Ultrasonic Testing (UT) uses high frequency sound energy to conduct examinations and make measurements. The simplest explanation of what happens in this method is that sound energy is introduced via a transducer and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the transducer and is displayed or recorded in a variety of ways. Both surface and subsurface defects can be detected making ultrasonics a volumetric testing method.

Ultrasonic testing is commonly used test method according to EN ISO 17640, ISO 11666 in shipping and offshore industry, fabrication industry and other general industries.