A ray acoustics model for the propagation of aircraft noise through the atmosphere

摘要

A ray-tracing tool, called RAYTRAC, has been developed to compute the propagation of aircraft noise through a stratified atmosphere. The mathematical model on which RAYTRAC is based is derived from first principles, i.e. the linearized Euler equations for a non-uniform atmosphere. The main result of the model consists of two equations: one for the location of the rays and one for the change in amplitude along each ray. An analysis of these equations is given with respect to their possible solutions under various atmospheric circumstances. Also an efficient iteration procedure is presented that finds the ray connecting the source and a specific observer point. It is shown how multiple rays can be added, with incorporation of a reflecting surface. Finally, the tool is demonstrated by application to two examples that are representative for an aircraft emitting sound to an observer on the ground.