This paper proposes a synthetic stereo acoustic echo cancellation structure with microphone array beamforming for multiple participant voice over Internet protocol (VoIP) conferencing. The proposed acoustic front-end combines a synthetic stereo structure, acoustic echo canceler and microphone array beamformer. Synthetic stereo is used to add spatial information to signals from multiple participants that facilitates distinguishing between participants. Microphone array beamforming is then combined with the single canceler per spatial region echo cancellation structure to reduce noise and reverberation for near-end speech pickup and to cancel echo.

This paper describes the application of array optimization techniques in the near-field of a microphone array. It is shown that the optimum weights obtained for microphone spacing equal to a half wavelength are real, aside from the propagation delay, and inversely proportional to the distance from each microphone to the focal point. When the microphone spacing is less than a half wavelength, the optimum weights are super-directive requiring both an amplitude and phase adjustment in addition to delay-and-sum beamforming. In the super directive regime, the maximum array gain increases as the distance to the focal points decreases. The technique is suitable for applications where the source of interest is located in the near-field region but interfering sources are located farther from the array.

This paper describes the application of array optimization techniques to improving the near-field response of an arbitrary microphone array. The optimization exploits the differences in wavefront curvature between near-field and far-field sound sources and is suitable for reverberation reduction in small rooms. The optimum near-field beamformer provides increased array gain over that obtained from a uniformly weighted delay-and-sum beamformer.