Sweep-induced acceleration in loudness change and the "bias for rising intensities"

A pure tone changing continuously in intensity shows sweep-induced fading (SIF) of loudness as intensity sweeps down and may show a lesser degree of sweep-induced enhancement (SIE) as intensity sweeps up (Canévet & Scharf, 1990); the former effect has been called decruitment, the latter upcruitment. An opposite effect-upsweeps being judged to show more loudness change than downsweeps--has been reported by Neuhoff (1998). These disparate results might stem from several procedural differences. We found that differences in the sweep's duration and intensity level did not account for the disparity, nor did the presence of a steady tone preceding the sweep. In a second experiment, direct judgments of sweep size, such as those Neuhoff's (1998) listeners made, were affected not only by sweep size itself, but also by the intensity at the end of the sweep. The latter effect was especially marked for upsweeps. Neuhoffs (1998) proposed "bias for rising intensities" was found only with a method for judging sweep size that is more sensitive to end level than to sweep size.