When the pulse-echo method is applied to the acoustic wave guide with discontinuity, the relation between the properties of discontinuity and the echo signal from the discontinuous part has been studied for non destructive testing.
The reflection coefficient of low frequency sound pulse at the discontinuous part was calculated by using the lumped elements which was well known in acoustic duct, or filter theory for several cases and we performed the experiment for some artificial discontinuity. Experimental data have the same trend as the calculated value.
From these results, a guiding to the proper condition to increase the sensitivity of detectability is suggested.
