The effect of atmospheric gradients on aircraft noise contours Free

Calculation of airport noise contours generally ignores atmospheric gradients. This is usually justified by the assumption that any effects will average out in the long run. An initial study has been conducted to evaluate this assumption. Noise contours have been computed for a single takeoff and landing of an F‐16C under various atmospheric conditions. Atmospheric conditions included clear daytime, cloudy daytime, and nighttime temperature profiles, with winds at several speeds and directions. The heuristic propagation algorithms of L’Esperance et al. [AIAA Pap. 93‐4405 (1993)] were incorporated into Wyle Laboratories NMSIM single‐event noise simulation model. Calculated SEL footprints exhibited substantial changes in shape, particularly in sideline regions under crosswind conditions. Some trends of increased area under windy conditions were seen. Application of this analysis to a long‐term set of actual weather data would validate (or invalidate) the ‘‘it all averages out’’ assumption. [Work supported by USAF Armstrong Laboratory. Atmospheric profiles and propagation routines provided by Andre L’Esperance.]