Temporal integration of loudness as a function of level

Abstract

This study compared temporal integration of loudness for 1-kHz tones and broadband noises. Absolute thresholds and levels required to produce equal loudness were measured for 5-, 30-, and 200-ms stimuli using adaptive, two-interval, two-alternative forced-choice procedures. Levels ranged from 5 to 80 dB SL for noises and from 5 to 90 dB SL for tones. Results for 6 listeners with normal hearing show that the amount of temporal integration, defined as the level difference between equally loud 5- and 200-ms stimuli, varies nonmonotonically with level. The average amount of temporal integration varies from about 10–12 dB near threshold, to a peak of 18–19 dB when the 5-ms tone is about 56 dB and the 5-ms noise is about 76 dB SPL; at higher levels, the amount of temporal integration decreases to 10 dB for tones and 13 dB for noises with levels around 100 dB SPL. These results indicate that modified power functions cannot account for the growth of loudness for tones at all durations. They also indicate that the growth of loudness may, at least in part, be consistent with the nonlinear input/output function of the basilar membrane. [Work supported by NIH-NIDCD R01DC02241.]