Masking Release for Sweeping Masker Components with Correlated Envelopes

To separate sounds from different sound sources, common properties of natural sounds are used by the auditory system, such as coherent temporal envelope fluctuations and correlated changes of frequency in different frequency regions. The present study investigates how the auditory systemprocesses a combination of these cues using a generalized comodulationmasking release (CMR) paradigm.

CMR is the effect of a better signal detectability in the presence of comodulated maskers than in the presence of maskers with uncorrelated envelope fluctuations across frequencies. Using a flanking-band paradigm, the results of the first experiment of the present study show that CMR is still observed for the masker and the signal coherently sweeping up or down in frequency over time, up to a sweep rate of six octaves per second.

Motivated by the successful modeling of CMR using filters sensitive to temporal modulations and recent physiological evidence of spectro-temporal modulation filters, the second experiment investigates whether CMR is also observed for spectro-temporal masker modulations generated using time-shifted versions of the masker envelope for each component.

The thresholds increase as soon as the temporally coherent masker modulation is changed to a spectro-temporal masker modulation,