A Hybrid Mono/Stereo Acoustic Echo Canceller

Abstract—In many applications, such as teleconferencing, mul-timedia workstations, televideo gaming, 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. In this paper, we propose a new acoustic echo canceler (AEC) based on a fundamental experimen-tal 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. Index Terms—Acoustic echo cancelation, adaptive filter, stereo. I