Noise-induced hearing loss and the comprehension of speech in noise.
Subjects suffering from noise-induced hearing loss (NIHL) with or without hearing loss at 2 kHz were examined by speech audiometry with a three-digit test, bisyllabic and monosyllabic PB word lists in silence, and in USASI noise with a masking effect of 44 dB and 68 dB at 1 kHz. Subjects with up to 20 dB hearing loss at 2 kHz had almost the same speech comprehension in noise as normal hearing subjects. Subjects with hearing loss greater than 20 dB at 2 kHz had increasing discrimination loss at increasing noise levels. They also needed a signal-to-noise ratio better than normal-hearing persons would yield at the noise levels used. The evaluation of hearing disablement in occupational noise-included hearing loss should therefore be based for one-half on the results of speech audiometry in silence, and for the other half, in noise.