Combined acoustic echo control and noise reduction for hands-free telephony

Abstract

In this paper we propose an algorithm for combined acoustic echo control and noise reduction. The algorithm is developed on the basis of a minimum mean-square error criterion and consists of a (conventional) echo canceller and an additional noise and residual echo reduction filter. A special feature of the algorithm is the procedure for estimating the residual echo power spectral density which relies on the assumption that the phase of the estimated echo is approximately equal to the phase of the true echo. This assumption is verified by experimental results. The residual echo power density estimate and the noise power density estimate are then adaptively combined and used as an argument for some spectral weighting rule such that the residual echo is attenuated and effectively masked by a low level of intentionally left background noise. The paper concludes with experimental results for a typical car environment.