Temporal integration and compression near absolute threshold in normal and impaired ears

Abstract

The decrease in absolute threshold with increasing stimulus duration is greater for listeners with normal hearing than for listeners with sensorineural hearing loss. It has been suggested that the difference is related to reduced basilar-membrane (BM) compression in the impaired group. This hypothesis was tested by comparing temporal integration and BM compression near absolute threshold in normal and impaired ears. In the first phase, absolute thresholds were measured for 4-, 24-, and 44-ms pure-tone signals, with frequencies (fs) of 2 and 4 kHz. The difference between the absolute thresholds for the 4- and 24-ms signals was used as a measure of temporal integration. In the second phase, compression near threshold was estimated by measuring the level of a 200-ms off-frequency (0.45 fs) pure-tone forward masker required to mask a 44-ms pure-tone signal presented at sensation levels of 5 and 10 dB. There was a significant negative correlation between the amount of temporal integration and absolute threshold, but there was no correlation between absolute threshold and compression at low levels; both normal and impaired ears showed a nearly linear response. The results suggest that the differences in integration between normal and impaired ears cannot be explained by differences in BM compression.