Microphone Arrays : A Tutorial

This report presents a tutorial of fundamental array processing and beamforming theory relevant to microphone array speech processing. A microphone array consists of multiple microphones placed at different spatial locations. Built upon a knowledge of sound propagation principles, the multiple inputs can be manipulated to enhance or attenuate signals emanating from particular directions. In this way, microphone arrays provide a means of enhancing a desired signal in the presence of corrupting noise sources. Moreover, this enhancement is based purely on knowledge of the source location, and so microphone array techniques are applicable to a wide variety of noise types. Microphone arrays have great potential in practical applications of speech processing, due to their ability to provide both noise robustness and hands-free signal acquisition. This report has been extracted from my PhD thesis, and can be referenced as : I..A. McCowan. ”Robust Speech Recognition using Microphone Arrays,” PhD Thesis, Queensland University of Technology, Australia, 2001. For a more in-depth discussion of key microphone processing techniques, the interested reader is refered to M. Brandstein and D. Ward (Eds). ”Microphone Arrays”, Springer, 2001. 1 Array Processing Fundamentals 1.