A hybrid frls/nlms stereo acoustic echo canceller

Teleconferencing systems employ acoustic echo cancelers to re-duce echoes that results from the coupling between loudspeaker and microphone. To enhance the sound realism, two-channel au-dio is necessary. However, stereophonic acoustic echo cancellation is more difficult to solve because of the necessity to uniquely iden-tify two acoustic paths, which becomes problematic since the two excitation signals are highly correlated. In this paper a wideband stereophonic acoustic echo canceler is presented. The fundamen-tal difficulty of stereophonic acoustic echo cancellation (SAEC) is described and an echo canceler based on a fast recursive least squares algorithm in a subband structure is proposed. The struc-ture has been used in a real-time implementation, with which ex-periments have been performed. In the paper, simulation results of this implementation on real life recordings, with 8 kHz bandwidth, are studied. The results clearly verify that the theoretic fundamen-tal problem of SAEC also applies in real-life situations. They also show that more sophisticated adaptive algorithms are needed in the lower frequency regions than in the higher regions. 1