7 - Mid- and high-frequency problems in vehicle noise and vibration refinement – statistical energy analysis and wave approaches

Abstract

Starting from the statistical energy analysis (SEA) modal approach, energy sharing between two oscillators and energy exchange in a multi-degree-of-freedom system are discussed, from which the SEA power balance equations are derived. Application procedures of the SEA approach are presented and the main SEA assumptions are highlighted. In order to introduce the SEA wave approach, room acoustics is reviewed; the SEA conceptual parameters such as wave number, wave number space, dispersion and modal density for energy storage are defined. In regard to energy transmission, the concepts of direct and reverberant fields, as well as coupling loss factors for different connections, are illustrated; panel acoustic radiations are introduced and evaluated; transfer matrices and insert loss of a trim lay-up are demonstrated; and leaks and aperture effects are discussed. For energy inputs, direct field impedance and input power are illustrated; distributed random loading and turbulent boundary layer loading are defined; and concepts of diffuse acoustic field loading and propagating acoustic field loading are explained. The hybrid deterministic and SEA approach is briefly introduced. An application example of vibro-acoustic analysis on a passenger car roof–cabin cavity system is given to validate the SEA approach.