Abstract:

This study uses measurements of loudness summation to examine the form of the loudness function for tones near threshold. An adaptive, two-interval, two-alternative, forced-choice, roving-level procedure was used to obtain loudness-balance measurements between a 1600-Hz tone and tone complexes centered at 1600 Hz. The complexes consisted of equal-SL components with levels between about -3 and 20 dB SL. Frequency separations were one, two, four, or six critical bands for four-tone complexes and one or two critical bands for ten-tone complexes. Results for six young listeners with normal hearing show that the SL difference between the pure tone and the components of the equally loud tone complex near threshold averages about 4 dB for the four-tone complexes and about 7 dB for the ten-tone complexes. When the component level of the four-tone complexes with wide frequency separations is around 20 dB SL, the equally loud pure tone is near 47 dB SL. These results indicate that loudness may grow approximately as I[sup 1.5] (where I is tone intensity) near threshold and as I[sup 0.2] at moderate levels. [Work supported by NIH-NIDCD R01DC02241.]