2.2. Modelling on Ultrasonic Signal Behaviour
Modelling on ultrasonic signal behaviour is important to determine the sensing mode of ultrasonic signal wave
propagation. The ultrasonic energy incident on target material is either based on transmission or reflection mode. In
this project, the ultrasonic signals travelled from the sensor to the target material (steel pipe) through the air medium
with 50 mm distance as shown in Fig.3. Z1 and Z2 are the acoustic impedances of medium 1 (air) and medium 2
(pipe coating), respectively. The value of acoustic impedance for air is 0.0004 kg/m².s x 106
and FBE coating
material is 2.7 kg/m².s x 106
[13].