Discrimination thresholds for glides in frequency as a function of transition span, duration, and direction

The study measured discrimination thresholds for glides in frequency as a function of magnitude of transition span, duration, and direction. The purpose was to determine whether the Weber fraction is constant across a range of transition spans, as suggested by an earlier study [J. P. Madden and K. M. Fire, J. Acoust. Soc. Am. 100, 3754–3760 (1996)]. Subjects were asked to distinguish between a comparison glide with a fixed transition span and a target glide with a greater transition span. Comparison signal frequency transition spans were 0.5, 1, 2, 4, and 8 times the ERB of the auditory filter at the signal center frequency. The nominal center frequency of the glides was 1.8 kHz, but the actual signals were roved over a range of center frequencies. Both up- and down-glides were used; signal durations were 50 ms and 400 ms. The results indicate that the Weber fraction is essentially constant for transition spans of 1–8 ERBs, but increases below 1 ERB. The effects of duration and direction were small. [Work supported by Research Grant No. 1 R15 DC 02662-01 from the National Institute on Deafness and Other Communication Disorders, National Institutes of Health.]