This is our last paper in Sensors journal (see ref):
“Air-Coupled and Resonant Pulse-Echo Ultrasonic Technique” T.E. Gómez Álvarez-Arenas and J. Camacho. Sensors, 19(10), 2221.
Access to the paper here
Download pdf version here
A fully pulse-echo air-coupled technique able to determine thickness of steel plates and pipes is presented.