Sharon M. Abel
Samuel Lunenfeld Res. Inst., Mount Sinai Hosp., 600 University Ave., Toronto, ON M5G 1X5, Canada
Sound localization ability was assessed in two groups of 24 normal-hearing subjects, aged 20--35 and 40--60 years. The test was conducted in a semi-reverberant chamber, using an array of six speakers, surrounding the subject at azimuth angles 60(degrees) apart, at a distance of 1 m. Three variables were investigated: the wearing of hearing protectors (unoccluded, conventional E-A-R plug and E-A-R muff, and Bilsom 2392 stereophonic muff with limited amplification), background (quiet vs 65 dB SPL white noise), and stimulus frequency (500 vs 4000 Hz). For each of the 16 listening conditions, one block of 120 trials was presented. Within a block, the test sound, an 80-dB SPL 300-ms one-third octave noise band, was randomly presented from each speaker on 20 trials. The subject judged the direction using a hand-held response box with an array of microswitches configured like the speaker array. Analysis of the overall and conditional proportions of correct response and the correct and incorrect response times is currently underway. Focii of interest are the effects of (1) stereophonic amplification on accuracy and (2) aging on decision reaction time.