The influence of modal behaviour on the energy transmission between two coupled plates

The ‘effective’ coupling loss factor (CLF) of a particular realization of two coupled subsystems within a notional ensemble can differ from the ensemble average CLF. The variability in the effective CLF, or the transmission efficiency, due to the modal behaviour of the source and receiver subsystems has been examined for a system comprising two plates. A systematic investigation involving finite width semi-infinite plates and finite plates has been performed using a combination of wave models and dynamic stiffness approaches. By making both the source and receiver plates either finite or semi-infinite, it is shown that the modal behaviour of both the source and receiver plates affects the energy transmission between the two subsystems. Large variations in the energy transmission are found due to the modal behaviour of the finite receiver plate. The damping of the receiver plate controls the magnitude of these variations. However, variations in the energy transmission can also be attributed to the source subsystem modal characteristics, as seen for a finite source plate coupled to a semi-infinite receiver plate. It is shown that this variation is due to the predominance of particular angles of incidence at a given frequency. Damping of the source plate has only a small influence. For the present example, using a damping loss factor of 0.1, the influence of source and receiver modal behaviour is of a similar magnitude. For lower levels of damping the modal behaviour of the receiver subsystem becomes relatively more important.