IMPROVED DOUBLE TALK DETECTOR FOR ECHO CANCELLERS

摘要

Three double talk detectors (DTD) are used in combination with an echo canceller having an adaptive filter (31) and a center clipper (35). First and second double talk detectors (36, 38) are used in the presence of double talk to selectively freeze the adaptive filter correction loop and to disable the center clipper (35). The third double talk detector (40) is used to detect the initial adaptive period of the echo canceller. Control of the adaptive filter (31) and clipper (35) is effectively transferred from the first to the second double talk detector (36, 38) upon termination of the initial adaptive period as determined by the third double talk detector (40). The third double talk detector (40) also detects a false double talk condition (where the distant talker pauses in speech) and overrides the second double talk detector (38) in order to maintain the flipper (35) in an active state.