New Aspects of Combining Echo Cancellers with Beamformers

Abstract

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 derivated, too.

Joint noise reduction and acoustic echo cancellation using the transfer-function generalized sidelobe canceller

“…It is important to note that, as opposed to the AEC-BF structure, the echo cancellers are adapted using the system output. In that sense, it is similar to other recently proposed structures (Herbordt et al, 2004;Kammeyer et al, 2005).…”

“…First, the convergence of the AEC filters in the ETF-GSC scheme is not impaired due to noise presence, since the error feedback is taken from the output signal after the noise is reduced (as in Herbordt et al, 2004;Kammeyer et al, 2005). As opposed to these contributions, the AEC in the ETF-GSC structure requires estimates of the transfer-functions b(e jx ), rather than a complex function thereof.…”

“…The efficiency of the proposed solution was demonstrated by speech recognition experiments under conditions of high-level background noise, time-varying echo paths, and frequent double-talk situations . Kammeyer et al (2005) explored several adaptation strategies for combined noise and echo reduction. They showed that in the AEC-BF structure, the echo canceller can be adapted by the output of the beamformer as well.…”

Statistical analysis of the jointly-optimized acoustic echo cancellation BF-AEC structure

“…Acoustic echo cancellation solutions in which BFs and acoustic echo cancelers (AECs) have complementary functions have raised a lot of interest recently [8][9][10][11][12][13]. BFs and AECs contribute by different means to reduce the residual echo.…”

Statistical Analysis of a Jointly Optimized Beamformer-Assisted Acoustic Echo Canceler

“…BFs and AECs contribute by different means to reduce the residual echo. Hence, using both techniques in a synergistic way can improve the acoustic echo cancellation performance [16]- [22]. BFs and AECs are usually combined by means of two basic structures [11], [23].…”