It is believed generally that Paul Langevin of France was the first to discover ultrasonic sound, but there are others also who made significant contribution in its discovery. Langevin created a device in 1917 that could detect the presence of submarines under the water by throwing sound waves in the sea and reading the echo of the sound waves coming back. In the 1940’s Donald Sproule from England and Adolf Trost from Germany worked separately to develop and fine tune several applications for the ultrasonic sound waves, including military use.