AEROACOUSTIC SOURCE CHARACTERISATION USING SUBSPACE AND DECONVOLUTION TECHNIQUES

The use of phased microphone arrays has become a standard technique for aeroacoustic testing. The ultimate goal is to characterise aeroacoustic source mechanisms with respect to their location, their strength and their spectrum. A number of different analysing methods are available, ranging from classic delay-and-sum beamforming to more sophisticated methods that involve deconvolution of the beamforming map. Practical results from wind tunnel measurements using different processing techniques are presented. Both aerofoil trailing edge noise and noise from a rod-aerofoil configuration serve as examples. The processing techniques used include classic methods as well as such using the signal subspace, such using the noise subspace, the deconvolution approach for the mapping of acoustic sources (DAMAS) and a deconvolution method based on spatial source coherence (CLEAN-SC). The comparison from the results of different techniques shows significant discrepancies. This leads to the conclusion that not a single technique should be used for source characterisation, but the right one should be chosen depending on whether the location or the source strength is of primary interest.