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Localization of Swept Free-Tip Airfoil Noise Sources by Microphone Array Processing

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A postprocessing methodology of microphone-array results for accurate source localization and separation is described. A method constrained iterative restoration algorithm with an assumption of uncorrelated sources is used to extract quantitative spectral results for multiple noise sources identified on a wall-mounted finite-span swept and cambered airfoil tested in an open-jet aeroacoustic facility. This allows understanding of the contribution of each source in the noise generation process. The total sound pressure level is reconstructed from the individual spectra of each noise source and extrapolated in the far field to be compared with a single-microphone spectrum. The Bayesian algorithm is used to improve the comparison between reconstructed and experimental spectra because it takes into account the coherent nature of the sources. The analytical models of the source mechanisms and of their spanwise correlation are proposed as a tool to define future improvements.


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