Audible Recall Device
Abstract
The modified Audible Recall Device (ARD) is a small explosively- loaded device designed to be used as an emergency diver recall device by the Special Warfare and Explosive Ordnance Disposal communities. The modified ARD was designed to reduce the acoustic and fragmentation hazards identified by the Navy Experimental Diving Unit (NEDU) during evaluation of the original ARD (NEDU Report 10-87). The modified ARD incorporates a 6.6 sec delay fuse and contains a sand and steel powder mixture to produce a negative buoyancy with average detonation depth approximately 3.38 m (11 ft) underwater. During evaluation of the original ARD, five U.S. Navy divers were exposed to ARD's at 7 m (21 ft) which produced a peak sound pressure level (SPL) of 186.2 dB in water, equivalent to an in-air value of 151.2 dB, 11.2 dB over the current exposure limit for impulse noise, in air. The impulse was described as very loud but not uncomfortable and none of the diver-subjects experienced any decrease in hearing sensitivity as tested by comparison audiograms. The distance for a modified ARD to produce 186.2 dB in 3.38 m (11 ft) of water was found to be 6 m (19.5 ft). The distance for a modified ARD to produce 175 dB in water, equivalent to 140 dB in air, the limit currently imposed was calculated to be 21.2 m (68.9 ft). Actual testing at this distance was not possible due to size limitations of the test facility. However, testing at 20.0 m (65 ft) produced 176.8 dB which was very close to the calculated value at that distance, lending a high degree of certainty to the formulas used. Keywords: Physiological effects, Audiometry, Underwater sound signals, Sound pressure.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1989
- Accession Number
- ADA208584
Entities
People
- Garry Ashton
- John A. Sterba
Organizations
- United States Navy Experimental Diving Unit