Loudness functions for long and short tones

Abstract

This study tests the equal-loudness ratio hypothesis [Florentine et al., J. Acoust. Soc. Am. 99, 1633–1644 (1996)], which states that the loudness ratio between equal-SPL long and short tones is independent of SPL. The amount of temporal integration (i.e., the level difference between equally loud long and short sounds) is maximal at moderate levels. Therefore, the equal-loudness ratio hypothesis predicts that the loudness function is shallower at moderate levels than at low and high levels. Equal-loudness matches and cross-modality string-length matches were used to assess the form of the loudness function for 200- and 5-ms tones at 1 kHz. Results from nine normal listeners show that (1) the amount of temporal integration is largest at moderate levels in agreement with previous studies, and (2) the loudness function is shallowest at moderate levels. For eight of the nine listeners, the loudness ratio between the 200- and 5-ms tones is approximately constant, except at low levels where it tends to increase. The average data show good agreement between the two methods, but discrepancies are apparent for some individuals. These findings support the equal-loudness ratio hypothesis, except perhaps at low levels. [Work supported by NIH/NIDCD Grant No. R01DC02241.]