Effect of level variation on intensity resolution in intensity‐discrimination and increment‐detection paradigms

Abstract

In studies of profile analysis, the level of the pedestal and increment have been varied together from interval to interval by up to 40 dB to reduce the likelihood that subjects could perform the task by comparing the overall level in the two observation intervals. This range of rove was chosen based on a calculation by Green [Profile Analysis (Oxford, New York, 1988)]. In the present study, adaptive thresholds for intensity resolution were obtained in intensity discrimination (pedestal and increment 100 ms) and increment detection (pedestal 100 ms, increment 300 ms) paradigms as a function of the range of interval‐to‐interval level variation (0 to 50 dB in 10‐dB steps). In roving conditions, the levels of pedestal and increment varied in parallel. In jittered conditions, only pedestal level varied from interval to interval. Increments were 2‐kHz sinusoids. Pedestals were 2‐kHz sinusoids or narrow‐band noises centered on 2 kHz. Effects of level variation were greater in roving than in jittered conditions. Increment detection was unaffected by roving level, whereas thresholds for intensity discrimination were poorer than Green’s best‐case prediction by a relatively constant amount for all rove ranges. [Work supported by NIH‐NIDCD.]