Structural Acoustics and Vibrations

Abstract

This acousticsstructural chapter is devoted to vibrations of structures and to their coupling with the acoustic field. Depending on the context, the radiated sound can be judged as desirable, as is mostly the case for musical instruments, or undesirable, like noise generated by machinery. In architectural acoustics, one main goal is to limit the transmission of sound through walls. In the automobile industry, the engineers have to control the noise generated inside and outside the passenger compartment. This can be achieved by means of passive or active damping. In general, there is a strong need for quieter products and better sound quality generated by the structures in our daily environment. Structural acoustics and vibration is an interdisciplinary area, with many different potential applications. Depending on the specific problem under investigation, one has to deal with material properties, structural modifications, signal processing and measurements, active control, modal analysis, identification and localization of sources or nonlinear vibrations, among other hot topics. In this chapter, the fundamental methods for the analysis of vibrations and sound radiation of structures are presented. It mainly focuses on general physical concepts rather than on specific applications such as those encountered in ships, planes, automobiles or buildings. The fluid–structure coupling is restricted to the case of light compressible fluids (such as air). Practical examples are given at the end of each section. After a brief presentation of the properties of the basic linear single-degree-of-freedom oscillator, the linear vibrations of strings, beams, membranes, plates and shells are reviewed. Then, the structural–acoustic coupling of some elementary systems is presented, followed by a presentation of the main dissipation mechanisms in structures. The last section is devoted to nonlinear vibrations. In conclusion, a brief overview of some advanced topics in structural acoustics and vibrations is given.