Heuristic model for outdoor sound propagation based on an extension of the geometrical ray theory in the case of a linear sound speed profile

L’Espérance, André; Nicolas, Jean; Herzog, Philippe; Daigle, Gilles A.

doi:10.1016/0003-682x(92)90022-k

Cited by 40 publications

(31 citation statements)

References 26 publications

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“…In our implementation, the atmosphere is divided into a grid of small rectangular cells. The cell division is chosen such that the change in the sound speed within each cell is small enough to be approximated by a linear profile, so that an analytical solution 8 can be used within each cell to determine the ray propagation trajectory. The rule of thumb is to set the grid size at 1 / 10 of the length scale of the fastest changing condition.…”

Section: The Ray Tracing Modelmentioning

confidence: 99%

“…8 However, as is common in all geometrical ray tracing methods, the procedure will fail to predict the sound pressure in the shadow zone of an upward refracting atmosphere. By definition no geometrical rays can penetrate into the shadow.…”

Section: The Ray Tracing Modelmentioning

confidence: 99%

“…However, this is not a practical solution in view of its limitations concerning the sound speed profile and turbulence. The comparisons published by L'Espérance et al 8 show that it can substantially over-estimate the attenuation in real life situations where turbulence is present. For realistic atmospheric conditions that include turbulence, a common approach is to introduce empirical scattering to the ray trajectory 9 or to use empirical estimates of the sound pressure.…”

Section: The Ray Tracing Modelmentioning

confidence: 99%

“…[6][7][8][9] All are based on geometrical considerations. The variations come from the different degrees of approximation they place on the wave behavior along the propagation path.…”

Section: Introductionmentioning

confidence: 99%

“…The basic ray tracing model is based on a discretized implementation of the heuristic model. 8 In an upward refracting case where a shadow is formed, the diffraction of sound into the shadow is assumed here to be analogous to the geometrical diffraction by an equivalent barrier in a homogeneous atmosphere. The scattering into the shadow zone due to turbulence is calculated from statistics that are determined from a Gaussian turbulence model of the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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An analytical model for turbulence scattered rays in the shadow zone for outdoor sound propagation calculation

Lam¹

2009

The Journal of the Acoustical Society of America

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In outdoor sound propagation, an inherent problem of the ray tracing method is its inability to determine the sound pressure level in the shadow zone, where geometrical rays do not penetrate. This is a serious problem in a turbulent atmosphere where significant sound energy will be scattered into the shadow. Empirical corrections that are determined from measurements or numerical simulations are limited to situations within the bounds of the empirical corrections. This paper describes a different approach where the ray tracing model is modified analytically into a scattered ray model. Rays are first diffracted from the shadow boundary, which is determined by the geometrical ray paths. The diffracted rays are then scattered by turbulence in their way to the receiver. The amount of scatter is determined from turbulence statistics that are determined from a Gaussian turbulence model. Most of the statistics are determined analytically except one element, which is determined empirically from numerical simulations. This turbulence scattered ray model is shown to have good accuracy against calculations based on the parabolic equation, and against previously published measurement data. It was found that the agreement is good both with and without turbulence, at distance up to 2 km from the shadow boundary.

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Section: The Ray Tracing Modelmentioning

confidence: 99%

Section: The Ray Tracing Modelmentioning

confidence: 99%

Section: The Ray Tracing Modelmentioning

confidence: 99%

“…[6][7][8][9] All are based on geometrical considerations. The variations come from the different degrees of approximation they place on the wave behavior along the propagation path.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An analytical model for turbulence scattered rays in the shadow zone for outdoor sound propagation calculation

Lam¹

2009

The Journal of the Acoustical Society of America

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Calculation of Ray Path Distances and Propagation Times for the Nord2000 Model

Hansen

Doolan

Hansen

2017

Wind Farm Noise: Measurement, Assessment

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Application of a ray theory model to the prediction of noise emissions from isolated wind turbines and wind parks

Prospathopoulos

Voutsinas

2006

Wind Energy

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Various propagation models have been developed to estimate the level of noise near residential areas. Predictions and measurements have proven that proper modelling of the propagation medium is of particular importance. In the present work, calculations are performed using a ray theory methodology. The ray trajectory and transport equations are derived from the linear acoustics equations for a moving medium in three dimensions. Ground and atmospheric absorption, wave refraction and diffraction and atmospheric turbulence are taken into account by introducing appropriate coefficients in the equations. In the case of a wind turbine (W/T) it is assumed that noise is produced by a point source located at the rotor centre. Given the sound power spectrum, the noise spectrum at the receiver is obtained by solving the axisymmetric propagation problem. The procedure consists of (a) finding the eigenrays, (b) calculating the energy losses along the eigenrays and (c) synthesizing the sound pressure level (SPL) by superposing the contributions of the eigenrays. In the case of a wind park the total SPL is calculated by superposing the contributions of all W/Ts. Application is made to five cases of isolated W/Ts in terrains of varying complexity. In flat or even smooth terrain the predictions agree well with the measurements. In complex terrain the predictions can be considered satisfactory, taking into account the assumption of constant wind velocity profile. Application to a wind park shows clearly the influence of the terrain on the wind velocity and consequently on the SPL. Copyright © 2006 John Wiley &Sons, Ltd.

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Heuristic model for outdoor sound propagation based on an extension of the geometrical ray theory in the case of a linear sound speed profile

Cited by 40 publications

References 26 publications

An analytical model for turbulence scattered rays in the shadow zone for outdoor sound propagation calculation

An analytical model for turbulence scattered rays in the shadow zone for outdoor sound propagation calculation

Calculation of Ray Path Distances and Propagation Times for the Nord2000 Model

Application of a ray theory model to the prediction of noise emissions from isolated wind turbines and wind parks

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