Long-term, global-scale statistics of sound propagation

The near-surface sound levels emitted due to a point source show a large variability caused by sound propagation through changing meteorological conditions. To assess this variability, this study uses a numerical model of sound propagation which accounts for ground reflection, atmospheric refraction, and turbulence effects. The atmospheric inputs to the model-including turbulence-are calculated from Numerical Weather Prediction data. The method is used to investigate the relative sound levels at a range of 1.5 km from a 40 Hz sound source. The outstanding diversity of sound propagation conditions is illustrated over the globe. Over the long term, the sound propagation climates at selected sites are found to be modulated by the dominant wind regimes, the seasonal and diurnal cycles. The explored sensitivities stress the need for a careful assessment of sound scattering by turbulence and absorption by the surface.