how was sonar invented
It was Lewis Nixon who invented the very first sonar-type listening device in 1906. He was seeking a way of detecting icebergs. But the sonar was not invented, its inventor was nobody, but developed through the years. Sonar had very humble beginnings, from crude instruments to advanced technology.
Acoustic location in air was used before the introduction of radar. Sonar may also be used in air for robot navigation, and SODAR (an upward looking in-air sonar) is used for atmospheric investigations. The term sonar is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known as underwater acoustics or hydroacoustics.