Noise-induced neurologic disturbances in divers exposed to intense water-borne sound: two case reports

Divers may be exposed to intense noise underwater. Two cases of neurologic disturbances during experimental exposures to 15 min of continuous underwat er sound are described. Sound exposure in the first case consisted of a war ble tone with center frequency of 240 Hz and a sound pressure level of 160 dB re 1 mu Pa. Symptoms during exposure consisted of somnolence, lightheade dness, and an inability to concentrate. No apparent effect on hearing was n oted. In the second case, a center frequency of 1,000 Hz at 181 dB was used . Lightheadedness, inability to concentrate, agitation, and head vibrations were noted during the exposure. The diver also exhibited a temporary audit ory threshold shift of 19.2 dB. In both cases, overt symptoms resolved with in 30 min alter exposure, but both divers reported recurrent symptoms days to weeks after the exposures. Medical histories and examinations, assessmen t of dive profiles, and breathing gas analysis failed to support a source o ther than the sound exposures to account for the symptoms observed. Potenti al mechanisms for the described symptoms are discussed.