This text considers the problem of the dynamic fluid-structure
interaction between a finite elastic structure and the acoustic field in
an unbounded fluid-filled exterior domain. The exterior acoustic field
is modelled through a boundary integral equation over the structure
surface. However, the classical boundary integral equation formulations
of this problem either have no solutions or do not have unique solutions
at certain characteristic frequencies (which depend on the surface
geometry) and it is necessary to employ modified boundary integral
equation formulations which are valid for all frequencies. The
particular approach adopted here involves an arbitrary coupling
parameter and the effect that this parameter has on the stability and
accuracy of the numerical method used to solve the integral equation is
examined. The boundary integral analysis of the exterior acoustic
problem is coupled with a finite element analysis of the elastic
structure in order to investigate the interaction between the dynamic
behaviour of the structure and the associated acoustic field. Recently
there has been some controversy over whether or not the coupled problem
also suffers from the non-uniqueness problems associated with the
classical integral equation formulations of the exterior acoustic
problem. This question is resolved by demonstrating that .the solution
to the coupled problem is not unique at the characteristic frequencies
and that it is necessary to employ an integral equation formulation
valid for all frequencies.