Lynne Marshall, Laurie M. Heller, Linda J.Westhusin
Naval Submarine Medical Research Laboratory, Groton, Connecticut
A four-year longitudinal study of noise-exposed people was conducted at the Naval Submarine Medical Research Laboratory. Audiograms and a test battery of evoked otoacoustic emissions (EOAEs) were administered annually. The EOAE test battery included transient-evoked otoacoustic emissions (TEOAEs) and distortion-product otoacoustic emissions (DPOAEs). Both noise-induced temporary shifts (NITTS) and noise-induced permanent threshold shifts (NIPTS) were identified. There were 12 samples of NITTS, and 9 clear-cut samples of NIPTS. Six additional subjects had a probable NIPTS (defined as a 15 dB shift after being noise-free for at least 14 hours, but unconfirmed by repeated testing). Case studies are used to illustrate the relationship of EOAEs to noise-induced temporary and permanent hearing-threshold shifts.
Supported by the Office of Naval Research.