ASA 124th Meeting New Orleans 1992 October

1pPP4. Temporal integration of noise band signals measured in a profile analysis task.

C. Formby

Dept. of Otolaryngol.-HNS, Johns Hopkins Univ., Box 1737, Baltimore, MD 21203

M. G. Heinz

C. E. Luna

Johns Hopkins Univ.

S. C. Elbert

Univ. of South Carolina, Columbia, SC 29208

Of interest in this study was whether temporal integration (TI) of brief noise band signals in a broadband masker reflects (1) a successive comparison between the intensities of the signal and nonsignal intervals of a trial or (2) a simultaneous comparison of the signal and background intensities within the signal interval (i.e., spectral shape discrimination). This issue was studied in a profile analysis paradigm in which the overall levels of the signal and background (masker) were randomized together from interval to interval of each 2IFC trial. Random level variation rendered successive comparison of intensities between intervals useless and forced the listener to discriminate changes in spectral shape. Accordingly, the hypothesis was that if TI depended on successive comparison of levels, then randomized level would disrupt performance; whereas if TI were independent of randomized level, then the listener must be discriminating spectral shape. Detection thresholds were measured for signal bandwidths from 125 to 4000 Hz, both with random level (35 to 50 dB) and fixed level, at six standard durations from 10 to 320 ms. The TI functions were independent of randomized level. These results are consistent with spectral shape judgments in detecting brief noise band signals in a broadband noise background.