A multistage minimum variance distortionless response beamformer for noise reduction.

This paper develops a multistage approach to the implementation of the minimum variance distortionless response (MVDR) beamformer. It first divides the microphone array of M sensors into M/2 subarrays with each subarray having only two microphones, and a two-channel MVDR beamformer is performed with each subarray. The M/2 subarrays' outputs are then treated as the inputs of M/4 subarrays of two channels in the next stage. Similarly, a two-channel MVDR beamformer is performed with each subarray in the second stage. This process is repeated till the last stage that has only a single output. This multistage MVDR beamformer has the following properties: (1) Its performance is identical to that of the conventional MVDR beamformer in spatially uncorrelated noise; (2) it is much more robust than the conventional MVDR beamformer in diffuse noise, i.e., it has a significantly higher white noise gain as compared to the traditional MVDR beamformer; and (3) its complexity is an order of magnitude smaller than that of the traditional MVDR beamformer. This basic principle can also be easily generalized to the case where every subarray has more than two microphones.