Aircraft Jet Plume Source Noise Measurement System

Jet engine technology is more sophisticated than ever, building on decades of learning and growth in the field. However, even the latest advances in jet engine design and technology have not been able to counter an age-old challenge noise. Noise issues persist and adversely impact both ground maintenance personnel and surrounding communities. There is continued research to combat this issue, but for these emerging tools to achieve their full potential, innovative measurement and analysis methods are necessary to characterize the jet noise source region. A near-field acoustic holography system has been developed to meet this need and provide high-quality acoustic data. These data can be used for model refinement and benchmarking, evaluation of noise control devices, and predicting ground maintenance personnel and community noise exposure. The design of the 150-channel measurement array and data acquisition system is presented here. The prototype system was used recently to perform jet source noise measurements of an F-22 at Holloman Air Force Base located near Alamogordo, NM. The measurement approach and sound pressure level measurement maps detailing the near-field levels, spatial extent, and frequency content for four power conditions are featured.