The mid-duration hump in the intensity-difference limen as a function of frequency: Further evidence for the frequency–time listening window of the human ear

Abstract

It has been suggested that the ear has a frequency–time listening window and that the stimulus that occupies the fewest frequency–time windows, i.e., that which has the smallest product of effective bandwidth and effective duration, should result in the largest intensity-difference limen (DL) [Van Schijndel et al., J. Acoust. Soc. Am. 105 (1999)]. Van Schijndel et al. identified the Gaussian-shaped tone-pip as the optimal stimulus, obtaining DLs at 1 kHz and 4 kHz. The DLs were greatest for the tone-pips whose frequency–time window was one critical band wide and 4 cycles long in equivalent square duration D (envelope duration/ 3.19). Here, DLs for Gaussian-shaped 250-Hz tone-pips were obtained from 5 subjects for Ds of 1.25–22.57 ms at levels of 40, 50, 60, 70, 80, and 90 dB SPL. These data were combined with earlier results showing a mid-duration rise at 40–60 dB SPL for Gaussian-shaped tone-pips of 6.5 kHz, 2 kHz, and 500 Hz. The peak in the DL is sharp for 6.5 kHz but flattens as frequency drops, being replaced by a broad rise for 250 Hz. The highest DLs correspond to approximately 4 cycles in D, not far from the ringing duration calculated as the inverse of the critical bandwidth.