ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pPP30. The effects of narrow-band noise maskers on overshoot.

Peter Marvit

Virginia M. Richards

Dept. of Psychol., Univ. of Pennsylvania, 3815 Walnut St., Philadelphia, PA 19104

The elevation of detection thresholds for a short signal added just after the onset of a masker versus when it is added later during the masker has been called ``overshoot.'' Previous work with broadband maskers suggests masker frequency component near, but not at, the signal frequency produce overshoot. The relative contribution of different frequency regions to the overshoot effect was investigated here with narrow-band noise maskers of different center frequencies. The 350-ms maskers were 1/2 octave wide with center frequencies ranging from 1400 to 8500 Hz. The 10-ms signal was 2500-Hz tone added 4 or 325 ms after the onset of the masker. Masker spectrum levels were 35 dB SPL. The three subjects generally showed little or no overshoot when the masker spectrally overlapped the signal, but showed a maximum overshoot of 8--12 dB for masker bands centered 1/2 to 1 octave above and below the signal frequency; increased signal-masker frequency difference diminished but did not abolish the overshoot effect. Detection thresholds were maximal when the masker band spectrally overlapped the signal and fell as signal-masker frequency separation grew. A similar pattern of results was obtained using low-pass, high-pass, band-pass, and notched noise maskers bounding on a 750-Hz-wide region around the 2500-Hz signal frequency. [Work supported by NIH.]