Nested generalized sidelobe canceller for joint dereverberation and noise reduction

Speech signal is often contaminated by both room reverberation and ambient noise. In this contribution, we propose a nested generalized sidelobe canceller (GSC) beamforming structure, comprising an inner and an outer GSC beamformers (BFs), that decouple the speech dereverberation and the noise reduction operations. The BFs are implemented in the short-time Fourier transform (STFT) domain. Two alternative reverberation models are adopted. In the first, used in the inner GSC, reverberation is assumed to comprise a coherent early component and a late reverberant component. In the second, used in the outer GSC, the influence of the entire acoustic transfer function (ATF) is modeled as a convolution along the frame index in each frequency. Unlike other BF designs for this problem that must be updated in each time-frame, the proposed BF is time-invariant in static scenarios. Experiments with both simulated and recorded environments verify the effectiveness of the proposed structure.