1944 - Maurice Ewing and a team of American scientists... believed there may be a layer in the ocean where a combination of pressure and temperature create a narrow channel where certain low-frequency sounds would travel long distances.
In the deep waters of the Atlantic, researches dropped several explosives containing four pounds of dynamite, each timed to detonate at a different depth. Using an underwater microphone called a hydrophone, a second boat stationed 900 miles away successfully detected the sounds.
Subsequent tests picked up the signal at a distance of 3,000 miles.
The discovery of the SOFAR sound channel opened up a new way to study the world's oceans, as well as a unique tool in the nation's defense.
(more)
