3.5 Liner Acoustics Jet engine nacelles or cowlings are equipped with liners to partially absorb fan tones before they propagate outside the engine. Typical liners today reduce community noise impact by 4 decibels. The goal of NASA research is to improve this by another 2 decibels. Recent research results have affected the whole liner design process, from determining the optimal acoustic properties of the liner (which must operate in the extreme flow conditions inside an engine) to validating that the desired properties have been achieved. The improved design process was validated in a wind tunnel test of a high-powered model fan where half of the goal, or a 1-decibel liner improvement, was achieved. Model and engine static tests are in progress to validate other innovations with the potential to achieve the full goal. Advanced Nacelle Wind Tunnel Model NASA POC: Dr. Joe Posey 757-864-7686 J.W.Posey@larc.nasa.gov

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