TITLE: 
Masking of a brief probe by sinusoidal frequency modulation.
AUTHORS: 
Edwards BW; Viemeister NF
AUTHOR AFFILIATION: 
Department of Psychology, University of Minnesota, Minneapolis 55455,
USA.
SOURCE: 
J Acoust Soc Am 1997 Feb;101(2):1010-8
CITATION IDS: 
PMID: 9035393 UI: 97187946
ABSTRACT: 
Contrary to level detection models, the thresholds for a brief-duration probe
masked by a sinusoidal frequency modulation (FM) masker increases as the
modulation index (beta) of FM increases [Zwicker, Acustica 31, 243-256
(1974)]. In this paper the reason for this phenomenon is investigated. In
experiment 1, a 10-ms, 1-kHz probe was detected in the presence of an FM
masker centered at 1 kHz and sinusoidally modulated at 16 Hz. Thresholds
increased by over 15 dB with increasing beta, consistent with Zwicker's
findings. In experiment 2, the instantaneous frequency changes of the
masker used in experiment 1 were clipped and the resulting thresholds
indicated that detection was determined primarily by the masker's total
frequency excursion rather than by its instantaneous sweep rate. In
experiment 3, the FM maskers from the first two experiments were passed
through a roex filter centered at 1 kHz and the resulting envelope was used
to amplitude modulate a 1-kHz tone, producing approximately the same
effective envelope at 1 kHz as the FM maskers. Threshold functions for the
amplitude modulated (AM) maskers were similar to those for their
corresponding FM maskers. Thresholds increased by over 15 dB while the
total energy of the AM masker decreased by over 10 dB, again contrary to
standard level- detection models. The results from these experiments can
be explained, at least qualitatively, by a model based on envelope shape
discrimination: similarities between the envelopes of the masker alone and
masker-plus-probe at the output of an auditory filter centered on the
frequency of the probe are primarily responsible for the observed masking,
particularly at large beta's.
MAIN MESH HEADINGS: 
*Auditory Perception
*Perceptual Masking