Studies suggest that spectrally disparate, co-occurring acoustic components are typically integrated by the auditory system into the same perceptual group, forming a single auditory image, if the components of the signal fluctuate synchronously in amplitude (Bregman, et aL, 1985; McAdams, 1984). Signal components that do not fluctuate synchronously in amplitude are less likely to be assigned to the same perceptual group. The """"""""strength"""""""" to which components are integrated (fused) into a single auditory image may be affected by the specific degree of temporal envelope correlation across the components of a composite signal. The goal of this investigation is to examine the effects of temporal envelope correlation (r= -1 to + 1) on the fusion strength of co-occurring noise-bands. Experiments related to the comodulation detection difference (CDD) and comodulation masking release (CMR) auditory phenomena will be conducted to assist in achieving the stated goal. In the first experiment (CDD type), detection threshold for a signal-band will be determined as a function of the degree of correlation of the signal-band envelope with that of a co- occurring flanker-band. In the second experiment (CMR type), detection threshold for a pure-tone spectrally centered in a masker-band will be determined as a function of envelope correlation of masker-band with a flanker-band. In the third experiment, subjects will decrease the interstimulus-interval between a two noise-band complex and a lone noise- band until fusion of the complex is disrupted by """"""""capturing"""""""" one noise- band of the complex into a sequential stream with the lone noise-band. The degree of temporal envelope correlation will vary for the pair of noise- bands within the co-occurring complex. This project should contribute to improving our understanding of the perceptual organization of sound (auditory streaming) based on temporal envelope similarity. Increased knowledge in this area may eventually be incorporated into the design of traditional type electronic hearing aids, as well as cochlear implants, to enhance the listening efficiency of users of these devices when in noisy environments. Also, increased knowledge pertaining to auditory streaming may eventually be incorporated in to the design of speech recognition modules of computers to assist these devices in extracting target messages from noise.
