ASA 127th Meeting M.I.T. 1994 June 6-10

3pPP12. The discrimination of independent samples of noise under monotic and dichotic conditions.

Laurie M. Heller

Constantine Trahiotis

Ctr. for Neurolog. Sci., Surgical Res. Ctr. and Dept. of Surgery Otolaryngol.), Univ. of Connecticut Health Ctr., Farmington, CT 06030

Listeners' ability to discriminate between independent tokens of 800-Hz-wide (79 dB SPL) bands of noise was measured in a two-cue, two-alternative, temporal forced-choice task where the second or third interval contained a noise that was different from that presented in each of the other three intervals. Discriminability was best in the diotic condition. Next-best performance occurred in a dichotic condition where the three nonsignal intervals contained identical noises that were uncorrelated across ears, while signal intervals contained new interaurally uncorrelated noises. Worst performance occurred in a dichotic condition where one noise was repeated in all four intervals in one ear, while another, independent noise, was presented in the other ear during the nonsignal intervals. The signal interval contained a new (and interaurally uncorrelated) sample of noise presented to the latter ear. Performance was poorer than that obtained in the strictly monaural condition. This indicates that listeners were unable, effectively, to ignore the identical, and hence noninformative, waveforms presented to one ear across the four temporal intervals of each trial. Data obtained from several other dichotic conditions will also be discussed. [Work supported by NIH and AFOSR.]