  A two-stage multi-channel speech enhancement method is proposed which
consists of a novel adaptive beamformer, Hybrid Minimum Variance Distortionless
Response (MVDR), Isotropic-MVDR (Iso), and a novel multi-channel spectral
Principal Components Analysis (PCA) denoising. In the first stage, the
Hybrid-MVDR performs multiple MVDRs using a dictionary of pre-defined noise
field models and picks the minimum-power outcome, which benefits from the
robustness of signal-independent beamforming and the performance of adaptive
beamforming. In the second stage, the outcomes of Hybrid and Iso are jointly
used in a two-channel PCA-based denoising to remove the 'musical noise'
produced by Hybrid beamformer. On a dataset of real 'cocktail-party' recordings
with head-worn array, the proposed method outperforms the baseline
superdirective beamformer in noise suppression (fwSegSNR, SDR, SIR, SAR) and
speech intelligibility (STOI) with similar speech quality (PESQ) improvement.
