SOUND LOCALIZATION - THE INTERACTION OF AGING, HEARING-LOSS AND HEARING PROTECTION

The effect of conventional ear plugs and ear muffs, and muffs with lim ited dichotic amplification on the ability to localize one-third octav e noise bands was investigated under semi-reverberant listening condit ions. Forty-eight normal-hearing subjects, half over 40 years of age, and 23 subjects with bilateral sensorineural hearing loss participated . Sound localization was assessed using an array of six loudspeakers s urrounding the subject at azimuth angles 60 degrees apart. One block o f 120 forced-choice speaker identification trials was presented for ea ch of 16 listening conditions defined by ear condition (unoccluded, E- A-R plug, E-A-R muff, and Bilsom 2392 muff), stimulus frequency (500 H z and 4000 Hz), and background (quiet and continuous 65 dB SPL-white n oise). Plugs and muffs, particularly active muffs, resulted in decreme nts in right/left judgments based on interaural intensity but not time -of-arrival differences. High-frequency front/back discrimination was affected more by muffs than by plugs. Error patterns for the conventio nal and active muffs were dissimilar. Aging resulted in a decrement in unoccluded front/back discrimination. Trends for the impaired subject s were the same as those for normal subjects at 500 Hz. Many could not hear 4000 Hz with conventional protectors. Their performance was no d ifferent from normal with the active muffs.