A hybrid mono/stereo acoustic echo canceler

In many applications, such as teleconferencing, multimedia workstations, televideo games, etc., stereo sound is already, or will soon be, implemented to give spatial realism that mono systems cannot offer. In such hands-free systems, stereophonic acoustic echo cancelers are absolutely necessary for full-duplex communication. We propose a new acoustic echo canceler (AEC) based on a fundamental experimental observation that the stereo effect is due mostly to sound energy below about 1000 Hz. The principle of the hybrid mono/stereo AEC is to use stereophonic sound with a stereo AEC at low frequencies (e.g., below 1000 Hz) and monophonic sound with a conventional mono AEC at higher frequencies (e.g., above 1000 Hz). This solution is a good compromise between the complexity of a full-band stereo AEC and spatial realism. For the stereo case we borrow from a previous innovation and add a small nonlinearity into each channel in order to accurately identify the two receiving room impulse responses.