The vibroacoustics of slightly distorted cylindrical shells: A model of the acoustic input impedance

The interaction between the wall vibrations of an elastic cylindrical tube and the inner acoustic field is considered. When the tube cross section is perfectly circular, acoustic modes are coupled with structural modes having the same circumferential symmetry. Coupling between modes of different circumferential orders occur when the shell has small faults in symmetry. An analytical model using the integro-modal method is developed in order to describe these additional couplings due to shell defects. Attention is focused on the interaction between the acoustic plane mode and the ovalling shell modes. The mechanical resonance and coincidence effects between the structural and acoustical modes are found; these account for the perturbations in the input impedance induced by the wall vibrations.