Backscattering by a tilted intermediate thickness cylindrical metal empty shell in water.

Backscattering by metal shells in water was investigated by Morse, Marston, and Kaduchak [J. Acoust Soc. Am. 103(2), 785-794 (1998)]. The evolution of the backscattering as a function of frequency and tilt angle, the "acoustic color," depended on the shell's thickness. The present study concerns scattering by a shell with an intermediate thickness-to-radius ratio (0.106). The results include: (a) meridional rays associated with a supersonic antisymmetric guided wave cause a prominent tilt-angle dependent enhancement at frequencies above the coincidence frequency; (b) a subsonic guided wave is also prominent over a range of frequencies and tilt angles; and (c) meridional ray contributions are evident in the time-frequency-angle domain.