Helmet Noise and Divers´ Hearing

The effects of diving helmet noise on the hearing of divers were assessed during two helium-oxygen saturation dives to simulated depths of 650 and 850 feet of sea water. Twelve male U.S. Navy divers in excellent health and possessing good hearing underwent a series of exposures to deep-sea diving helmet noise for periods up to 4 hours per day. Audiograms were conducted before and after each noise exposure. Noise from inside the manned helmet was recorded while the diver was exercising and resting. Noise levels actually recorded from inside two helmets at depth would normally have limited diver exposure to one hour or less by present U.S. Navy airborne noise standards. However, close monitoring of divers´ hearing indicated that dives up to 4 hours in duration could be accomplished in these diving helmets. Moderate threshold shifts were observed in all divers after 4-hour helmet noise exposures; however, these shifts were temporary and divers´ hearing returned to within 5 dB of pre-noise exposure levels by 24 hours post-exposure. Follow-up studies indicated no permanent hearing loss was incurred.