The acoustics of a lined duct with flow

The present report describes a theory to calculate the sound propagation (including attenuation, reflection, radiation) through a three-sectioned cylindrical flow duct, modelling an aero-engine inlet. The flow is uniform apart from a thin boundary layer; two of the three sections are hardwalled, with an impedance-walled section in between. The...

The NLR/NGTE joint programme on the measurement of attenuation and impedance in acoustic flow duct facilities.

The National Aerospace Laboratory NLR in the Netherlands and the National Gas Turbine Establishment NOTE operate similar acoustic flow duct facilities but with differences in their respective approaches to the measurement of attenuation and impedance of duct linings. A joint exercise was arranged with the object of comparing methods and results,...