Abstract:
The evolution of voice communications technology promises high-fidelity teleconferencing systems without encumbering the user with hand-held devices. The freedom of movement provided by hands-free devices yields dynamic acoustic environments and allows for greater separation between source and receiver. Furthermore, these teleconferencing environments may feature communication over multiple audio channels. The sound quality in such environments is typically degraded due to acoustic reflections from nearby walls, people, and objects. These undesired echoes must be removed if one is to maintain a high sound quality. In this work the problem of acoustic echo cancellation is examined. The technique for acoustic echo cancellation is based on sub-band decomposition. For a reverberant room, the source to receiver impulse response is computed by an image- based method. The influence of scattering from objects with high acoustical contrast is computed by a Pade approximants based method. A model for the impulse response resulting from nonideal images, frequency-dependent wall impedance and acoustic scattering is presented. Results compare single and multiple scattering effects. The variations in scattering amplitude due to scatterer motion are examined. The impact of these features on echo-canceller performance is evaluated.