An enhanced post-filter for improving the performance of an acoustic echo canceller in mobile application

In this paper, we consider an enhanced post-filter system to improve the performance of an acoustic echo canceller especially in mobile hands-free application. The proposed system includes noise reduction, linear prediction inverse filtering, pitch inverse filtering, and center clipping. The residual echo is first whitened via a linear prediction inverse filter followed by a pitch inverse filter during no near-end talker period. With the aid of these inverse filters, we can remove speech characteristics from the echo and obtain whitened residual echo in result. Then noise reduction technique based on spectral analysis is applied to reduce the power of the residual echo as well as ambient noise. Finally, the level of the residual echo is further attenuated by a center clipper placed in the send path of an echo canceller. For the hands-free application in a moving car, the proposed system attenuated interferences more than 18 dB at a constant speed of 30 and 80 km/h.