On the attenuation of sound by turbulence

Brown, Edmund H.; Clifford, S. F.

doi:10.1121/1.381159

Cited by 53 publications

(23 citation statements)

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“…This model is able to consider multiple scattering, whereas previous models were restricted to the hypothesis of single scattering. Turbulent scattering was also studied by Brown 2 and Brown & Clifford 3,4 in the context of propagation through a turbulent atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Numerical assessment of the scattering of acoustic waves by turbulent structures

Clair

Gabard

2015

21st AIAA/CEAS Aeroacoustics Conference

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The scattering of harmonic sound waves by a single vortex is studied to provide some insight into the more complex problem of sound scattering by a turbulent layer. Two different methods are used to model the scattering by a steady vortex or by a vortex convected in a uniform mean flow. The first method is based on the linearized Euler equations in the frequency domain and is used to study the scattering by a steady vortex. The speed of this method allows to perform a study of the spatial scattering of a plane wave over a wide range of frequencies, where analytical models previously developed are restricted either to low or high frequencies. The second method uses a finite difference solver, also based on the linearized Euler equations but in the time domain. This method is used to study the scattering by a vortex convected in a uniform mean fow, where a spectral scattering occurs in addition to the spatial scattering. A parametric study is realized, focusing on four parameters including the source frequency and the convection velocity. The spectra deduced from this study show a pattern similar to the haystacking observed in existing studies of the scattering by a turbulent shear layer. Some of the trends deduced from the parametric study are also in agreement with these previous observations. Thus, the detailled study of the scattering by a single eddy is able to provide further understanding of the turbulence scattering.

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Section: Introductionmentioning

confidence: 99%

Numerical assessment of the scattering of acoustic waves by turbulent structures

Clair

Gabard

2015

21st AIAA/CEAS Aeroacoustics Conference

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“…Excess attenuation can also be caused by turbulent beam broadening (Brown and Clifford, 1976). This mechanism can be included in the radar equation by increasing the acoustic wavelength (Neff, 1978).…”

Section: Numerical Resultsmentioning

confidence: 99%

A general radar equation for the bistatic acoustic sounder

Moulsley

Cole

1980

Boundary-Layer Meteorol

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A radar equation which can be applied to any bistatic acoustic sounder is derived. The equation reduces to the expression normally used for the special case of the monostatic sounder. Numerical results using this equation are given for specific acoustic sounders, including the relative contributions to the scattering from the temperature and velocity parameters (C: and C:), the effect of wind speed on the scattered intensity and the measurement of horizontal wind velocity.

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“…The first two are functions of temperature, humidity and to a lesser extent pressure, and can be accurately calculated from measurements of these parameters (Sutherland, 1975) for any given frequency. Excess attenuation is the term used for loss of acoustic intensity due to refraction by the wind (Neff, 1978;Moulsley and Cole, 1980) and turbulent beam broadening (Brown and Clifford, 1976;Clifford and Brown, 1980). Refraction results in a change in the angle of arrival of the backscattered sound which gives rise to loss of received intensity due to the lower-sensitivity of the receiving antenna off-axis.…”

Section: Acoustic Soundermeasurementsmentioning

confidence: 99%

A quantitative comparison of horizontal and vertical acoustic sounding with in-situ measurements

Moulsley

Asimakopoulos

Helmis

et al. 1985

Boundary-Layer Meteorol

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In this paper, we present some results on an experiment to test the accuracy and utility of a horizontally-aimed acoustic sounder. A high-frequency, high-resolution mini-sounder was mounted on the mast of the Boulder Atmospheric Observatory aimed in the cross-wind direction. Measurements of C$, wind velocity and temperature and velocity variances were obtained under both stable and unstable conditions. These measurements were found to be in agreement with the equivalent values obtained, where appropriate, by the tower-fixed instrumentation and a vertically-pointed sounder, confirming the accuracy of the horizontal sounder. In addition, some information into the horizontal structure of plumes and gravity waves was obtained along with evidence of lack of excess attenuation at least for lengths within the unambiguous range of mini-sounders.

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On the attenuation of sound by turbulence

Cited by 53 publications

References 0 publications

Numerical assessment of the scattering of acoustic waves by turbulent structures

Numerical assessment of the scattering of acoustic waves by turbulent structures

A general radar equation for the bistatic acoustic sounder

A quantitative comparison of horizontal and vertical acoustic sounding with in-situ measurements

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