ABSTRACT
Many engineering structures are subject to excitation by unsteady forces of which the spectra extend far up the audio-frequency range (20Hz-20 kHz). Examples include railway trains, cars, aircraft, ships, gas pipelines, buildings, industrial plant and space rockets. The qualification ‘high’ in the title implies that the frequency range of concern extends to many times the fundamental natural frequency of the system; ultrasonic frequencies are not considered here. High-frequency vibration is of concern to engineers because of the potential for excessive sound transmission and radiation and for fatigue damage. The former aspects are commercial, ergonomic, regulatory, environmental and health concerns; the latter is a safety and commercial matter. This chapter begins with a qualitative introduction to the physics of high-
frequency structural vibration and its distinguishing features. It continues with an explanation of the difficulties that it poses to mathematical modellers and analysts. The parameters relevant to the characterisation of high-frequency structural vibration are then introduced in a qualitative manner as an entrée to Section 11.4, which presents a mathematical description of high-frequency structural vibration. Various forms of deterministic model and numerical solution are described, together with their merits and weaknesses. As an alternative, the probabilistic statistical energy analysis (SEA) model is introduced. The two approaches to estimating SEA subsystem coupling coefficients are explained and the power balance equations are presented. The problem of subsystem selection is illustrated by reference to the modelling of a passenger car. The chapter closes with brief accounts of the various alternatives to SEA that are currently being researched.
