Behind Start of Take-off Roll Aircraft Sound Level Directivity Study – Revision 1

The National Aeronautics and Space Administration (NASA), Langley Research Center (LaRC) and the Environmental Measurement and Modeling Division of the United States Department of Transportation’s John A. Volpe National Transportation Systems Center (Volpe) conducted a noise measurement study to examine the sound level directivity pattern behind aircraft start-of-takeoff roll. This report discusses the procedures and methodologies used to measure and quantify data acquired from the Study. This is a revision to the December 2012 that addresses a rounding error in equation 4 (Section 5.4) and the supporting text in Section 5 and Appendix F.