ASA 127th Meeting M.I.T. 1994 June 6-10

5aPP1. A directional adaptive LMS acoustic array for hearing enhancement.

Elaine D. McKinney

Victor E. DeBrunner

School of Elect. Eng., University of Oklahoma, 202 West Boyd St., Rm. 219, Norman, OK 73019-0631

Acoustic fixed arrays are designed to match a focused array gain pattern, while acoustic adaptive arrays are designed to respond to changing environments. However, as currently constructed, adaptive arrays cannot stay focused with the limited number of microphones available in a cosmetically acceptable hearing aid. In this paper, a technique that combines fixed and adaptive arrays in a system that enhances the desired signal while effectively attenuating interference speech and background noises is discussed. In particular, the design and performance of a directional adaptive four-supercardioid microphone array is examined. This idea was formed independently from the use by Soede et al. [J. Acoust. Soc. Am. 94, 785--798 (1993)] of fixed arrays with cardioid microphones. Thus it is confirmed that using directional microphones improves array directivity in the hearing aid application. Simulations show that the directivity of this adaptive array is improved to 7.15--7.71 dB. The array reduces interferences from different directions by about 15--30 dB and provides a SNR improvement of about 9--12 dB over a single omni-directional microphone. A sensitivity analysis is also discussed. [Work partially supported by Deafness Research Foundation.]