Development of the Modern Theory of Sound Propagation in the Turbulent Atmosphere PDF Download
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Languages : en
Pages : 0
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The foundations of the modern theory of sound propagation and scattering in a homogeneous and isotropic atmospheric turbulence are developed: The sound scattering cross-section for von Karman spectra of temperature and wind velocity fluctuations is calculated; the rigouros theory of line of sight sound propagation in an atmosphere with Kolmogorov, Gaussian and von Karman spectra of temperature and wind velocity fluctuations is developed; a new theoretical formulation of the interference of the direct wave from source to receiver and that reflected from the ground in a turbulent atmosphere is presented; the sound scattering cross section in an atmosphere with arbitrary profiles of temperature and wind velocity is calculated; some predictions of the modern theory are verified experimentally; correct wideangle parabolic equations for sound waves in a turbulent atmosphere are derived and used for numerical simulations of sound propagation. The modern theory has already been adopted by scientists for calculations of sound propagation in turbulent media and as a basis for development of new acoustic remote sensing techniques of the atmosphere and ocean in several countries and organizations including the U.S. Army Research Laboratory.
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Languages : en
Pages : 0
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Book Description
The foundations of the modern theory of sound propagation and scattering in a homogeneous and isotropic atmospheric turbulence are developed: The sound scattering cross-section for von Karman spectra of temperature and wind velocity fluctuations is calculated; the rigouros theory of line of sight sound propagation in an atmosphere with Kolmogorov, Gaussian and von Karman spectra of temperature and wind velocity fluctuations is developed; a new theoretical formulation of the interference of the direct wave from source to receiver and that reflected from the ground in a turbulent atmosphere is presented; the sound scattering cross section in an atmosphere with arbitrary profiles of temperature and wind velocity is calculated; some predictions of the modern theory are verified experimentally; correct wideangle parabolic equations for sound waves in a turbulent atmosphere are derived and used for numerical simulations of sound propagation. The modern theory has already been adopted by scientists for calculations of sound propagation in turbulent media and as a basis for development of new acoustic remote sensing techniques of the atmosphere and ocean in several countries and organizations including the U.S. Army Research Laboratory.
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Languages : en
Pages : 0
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Three-dimensional models of anisotropic and inhomogeneous spectra of temperature and wind velocity fluctuations in unstable atmospheric boundary layers have been developed, modified or extended. Furthermore, theories of sound propagation through anisotropic, inhomogeneous, and intermittent atmospheric turbulence have been developed. These theories allow consideration of different geometries of sound propagation: line-of-sight sound propagation, interference of the direct and ground reflected waves, sound scattering into a refractive shadow zone, and waveguide sound propagation. Using the spectra developed or adopted from the literature, it was shown that anisotropy, inhomogeneity, and intermittency of atmospheric turbulence can significantly affect the statistical moments of a sound field for these geometries. Some of the theoretical results obtained have been verified experimentally. Two related tasks have also been accomplished. First, a new scheme of source localization in the atmosphere by means of acoustic tomography was proposed. The scheme accounts for sound refraction in the atmosphere and allows retrieval of vertical profiles of temperature and wind velocity. Secondly, it was shown that, in many cases, the effects of sound refraction on acoustic remote sensing of wind velocity and the structure parameters of temperature and velocity fluctuations are significant. Algorithms were developed to account for these effects in acoustic remote sensing of the atmosphere.
Author: Thomas Rossing
Publisher: Springer Science & Business Media
ISBN: 0387304460
Category : Science
Languages : en
Pages : 1179
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Book Description
This is an unparalleled modern handbook reflecting the richly interdisciplinary nature of acoustics edited by an acknowledged master in the field. The handbook reviews the most important areas of the subject, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest research and applications are incorporated throughout, including computer recognition and synthesis of speech, physiological acoustics, diagnostic imaging and therapeutic applications and acoustical oceanography. An accompanying CD-ROM contains audio and video files.
