Arrangement and method for rapidly detecting double talk in long

Abstract

Double talk is rapidly detected for effectively preventing degradation of echo cancellation in a long distance telephone communications system. An echo estimator includes a transversal filter and receives an incoming signal and tap coefficients, and then adaptively produces an estimated echo signal. A subtractor is adapted to subtract the estimated echo signal from an echo signal applied thereto, and outputting an error signal indicating residual echo. A tap coefficient updating circuit is coupled to receive the error signal and the incoming signal and the tap coefficients, and renews the tap coefficients. A double talk detector is coupled to receive the error signal and the incoming signal and the echo signal. The double talk detector issues a double talk detection signal in the event that a cross-correlation value between the incoming and echo signals is less than a first predetermined level while an estimated echo cancellation is larger than a second predetermined level.