Spectral profile cues in comodulation masking release

Abstract

Previous work on spectral profile discrimination has shown that sensitivity is dependent on position of the signal in the standard complex, with a profile bowl shape demonstrated for components spanning 0.2–5 kHz [Green, Profile Analysis, 1988]. Dynamic spectral cues similar to those in profile analysis are present in comodulation masking release (CMR) stimuli, and the current study examined whether a similar bowl occurs for CMR. Maskers were 11 bands of noise, 15-Hz wide, logarithmically spaced 0.2–5 kHz, and maskers were either random or coherently modulated. The signal was either a pure tone at center frequency of one of these masker bands or the on-signal masker band itself. In the random conditions, thresholds were consistent across signal frequency for both signal types. In the coherent modulation conditions a bowl shape was obtained for the narrowband noise signal, but when the signal was a pure tone thresholds improved as a function of signal frequency and showed little evidence rising again at the highest signal frequencies tested. Data collected with the signal and on-signal masker presented contralateral to the flanking maskers indicate a reduced effect of signal type. Contribution of within- and across-channel cues will be discussed.