Modulation-Rate Perception: Identification and Discrimination of Modulation Rate Using a Noise Carrier

摘要

Modulation-rate thresholds were measured for three tasks: a fixed-standard, forced-choice discrimination task with a 500-ms interstimulus interval; a random-standard, forced-choice discrimination task with an 8-sec interstimulus interval; and an identification task. Thresholds were obtained for modulation rates from 14 to 224 Hz with noise carriers band-pass filtered from 500-4000 Hz, 500-1600 Hz, 1700-2800 Hz, and 2900-4000 Hz. The four bands yielded similar results except for modulation rates of 150 Hz and greater, where the 500-1600 Hz thresholds were higher. Fixed-standard discrimination thresholds were a relatively constant 3 Hz for modulation rates up to 66 Hz. The increase of thresholds for modulation rates above 66 Hz could be due to temporal resolution limits with a time constant of about 2.4 msec. For modulation rates above 100 Hz, critical-band filtering decreases sensitivity to modulation rate for the 500-1600 Hz noise band. Resolution in the random-standard discrimination task was similar to that for the identification task. Thresholds were elevated relative to fixed-standard thresholds except at the edges of the stimulus range. In the random-standard discrimination task, a pronounced criterion bias was present for stimuli near the edge of the range. Durlach & Braida's (1969) model describes the data well and provides quantitative measures in good agreement with those for intensity perception. Keywords: Amplitude modulation; Auditory perception; Psychoacoustics. (aw)