Using the Green's Function Parabolic Equation Method to Predict Sound Propagation Outdoors in the Presence of Weather and Complex Terrain PDF Download
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Author: Whitney L. Coyle
Publisher:
ISBN:
Category :
Languages : en
Pages : 146
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Author: Whitney L. Coyle
Publisher:
ISBN:
Category :
Languages : en
Pages : 146
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Author: Keith Attenborough
Publisher: CRC Press
ISBN: 1482295024
Category : Technology & Engineering
Languages : en
Pages : 457
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Book Description
Predicting Outdoor Sound provides a scholarly yet practical examination of the phenomena that affect outdoor sound close to the ground and its prediction. It is devoted to bringing together theories and data to give both researchers and practitioners the basis for deciding which model to use in a given situation. The book covers recent advances in
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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In complex environments the modelling of outdoor sound propagation implies to take into account the mixed influence of ground characteristics (topography, obstacles, impedance, etc.) and atmospheric conditions (refraction and turbulence). During the last decade significant progress has been made in the modelling of sound propagation over distances ranging from hundreds meters to kilometres, and the agreement between calculated and measured fields has been greatly improved. New developments appear in the parabolic-equation method. In this paper we present a method which evaluates the propagation of an acoustic wave above uneven terrains including realistic meteorological parameters. In our approach the effects of the topography are modelled using appropriate rotated co-ordinates systems in order to treat the non-flat ground as a succession of flat domains. We also examine the influence of scale resolution on numerical simulation of long range sound propagation through the turbulent atmosphere. Currently, we generate the turbulence using a Random Fourier Modes technique, such that the turbulent fluctuation at any point in the medium (either scalar or vectorial in nature) is calculated from the sum of a chosen number of modes. Our model of outdoors sound propagation is validated both with classical numerical benchmark cases and recent outdoor experiments.
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ISBN:
Category :
Languages : en
Pages : 68
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Parabolic equations can be used to find approximate solutions to the reduced wave equation. By reducing the equation to first order in the range derivative, the solution can be found by marching forward in range. Several numerical techniques can be applied to the solution of the parabolic equation (PE), including finite elements, finite differences, and a Fourier Transform method known as the split-step PE. The split-step solves for each range increment in two steps. First, it propagates forward through a homogenous atmosphere, using the Fourier Transform. It then applies a multiplicative phase correction for index-of-refraction variations. The split-step method leads to a computationally fast model for two reasons: the range steps are several wavelengths, and the Fourier Transform can be evaluated by a Fast Fourier Transform. One of the difficulties encountered in applying the split-step PE to outdoor sound propagation is accommodation of the complex ground impedance. The Green's function PE is a split-step PE which solves for the one-dimensional height-dependant Green's function in a homogenous atmosphere. This Green's function incorporates the complex ground impedance as a complex, angle-dependant plane-wave reflection coefficient. (AN).
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 768
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Author: M. West
Publisher:
ISBN:
Category : Atmosphere
Languages : en
Pages :
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Author: Santosh Parakkal
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
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The aim of this work is to establish an accurate and practical numerical method to determine the acoustic field at any point on the Earth's surface in the presence of range-dependent (atmosphere and terrain) conditions. In the sound propagation over irregular terrain, the approach is to map the terrain coordinates in to a flat or smooth earth coordinate system. This results in a modified parabolic equation (PE) which is subjected to modified surface boundary conditions. The Beilis and Tappert PE method is studied in applications of sound propagation over irregular terrain. The correct ground impedance boundary condition for porous ground is derived and applied to the propagation predictions over hills with different slope angles. The Generalized Polar Coordinate parabolic equation method (Polar-PE method) was developed partly to provide a very solid numerical benchmark to the Beilis and Tappert PE method. The Polar-PE method makes it possible to compute sound propagation over arbitrary large-scale terrain where the local radii of curvature are large compared to the acoustic wavelength. Both approaches are outlined and a comparison is made of the accuracy and computational demands of the methods. Also, the theoretical predictions from the two methods are compared to acoustic field measurements.
Author: Marta Galindo Arranz
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Marta Galindo Arranz
Publisher:
ISBN:
Category :
Languages : en
Pages : 163
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Author: David Hattis Marlin
Publisher:
ISBN:
Category : Atmospheric turbulence
Languages : en
Pages : 336
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