Loudest artificial sound underwater

The loudest human-made underwater sound was the Operation Wigwam nuclear test, which saw the US Navy detonate a 30-kiloton Mark 90 fission device at a depth of 2,000 ft (610 m) off the coast of California, on 14 May 1955. The explosion generated a shockwave that was calculated to have been 328 dB (re 1 μPa) at its point of origin.

The sound of the Wigwam blast reverberated around the Pacific Ocean for several hours after the event. A Navy hydrophone array in Kaneohe, Hawaii, detected acoustic reflections from features as far distant as French Polynesia – meaning that the sound was intense enough to travel more than 6,200 km (3,850 mi) from its origin off the coast of San Diego, then another 4,400 km (2,700 mi) from French Polynesia to Hawaii.

Very little attention was paid to the environmental damage this explosion caused at the time. The details of the explosion were classified and the military reports were only concerned with the operational aims of the test (which was concerned with the effects of nuclear shockwaves on the pressure-hulls of submarines). Eyewitnesses describe the surface of the sea being littered with dead marine animals as far as the eye could see, killed either by the shockwave or by the intense burst of radiation.