4aPP7. Processing transitions in a band-widening experiment.

Session: Thursday Morning, May 16

Time: 9:30

Author: Bruce G. Berg
Author: Curt Southworth
Author: Brian K. Branstetter
Location: Dept. of Cognit. Sciences, Univ. of California, Irvine, CA 92717


Literature suggests that in the absence of single-channel level information, discriminations of narrow-band sounds are temporally based, whereas discriminations of wideband sounds rely on across-channel level comparisons. The transition between processes is investigated using a band-widening paradigm. Thresholds are estimated for increments in the intensity of the central tone of a band of equal intensity, random phase tones evenly separated in frequency (parametrically varied between 10 and 160 Hz). A 20-dB roving-level procedure degrades overall-level information. Uniformly distributed frequency shifts of the complex over a 100-Hz range degrade pitch cues. As the number of tones is increased, thresholds increase up to a certain bandwidth, after which thresholds decrease or remain constant. It is proposed that these breakpoints in threshold functions represent a transition from temporal to spectral discrimination processes. The mean ratio of breakpoints to center frequencies of 500, 1000, 2000, and 4000 Hz is approximately 0.4. Regarding individual differences, a significant positive correlation exists between breakpoints and thresholds in a wideband profile analysis task. [Work supported by ONR.]

from ASA 131st Meeting, Indianapolis, May 1996