Abstract:
Localization performance has been shown to deteriorate when source spectra are variable, but the few studies investigating this have confounded trial-to-trial variability with spectral irregularity present in each stimulus. In this experiment these factors were varied independently. Blindfolded listeners seated in an anechoic chamber reported the apparent locations of wideband noise bursts having either smoothly sloping spectra or 1/3-oct scrambled spectra. The spectra were either varied from trial to trial or held constant throughout an experimental session. Localization performance was compared to that obtained in a baseline condition using flat-spectrum stimuli. Despite trial-to-trial uncertainty, performance with the smoothly varying spectra was equivalent to baseline. The responses to the majority of the scrambled spectrum stimuli were similar to baseline, but pronounced bias and elevated variability were observed at certain pairings of source spectrum and location that varied between listeners. The degree of uncertainty had no substantial effect on performance with these stimuli. The results suggest that source spectrum familiarity cannot effectively compensate for the interference of spectral irregularity with the processing of spectral localization cues. However, this processing appears to be surprisingly immune to such interference over much of auditory space. [Work supported by NIDCD.]