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Principle

In an acoustic emission test, an inspector records elastic ultrasonic waves traveling through the surface of a solid material using one or more sensors.

As an acoustic wave travels on or through the surface of an object any defect it encounters can change that wave, both in terms of its speed and in terms of its amplitude. And inspectors look for these changes to identify the presence of defects.

The range of ultrasound typically used for acoustic emission testing is 20 KiloHertZ (KHZ) and 1 MegaHertZ (MHZ). (One KiloHertZ is equal to one one thousand Hertz, or cycles per second; one MegaHertZ is equal to one million Hertz, or cycles per second).

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