ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pPP34. Short-term temporal integration at high-frequencies: Evidence for the influence of peripheral nonlinearity?

Andrew J. Oxenham

Brian C. J. Moore

Dept. of Exp. Psychol., Univ. of Cambridge, Downing St., Cambridge CB2 3EB, UK

Temporal integration in the auditory system can be modeled by a compressive nonlinearity followed by a temporal integrator. For a fixed integrator, the more compressive the nonlinearity, the greater the effective integration. Compressive nonlinearity on the basilar membrane is marked at medium levels, but is reduced at low and high levels. To assess whether this influences temporal integration, thresholds of a 6.5-kHz sinusoid were measured in the presence of a long-duration broadband-noise masker as function of signal duration, using three different noise spectrum levels, -10, 20, and 50 dB (re: 20 (mu)Pa). Signal level dB was plotted against log(time) for each level. For signal durations between 20 and 200 ms, there was no significant difference in the slopes of the three functions. However, between 1 and 10 ms the slope of the function for the mid-level masker was steeper by a factor of between 1.5 and 2. This is consistent with the greater mid-level compression on the basilar membrane, if one assumes a fixed short-term temporal integrator. Performance in other psychoacoustic tasks, including differences between normal-hearing and hearing-impaired listeners, is also discussed in terms of peripheral processing. [Work supported by the MRC, EPSRC, and Meridian Audio (UK).]