Study on over-ground lateral attenuation for prediction model of military aircraft noise

For noise prediction of aircraft moving on the runway and flying-over, the overground lateral attenuation is corrected to the A-weighted sound level (noise level) calculated from the NPD database and propagation distance at the point on the side of the moving path. Existing equations indicated by SAE/AIR 1751 and 5662 are used for aircraft noise prediction. And the modified SAE/AIR 1751 ("1751M") has also been proposed a calculation method to predict lateral attenuation under various meteorological conditions. On the other hand, the Noisemap's method is also applied to noise prediction of military aircraft. Regarding civil aviation aircraft, the correction method of lateral attenuation is verified for currently operated aircraft, because the occurrence situation of noise is changing as the aircraft model is updated. For military aircraft (especially jet fighter aircraft) in Japan, although there was little change in model, we thought that it was necessary to verify the lateral attenuation of military aircraft noise because aircraft are in operation for a long time. Therefore, we conducted a field measurement for several days and confirmed the characteristic of over-ground sound propagation for military aircraft. As a result of comparing the over ground lateral attenuation calculated by the difference between the noise level measured on the side of the runway in the upwind conditions and the predicted noise level without lateral attenuation, it was confirmed that the results were good agreement with lateral attenuation calculated under upwind condition proposed in 1751M.