CNL Lunch

Huan Luo

(with M. Gordon, A. Boemio, D. Poeppel)

The Perception of FM Sweeps by Chinese and English Listeners

Thursday February 13th, 12:30pm, 3416 Marie Mount Hall

IThe perception of frequency-modulated sweeps (FM) is important for many aspects of speech perception, including the analysis of formant transitions and pitch variation in tone languages. The ability of human subjects to identify the direction (up vs. down) of FM sweeps is examined in a series of psychophysical experiments (2AFC, 2IFC, 3IFC). Specifically we investigated (i) how rapid a sweep can be correctly detected and (ii) whether language experience affects the performance in a basic psychoacoustic task. English and Chinese subjects were presented with FM sweeps at different durations/rates (at suprathreshold signal levels). Linear FM sweeps ranged from 600-900Hz (approximating the F1 range) and 2000-3000Hz (approximating F3). FM rate was parameterized by varying signal duration (5ms to 320ms). We hypothesized that Chinese speakers have lower thresholds because of their experience in a tone language. The main finding is that 20-25 msec is the general detection threshold for both language groups: at durations exceeding 25ms, all subjects detected FM direction perfectly. This observation supports the relevance of the order threshold of ~20msec (Hirsh 1959) for basic auditory tasks. Using a more sensitive measure (3IFC), 20ms surprisingly again emerges as the discrimination threshold. We suggest that 20-25msec is a fundamental perceptual threshold that is pre-linguistic and therefore constant for different language groups, regardless of native language experience.