Vibro-acoustic properties of sandwich structures

The vibro-acoustic properties of three-layered sandwich elements depend on the bending stiffness of the structure. It is found that the apparent bending stiffness of a sandwich beam depends on frequency, its length and boundary conditions. A beam with free ends appears stiffer than the same beam clamped at both ends. The apparent bending stiffness of a sandwich beam with clamped ends decreases as the length of the beam is reduced. The opposite is the case for a beam with free ends. A method for estimating the material parameters of a sandwich beam is described. The frequency and space averages of the point mobility of a finite sandwich beam is found to be equal to the point mobility of an infinite sandwich beam of the same type. Coupling loss factors between sandwich beam elements for some simple types of junctions are given.