Aircraft noise in situations with grazing sound incidence-Comparing different modeling approaches

Current best-practice aircraft noise calculation models usually apply a so-called lateral attenuation term, i.e., an empirical formula to account for sound propagation phenomena in situations with grazing sound incidence. The recently developed aircraft noise model sonAIR features a physically based sound propagation core that claims to implicitly account for the phenomena condensed in this correction. The current study compares calculations for situations with grazing sound incidence of sonAIR and two best-practice models, AEDT and FLULA2, with measurements. The validation dataset includes on the one hand a large number of commercial aircraft during final approach and on the other hand departures of a jet fighter aircraft, with measurement distances up to 2.8 km. The comparisons show that a lateral attenuation term is justified for best-practice models, resulting in a better agreement with measurements. However, sonAIR yields better results than the two other models, with deviations on the order of only ±1 dB at all measurement locations. A further advantage of a physically based modeling approach, as used in sonAIR, is its ability to account for varying conditions affecting lateral attenuation, like systematic differences in the temperature stratification between day and night or ground cover other than grassland.