A cascaded non-linear acoustic echo canceller combining power filtering and clipping compensation

This report presents a novel, cascaded approach to non-linear acoustic echo cancellation (AEC). The loudspeaker enclosure microphone (LEM) system is divided into two blocks: non-linear clipping and power filtering, and a conventional, linear AEC. They represent the non-linear amplifier and loudspeaker and linear acoustic channel and up-link path in a typical mobile communication scenario. We propose an efficient approach for clipping compensation to improve the performance of the non-linear AEC in the presence of amplifier distortion. It is shown to give a reliable estimate of quasi static clipping in both artificial and practical environments with real speech signals. The cascaded approach to clipping compensation and power filtering is also more efficient than the alternative approach where clipping compensation is integrated into a higher-order power filter.