This is another ndt metho which works on priciple of sound reflection, refacted through the material like steel, aluminium and copper etc.
Ultrasonic waves are generated by piezo electric material called traducers which converts electric enery to mechnical vibrations and vice versa.
Most commony used frequency range for industrial inspection is 0.5 - 25 mega hertz.
This method have various technique such as..
Method is very much suitable to all type material but only operator skill is very much essential.