitally converts the volume of the 10 frequency components
passed through the frequency band pass f wave unit 16 and selects, for example, five from the
largest ones read by the microcomputer, and the control circuit 18 To the variable frequency
rejecter 15.
The variable frequency rejecter 15 has, for example, an r waver that rejects 10 kinds of
frequencies, and the r waver that rejects these frequency components with the signals of the 5
kinds of frequency components sent from the control circuit 18 Are inserted between the
microphone coupling circuit 3 and the automatic loss adjuster 4. In this manner, while it is
possible to suppress the frequency component having a high degree of coupling acoustically to
the microphone from the speaker 13.14, the switches SWI and SW2 are opened, and the voice
teleconferencing device is used. In this way, the frequency component with a high possibility of
causing urling does not appear in the output of the variable-frequency one-detector transducer
15. Howling can easily be prevented without changing the environmental conditions. The
operations of the automatic loss adjusters 4 and 5 and the ring prevention circuit are the same as
in FIG. (G) Effects of the Invention As described in detail above, according to the present
invention, the amount of insertion into the speaker microphone is large, and howling can not be
prevented by the conventional howling prevention method using an automatic loss adjuster or
the like. There is an effect that the environment can be easily prevented.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram showing the circuit configuration of the main part of the conventional
audio teleconferencing device, and FIG. 2 is the block diagram showing the circuit configuration
of the main part of the audio teleconference device of the embodiment of the present invention.
In the figure, 1 and 2 are microphones, 3 is a microphone coupling amplifier, 4 and 5 are
automatic loss regulators, 6 and 7 are amplifier, 8.9 is a rectifier, 10.11 is a voltage detector, 12
is a subtraction 13, 14 are speakers, 15 is a variable frequency reflector, 16 is a variable
frequency band pass f wave device, 17 is a MA component insertion detector, 18 is a control
circuit, 19 is an automatic frequency switching oscillator, and 20 is a noise generator , SWI, 8W2
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indicate switches.
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