A general approach to the design and implementation of linear differential microphone arrays

The design of differential microphone arrays (DMAs) and the associated beamforming algorithms have become very important problems. Traditionally, an Nth order DMA is formed by subtractively combining the outputs of two DMAs of order N-1. This method, though simple and easy to implement, suffers from a number of limitations. For example, it is difficult to design the equalization filter that is needed for compensating the array's non-uniform frequency response, particularly for high-order DMAs. In this paper, we propose a new approach to the design and implementation of linear DMAs for speech enhancement. Unlike the traditional method that works in the time domain, this proposed approach works in the short-time Fourier transform (STFT) domain. The core issue with this framework is how to design the desired differential beamformer in each subband, which is accomplished by solving a linear system consisting of N +1 fundamental constraints for an Nth-order DMA.