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Description
The development of an acoustic measurement platform using UAVs enables noise field mapping and sound source characterization of outdoor low-frequency noise sources that are, otherwise, difficult to be measured in laboratory environment due to dimensional constraints. A simplified analytical model using spherical harmonics and a multipole expansion of the Green’s function has been developed for estimating the acoustic source signature from near-field measurements. In addition to the simplification of measurement methodology, the multipole expansion method increases the computation efficiency compared to traditional Boundary Element Method. Furthermore, the model predictions are validated with a self-calibrated low frequency laboratory test source in an outdoor free field environment. The methodology developed here can facilitate the quantification of low-frequency noise emission from renewable energy sources and the determination of the propagation characteristics in the lower atmosphere.