ultrahelimeetodil põhinev mittepurustav katse; eristatakse kahte peamist katsetusmeetodit: ultraheliläbivalgustuskatse ja ultraheliimpulss-kajakatse, a method of testing for flaws in which an ultrasonic source is pressed against the part to be tested, using some form of gel to act as a some coupling to the surface, and sound is passed into material