Telephonic communications – Substation or terminal circuitry – For loudspeaking terminal
Patent
1995-09-21
1997-07-08
Zele, Krista M.
Telephonic communications
Substation or terminal circuitry
For loudspeaking terminal
379388, 379389, 379406, 379410, H04M 908, H04B 323
Patent
active
056469900
ABSTRACT:
A cost-effective anti-howling system and method enables fast detection of the presence of true double talk, and substantially eliminates undesirable howling attributable to sudden changes in the acoustic echo path between a speakerphone microphone and loudspeaker during speakerphone conversations. Speakerphone embodiments include a delay-compensated and normalized cross-product calculation performed by a system processor having at least two memory buffers. One buffer is associated with the loudspeaker signal and the other buffer is associated with the microphone signal. The delay-compensated cross-product of the microphone voice signal input and the loudspeaker voice signal output is determined and normalized by energy estimates of the two signals to reduce the calculation error made by variance in the signal level.
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Cray William C.
Kumar Devendra T.
Oh Susie H.
Rockwell International Corporation
Zele Krista M.
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