4pPP30. Amplitude-modulation depth discrimination of a sinusoidal carrier.

Session: Thursday Afternoon, May 16

Author: Jungmee Lee
Author: Sid P. Bacon
Location: Psychoacoustics Lab., Dept. of Speech and Hearing Sci., Arizona State Univ., Tempe, AZ 85287-1908


Discrimination of the change in depth of sinusoidal amplitude modulation was investigated for a 4000-Hz carrier. The just noticeable change in the modulation depth ((Delta)m) was measured as a function of (1) standard modulation depth (m = 0.1, 0.18, or 0.3), (2) modulation rate (f[inf m]=10, 20, 40, or 80 Hz), and (3) stimulus duration (T=25, 50, 100, 200, 400, or 800 ms). For modulation rates less than 80 Hz, threshold ((Delta)m) was higher at a standard depth of 0.3 than at the other standard depths. When f[inf m]=80 Hz, the threshold was almost the same across different standard modulation depths. For all standard depths and modulation rates, the threshold decreased by more than a factor of 2 as stimulus duration increased to a certain T (critical duration). For durations longer than the critical duration, the threshold decreased only slightly or remained constant. The critical duration corresponded to about four cycles of modulation. Psychometric functions were measured for different stimulus durations. The data were evaluated in terms of a multiple-looks model. [Work supported by NIDCD.]

from ASA 131st Meeting, Indianapolis, May 1996