In ultrasonic testing (UT), The very short frequency ultrasonic pulse-waves with frequencies ranging from 0.1-15 MHz and occasionally up to 50 MHz are transmitted into materials to detect internal flaws or to characterize materials. A common example is ultrasonic thickness measurement, which tests the thickness of the test object where other side is not accessible like pipes and pipe corrosion.

Ultrasonic testing is often performed on steel, other metals and alloys, though it can also be used on concrete, wood and composites, albeit with less resolution. It is a form of non-destructive testing used in many industries including aerospace, automotive and other transportation sectors.

It works on the principle of high frequency sound waves travelling in a solid medium and the waves and its back echo to give scan results. Even jobs in which the other side is not accessible (as needed in Radiography Testing) the Ultrasonic testing can be done .There is recording system in the Digital Ultrasonic machines where complete scanning can be recorded. The UT machines are operated by chargeable batteries and therefore can be taken easily at site even at heights.