ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

3pAA2. Spatial selectivity of differential microphone arrays in rectangular enclosures.

Ea-Ee Jan

James L. Flanagan

CAIP Ctr., Rutgers Univ., Piscataway, NJ 08855-1390

Omni-directional microphones have been employed in delay-and-sum beamformers to mitigate room reverberation and ambient noise. A one-dimensional beamformer has spatial selectivity in only one dimension. Therefore, higher-dimensional arrays are used to improve spatial selectivity. In comparison, a single differential microphone provides fixed spatial selectivity. This report discusses the performance of arrays of differential microphones. To compute sound behavior in the enclosure, calculation of the incident angle for every arriving signal is required. An image model using the ray-tracing method has been developed to calculate the multipath in an enclosure up to a prescribed order of images. Nonuniform wall reflectivities can be included. For the special case of rectangular enclosures, the algorithm efficiently calculates the incident angle for each arriving signal and all of its associated reflection points. Additionally, it is noted that the number of images for a given order more nearly resembles an arithmetic series instead of a geometric series. [Research supported by NSF Grant No. MIP-9121541 and NSF Subcontract 397-26740.]