Reducing the effects of target misalignment in an adaptive beamformer for hearing aids
Julie E. Greenberg, Patrick M. Zurek, Patrick M. Peterson · The Journal of the Acoustical Society of America · 1989
Previous work [Peterson et al., Acta Otolaryngol. (in press)] has shown that a multimicrophone adaptive beamforming system for hearing aids reduced noise effectively at input target-to-jammer ratios (TJRs) up to about 0 dB. However, that beamforming algorithm assumed that the target signal was identical at the microphones, and violation of this assumption caused degrading target cancellation when input TJR was greater than 0 dB. The present system uses a measure of intermicrophone correlation to estimate short-time TJR and inhibits adaptation dynamically when TJR exceeds a selected threshold. Computer simulations of a two-microphone system in anechoic and moderately reverberant environments show that this method reduces (speech) target cancellation when the identical target assumption is violated. The improved system reduces noise at both positive and negative input TJRs (±20 dB), with target misalignments up to 10 deg. Additionally, this processing scheme reduces the misadjustment noise caused by strong target signals in the adaptive feedback loop. [Work supported by NIH.]