Curt Southworth
Bruce G. Berg
Dept. of Cognitive Sci., Univ. of California, Irvine, CA 92717
The ability to discriminate changes in narrow-band sounds by selectively attending to level, pitch, and envelope cues is examined. The listener's task is to detect an increment in the level of a 1000-Hz component of an equal-amplitude, three-tone complex with sidebands at 960 and 1040 Hz. Spectral weights are estimated according to the method of COSS analysis [B. G. Berg, J. Acoust. Soc. Am. 86, 1743--1746 (1989)] for five experimental conditions. Following a baseline condition of minimal instruction, listeners are instructed to discriminate the stimuli according to differences in loudness, pitch, and roughness. The final condition involves procedures intended to limit the information available to a process of envelope discrimination. Spectral weight estimates reveal that different listeners employ different cues in the absence of specific instructions of strict physical manipulations of the stimuli (e.g., baseline condition). Moreover, changes in spectral weight patterns indicate that narrow-band sounds are discriminable on the basis of multiple auditory processes that are subject to a mechanism of selective attention. Weight estimates closely follow the predicted weight patterns for models that simulate discriminations on the basis of level, pitch, and envelope cues. [Work supported by ONR.]