Evaluation of an adaptive beamforming method for hearing aids.
In this paper evaluations of a two-microphone adaptive beamforming system for hearing aids are presented. The system, based on the constrained adaptive beamformer described by Griffiths and Jim [IEEE Trans. Antennas Propag. AP-30, 27-34 (1982)], adapts to preserve target signals from straight ahead and to minimize jammer signals arriving from other directions. Modifications of the basic Griffiths-Jim algorithm are proposed to alleviate problems of target cancellation and misadjustment that arise in the presence of strong target signals. The evaluations employ both computer simulations and a real-time hardware implementation and are restricted to the case of a single jammer. Performance is measured by the spectrally weighted gain in the target-to-jammer ratio in the steady state. Results show that in environments with relatively little reverberation: (1) the modifications allow good performance even with misaligned arrays and high input target-to-jammer ratios; and (2) performance is better with a broadside array with 7-cm spacing between microphones than with a 26-cm broadside or a 7-cm endfire configuration. Performance degrades in reverberant environments; at the critical distance of a room, improvement with a practical system is limited to a few dB.
Greenberg
J E
JE
Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge 02139.
Zurek
P M
PM
D004867:Equipment Design; D006310:Hearing Aids; D006801:Humans; D008144:Loudness Perception; D008838:Microcomputers; D011571:Psychoacoustics; D012984:Software; D013017:Sound Localization; D013067:Speech Perception