Effect of a Vibrating Substructure on Acoustic Radiation from a Cylindrical Shell

The presence of a substructure in a cylindrical shell gives rise to dynamic interactions, including resonance effects, which have an influence on the radiated acoustic field. The lowest mode of the substructure may interact vigorously with a higher order mode of the shell. In this paper a Lagrangian formulation is used to analyze the forced motion of the immersed shell/substructure system. In addition, the frequency window method is used to reduce the complexity of the resulting expressions and to obtain approximate solutions in a frequency range of interest. The particular example is concerned with a spring-mass system, which is attached to the shell. Three cases of forced harmonic motion are considered. The radiated pressure is computed as a function of the frequency. The radiated pressure for the shell/substructure system is compared with that for a shell without an oscillator subjected to the same input force.