SOME PRACTICAL CONSIDERATIONS FOR PREDICTING OUTDOOR SOUND-PROPAGATION IN THE PRESENCE OF WIND AND TEMPERATURE-GRADIENTS

The propagation of low-frequency sound above an impedance plane in a v ertically stratified medium is considered. The combined effects due to the vector wind and temperature gradients on sound propagation are st udied. Recently, a WKB-type approximation has been combined with turni ng point theory and applied to the efficient computation of the height -dependent Green's function, which, in turn, has been used in the fast field program (FFP). Although this method is applied to a temperature -stratified medium, it leads to a significant reduction in the computa tional time for predicting sound propagation outdoors. The present pap er extends such a WKB-type approximation to include vector wind. Atten tion is focused on the development of efficient algorithms for numeric al evaluation of the inverse Fourier transform and on considerations o f numerical stability. The limitations of the approximation are examin ed for logarithmic profiles in particular. (C) 1997 Elsevier Science L td.