A hybrid near-field superdirective GSC and post-filter for speech enhancement

This paper deals with the problem of microphone array speech enhancement using a hybrid Generalized Sidelobe Canceller (GSC), Near-Field Super-Directive (NFSD) beamformer, and post-filter. In this research, we employ a near field compensation block before the blocking matrix (of the GSC) to prevent signal leakage in the reference noise and a Linear Constrained Minimum Variance (LCMV) beamformer instead of blocking matrix to generalize the appropriate performance of the system for different arrival directions of desired speech. We also consider the application of the post-filters on the beamformer output. A modified version of McCowan post-filter is presented by calculating coherence function from microphone-array inputs. Considering similar idea, we also propose a multichannel version of Short-Time Spectral Amplitude (STSA) post-filter. Our evaluations clearly demonstrate the effectiveness of the proposed modifications in the enhancement of the noisy speech.