US 5,386,465 AGranted

Audio processing system for teleconferencing with high and low transmission delays

AssigneeBell Communications Research, Inc.

InventorsEric J. Addeo, Joseph J. Desmarais, Gennady Shtirmer

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Abstract

An audio processing system for use in teleconferencing systems having high and low transmission delays. The audio processing system utilizes complementary comb filters in combination with auxiliary echo suppressors, a frequency scaler, expander/gates and automatic level controlling devices to substantially improve acoustic stability margin and reduce far-end talker echo.

Claims9

Dependent claims

An audio processing system for teleconferencing systems, said audio .processing system having high and low transmission delays, comprising:

at a first station, first microphone means for detecting and transmitting a first signal having an intensity, and first speaker means for receiving a second signal having an intensity,
at a second station, which is remotely located from the first station, second microphone means for detecting and transmitting said second signal for transmission to said first speaker means and second speaker means for receiving said first signal from said first microphone means;
a first audio channel connecting said first microphone means with said second speaker means through a transmission system;
a second audio channel connecting said second microphone means with said first speaker means through said transmission system;
first echo suppressor means connected to said first microphone means and said first speaker means for generating and inserting a first variable attenuation in said first channel at the output of said first microphone means, said first variable attenuation being generated based upon the intensity of said first signal transmitted from said first microphone means and the intensity of said second signal being received by said first speaker means;
second echo suppressor means connected to said second microphone means and said second speaker means for inserting a second variable attenuation in said second channel at the output of said second microphone means, said second variable attenuation being generated based upon the intensity of said second signal transmitted from said second microphone means and the intensity of said first signal being received by said second speaker means;
and
first and second comb filters having complementary pass and stop bands located in said first and second channels, respectively, said first comb filter being located between said first microphone means and said first echo suppressor means and said second comb filter being located between said second microphone means and said echo suppressor means, said first and second comb filters attenuating echo, which includes signals coupled between said first speaker means and said first microphone means at said first station and between said second speaker means and said second microphone means at said second station, such that said first and said second echo suppressor means generate said first and said second variable attenuation, respectively, based on said first and second signals substantially excluding echo to improve the performance of said first and second echo suppressor means.

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Dependencies are inferred from the claim text.

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Abstract

An audio processing system for teleconferencing systems, said audio .processing system having high and low transmission delays, comprising:

at a first station, first microphone means for detecting and transmitting a first signal having an intensity, and first speaker means for receiving a second signal having an intensity,
at a second station, which is remotely located from the first station, second microphone means for detecting and transmitting said second signal for transmission to said first speaker means and second speaker means for receiving said first signal from said first microphone means;
a first audio channel connecting said first microphone means with said second speaker means through a transmission system;
a second audio channel connecting said second microphone means with said first speaker means through said transmission system;
first echo suppressor means connected to said first microphone means and said first speaker means for generating and inserting a first variable attenuation in said first channel at the output of said first microphone means, said first variable attenuation being generated based upon the intensity of said first signal transmitted from said first microphone means and the intensity of said second signal being received by said first speaker means;
second echo suppressor means connected to said second microphone means and said second speaker means for inserting a second variable attenuation in said second channel at the output of said second microphone means, said second variable attenuation being generated based upon the intensity of said second signal transmitted from said second microphone means and the intensity of said first signal being received by said second speaker means;
and
first and second comb filters having complementary pass and stop bands located in said first and second channels, respectively, said first comb filter being located between said first microphone means and said first echo suppressor means and said second comb filter being located between said second microphone means and said echo suppressor means, said first and second comb filters attenuating echo, which includes signals coupled between said first speaker means and said first microphone means at said first station and between said second speaker means and said second microphone means at said second station, such that said first and said second echo suppressor means generate said first and said second variable attenuation, respectively, based on said first and second signals substantially excluding echo to improve the performance of said first and second echo suppressor means.

5 more elements