Evolution of navy diver exposure standards for deterministic underwater sound in the 100-500 hertz band Free

US Navy development of Low Frequency Active (LFA) sonar at the end of the Cold War resulted in the adverse exposure of Navy divers to high levels of LFA sound. An initial 30 month study into the effects on Navy divers of deterministic waveforms in the frequency band 160-320 HZ was conducted. Sound pressure levels up to 160 dB re 1μPa were utilized in a series of experimental observations. Auditory, animal, and human diver studies were completed. Additionally, modeling studies were conducted in the areas of cavitation, hyperthermia, tissue shearing, chest wall/lung displacement and rectified diffusion. Ultimately, 453 exposures using 87 different test subjects were conducted. These tests yielded a baseline set of guidelines for the exposure of Navy divers to deterministic sonar transmissions in the subject test band. The Navy has continued to refine and expand these guidelines to the present day utilizing both modeling and field exposure studies. A summary of the initial and subsequent testing and a tracing of the evolution of the current guidelines will be presented.