Validity of aircraft noise data

Abstract

An analysis of noise measurements taken at various distances from a number of aircraft during noise flight testing is presented. Data scatter is shown to increase with distance and with decreasing aircraft/observer angle. Data normalization techniques, utilizing current standards, are inadequate at large distances and low airplane/observer angles. Aircraft noise measurements taken under uncontrolled situations are of doubtful value in predicting community noise. Noise measurements obtained directly beneath the airplane flightpath, under carefully controlled conditions, are highly repeatable and adjustable for moderate distances (within 1 to 2 EPNdB); however, when adjusted to sideline distances, these data can lead to variations on the order of 5 EPNdB. The accuracy of these sideline noise estimates is of prime concern since they are used to determine aircraft noise ’’footprints’’ in noise-exposure studies. Because a 3-EPNdB change in EPNL can lead to area halving or doubling, it is concluded, based on current technology, that the use of footprints in community noise-impact studies can be extremely misleading. Subject Classification; 50.20, 50.75, 50.80.