Duration shift and loudness enhancement: Separate but similar phenomena

Abstract

In duration shift (see Pokorny et al., this issue) and in loudness enhancement [e.g., J. Acoust Soc. Am. 58, 229–234 (1975)] subjective perceptions of one signal (the target) move toward those of another signal (the conditioner) presented nearby in time. Because the loudness of short signals increases with their duration (loudness summation), however, a duration shift experiment might merely be a loudness enhancement experiment in which subjects, contrary to instructions, match target loudness instead of target duration. The present study addresses this issue. Both conditioner duration (10 or 40 msec) and conditioner intensity (61, 75, or 89 dB SPL) were varied in the monaural forward paradigm while subjects matched 75 dB white-noise targets of 20- and 25-msec duration. When they matched target duration in these 12 different conditions, changes in conditioner duration produced the greater shifts and when they matched the same signals for target loudness, changes in conditioner intensity produced the greater shifts. Thus, while duration shifts and loudness enhancement share many common characteristics, they are separate perceptual phenomena.