ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

1pPA10. Seasonal acoustic propagation effect.

Wayne R. Lundberg

3312 Braddock St., Kettering, OH 45420

Seasonal variations in wind and temperature gradients are known to influence the propagation of aircraft noise and sonic booms. This paper examines predictive techniques in current use for potential refinement and application to seasonal environmental impact statements. The effects of seasonally averaged refractive atmospheres were studied using sonic-boom propagation models which include refractive effects. The atmospheric environment was chosen to be that near Edwards Air Force Base where sonic booms are known to affect the public. Sonic-boom carpet predictions for a representative flight of an F-111 at Mach 1.3 and 10 000 ft above mean sea level were documented. The effect of such atmospheres on predicted noise exposure contours due to a real-world mix of supersonic flights was calculated using appropriate adjustments to the CORBOOM model. Two distinct atmospheric averaging techniques were applied for seasonal and annual comparisons. The resulting single-event and sonic-boom exposure predictions were compared to each other and to predictions obtained using the U.S. Standard Day Atmosphere and the Annual Reference Atmosphere for Edwards AFB. The results show the potential benefit of conducting seasonal acoustic predictions in forecasting the effects which low-altitude aircraft flight operations have on the public.