Inverse methods in aeroacoustic three-dimensional volumetric noise source localization

Acoustic source mapping with microphone arrays usually involves the implicit assumption that sources are situated on the surface where the calculation points are located. However, in some application, such as aeroacoustic source localization, this assumption may produce misleading results. This paper describes the use of inverse methods in the context of aeroacoustic volumetric source imaging. A comparative investigation in exploiting a single planar array or multiple planar arrays, observing noise sources from different directions, is performed. Moreover, since aeroacoustic data are often spoiled by noise and different sources of quite different strengths are present, a novel use of CLEAN-SC as pre-processing step for inverse methods is discussed. The simulated and experimental results presented in the paper refer to a Counter Rotating Open Rotor installed on a 1/7th scale aircraft model placed in a large Low Speed Wind Tunnel.