Diffraction of sound around barriers: Comparison between procedures of forecasting in sound propagation in a quarry

The aim of this work is to compare the accuracy of numerical previsions of sound propagation in a quarry obtained with different algorithms with particular attention to the diffracted waves over barriers. Comparison is between the ISO 9613 Standard "Attenuation of sound during propagation outdoors", a new simplified algorithm based on the Huyghens principle, a pyramid beam tracing method. The ISO 9613 (parts 2) Standard proposes a method taking into account the meteorological conditions (K met). It also takes into account the effects caused by the propagation over soil with varying properties, shielding both from thin and thick obstacles as well as the effects of vegetation layers and excess attenuation. The new algorithm simplifies ISO codes proposing an easy method, specific for a quarry. Pyramid beam tracing, implemented in Ramsete, a sound propagation software, suited to simulate sound fields in large rooms and also outdoors. Experimental and simulated data have been used to built graphic plots, enabling a direct comparison of the results.