Beamforming for a microphone array embedded in asymmetrically shaped objects

Abstract

Broadband frequency invariant beamforming for circular arrays or linear arrays are quite common but not when they are embedded in a diffracting structure. Meyer [J. Acoust. Soc. Am. 109, 185–193 (2001)] describes arrays embedded in a diffracting sphere, and provides an analytical solution for the wave equation in acoustics. For arrays of simple shape like circular rings embedded in a more complex shape one must make use of numerical methods (e.g., boundary element methods). Microphone arrays in shapes that are not symmetric or axisymmetric can also be solved this way but result in very asymmetrical beams. One example of such an obstacle is a telephone incorporating a microphone array. This presentation will show results from simulations and measurements of a six-microphone array. A design approach to obtain reasonably well behaved beams relies on constrained optimization, with a constraint build using a set of vectors containing the sensor signal for acoustic waves with specific directions of arrival. [Work supported in part by Carleton University.]