In May of 1940, Floyd Firestone, a Professor in the department of Physics at the University of Michigan, filed US patent 2280226 in which he described an instrument for the detection of flaws and measuring thickness in metal objects. Dr. Firestone used the term “Supersonic Vibration Waves” to describe what we now refer to as pulse-echo Ultrasound Testing (UT).

The term “Supersonic Inspection” was used in reference to UT officially until the first manned aircraft flight by USAF Captain Chuck Yeager exc
Source: NDT