Study and design of robust differential beamformers with linear microphone arrays

Abstract

Differential beamformers can generate frequency-invariant spatial responses and therefore have the great potential to solve many broadband acoustic signal processing problems such as noise reduction, signal separation, dereverberation, etc. The design of such beamformers, however, is not a trivial task. This paper is devoted to the study and design of differential beamformers with linear array geometry. The objective is to design robust differential beamformers that can form frequency-invariant beampatterns. The major contribution consists of the following aspects. (1) It discusses a general approach to the design of linear DMAs that can use any number of microphones to design a given order DMA as long as the number of microphones is at least one more than the order of the DMA. (2) It presents a method that can maximize the white noise gain with a given number of microphones and order of the DMA; so the resulting beamformer is more robust to sensor noise than the beamformer designed with the traditional DMA method. (3) It discusses how to use nonuniform geometries to further improve robustness of differential beamformers. (4) It investigates the possibility to improve the robustness of differential beamformers with the use of the diagonal loading technique.