Temporal resolution of frequency-modulated and virtual frequency signals

Abstract

Discrimination of ‘‘glide’’ versus ‘‘step’’ transition was investigated for two classes of signals: frequency modulated (FM) tones and virtual frequency signals [Lublinskaya (1996); Anantharaman et al. (1997)]. A ‘‘virtual frequency signal’’ refers to the frequency transition perceived in an amplitude-modulated two-tone complex when the amplitude of one of the tones increases with duration, while that of the other decreases. In the FM tone experiment, the glide signal traverses a certain frequency range in a linear trajectory, whereas the step signal traverses the same frequency range in a series of discrete steps. In the virtual frequency signal experiment, the glide signal has a linear amplitude transition whereas the step signal has a staircase-like amplitude transition. Listeners heard these signals in an adaptive 2Q, 2AFC paradigm. The experimental parameters for both classes of signals were center frequency (500, 1000, and 4000 Hz) and number of steps. The signal duration was retained constant at 250 ms. The smallest ERB separation for which the step signal could be distinguished from the glide signal was determined. Results from these experiments will be discussed along with implications for temporal resolution and spectral integration of virtual frequency signals. [Work supported by a grant from The Ohio State University College of Social and Behavioral Sciences.]