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Microphone array measurements with the DLR research aircraft ATRA flying in different configurations are presented with a focus on the analysis of sources in the engine jets. The free jets exiting the engine nozzles are large distributed source regions with locally and temporally fluctuating source distributions that evolve in the downstream direction. The source maps from the array data calculated with a deconvolution method for moving sources are divided into integration regions for the different noise sources of the engine and the free jet downstream. Frequency spectra of the integrated noise powers from the source regions of the engine inlets, the nozzles, and the jets for fly-overs in three different configurations with high engine speeds are presented and compared.

Simultaneous flow and acoustic measurements have been acquired for an aircraft, during ground operation. Measurements of velocity field data with stereoscopic particle image velocimetry (SPIV) on the engine-exhaust jet are correlated with the acoustic-pressure signals of a 120 microphone linear array. The turbulent velocity and the applied-stress components of the Lighthill- and Lilley-analogy source terms in the SPIV region are correlated with the microphone array. Convection effects on the propagating sound waves are neglected in the present study. The self-noise term in the Lighthill quadrupole, shows a hot spot for the correlation in the by-pass to ambient shear layer. This high correlation region is clearly visible in one of the analysed test points only, while in general a poor statistical convergence seems to affect the test-source correlation.