Reginald Fessenden
Reginald Aubrey Fessenden (October 6, 1866 – July 22, 1932) was a Canadian-born inventor, who did a majority of his work in the United States and also claimed U.S. citizenship through his American-born father. During his life he received hundreds of patents in various fields, most notably ones related to radio and sonar.
Radio acoustic ranging
The sinking of in 1912 spurred the Canadian inventor Reginald Fessenden (1866–1932) to begin work on a long-distance underwater sound transmission and reception system that could detect hazards in the path of a ship. This led to the invention of the Fessenden oscillator, an electro-acoustic transducer which by 1914 had a proven ability to transmit and receive sound at a distance of 31 miles across Massachusetts Bay and to detect an iceberg ahead of a ship at a range of two miles by bouncing sound off it and detecting the echo, as well as an occasional ability to detect the reflection of sound off the ocean bottom. Further impetus to developing practical applications of underwater acoustics came from World War I, which prompted the Royal Navy, United States Navy, and United States Army Coast Artillery Corps to experiment with sound as a means of detecting submerged submarines. In postwar experiments, the Coast Artillery Corps's Subaqueous Sound Ranging Section conducted experiments in shallow water in Vineyard Sound off Massachusetts in which it detonated explosive charges underwater at the ends of established baselines and measured the amount of time it took for the sound to arrive at hydrophones at the other ends of the baselines in order to establish very accurate measurements of the speed of sound through water. And in 1923, the Submarine Signal Company improved upon its underwater signaling devices by equipping them with radio transmitters that sent signals both to identify the particular device and to indicate to approaching ships that it would generate an acoustic signal at a specific time interval after it sent the radio signal, allowing ships to identify the specific navigational aid they were approaching and to take advantage of a one-way ranging capability that let their crews determine their direction and distance from the navigational aid.