Acoustic Emission 

AEAcoustic Emission – is a term used to describe the transient elastic waves generated by the release of energy within a material or by a process (see BS EN1330-9:2000 Non-destructive Testing Terminology Part 9: Terms used in acoustic emission testing). More generally, it is the name given to the monitoring of a structure, a plant component or a piece of machinery by listening to it and by determining its condition or the presence of damage by analysis of the acoustic noise detected. This noise may be transient or it could also be continuous.

AE is a passive technique. That means it doesn't stimulate the component in any way. It just listens to the item. There are many sources of noise that can indicate damage. Growing cracks can produce acoustic pulses as the material breaks. AE is used on pressure vessels during a pressurisation test to detect defects which may grow during the test. In the testing of atmospheric storage tanks it is the spalling or breaking and collapse of corrosion products which is detected and used to assess the condition of the tank. Liquid leaking through a hole in the tank may also be detected by the noise it generates.

The noise from different sources can be identified by the characteristics of the sound received. These include: duration; amplitude; rise time; frequency. By measuring the time delays between a transient noise signal arriving at a number of different transducers placed at various locations it is possible to use triangulation to identify the position of the source of the noise. Extra transducers or guard sensors can be used to reduce the impact of noise arising from outside the region of interest.

For more information on AE see:
'Acoustic Emission Monitoring as a tool in Risk Based Assessments', Dr G Martin and J Dimopoulos, 12th A-PCNDT  Auckland, New Zealand 2006. Which can be found at:

What the hec?! articles are not intended to be the definitive account on the topic or acronym in question. Readers’ comments and contributions are welcomed. Email: