Considerations for near-field acoustical inverse measurements on partially correlated sources.

Abstract

Array-based acoustical inverse methods are being explored for the localization of noise sources in the jet plume of high-power military aircraft. For any partially spatially correlated source, the appropriate localization technique depends largely on the source correlation properties and the proximity of the measurement array to the source. Since correlation characteristics in high-power jets are difficult to measure, the coherence lengths measured in the near field are explored to guide the selection of the appropriate technique. Near-field coherence length and wavenumber decomposition results are presented for numerically simulated, partially spatially correlated sources to benchmark the technique. The coherence lengths of data measured near a high-power military jet aircraft are shown and the implications for the feasibility of various acoustical inverse methods for source localization are presented. [Work supported by Air Force Research Laboratory SBIR.]