A weather dependent noise contour prediction concept: Calculating multi-event noise contours with ray-tracing

Abstract

This paper expands recent work on a standard aircraft noise model with an advanced excess attenuation method. The most frequently used excess attenuation method for noise contour models is called the lateral attenuation correction and this empirical method disregards varying atmospheric conditions. However, it is known that for single-event cases varying atmospheric conditions can lead to large discrepancies in results. This paper studies these effects for a longer period, involving multi-event calculations. An ECAC Doc.29 compliant noise model is utilized which is extended with the functionality to apply results from a ray tracing excess attenuation calculation. Results are shown for monthly and yearly noise contours around a fictive airport using different modeling options. In the end the differences in results between the three modeling options are small. However, some differences can be distinguished for both the 58 LDEN and 48 LDEN contour. The most prominent difference is a smaller 58 LDEN contour area and a larger 48 LDEN contour area. Based on the results, it is argued that the effects of refraction, ground attenuation and atmospheric absorption each play a distinctive role in the found differences. In conclusion, the lateral attenuation model, used to estimate the average excess attenuation in a varying atmosphere, provides a practical and realistic estimate for a yearly and monthly noise contour.