High frequency sound waves are introduced into a material and they are reflected back from surfaces as flaws.

Reflected sound energy is displayed versus time, and inspector can visualize a cross section of the specimen showing the depth of features that reflect sound.

UT uses the transmission of high frequency sound waves into a material to detect imperfections within the material, or changes in material properties. The most commonly used ultrasonic testing technique is pulse-echo testing, wherein sound is introduced into the test object and reflections (echoes) are returned to a receiver from internal imperfections or from geometrical surfaces of the part.

Stuctural Steel Ultrasonic Weld Inspection: