Modulation-Rate Perception: Identification and Discrimination of Modulation Rate Using a Noise Carrier
Technical rept. Oct 1987-Oct 1988
NAVAL SUBMARINE MEDICAL RESEARCH LAB GROTON CT
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Modulation-rate thresholds were measured for three tasks a fixed- standard, forced-choice discrimination task with a 500-ms interestimulus 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 Braidas 1969 model describes the data well and provides quantitative measures in good agreement with those for intensity perception. Keywords Amplitude modulation Auditory perception Psychoacoustics.
- Anatomy and Physiology