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Languages : en
Pages : 11
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A stably stratified atmosphere supports propagation of internal gravity waves (IGW). These waves result in highly anisotropic fluctuations in temperature and wind velocity that are stretched in a horizontal direction. As a result, (IGW) can significantly affect propagation of sound waves in nighttime boundary layers and infrasound waves in the stratosphere. In this paper, a theory of sound propagation through, and scattering by, (IGW) is developed. First, 3D spectra of temperature and wind velocity fluctuations due to (IGW), which were recently derived in the literature for the case of large wave numbers, are generalized to account for small wave numbers. The generalized 3D spectra are then used to calculate the sound scattering cross section in an atmosphere with (IGW). The dependencies of the obtained scattering cross section on the sound frequency, scattering angle, and other parameters of the problem are qualitatively different from those for the case of sound scattering by isotropic turbulence with the von K rm n spectra of temperature and wind velocity fluctuations. Furthermore, the generalized 3D spectra are used to calculate the mean sound field and the transverse coherence function of a plane sound wave propagating through (IGW). The results obtained also significantly differ from those for the case of sound propagation through isotropic turbulence.
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Category :
Languages : en
Pages : 198
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Book Description
Propagation of sound waves close to the ground is a complex problem involving many interesting mechanisms. In addition to geometrical spreading and molecular absorption, which are reasonably well understood, the three main mechanisms which influence the acoustic field are reflection with phase change due to the finite impedence of the ground, refraction by wind and temperature gradients, and scattering by atmospheric turbulence. Outdoor sound propagation in a turbulent medium is not a well understood process and has only recently begun to receive serious attention. This report is the first of a series of reports on sound propagation through a turbulent atmosphere. It documents the experimental configuration and describes data analysis. The data analysis includes plots of the real and imaginary parts of the acoustic pressure as a function of time (scatter plots), probability of observing a particular amplitude, and the more familiar structure functions. A preliminary analysis of data suggests reasonable agreement in structure functions at frequencies of 500 Hz and above. At lower frequencies, phase and log amplitude structure functions are both larger than predicted from theory. A tentative explanation for this difference is under development and will be presented in the third of the three volume series. The second volume will be devoted to refractive effects. Keywords: Computer programs; Outdoor sound.
Author: Vladimir E. Ostashev
Publisher:
ISBN:
Category : Atmosphere
Languages : en
Pages : 15
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Book Description
Most previous research on sound propagation in the turbulent atmosphere has focused on nearly horizontal propagation. Sound propagation over vertical and slanted paths is fundamentally different from horizontal propagation in that the variances and length scales of the turbulence depend on the height above the ground. In this paper, propagation over vertical and slanted paths is studied using approaches and methods developed for wave propagation through inhomogeneous, random media. Statistical characteristics of sound signals such as the extinction coefficient of the mean sound field, the strength parameter, the transverse mutual coherence function, the coherence radius, and the correlation functions and variances of the phase and log-amplitude fluctuations are calculated for arbitrary spectra of temperature and wind velocity fluctuations, and then specialized to the von Kármán model for the turbulence spectra. The extinction coefficient and coherence radius are analyzed numerically for various meteorological conditions of the atmospheric boundary layer. The results obtained are compared with those for near-horizontal sound propagation. The theory has applications to localization of elevated sound sources with ground-based microphone arrays, and the detection of ground-based sources with elevated arrays.
Author: Richard H. Lyon
Publisher:
ISBN:
Category : Sound-waves
Languages : en
Pages : 28
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Author:
Publisher:
ISBN:
Category : Atmosphere
Languages : en
Pages : 1182
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Author: Vladimir Ostashev
Publisher:
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Category : Acoustical engineering
Languages : en
Pages : 20
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Author:
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Category :
Languages : en
Pages : 64
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Propagation of acoustic waves in the atmosphere is affected by several mechanisms. Two of the effects are the scattering of sound by small-scale atmospheric turbulence and fluctuation of the speed of sound gradients by the passage of large-scale atmospheric turbulence. Small- and large-scale atmospheric turbulence causes the acoustic waves to be altered by different mechanisms. Until recently, the majority of work in turbulence effect on acoustics has concentrated on the small-scale turbulence regime of the inertial subrange of the Kolmogorov spectrum. Earlier small-scale turbulence models have concentrated on the statistical-based work of Tatarski. Current turbulence models deal more with the structural nature of the turbulence because the statistical approach does not account for all of the turbulence effects being measured during acoustic propagation experiments. The large-scale turbulence problem cannot be handled very well with a statistical approach to atmospheric turbulence because the regime of the large-scale turbulence extends into the energy containing subrange or sometimes referred to as the source region. This report discusses the current and past turbulence models used to treat the effect of small- and large-scale turbulence on atmospheric acoustic propagation. (AN).
