Development of a Near-field Acoustical Holography System for Aircraft Jet Source Noise Measurements

The current and next generation military jet aircraft are exposing both ground maintenance personnel and the community to high levels of noise. The DoD is funding research to develop advanced modeling tools for community noise exposure and for noise reduction techniques. As these tools are being developed to address to the overall military jet noise problem, the lack of understanding of the actual jet noise source has been identified as a limiting factor. For these tools to achieve their full potential in addressing the noise problem, innovative measurement and analysis methods are necessary to characterize and map the noise source region in the jet. Near-field acoustic holography (NAH) offers the best general method to measuring the magnitude, directivity, and spectral content as well as the spatial distribution of the noise emitted from a jet. The objective of this proposed effort will be to develop a portable NAH system that can characterize jet noise emissions. To develop the most efficient measurement system, several NAH approaches will be tested using risk reduction laboratory testing and evaluation procedures. These evaluations will determine the NAH approaches that meet the high fidelity data requirements outlined in the SOW while providing practical field system.