Auditory dysfunction accompanying noise-induced hearing loss

Two groups of 16 young male subjects with normal low- and midfrequency hearing were compared on a series of audiometric measures. One group was composed of subjects with 12- to 24-month histories of noise exposure and hearing loss at 4000 Hz greater than 40 dB; the other group was composed of normal-hearing subjects with no history of unusual noise exposure. On fixed-frequency Bekesy audiometry at 2000 Hz, 12 of the noise-exposed subjects demonstrated separation of 5 dB or more between pulsed- and continuous-tone tracings; similar separation occurred for only one of the non-noise-exposed subjects. Significant between-group differences also occurred on three tests of speech discrimination: PB-50 word lists and CID W-22 lists presented with two forms of competing noise.