MICROPHONE-ARRAY HEARING-AIDS WITH BINAURAL OUTPUT .2. A 2-MICROPHONEADAPTIVE SYSTEM

As in the preceding article in this issue, this work is aimed at devel oping a design for the use of a microphone array with binaural hearing aids, The goal of such a hearing aid is to provide both the spatial-f iltering benefits of the array and the natural benefits to sound local ization ability and speech intelligibility that result from binaural l istening, The present study examines a design in which two ear-level o mnidirectional microphones constitute the array, Merging of array proc essing with binaural listening is accomplished by dividing the frequen cy spectrum, devoting the lowpass part to binaural processing and the highpass part to adaptive array processing. Acoustic and behavioral me asurements were made in an anechoic chamber and in a moderately reverb erant room to assess the trade-off between sound localization and spee ch reception as the cutoff frequency was varied, A lowpass/highpass cu toff frequency of 500 Hz provided an improvement of 40 percentage poin ts in sentence intelligibility over unaided listening for normal-heari ng listeners, while still allowing adequate localization performance, Comparison of this binaural adaptive system to traditional amplificati on configurations with normal-hearing listeners showed improvements in speech reception in noise in a mildly reverberant room of approximate ly 3 dB over simple binaural amplification and 5 dB over monaural ampl ification.