New aspects of combining echo cancellers with beamformers

In this contribution, we introduce a novel framework for combining approaches for acoustic echo cancellation and beamforming. Classical schemes of combination incorporate the simple concatenation of both subsystems. However, if the echo cancellers come first, they cannot exploit the noise reduction capabilities of the beamformer. In the other setup, a time-variant beamformer can heavily disturb the succeeding echo canceller´s convergence. The new approach establishes a possibility to smoothly switch between two possible target functions: the mean squared errors at the beamformer´s inputs and its output, respectively. Thus, one combined system benefits from advantages of both classical schemes. The paper contains a theoretical analysis of possible solutions for preceding echo cancellers, which are adapted using the beamformer output. The appropriate modification of the normalized least mean squares algorithm is derived too.