4aPP5. Auditory temporal microstructure: Evidence of under- and over-shoot at onset and offset of a narrow-band noise masker measured in an off-frequency masked detection task.

Session: Thursday Morning, December 4


Author: Craig Formby
Location: Div. of Otolaryngol.---HNS, Univ. of Maryland School of Medicine, 16 S. Eutaw St., Ste. 500, Baltimore, MD 21201, cformby@surgery2.ab.umd.edu
Author: Sarah H. Ferguson
Location: Div. of Otolaryngol.---HNS, Univ. of Maryland School of Medicine, 16 S. Eutaw St., Ste. 500, Baltimore, MD 21201, cformby@surgery2.ab.umd.edu
Author: Michael G. Heinz
Location: Harvard-MIT, Cambridge, MA 02139

Abstract:

Detection thresholds were measured as a function of the temporal position of a 5-ms sinusoidal signal presented within one of two 500-ms observation intervals. Both intervals contained a 400-Hz-wide noise masker, logarithmically centered at 2500 Hz, that was gated on at 150 ms and off at 350 ms within each interval. The signal and masker were both gated with 2-ms linear ramps. The level of the signal was tracked adaptively in blocks of forty 2I 2AFC trials to estimate a 70.7% correct detection threshold. Thresholds were measured at 43 temporal signal positions within the observation interval, with detailed sampling around the onset and offset of the masker to assess temporal edge effects. Experiments to date with four listeners have focused on signals presented at 1900 or 2100 Hz. The temporal microstructure of the detection functions has characteristically revealed a complex pattern of under- and over-shoot (i.e., enhanced and diminished detection, respectively). These effects, which have been observed at both the onset and offset of the masker for virtually all masker spectrum levels between N[inf 0]=0 and 70 dB, may accentuate the temporal edges of the masker and, in general, enhance detection of acoustic onsets and offsets. [sup a)]Currently at Dept. of Speech and Hearing Sci., Indiana Univ.


ASA 134th Meeting - San Diego CA, December 1997