The technique is also commonly used to determine the thickness of the test   object, for example, to monitor pipework corrosion.                   
                 
                  Ultrasonic testing   uses high frequency, highly directional sound waves to measure material   thickness, find hidden internal flaws, or analyze material properties in metals,   plastics, composites, ceramics, rubber, and glass.  
                   
                  Using frequencies beyond the   limit of human hearing, ultrasonic instruments generate shorts bursts of sound   energy that are coupled into the test piece, and the instrument monitors and   analyzes reflected or transmitted wave patterns to generate test   results. 
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