Gaussian-noise discrimination and its relation to auditory object formation.

This study used a same/different experiment to assess the ability of human listeners to discriminate Gaussian-noise tokens with a spectral range of 350-850 Hz and a duration of 50 ms. For this duration, discrimination ability is high. However, when an identical 200-ms noise fringe with the same statistical properties as the 50-ms target tokens is appended to the end of the two target tokens, listeners show very poor discrimination. It was investigated whether altering the properties of the fringes with respect to those of the target improved the ability to discriminate the target tokens. This method was used to investigate the influence of changing fringe properties such as spectral range, level, interaural level difference, and interaural time delay on discrimination performance for the target. Spectral and temporal separation showed the strongest improvements, whereas no effect was found for doubling the fringe bandwidth, 5-dB level increases or decreases, or 10 dB interaural level differences. In the second experiment, subjects were asked to indicate whether they perceived one or two auditory objects for these stimuli. The results of the two experiments indicate that perceiving two objects is a necessary but not sufficient condition for good target discrimination.