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

3aPP9. Auditory localization in noise. I. The effects of signal-to-noise ratio.

Michael D. Good

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

Ford Motor Co., Manufacturing Systems Dept., Dearborn, MI 48124

Robert H. Gilkey

Wright State Univ., Dayton, OH 45435

Wright-Patterson AFB, Dayton, OH 45433-6573

While several studies have examined localization of a single sound in the quiet, there have been few studies of localization in the presence of noise. In the present investigation, localization of a broadband click-train signal, masked by a broadband noise (located directly in front of the subject), was measured in the free-field as a function of signal-to-noise ratio. Subjects judged the direction of the signal, which could emanate from any of 239 spatial directions (surrounding the subject in azimuth and ranging from -45(degrees) to 90(degrees) in elevation), by pointing at a 20-cm-diam spherical model of auditory space. The ability to determine the direction of the signal decreased nearly monotonically as the signal-to-noise ratio was reduced. When the data were described in a ``three-pole'' coordinate system, it was evident that the accuracy of localization judgments, relative to the frontal plane (the ``front/back'' dimension), was degraded at much higher signal-to-noise ratios than was the accuracy relative to either the median plane (the ``left/right'' dimension) or the horizontal plane (the ``up/down'' dimension). Differences in the salience of cues for localization will be considered. [Work supported by AFOSR-91-0289.]