UT uses high-frequency sound waves to detect internal and surface defects in materials. It is highly accurate and widely used in industrial applications.

In ultrasonic testing, high-frequency sound waves are transmitted into a material to detect imperfections or identify changes in material properties. The most commonly used ultrasonic testing technique is pulse-echo, where sound is introduced into a test object, and reflections (echoes) from internal imperfections or the object's geometric surfaces are returned to a receiver. Below is an example of a shear wave weld inspection. Notice the indication extending to the upper limits of the screen; this indication results from sound reflected from a defect within the weld. It is commonly used for weld inspections, thickness measurements, and flaw detection in pipelines and tanks.