This document has been declared "Stabilized" and will no longer be subjected to periodic reviews for currency. Users are responsible for verifying references and continued suitability or technical requirements. New technology may exist.The SAE A-21 Committee on Aircraft Noise undertook in 1979 the development of a uniform and consistent method for the prediction of lateral attenuation. The project was divided into two phases: (1) A short-term phase in which correlations of flight data were made using frequency-weighted and time-integrated measures of the noise, such as Effective Perceived Noise Level (EPNL) and Sound Exposure Level (SEL), see Appendix A; and (2) A long-term phase in which the effects of various sound-propagation phenomena would include ground reflection effects, refraction effects, and airplane shielding effects, as well as other ground and engine/airplane installation effects. This Aerospace Information Report is directed to the short-term phase in order to produce an interim prediction method as soon as possible.
