The discrimination of interaurally correlated noise bands

Abstract

Models of binaural unmasking suggest that the auditory system detects deviations from unity in the interaural coherence of the waveforms at the two ears. Since anticorrelated noise has high coherence within a frequency channel, such a coherence-detection mechanism should be unable to distinguish a correlation of −1.0 from a high positive correlation. A 3I-2AFC paradigm was used to test whether such a limitation can be observed behaviorally. Stimuli consisted of a 1-ERB-wide sub-band of interaurally correlated noise centered at 500 Hz (i.e. 462–538 Hz) flanked by two spectrally remote bands of noise (0–329 Hz and 717–3000 Hz) with an interaural correlation of 1.0. The flanking bands were intended to reduce cues from the perceived laterality of the stimuli. Participants were presented with three stimuli (reference, target, and distracter) and asked to choose the odd-one-out: the reference and distracter intervals contained sub-bands of anticorrelated noise while the target interval contained a sub-band of noise with interaural correlation between 0.7 and 1.0. Preliminary results indicate that different participants find different values of interaural correlation to be more distinguishable than others.