Time, wavelet and Hilbert-Huang domain analysis of signals from ultrasonic based NDT

In this paper we compare the effectiveness of the time, wavelet and Hilbert Huang domain analysis of waveforms from a Non Destructive Test (NDT) equipment. The analysis of the signals from NDT systems is one of the most important activities since it allows to locate the actual defects. Very often the echoes traveling back to the sensors are superimposed with the signal from the transducer. We analyze the waveforms obtained by couples of sensors in order to extract the echoes and to recognize the points were they originate. A preliminary numerical analysis has been used to catch the main features of the elastic waves propagations in inhomogeneous materials.