Modeling of random ground roughness effects by an effective impedance and application to time-domain methods

Faure, Olivier; Gauvreau, Benoît; Junker, Fabrice; Lafon, Philippe; Bourlier, Christophe

doi:10.1016/j.apacoust.2016.11.019

Cited by 4 publications

(2 citation statements)

References 35 publications

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“…Thus, the first ground dip is located at a frequency of 500 Hz for the unperturbed problem, but in the random case it is at 495 Hz for L ¼ 0.5 m and 490 Hz for L ¼ 5 m. This effect was also noticed for random roughness. 22 Besides, the agreement between the mean pressure computed with the Bourret approximation and by an ensemble-averaging over 200 realizations is satisfactory. In particular, for L ¼ 0.5 m, the curves depicting these two solutions are almost superimposed for both receiver heights.…”

Section: A Numerical Specificationmentioning

confidence: 70%

“…In acoustics, it has been used formerly to derive the average sound field or effective media quantities for multiple scattering problems, such as the propagation through a turbulent medium 4 or through a layer of scatterers. 21 Recently, based on this approach, Faure et al 22 have proposed an effective admittance to represent the reflection over rough surfaces.…”

Section: B Analytical Solution In the Fourier Spacementioning

confidence: 99%

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Sound propagation over the ground with a random spatially-varying surface admittance

Dragna

Blanc‐Benon

2017

The Journal of the Acoustical Society of America

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Sound propagation over the ground with a random spatially-varying surface admittance is investigated. Starting from the Green's theorem, a Dyson equation is derived for the coherent acoustic pressure. Under the Bourret approximation, an explicit expression is deduced and an effective admittance that depends on the correlation function of the admittance fluctuations is exhibited. An asymptotic expression at long range is then obtained. Influence of the randomness on the amplitude of the reflection coefficient and on the wavenumbers of the surface wave component is analyzed. Afterwards, numerical simulations of the linearized Euler equations are carried out and the coherent pressure obtained by an ensemble-averaging over 200 realizations of the admittance is found to be in good agreement with the analytical solution. In the considered examples of grounds, the mean intensity is shown to be similar to the intensity in the non-random case, except near interferences that are smoothened out due to randomness. It is however exemplified that the intensity fluctuations can be large, especially near destructive interferences.

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Section: A Numerical Specificationmentioning

confidence: 70%

Section: B Analytical Solution In the Fourier Spacementioning

confidence: 99%

Sound propagation over the ground with a random spatially-varying surface admittance

Dragna

Blanc‐Benon

2017

The Journal of the Acoustical Society of America

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Propagation of spherical weak blast waves over rough periodic surfaces

et al. 2021

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Efficient prediction of acoustic pulses accounting for fractional travel time

Vecherin

Albert

2018

The Journal of the Acoustical Society of America

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Predicting a full waveform of an acoustic broadband signal propagating over different impedance surfaces is a stringent test of both the method used in the modeling of propagation and the surface impedance models. It has been shown that predicted waveforms might be sensitive to the fractional travel time, when the propagation time of the pulse does not equal an integer number of computational time steps. A method overcoming this issue is developed and demonstrated for different propagation conditions: a pulse propagating over a snow layer, frozen ground, and their combinations along the propagating path with homogeneous and vertically stratified atmosphere for a range of 60 m. For the numerical simulations, a conventional one-way parabolic equation with the Crank-Nicholson numerical algorithm is modified to improve computational efficiency and insure that the experimental time of arrival and spatial location of the receiver are matched exactly to the digital grids used in the simulations. The results are in a good agreement with experimental measurements and prior knowledge, and confirm that physical properties of a snow layer, sublayer ground, atmospheric conditions, and the order of range dependent ground properties affect the pulse waveforms.

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Modeling of random ground roughness effects by an effective impedance and application to time-domain methods

Cited by 4 publications

References 35 publications

Sound propagation over the ground with a random spatially-varying surface admittance

Sound propagation over the ground with a random spatially-varying surface admittance

Propagation of spherical weak blast waves over rough periodic surfaces

Efficient prediction of acoustic pulses accounting for fractional travel time

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