### 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.]