Enhancing the characterisation of ducted noise sources using a spectral formulation

The characterization of ducted sound sources is very useful to the aeronautical and automotive industries. It provides inputs to models used for predicting flow-generated noise at the design stage. Conventional inverse approaches, such as the Equivalent Source Method, offer accurate reconstruction results. But they require either a large number of in-duct field pressure measurements or a suitable location of a few number of equivalent sources. This research proposes an alternative approach formulated in the spectral domain: the Spectral Decomposition Method. It directly provides a cross-sectional imaging of the source velocity distribution from pressure data measured at small or large stand-off distance to the source. Wellresolved imaging results of the axial acoustic velocity generated by wall-mounted drivers have been obtained from either induct or wall-pressure measurements acquired respectively without or with flow.