ASA 124th Meeting New Orleans 1992 October

3aPP12. Loudness growth in forward masking.

Fan-Gang Zeng

House Ear Inst., 2100 W. 3rd St., Los Angeles, CA 90057

The growth of loudness as a function of intensity was measured for a brief tone burst following a forward masker. The level of the forward-masked tone was adjusted to balance the loudness of a standard tone presented without a forward masker, using a 2AFC, double-staircase, tracking procedure. The forward masker was a 90 dB SPL, 100-ms, 1000-Hz pure tone. The standard and the balanced stimuli were 25-ms, 1000-Hz tones. The forward masker and the balanced tone were always presented in the first interval and the delay between them was 100 ms. In general, the masker caused the following tone to appear louder than it would if it had not been masked, a phenomenon termed ``loudness enhancement'' [Zwislocki and Sokolich, Percept. Psychophys. 16, 80--90 (1974); Elmasian and Galambos, J. Acoust. Soc. Am. 58, 229--234 (1975)]. In addition, the present results show a nonmonotonic function; a 10- to 20-dB enhancement effect for midlevel tones and no enhancement for low- and high-level tones. The loudness jnd's derived from the upper and lower sequences, also show a similar nonmonotonic function. The present data indicate that loudness grows much steeper following a forward masker and there is a strong relationship between loudness and the jnd's. [Work supported by NIDCD.]