Stereo Acoustic Echo Control Using A Simplified Echo Path Model

In handsfree tele- or video-communication, acoustic echoes arise due to the coupling between the loudspeakers and microphones. It is much more challenging to remove the undesired acoustic echoes for stereo or multi-channel tele-communication systems than for mono systems due to the non-uniqueness problem. While non-uniqueness can be prevented by introducing independent distortions into the left and right loudspeaker signals, stereo echo cancellation is more challenging in terms of convergence speed and computational complexity than mono echo cancellation. The proposed stereo echo control algorithm circumvents the non-uniqueness problem by using simplified echo path models consisting of delays and short-time spectral modification. It is shown that for reasonably symmetric systems the left and right echo path models are similar enough that a single echo path model can be used for estimating the total echo power spectrum and a gain filter for removing the echo from the microphone channels. The proposed algorithm is also applicable to multi-channel systems and the computational complexity is very low.