Directional microphone in hearing aids. Effects on speech discrimination in noise

This study was designed to investigate the amount of directionality among three directional aids of different brands and to compare speech discrimination ability of hearing-impaired persons using directional and nondirectional hearing aids in competing background noise. For each hearing aid under study, the full-on gain curves were obtained at 45, 135, 225,, and 315 degree azimuths in an anechoic chamber. Thirty-two hearing aid users were included. Discrimination ability was assessed, using commercially available W-22 disc recordings. Findings indicate directionality varies among directioalaids. The hearing aid that shows the greatest directional effect was found to provide the listeners with best speech discrimination ability under relatively difficult listening conditions. However, it is inadvisable to recommend just any directional aid without careful evaluation of its directional capability under competing noise.