Echo Eliminator with echo path change detector

Abstract

An echo canceler includes an adaptive filter that adapts to changes in an echo path, a double-talk detector, and an echo path change detector. The echo path change detector estimates the loss on the echo path, thereby distinguishing true double-talk from apparent double-talk detected by mistake because of a change in the echo path. The adaptive filter continues normal adaptation during the apparent double-talk state when echo path change is also detected. The necessary conditions for detection of echo path change preferably include a small separation between the estimated loss on the echo path and a long-term smoothed value of the estimated loss. The echo path change detector is useful in, for example, the cancellation of line echo in telephone switching systems.

Description

technical field [0001] The present invention relates to an echo canceller, in particular to an echo canceller capable of detecting changes in echo paths. Background technique [0002] Echo cancellers are used in telecommunications systems to eliminate far-end echoes in signals sent from a near-end to a far-end. One type of echo canceller includes an adaptive filter whose tap coefficients are modified by a mathematical algorithm to adapt to changes in the echo path. The known algorithm can achieve a better effect when only one party at the far end is talking, but it does not perform well in a double-talking state where two parties talk at the same time. Therefore, a double-talk detector is included in conventional echo cancellers to suspend the adaptation process in double-talk conditions. [0003] Unfortunately, the double talk detector tends to misinterpret changes in the echo path as double talk, causing the adaptive adjustment to be paused when it is most needed. This ...

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Problems solved by technology

But the correlation method used by this echo canceller is not reliable when there is background noise of human voice, such as office noise

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