Abstract:

Normally hearing people have much lower speech reception thresholds (SRTs) in a background of a single talker than in the background of speech-shaped noise, whereas hearing-impaired people do not. The hearing impaired appear to be less able than normal to take advantage of temporal and spectral ``dips'' in interfering speech. SRTs were measured in background sounds that varied to the extent that they contained such dips. The subjects tested were: (a) young with normal hearing; (b) elderly with near-normal hearing; (c) young with moderate to severe cochlear hearing loss and (d) elderly with moderate to severe cochlear hearing loss. In a background that contained both spectral and temporal dips, the hearing-impaired and elderly with near-normal hearing performed much more poorly than normals. The signal-to-background ratio required for 50% intelligibility was about 19 dB higher for elderly hearing impaired than for young normals. Young hearing-impaired subjects showed a slightly smaller deficit, but still a substantial one. Linear amplification combined with appropriate frequency-response shaping (NAL amplification) only partially compensated for these deficits. It is proposed that noise with spectral and temporal dips provides a potentially useful way of evaluating the effects of signal processing such as frequency-selective amplification and compression.