Acoustic emission is a nondestructive testing technique that detects the stress wave emissions from deformation and fracture processes within a loaded structure; these signals are the result of various processes that occur within the body. Some potential sources of acoustic emission include: crack propagation and arrest, fretting between fracture surfaces, dislocation movement, microcracking, twinning and phase transformations. In addition to these failure related mechanisms, other phenomena such as fastener and joint fretting, structural vibration, cavitation, and electromagnetic noise can create signals which are picked up by acoustic emission instrumentation. The ability to isolate crack growth signals from other events would greatly enhance the current acoustic emission signal processing capability.