Sound radiation properties of complex modes of vibration

Abstract

The sound radiation of vibrating plates is often characterized by modal radiation efficiencies. In most cases it is assumed that the spatial distribution of damping is homogeneous and structural modes of vibration are real valued. With the increasing use of high-performance, lightweight structures and rising acoustic requirements the demand of damping treatments is growing. For reasons of weight minimization, these treatments may be distributed locally at some critical locations of the structure, so that the assumption of homogeneity is violated. In this case the dynamics of the system within the resonances is no longer dominated by pure standing waves, but also by a superposition with travelling waves. These phenomena are generally known as complex modes of vibration. This paper summarizes the results of a numerical study on sound radiation properties of complex modes of vibration.