Diffraction effects in insertion mode estimation of ultrasonicgroup velocity

摘要

We describe diffraction effects in ultrasonic group velocitynestimation using an insertion technique. We characterize the estimationnerror produced by diffraction as a function of distance and nominalnvelocity values. A new method termed Group Velocity DiffractionnCorrection (GVDC) which corrects for the diffraction effect isnpresented. Experimental validation of the technique is also presentednusing measurements made with both 1 MHz and 500 kHz ultrasonicntransducer pairs. The results demonstrate that diffraction effects onnultrasonic group velocity estimation are usually small, and may often benneglected. Significant improvement, up to about 50%, in the accuracy ofnthe group velocity estimate can however be obtained using the methodndescribed here in those cases in which higher degrees of accuracy arenrequired