Adaptive optimization of microphone arrays under a nonlinear constraint

In this paper we describe an algorithm for optimizing a microphone array with the objective of receiving a desired speech signal from a known direction, in the presence of broad band noise sources with unknown locations and possibly slowly varying characteristics. Each microphone feeds a tapped-delay-line filter, and the outputs of the filters are summed to give the final output. The tap weights of the filters are adjusted adaptively to minimize the output power subject to a constraint on the allowed distortion of the desired speech signal. Since the quality of a speech signal is quite insensitive to phase distortion, the constraint is on the magnitude transfer function from the source to the output. It is this choice of constraint that differentiates our approach from other methods of adapting arrays.