ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pPP13. On the perceptual asymmetry in frequency modulation discrimination.

Dept. of Speech and Hear. Sci. & Elec. Eng., Ohio State Univ., Columbus, OH 43210

Several researchers have observed perceptual asymmetry in frequency modulation discrimination experiments. Porter et al. (1991) found that when listening to a formant transition followed by a frequency plateau, listeners detected the onset frequency much better for the falling transition than for the rising transition. Demany and McAnally (1994) discovered that the frequency difference limen measured at frequency maxima of a 5-Hz cosine frequency modulation is significantly smaller than at frequency minima. Heil et al. (1992) also observed asymmetry in the FM response in chick auditory cortex. They proposed that this effect was due to the asymmetrical lateral inhibition in the unit. Preliminary results in this lab indicated that this perceptual asymmetry also exists when listeners were asked to discriminate between a sinusoidal plus linear ramp frequency modulation (SLRFM) and a linear ramp frequency modulation (LRFM) (Zhang et al., 1994). In this presentation, perceptual asymmetry is systematically studied for both rising and falling LRFMs. The effect of starting phase of a SLRFM signal is also examined. The experimental results are discussed in terms of existing modulation models and physiological explanations. [Work supported by AFOSR.]