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

3pPP11. Effects of interaural configuration of wideband forward and backward fringes on detection of an interaural phase shift of a narrow portion of wideband noise.

A. N. Grange

R. H. Dye, Jr.

Parmly Hear. Inst., Loyola Univ., 6525 N. Sheridan Rd., Chicago, IL 60626

Threshold interaural phase shifts were measured for a 20-Hz-wide section (CF=500 Hz) of wideband noise. Each interval of a 2-afc task consisted of an observation interval (either 100 or 250 ms), and forward and backward temporal fringes, all having identical amplitude spectra. A spectral band (250, 500, or 750 Hz wide) surrounding the target band was diotic throughout the entire stimulus presentation. Interaural phases of frequencies above and below the diotic band (flanking bands) differed for the temporal fringes and the observation interval. For one set of conditions, the flanking bands were diotic during the temporal fringes and interaurally phase-shifted (plus or minus)90(degrees) during the observation interval. In other conditions, the flanking bands contained the 90(degrees) interaural phase shift in the temporal fringes, and were diotic in the observation interval. In general, thresholds were higher for conditions in which the temporal fringes were completely diotic, compared to conditions in which the interaural parameters of the flanking bands initially differed from the diotic band surrounding the target. This difference in thresholds decreased as the width of the diotic band and the duration of the observation interval increased. [Work supported by NIH.]