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

3aPP1. Lateralization of comodulated bands of noise.

Kourosh Saberi

Psychoacoust. Lab., Dept. of Psychol., Univ. of Florida, Gainesville, FL 32611-2065

Lateralization thresholds were measured in a 2IFC task for two conditions. The 400-ms signal consisted of two high-frequency narrow bands of noise with common interaural delays (cf.=2.55 and 3.35 kHz; bandwidths=50,100,200,400 Hz). In the first condition, the temporal envelopes of the two bands were the same (comodulated) and, in the second condition, they were independent. Results of this experiment showed improvements in lateralization when the bands were comodulated compared to independently modulated bands. In a second experiment, the two noise bands were replaced by two sinusoidally amplitude modulated (SAM) tones (cf.=2.55 and 4 kHz; modulation rate=100 Hz) and lateralization thresholds were measured as a function of the relative phase of modulation between the two SAMs. Thresholds were lowest when the envelope of the two SAMs were in phase and monotonically increased as the envelopes were increasingly shifted out of phase up to 180(degrees). In a third experiment, binaural interference was examined. Results are discussed in terms of cross-correlation models of binaural hearing. [Work supported by NIH and AFOSR.]