Detection of the break in interaural correlation is affected by interaural delay, aging, and center frequency

This study investigated whether interaural integration is affected by introducing an interaural delay. In Experiment 1, both younger adults with normal hearing and older adults in the early stages of presbycusis were able to detect a transient break in interaural correlation (BIC) in the temporal middle of interaurally correlated wideband noises. However, their duration thresholds for detecting the BIC became larger with increasing interaural time difference (ITD) from 0 to 6 ms, and the threshold increase for older participants was larger than that for younger participants. In Experiment 2, to investigate whether the effect of changing ITD on the BIC detection is frequency-dependent, 1/3-octave narrowband noises with various center frequencies were used as stimuli. Results show that the duration threshold for detecting the BIC was higher for high-frequency noises than for low-frequency noises. Also, with increasing ITD from 0 to 4 ms, the threshold increase was larger for high-frequency noises than for low-frequency noises. The results suggest that there are age- and frequency-related temporal declines in maintaining fine-structure signals for interaural integration. These declines may affect the recognition of sound sources in reverberant environments.