Ultrasonic Testing is a Non-Destructive Testing (NDT) method. Unlike surface inspection methods, UT makes it possible to find flaws inside the material. High-frequency sound waves are sent into the material with an ultrasonic transducer. The ultrasound that reflects off defects in the material is made visible in a graph. Ultrasonic Testing gives insight in the depth, size, nature and orientation of the detected indications. The thickness of the material, such as wall thickness of pipes, can also be measured. This method comprises a range of NDT techniques that send ultrasonic waves through an object or material.

These high frequency sound waves are transmitted into materials to characterize the material or for flaw detecting. Most UT inspection applications use short pulse waves with frequencies ranging from 0.1-15 MHz, although frequencies up to 50 MHz can be used. One common application for this test method is ultrasonic thickness measurement, which is used to ascertain the thickness of an object such as when assessing pipework corrosion.