Double talk and echo path change detection in a telephony system

Abstract

A double talk and echo path change detector is provided for use in an echo canceller that makes a determination about whether a residual signal is dominated by echo or by a 'near end' signal. In order to make this determination, a first measure of linear dependency is computed between the residual signal and an echo estimate, and a second measure of linear dependency is computed between the residual signal and a desired signal. The two results are compared with each other, and if they are of about the same order, no further action is needed. However, if the comparison determines that the dependence between the residual signal and the desired signal is much stronger than the dependence between the residual signal and the echo estimate, the present detector assumes that double talk has been detected and a signal denoting that result is output. On the other hand, if the dependence between the residual signal and the desired signal is much weaker than the dependence between the residual signal and the echo estimate, the detector assumes that an echo path change has been detected and a signal denoting that result is output. As such, a reliable and computationally effective method and apparatus are provided to give the echo canceller useful information about double talk and echo path changes that have occurred.