Spectral-shape discrimination. I. Results from normal-hearing listeners for stationary broadband noises.

This research is concerned with the ability of normal-hearing listeners to discriminate broadband signals on the basis of spectral shape. The signals were six broadband noises whose spectral shapes were modeled after the spectra of unvoiced fricative and plosive consonants. The difficulty of the discriminations was controlled by the addition of noise filtered to match the long-term speech spectrum. Two-interval discrimination measurements were made in which loudness cues were eliminated by randomizing (roving) the overall stimulus level between presentation intervals. Experimental results, examined as a function of intensity rove width, stimulus duration, and stimulus pair, were related to the predictions of a simple filter-bank model whose fitting parameter provides an estimate of internal noise. Most results, with the notable exception of duration effects, were predicted by the model. Estimates of internal noise in each frequency channel averaged roughly 7 dB for long-duration stimuli and 13 dB for short-duration stimuli. Results and predictions are compared to results of other studies concerned with the discrimination of spectral shape.