Study of lateral attenuation under meteorological conditions for airport noise modeling

This paper describes a result of examination on the validity of equations for lateral attenuation of over-ground sound propagation during aircraft flyover under various meteorological conditions, using long-term unattended noise monitoring at Narita Airport. The well-known SAE/AIR1751 equation was said to bring a little overestimation. Thus, we had examined the validity of the equation by following the procedure to construct AIR1751. As a result, we had found that lateral attenuation strongly changes dependent on meteorological conditions and that lateral attenuation by AIR1751 corresponds to upwind conditions. Based on these, we had proposed a modified equation 1751M available under various meteorological conditions, and decided to use it on condition of wind calm and temperature gradient neutral for long term average noise prediction. Afterwards, a lot of new types of aircraft have been introduced, and comparing noise predictions with measurements suggests that 1751M gives a bit underestimation. Besides, another new SAE/AIR5662 equation gives a bit higher value of lateral attenuation. Thus, we made this study to check the validity of lateral attenuation equations, following the same procedure we used when constructing 1751M. This paper describes the result as well as discusses further issues related to lateral attenuation in airport noise modeling.