(Dear Sir,

The classic definition of Acoustic Emission (AE) refers to the generation of transient elastic waves in the form of stress waves.

These stress waves can be originated from deep in the components (other than the pipes) having considerable thicknesses and are propagated in all directions. Eventually they reach the surface and can travel several meters and are picked up by the sensors.

When they reach the surface and propagate they can certainly be treated as Lamb waves but not very sure before they reach the surface from several centimeters from inside the component.

Best wishes