Effect of modulation maskers on the detection of second-order amplitude modulation with and without notched noise.
The mechanisms underlying the detection of second-order amplitude modulation (AM) were explored. The detectability of second-order AM (fixed depth for each subject) was measured for first- and second-order modulation rates of 16 and 2 Hz, respectively (slow-rate pair), and 50 and 10 Hz, respectively (fast-rate pair), with no masker, a low-band modulation masker (centered at 2 or 10 Hz), and a high-band modulation masker (centered at 16 or 50 Hz). This was done in the absence and presence of an audio-frequency notched noise centered at the carrier frequency of 4000 Hz. Both modulation maskers were "low-noise" noises, to prevent overmodulation. In the absence of notched noise, both modulation maskers impaired performance for the slow-rate pair, but only the low-band masker impaired performance for the fast-rate pair. When notched noise was present, the low-band masker had no significant effect for either rate pair and the high-band masker had an effect only for the slow-rate pair. These results suggest that second-order AM detection is mediated both by an envelope distortion component at the second-order rate and by slow fluctuations in the output of a modulation filter tuned to the first-order rate. When notched noise is present, the distortion component plays little role.
Uchanski
Rosalie M
RM
Department of Otolaryngology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA. ruchanski@wustl.edu
Moore
Brian C J
BC
Glasberg
Brian R
BR
D000328:Adult; D001301:Audiometry, Pure-Tone; D006801:Humans; D008144:Loudness Perception / Q000502:physiology*; D008875:Middle Aged; D009622:Noise; D010469:Perceptual Distortion; D010470:Perceptual Masking / Q000502:physiology*; D011571:Psychoacoustics