In order to measure the thickness of a given material using ultrasound, such as a metal bar, a pulse-echo
technique is used. This technique is established by starting a timer at the same time the ultrasound pulse is
generated, and consequently stopping the timer when the echoed pulse is detected. The measured time is referred to
as the time difference of arrival (TDOA). By multiplying TDOA by the ultrasound velocity in the given known
material, we calculate the total travelled distance of the ultrasound wave, which is twice the thickness of the
material, as seen in Figure 1 (a). The ultrasound pulse will echo back and forth in the measured material until the
amplitude is adequately attenuated as it travels through the material, as depicted in Figure 1 (b). The TDOA between
the echoes can be measured and averaged to obtain an averaged reading of the material thickness.