PRACTICAL FLOW DUCT ACOUSTICS

Predictions of plane acoustic wave propagation through acoustically reactive flow duct systems are of practical relevance in design studies for industrial, transportation and environmental noise application. Acoustic conditions throughout the flow duct are described by the complex values of the incident and reflected wave amplitudes relative to that of the wave component incident at an open duct termination. Examples are given of the calculation of these amplitudes with a range of typical flow duct configurations. The practical consequences of wave attenuation and other losses are quantified, but consideration is restricted to plane wave propagation. In application of the flux of acoustic energy from a source through some system will be governed by the acoustic character characteristics of both. To maintain generality of application, sources are represented by equivalent specified termination conditions. The emphasis throughout is based on fluid dynamic and acoustic principles and directed towards the development of physical insight with the identification of the relevant processes controlling wave propagation.