ACOUSTIC EXCITATION OF SCHOLTE-STONELEY AND LAMB WAVES ON A REINFORCED CYLINDRICAL SHELL

Abstract

The scattering of sound from a submerged elastic cylindrical shell, evacuated and bare of reinforcements, is known to excite the pseudo-Lamb S 0 wave propagating circumferentially around the shell, and also the Scholte-Stoneley (A) wave, but the latter only in a limited frequency region. For thin shells (of less than 10% thickness), excitation of the A 0 wave has not been observed in a distinct resonant fashion, at least at moderate frequencies around and above coincidence. (Its excitation in a nonresonant fashion, i.e., immediately beyond the locus of its generation, has, however, recently been observed experimentally.1) We show here that even the presence of internal attachments to the shell will not cause the excitation of the A 0 wave, while greatly extending the excitation region of the A wave, however. A modification of resonance frequencies by the internal attachments ("frequency doubling") is discussed, and is explained by the phase matching principle of resonance excitation.