Auditory streaming based on temporal structure in hearing-impaired listeners.

The influence of temporal cues on sequential stream segregation was investigated using five elderly hearing-impaired listeners. In experiment 1, an alternating pattern of A and B tones was used. Each tone was a harmonic complex with a 100-Hz fundamental, with one of three passbands (1250-2500, 1768-3636, or 2500-5000 Hz) and one of three component-phase relationships (cosine, alternating, or random). The complexes had an overall level of 96 dB SPL. The detection of a change in relative timing of the A and B tones was measured in a two-interval-forced-choice paradigm. The sequence in one interval remained isochronous while the sequence in the other started isochronously but became increasingly irregular with the addition of a cumulative delay between the A and B tones. Component phase relationship and passband difference both had significant effects on the minimum detectable delay, indicating that temporal structure produced obligatory stream segregation. In experiment 2, subjects continuously reported whether tones presented in a 30-s ABA-ABA- sequence were perceived as segregated or integrated. Differences in component phase between A and B significantly increased perceived segregation, but passband did not. In conclusion, stream segregation due to differences in temporal structure is robust in elderly subjects with cochlear hearing loss and comparable to that found previously in young normally hearing subjects.