Archaeological sonar recordings, Helike (Aigion, Greece), 1966-11
When a strobe would not do the trick in murky waters, Edgerton began working on sonar techniques to “see” with sound. Sonar works by bouncing a sound signal off to something. By measuring the time that it takes for the signal to return, the distance to the object can be calculated.
Doc’s “pinger” measured the distance to the sea bottom. The “boomer’s” signal probed beneath the ocean floor. And the side-scan “fish” was used to find objects that projected up from the bottom. Doc found several sunken ships with side-scan sonar.
Watch this video about sonar “making pictures” with sound!