Ray tracing in a moving medium with two-dimensional sound-speed variation and application to sound propagation over terrain discontinuities

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Abstract
The development of an efficient method for tracing rays and determining sound pressure levels in a moving medium is described. The medium is specified with horizontal and vertical variations in temperature and vectorial wind velocity. Reflections from a nonlevel ground surface of complex impedance are treated and an adaptive time step numerical integration is implemented for high accuracy. Two integration algorithms are compared for accuracy and computational efficiency. Recommendations are given for improved discretization of the medium and for accurate ray tracing through a ground reflection. This model is used to investigate the effect that terrain discontinuities, such as hills, have on atmospheric sound propagation. The importance of correct inclusion of the vectorial nature of wind is demonstrated.