The influence of sound radiation on vibration of mechanical structures

Abstract

Two methods of inclusion of coupling between the vibrating structure and produced acoustic field are discussed. The first iterative method consists of calculation of successive corrections of exciting nodal forces caused by sound pressure and solving the FEM equation of the structure. It has been proved that near the resonances of the structure this method can be nonconvergent. The second method consists of calculation of the generalized complex stiffness matrix of the sound field on the surface of the structure and including it into the stiffness matrix of the structure. The resulting stiffness matrix is a full matrix, and the algorithm for solving the FEM equation system is time consuming. It has been shown that near resonances of the structure, the global mechanical power provided to the radiating structure decreases in comparison to the power provided to the nonradiating structure. Near the antiresonant frequencies, the power provided to the structure with included radiation is greater. On this basis, a simple method of calculation of mechanoacoustical efficiency near the resonances and antiresonances of the structure is derived. The considerations are useful for calculation of efficiency of electroacoustical transducers. The results of calculation for vibrating and radiating shells of revolution are given.