Doppler's shift on aircraft noise propagation in modern aircraft noise prediction tools

Abstract

Doppler’s effect is an important factor in the prediction of the noise levels caused by en-route aircrafts. This study is focused on the influence of Doppler’s effect on the propagation of aircraft noise. The received sound pressure can be increased/decreased by Doppler’s effect depending on the relative location of the sound source and receiver. At the same time, the spectral shape of the noise is shifted by this effect which has an impact on the measured A-weighted noise levels. This influence is largely due to the fact that A-weighted correction factors of mid-frequency range are much larger than that those in the low-frequency regime. In this paper, a series of field trial was used to study the propagation effect of noise generated by a propeller-driven aircraft. Aviation Environment Design Tool (AEDT), a widely accepted noise prediction model of aircraft noise, is used to compare with the predictions according to a ray-based numerical model. The inclusion of Doppler’s effect in the noise prediction model has shown to have a better agreement with the field measurement results. The influence of Doppler’s effect on the noise-power-distance (NPD) curves of several different aircrafts is also presented. [Work sponsored by ASCENT, FAA Center of Excellence for Alternative Jet Fuels and Environment.]