Some practical considerations for predicting outdoor sound propagation in the presence of wind and temperature gradients

Taherzadeh, Shahram; Li, K.M.; Attenborough, Keith

doi:10.1016/s0003-682x(97)00069-8

Cited by 7 publications

(4 citation statements)

References 13 publications

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“…In this example, 1000 layers ͑with thickness increasing with height͒ were used in the FFP calculation. 20 The thickness of each layer near the ground plane was of order of a millimeter for accurate discretization of the logarithmic sound speed profile. The problem for the ray-trace method ͑as for the WKBAiry formulation of the FFP 20 ͒ arises from violation of the approximation that requires small change in sound/wind ve- locity per wavelength.…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

An improved ray-tracing algorithm for predicting sound propagation outdoors

Taherzadeh

Attenborough

1998

The Journal of the Acoustical Society of America

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A new ray-tracing method for predicting the sound field near a flat impedance ground in a refracting atmosphere is developed that includes the effect of vector wind and turbulence explicitly. Improvements on previous ray-tracing schemes include the use of a generalized Snell's law, an integration by means of a Gaussian quadrature, and a bracketing method for finding the ray paths. For the turbulence calculations, the interray coherence is determined from turning point heights rather than from integrals along the ray paths. A more efficient algorithm is developed for computing the sound field above an impedance plane in a realistic atmosphere. Despite the inherent limitations of the ray-trace approach, particularly in respect of logarithmic wind profiles, the algorithm is valid over a wide range of practical situations.

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Section: Numerical Results and Discussionmentioning

confidence: 99%

An improved ray-tracing algorithm for predicting sound propagation outdoors

Taherzadeh

Attenborough

1998

The Journal of the Acoustical Society of America

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“…In many instances the profiles are assumed to be logarithmic, based on simple similarity theory and surfacelayer assumptions [2][3][4]. In some cases the profiles are just classified by the effect they have on sound propagation, namely upward-or downward-refracting profiles [5,6].…”

Section: Introductionmentioning

confidence: 99%

Phase Error Sensitivity to the Inversion Strength and Depth of the Boundary Layer in a Conventionally Neutral Regime

Libianchi,

Kelly,

Shabalina

et al. 2024

Proceedings of the 10th Convention of the European Acoustics Association Forum Acusticum 2023

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In outdoor sound propagation, the variation of wind speed with height plays an important role and a logarithmic profile is often assumed. This is an accurate description in a neutral boundary layer according to MOST. However, the neutral boundary layer can be either truly neutral or conventionally neutral depending on the stability condition at the top of the ABL. While the logarithmic profile is suitable in a truly neutral regime, the conventionally neutral is more commonly found. This regime is characterized by a stable stratification aloft that result in super geostrophic wind speed close to the top of the ABL and higher speed and steeper gradient close to the ground than predicted by the logarithmic profile. This work uses numerical simulations based on the Crank-Nicholson parabolic equation to derive the sensitivity of the phase to the ABL depth and inversion strength as a function of the distance from the source. The results show that a stronger inversion increases the phase differences that can be as large as 60 • already at 1 km from the source. Stronger inversions and a deeper ABL produce more complex interference on the ground, showing only after approximately 2 km, that af-

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“…In many outdoor sound propagation studies, the effect of an inhomogeneous and/or moving medium is incorporated via simplified models for the vertical profiles of wind and temperature (and thus, the speed of sound). In many instances, the profiles are assumed to be logarithmic, based on simple similarity theory and surface-layer assumptions (Hornikx et al, 2010;Taherzadeh et al, 1998;Van Den Berg, 2004). In some cases, the profiles are just classified by the effect they have on sound propagation, namely, upwardor downward-refracting profiles (e.g., Junker et al, 2007;Salomons, 1998).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of the predicted acoustic pressure field to the wind and temperature profiles in a conventionally neutral boundary layer

Libianchi

Shabalina

Kelly

et al. 2023

The Journal of the Acoustical Society of America

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Simulations are widely used to predict noise emissions from traffic, railroad, aircraft, and wind farms and for sound field control. The latter employs multiple sources interacting and it requires accurate phase information. Acoustic models require precise characterization of the medium properties. The logarithmic profile is one of the most commonly used forms to model the wind speed. However, this profile is accurate only in neutral conditions, i.e., when there is not heat flux at the surface. The conventionally neutral boundary layer (CNBL) is the most frequently occurring neutral regime. In this case, the logarithmic profile underestimates the wind speed. This paper analyses the effect that this modelling error has on the sound field close to the ground, for near-ground sources. The first section introduces an approximation of the wind and temperature profiles in such a regime. Afterwards, the sound fields corresponding to the logarithmic profile, a representative CNBL profile, and three more test cases are simulated using the Crank–Nicholson parabolic equation; these are compared employing different metrics. The difference in wind speed introduces a phase error that increases with distance. Moreover, wind speed underestimations also lead to underpredictions of the energy refracted downward.

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Some practical considerations for predicting outdoor sound propagation in the presence of wind and temperature gradients

Cited by 7 publications

References 13 publications

An improved ray-tracing algorithm for predicting sound propagation outdoors

An improved ray-tracing algorithm for predicting sound propagation outdoors

Phase Error Sensitivity to the Inversion Strength and Depth of the Boundary Layer in a Conventionally Neutral Regime

Sensitivity of the predicted acoustic pressure field to the wind and temperature profiles in a conventionally neutral boundary layer

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