Resonant acoustic scattering from elastic cylindrical shells

The normal mode solution of the scattered pressure due to a normally incident plane acoustic wave on an infinitely long, air‐filled aluminum cylindrical shell in water is analyzed. Our study yields a physical interpretation of normal mode contributions to the backscattering function. The modes in the near‐soft (thin‐shell) region are compared to theoretical predictions and empirical observations. Transitions from Rayleigh‐type surface waves to Lamb‐type waves are found to take place for thin shells. A smooth transition of the first transverse wave on a thick shell to that of the first symmetric Lamb wave on a thin shell is shown to occur, and the inception of these thin‐wall modes is investigated as a function of shell thickness. Also, the antisymmetric Lamb mode is shown to exist and its intermittent nature is examined.