Improving source localisation with SODIX for a sparse microphone array

SODIX is an acoustic source localisation method that is able to resolve the directivity of the sound sources. In this paper, SODIX is applied to array measurements with a full- scale turbofan engine. Two different microphone arrays were used: 1) a linear array near the engine that was relatively densely populated with a total number of 248 microphones, and 2) a sparse microphone array in the far-field with only 31 microphones covering an angular range from 10 to 160 degrees. The source localisation results obtained from the analysis of both arrays are compared and it will be shown, that also the sparse array yields very good results. One free parameter in the SODIX algorithm is a penalty function that sets a constraint on the directivities of the sources, i.e. the amplitude changes from a single source to different microphones. The influence of this penalty function on the quality of the results is investigated on the basis of the experimental data and synthetic data generated from a relatively simple engine noise model. A practical improvement for the setup of the sparse far-field microphone array is proposed for future measurements