In recent years there has been a growing body of psychoacoustical evidence demonstrating that stimulus components falling outside of the frequency region of a signal can have a significant effect on the processing of that signal. In profile analysis and in comodulation masking release (CMR) that effect is to decrease thresholds: the presence of flanking stimulus components tends to improve sensitivity. In other phenomena, such as across channel masking, the effect of flanking components is to elevate thresholds. The goal of the current project is to de'velop a model of across-channel processing that captures both facilitation and interference effects. This model is based on the premise that the most ecologically relevant characteristic of an auditory object is its spectral content as a function of time, and that stimulus conditions associated with synthetic listening (e.g., common onset across frequency) can be understood in terms of the spectral profile, regardless of whether this type of processing is optimal. Further, it is proposed that a psychoacoustical phenomenon demonstrating across-channel processing with amplitude modulated stimulus components, such as CMR, can be understood in terms of short-term spectral cues. Experiments will use standard psychoacoustical methods with human observers to test qualitative predictions of this approach, using paradigms associated with both facilitation and interference. Results will be analyzed using standard parametric statistical techniques, primarily repeated measures ANOVA. Data from these as well as published studies will be modeled in order to obtain quantitative predictions for a range of phenomena involving across- frequency masking and masking release.
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