Audiologic, 6655 Lookout Rd., Boulder, CO 80301
A computerized version of the California consonant test [Terry et al., Ear Hear. 13, 70--79 (1992)] was used to evaluate a wearable digital beam-forming binaural hearing aid. The binaural aid uses an analysis--synthesis method where phase and magnitude cues, derived from microphone placement at the ears, are used to attenuate sounds from locations other than the 0-deg azimuth position. Normal hearing subjects, with their left ear occluded to reduce binaural cues, were used together with hearing impaired subjects for evaluation. Speech at 0 azimuth was presented via loudspeaker at 50 dBA. In the noise condition four talker babble at 35-deg azimuth (54 dBA) was mixed with the target speech. The hearing aid was programmed to give a basic 6-dB/oct preemphasis. Overall gain for the hearing impaired subjects was initially adjusted to give approximately a 70% intelligibility score for the speech alone condition. Subjects were instructed to maintain body and head position while responding to word choices shown on a screen positioned above the target speaker. Both subject groups showed a relative improvement in intelligibility and response times for the beam processing mode in the speech in noise condition.