Spectral integration under conditions of comodulation masking release

Detection of a pure tone signal in a narrowband noise masker can be improved by the introduction of coherently amplitude modulated masker bands in neighboring frequency regions, an effect called comodulation masking release (CMR). Experiment 1 tested the hypothesis that detection of a spectrally complex signal in a comodulated masker critically depends on the signal/masker interaction, with best sensitivity in conditions where the signal introduces across-frequency stimulus envelope differences. Consistent with this hypothesis, thresholds for a multi-frequency signal differed by approximately 10 dB depending on the relative patterns of signal/masker interaction across frequency. In comodulated maskers, there was no improvement in threshold relative to the single-frequency signal threshold even in cases where the multi-frequency signal introduced across-frequency envelope differences. Experiment 2 tested conditions that have previously been associated with large spectral integration in comodulated but not random maskers. Results depended on the masker configuration used as the reference condition, with comparable integration for random and comodulated noise in some cases. The results suggest that CMR obtained with a pure tone signal can differ greatly from that obtained with a complex signal, and that spectral integration is inversely related to the amount of CMR under some conditions.