Application of the parabolic equation to sound propagation in a refracting atmosphere

Abstract

A wide-angle parabolic equation (PE) model is presented that is applicable to sound propagation in a steady (nonturbulent) atmosphere overlying a flat, locally reacting ground surface. The numerical accuracy of the PE model is shown by comparing PE calculations to calculations from a ‘‘fast-field program’’ (FFP). For upward refraction, the PE and FFP solutions agree to within 1 dB out to ranges where the sound-pressure levels drop below the accuracy limits of both models. For downward refraction, the PE and FFP agree to within 1 dB except at deep interference minima. Parabolic equation calculations are also compared to measured values of excess attenuation for 15 different combinations of frequencies and ranges. In general, the PE model gives good agreement with the average experimental values. For upward refraction at the highest frequency (630 Hz), however, the PE predicts a strong shadow zone that is not observed in the data.