Understanding Acoustic Emission Testing- Reading 1 Part B-A

AE Technique
The AE technique (AET) is based on the detection and conversion of high
frequency elastic waves emanating from the source to electrical signals. This
is accomplished by directly coupling piezoelectric transducers on the surface
of the structure under test and loading the structure. The output of the
piezoelectric sensors (during stimulus) is amplified through a low-noise
preamplifier, filtered to remove any extraneous noise and further processed
by suitable electronics. AET can non-destructively predict early failure of
structures. Further, a whole structure can be monitored from a few locations
and while the structure is in operation. AET is widely used in industries for
detection of faults or leakage in pressure vessels, tanks, and piping systems
and also for on-line monitoring welding and corrosion.
The difference between AET and other non-destructive testing (NDT)
techniques is that AET detects activities inside materials, while other
techniques attempt to examine the internal structures of materials by sending
and receiving some form of energy.
Charlie Chong/ Fion Zhang
http://www.geocities.ws/raobpc/AET.html