The Radiation Efficiency of a Plate with a Large Number of Modes

Abstract

The radiation efficiency of a plate excited with a large number of modes has been examined. Modal approach has been conducted for an acoustic cavity which has a flexible portion (plate) of the wall surface. The simple expression for the radiation efficiency of the plate has been derived under the condition that the coupling between plate and cavity is weak. Though the expression includes the terms of the interaction between structural modes of the plate and acoustic modes of the cavity, it is simpler rather than full-coupled expression. Numerical experiment has been carried out for a rectangular enclosure with a surface vibrating as a simply supported plate. Simulation results show the classical Maidanik equation has somewhat errors in case of radiation to a cavity at frequency range below coincidence. The radiation efficiency fluctuates largely when the number of modes is small and the loss factors of a plate and an enclosure are extremely small. In those cases, the expression derived in this paper is useful to calculate the radiation efficiency of a plate.