ASA 126th Meeting Denver 1993 October 4-8

5aSA5. Observation of the prompt high-frequency enhancement of tone bursts backscattered by a thin spherical shell near the first longitudinal resonance.

Gregory Kaduchak Philip L. Marston

Dept. of Phys., Washington State Univ., Pullman, WA 99164-2814

A prominent feature predicted for the backscattering of tone bursts by thin spherical shells is an enhancement of a guided wave contribution near the first longitudinal resonance. This has been explained with a backward ray model of a leaky Lamb wave where energy is leaked off without having circumnavigated the back side of the shell [P. L. Marston et al., J. Acoust. Soc. Am. 90, 2341 (1991); D. H. Hughes, Ph.D. thesis, Washington State University (1992)]. The relevant s[sub 2b] Lamb wave has opposing group and phase velocities giving rise to prompt radiation following the direct specular echo. The present research gives a comparison between a ray theory approximation and experiments in which tone bursts having carrier frequencies in the range 595