Benchmark cases for outdoor sound propagation models

Abstract

The computational tools available for prediction of sound propagation through the atmosphere have increased dramatically during the past decade. The numerical techniques include analytical solutions for selected index of refraction profiles, ray trace techniques which include interaction with a complex impedance boundary, a Gaussian beam ray trace algorithm, and more sophisticated approximate solutions to the full wave equation; the fast field program (FFP) and the parabolic equation (PE) solutions. This large array of computational approaches raises questions concerning under what conditions the various approaches are reliable and concerns about possible errors in specific implementations. This paper presents comparisons of predictions from the several models assuming a complex impedance ground and four atmospheric conditions. For the cases studied, it was found that the FFP and PE algorithms agree to within numerical accuracy over the full range of conditions and agree with the analytical solutions where available. Comparisons to ray solutions define regimes where ray approaches can be used. There is no attempt to compare calculated transmission losses to measurements.

Urban Noise Modelling in Boka Kotorska Bay

“…Due to the influence on the generated noise regarding to distance from the source (ferries), the selected experiment positions were at a distance from 5 m to 100 m from the ferries port. In order to obtain the noise prediction model as realistic as possible, care was taken that the meteorological conditions had been taken into account [15,16]. The experiment was conducted under conditions favourable to the sound propagation (dry weather, wind speed less than 5 m/s, without negative temperature gradient nearby).…”

A forward-advancing wave expansion method for numerical solution of large-scale sound propagation problems

“…Speed of sound gradients can be included in the models even though the mathem atical conditions for ray solutions are seldom met in the real life problem [24]. In most cases the sound speed and wind speed are assumed to vary linearly w'ith height.…”

“…Ray tracing has been used to predict outdoor sound propagation [17,[20][21][22][23][24][25][26][27].…”

Sensitivities of outdoor sound propagation predictions to environmental input parameters

“…The PE is an approximation to the Helmholtz wave equation and is one of the most powerful numerical methods effective for long-range, forward-wave propagation thought relatively general media. 5,6 Introduced at the beginning of the 1940s in order to solve electromagnetism problems, this theory has been applied to ocean acoustics and then to atmospheric sound propagation. 7 One of the PE developments, called GFPE ͑Green Function Parabolic Equation͒, was adapted for the atmospheric propagation by Gilbert and Di 8,9 at the beginning of the 1990s.…”