ASA 124th Meeting New Orleans 1992 October

3aPP14. Forward- and backward-masked intensity discrimination measured using an adjustment procedure.

Christopher W. Turner

Amy R. Horwitz

Pamela E. Souza

Dept. of Commun. Sci. and Disord. and the Inst. for Sensory Res., Syracuse Univ., 805 South Crouse Ave., Syracuse, NY 13244

A ``mid-level hump'' in the intensity jnd has been reported for pure tones preceded [Zeng et al., Hearing Res. 55, 223--230 (1991)] or followed [Plack and Viemeister, J. Acoust. Soc. Am. 91, 2457 (A) (1992)] by an intense masker where the signal-masker interval was 100 ms. Both of these studies used forced-choice procedures, in which subjects heard two test signals and were required to indicate the more intense tone. The present experiment used the method of adjustment to obtain intensity jnd's. Subjects listened to an alternating sequence of standard and variable tones, and adjusted the variable tone to the same loudness as the standard. The subject was allowed to listen to the sequence as long as desired before ending the sequence. The jnd was taken as the standard deviation of repeated adjustments. With this method, there was no difference between jnd's obtained in unmasked conditions versus those obtained with forward or backward maskers. [Work supported by NIDCD.]