This paper describes an experimental comparison of the stress waves generated by three sources of simulated acoustic emission events: a piezoelectric generator, an electric spark, and a pulsed laser. The stress waves produced by the electric spark indicate that the stress generating mechanism is the thermally excited pressure pulse in the air surrounding the spark. Each of the sources is shown to be capable of producing stress waves of less than 1-μs duration, but the piezoelectric generator appears to be the most advantageous technique.
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