Abstract:

The perceptual organization of sequences of short-duration 200-Hz-wide modulated noise bands was investigated. Sequences with one of two possible rhythms were presented over headphones or in a semi-circular array of 13 speakers. The ``rhythm'' was embedded in an irregular sequence of ``maskers'' with the same frequencies and energy. Adding ``flankers'' in other critical bands, synchronous with the irregular maskers released the rhythm from masking. RMR as measured by the correct identification of the rhythm and its perceived clarity was assumed to be contingent upon the perceptual grouping of the maskers and flankers. Using a 2-AFC procedure with a four-point clarity rating for each alternative, the effect of the following relations between the maskers and flankers on their simultaneous grouping was investigated: stimulus onset asynchrony (SOA), frequency separation ((Delta)F), commonality of microstructure, and angular separation of their sources ((Delta)(theta)). RMR decreased significantly with SOA, (Delta)(theta), differences in microstructure and with (Delta)F for spatially separated maskers and flankers. RMR will be compared to other paradigms which have been claimed to result from a cross-spectral binaural analysis of the temporal envelope, such as dichotic CMR and/or of the fine temporal structure such as BMLD [Hall et al., J. Acoust. Am. 83, 1839--45 (1988)].