ASA 127th Meeting M.I.T. 1994 June 6-10

3aPP13. Binaural and monaural influences on ``free-field'' masking for real and virtual sound sources.

Jennifer M. Ball

Dept. of Psychol., Wright State Univ., Dayton, OH 45435

Robert H. Gilkey

Wright-Patterson AFB, Dayton, OH 45433-6573

Wright State Univ., Dayton, OH 45435

Michael D. Good

Wright State Univ., Dayton, OH 45435

Ford Motor Co., Dearborn, MI 48124

Gilkey and Good [J. Acoust. Soc. Am. 92, 2334 (1992)] found that the detectability of a click-train signal, presented in the free-field, increased dramatically when the signal was spatially separated from a noise masker, in either azimuth or elevation. In separate conditions, stimuli were filtered into low-, mid-, and high-frequency regions. The pattern of results suggested that the increases in detectability might have been based on monaural, rather than binaural, processing. Here, this study was partially replicated using ``virtual'' sound sources. The stimuli were filtered through head-related transfer functions and presented through headphones. Binaural, left-ear monaural, and right-ear monaural stimulus presentations were compared. Thresholds in the binaural condition were in good agreement with the free-field data. Although there was evidence under some conditions of a small binaural advantage at low frequencies, in general, binaural performance was no better than monaural performance with the ``better ear.'' Overall, the results suggest that the subjects of Gilkey and Good could have performed as well as they did based on monaural processing alone. [Work supported by NIH-DC-00786 and AFOSR-91-0289.]