Comparison of LMS Adaptive Beamforming Techniques in Microphone Arrays

Abstract

This paper discusses principles of microphone array beamforming, specifically the use of LMS algorithm with training sequence. The problem of wideband nature of acoustical signals and its impact on the techniques of beamforming are discussed. Detailed explanation of classic narrowband and wideband LMS beamformers is presented, as well as the modification of narrowband algorithm with pre-steering. Experimental testing and comparison of algorithm performances was conducted and measurement results are presented. The used microphone array is part of Brüel & Kjær acoustical camera, and is comprised of 18 omnidirectional non-uniformly spaced microphones.