Sonic pulses are also sent out to detect underwater objects by the same principle. During World War II the name ( .... sound wave

Sonic depth finders can be operated repetitively, recording thousands of soundings per hour, to prepare a profile of the ocean floor. One of the first practical depth sounders, the so-called Hayes sonic depth finder, developed by the U.S. Navy in 1919, consisted of (1) a device to generate and send sound waves to the ocean floor and receive the reflected waves and (2) a timer calibrated at the speed of sound in seawater that directly indicated water depth. In the modern system a transmitter supplies a powerful pulse of electrical energy, and a transducer converts the pulse into an acoustical pressure wave in the water and receives its echo, converting it back into electrical energy, which can be amplified and applied to an indicator.