Abstract
The Minimum Variance Distortionless Response (MVDR) beam-former is a popular multi-microphone noise reduction and speech enhancement strategy that can be implemented either as a fixed-constraint MVDR beamformer, with a pre-defined Relative Transfer Function (RTF) or based on a Multi-channel Wiener Filter (MWF) estimate. However, each implementation is not fully robust within a dynamic acoustic environment. For instance, performance degradations exist for the fixed-constraint MVDR beamformer when the source is not in the constraint direction and also for the MWF when the estimated RTF is poor. In this paper, we propose a contingency noise reduction strategy that uses a Linearly Constrained MWF (LC-MWF) to combine the positive aspects of both implementations. We proceed to derive the LC-MWF in relation to the MVDR beam-former implementations and demonstrate through simulations that the LC-MWF is indeed an intermediary solution that encompasses a wider range of acoustic conditions.