Donald G. Jamieson
Hear. Health Care Res. Unit, Elborn College, Univ. of Western Ontario, London, ON N6G 1H1, Canada
Rob Brennan
Unitron Industries Ltd.
Leonard E. Cornelisse
Hear. Health Care Res. Unit
A common complaint of hearing aid wearers is that they have difficulty when listening in a background of noise. The ability of a digital adaptive noise reduction filter to reduce background noise without degrading speech perception has been evaluated. Each of four normal-hearing and six hearing-impaired subjects completed two behavioral tests of speech perception---the speech reception threshold (SRT) and the modified distinctive features differences test [DFD(m)]---and one subjective measure of listener preference (paired comparisons). Each test was performed in three types of background noise presented at a level of 65 dB: white noise, low-pass filtered at 8.0 kHz; white noise, low-pass filtered at 1 kHz; and multitalker speech babble. For hearing-impaired subjects, the speech-plus-noise signal was filtered and amplified to provide the NAL real-ear insertion gain. Results indicated that all subjects preferred the noise-reduction-processed speech-plus-noise signal over the unprocessed signal at positive signal to noise ratios. The effect of the adaptive digital filter on speech perception depended on hearing loss, noise type, and SNR. Feature analysis of DFD(m) responses indicated that processing had different effects on the error patterns for normal and hearing-impaired listeners.