Robust time-domain processing of broadband microphone array data

Abstract

The paper describes a general broadband, time-domain, robust beamformer design technique and demonstrates its effectiveness. The basic beamforming approach considered is constrained power minimization. The most important quality of this constrained adaptive processor is that the amount of cancellation of the desired signal is directly limited. The processor is designed as follows. An acceptable amount of cancellation of the desired signal is specified. Source models of anticipated types of array imperfections such as misteer, element placement uncertainty, and element response uncertainty are then derived from either modeled or measured array responses. These source models are the basis of both robust linear constraints as well as a single quadratic constraint that define the robust broadband spatial filter. The robust processor design is demonstrated for a headworn array of microphones (hearing aid). A simple, effective adaptive algorithm for processing speech input is also described. Small room reverberation and acoustic headshadow effects are included in the simulations. The resulting processor limits the amount of cancellation of the desired signal that occurs to the allowable amount in the presence of the array imperfections under all input SNR conditions. Effective attenuation of interfering sounds is also exhibited. >