Experimental verification of the opposite effect of fluid loading on the velocity of dilatational waves in thin plates and rods

In a recent paper [J. Acoust. Soc. Am. 102, 3478 (1997)], it was demonstrat ed by analytical means that radiation loading increases the velocity of dil atational waves in immersed thin plates, but decreases it in thin rods. The main goal of this paper is to verify experimentally the predicted opposite effect, which is particularly interesting because in almost every respect, the lowest-order dilatational modes of wave propagation in thin plates and rods are very similar. Experimental verification of the predicted small ra diation-induced velocity change is rather difficult, partly because of the accompanying strong attenuation effect caused by radiation losses, and part ly because of the presence of an additional velocity change caused by visco us drag even in low-viscosity fluids like water. In spite of these inherent difficulties, the presented experimental results provide unequivocal verif ication of the earlier theoretical predictions. (C) 1999 Acoustical Society of America. [S0001-4966(99)03005-2].