Sam Gilman Assoc., P.O. Box 25176, W. Los Angeles, CA 90025
The hearing aid is a 13-channel system, each channel controlled by its own amplifier to maintain both the sound level and spectrum at the eardrum at levels preset by the audiologist. A built-in microphone measured the sound at the eardrum and a digital processor controlled each channel from this feedback signal. Objective tests using speech-shaped noise and simulated speech signals showed a (plus or minus) 3-dB control for each channel over an input dynamic range of 30 dB. Subject tests were performed using standard prescription procedures to preset the target levels for each channel. Test materials were speech-shaped noise, nonsense syllables, and continuous speech. Results of the subject tests qualitatively show improvement due to the control. However, statistical analysis of the data show that the results are inconclusive. An examination of our test procedures and materials have been made to determine possible reasons for the inconclusive results.