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Using The Greens Function Parabolic Equation Method To Predict Sound Propagation Outdoors In The Presence Of Weather And Complex Terrain
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Book Synopsis Using the Green's Function Parabolic Equation Method to Predict Sound Propagation Outdoors in the Presence of Weather and Complex Terrain by : Whitney L. Coyle
Download or read book Using the Green's Function Parabolic Equation Method to Predict Sound Propagation Outdoors in the Presence of Weather and Complex Terrain written by Whitney L. Coyle and published by . This book was released on 2012 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Predicting Outdoor Sound by : Keith Attenborough
Download or read book Predicting Outdoor Sound written by Keith Attenborough and published by CRC Press. This book was released on 2006-11-17 with total page 457 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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
Book Synopsis Outdoor Sound Propagation Modelling in Complex Environments: Recent Developments in the Parabolic Equation Method by :
Download or read book Outdoor Sound Propagation Modelling in Complex Environments: Recent Developments in the Parabolic Equation Method written by and published by . This book was released on 2006 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Fast Parabolic Approximations for Acoustic Propagation in the Atmosphere by :
Download or read book Fast Parabolic Approximations for Acoustic Propagation in the Atmosphere written by and published by . This book was released on 1995 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).
Book Synopsis Atmospheric and Terrain Effects on Acoustic Propagation by : M. West
Download or read book Atmospheric and Terrain Effects on Acoustic Propagation written by M. West and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Theoretical Models to Investigate Sound Propagation Over Irregular Terrain by : Santosh Parakkal
Download or read book Theoretical Models to Investigate Sound Propagation Over Irregular Terrain written by Santosh Parakkal and published by . This book was released on 2010 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2004 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Report written by Marta Galindo Arranz and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Parabolic Equation Method for Outdoor Sound Propagation by : Marta Galindo Arranz
Download or read book The Parabolic Equation Method for Outdoor Sound Propagation written by Marta Galindo Arranz and published by . This book was released on 1996 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Acoustic Propagation Through Turbulence by : David Hattis Marlin
Download or read book Acoustic Propagation Through Turbulence written by David Hattis Marlin and published by . This book was released on 1996 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis On the Long Range Propagation of Sound Over Irregular Terrain by : M. S. Howe
Download or read book On the Long Range Propagation of Sound Over Irregular Terrain written by M. S. Howe and published by . This book was released on 1984 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Nonlinear Acoustic Wave Propagation in Complex Media by : Thomas Leissing
Download or read book Nonlinear Acoustic Wave Propagation in Complex Media written by Thomas Leissing and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research aims at developing and validating a numerical model for the study of blast wave propagation over large distances and over urban environments. The approach consists in using the Nonlinear Parabolic Equation (NPE) model as a basis. The model is then extended to handle various features of sound propagation outdoors (non-flat ground topographies, porous ground layers, etc.). The NPE is solved using the finite-difference method and is proved to be in good agreement with other numerical methods. This deterministic model is then used as a basis for the construction of a stochastic model for sound propagation over urban environments. Information Theory and the Maximum Entropy Principle enable the construction of a probabilistic model of uncertainties, which takes into account the variability of the urban environment within the NPE model. Reference results are obtained with an exact numerical method and allow us to validate the theoretical developments and the approach used.
Book Synopsis Modeling of Sound Propagation in Forests Using the Transmission Line Matrix Method by : Pierre Chobeau
Download or read book Modeling of Sound Propagation in Forests Using the Transmission Line Matrix Method written by Pierre Chobeau and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The prediction of sound propagation in presence of forest remains a major challenge for the outdoor sound propagation community. Reference numerical models such as the Transmission Line Matrix (TLM) method can be developed in order to accurately predict each acoustical phenomenon that takes place inside forest. The first need for the TLM method is an efficient theory-based absorbing layer formulation that enables the truncation of the numerical domain. The two proposed absorbing layer formulations are based on the approximation of the perfectly matched layer theory. The most efficient proposed formulation is shown to be equivalent to wave propagation in a lossy media, which, in the TLM method formulation, is introduced using an additional dissipation term. Then, the ability of the TLM method for the simulation of scattering is studied comparing the numerical results to both analytical solutions and measurements on scale models. Lastly, the attenuation of acoustic levels by a simplified forest is numerically studied using several arrangements of cylinders placed normal to either reflecting or absorbing ground. It is observed that randomly spaced arrangements are more inclined to attenuate acoustic waves than periodic arrangements. Moreover, the sensitivity to the density, the length of the array and the ground absorption is tested. The main trend shows that the density and the distribution are two important parameters for the attenuation. In future work, it can be interesting to look at the sensitivity of each parameter. This study could then be used to relate the morphology (i.e. distribution, density, length) of a forest to the acoustical properties of the forest.
Book Synopsis The Use of the Parabolic Equation Method in Sound Propagation Modelling by : Finn Jensen
Download or read book The Use of the Parabolic Equation Method in Sound Propagation Modelling written by Finn Jensen and published by . This book was released on 1975 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: The parabolic equation method (PE method) is the latest major development in the field of acoustic modelling. A detailed description of the derivation of the parabolic equation from the wave equation is given together with a description of a marching solution technique based on Fast Fourier Transforms (FFT). Limitations on the method in terms of allowable step length in range, number of FFT points to be used, and restrictions on pressure field behaviour in order to obtain a stable solution, are mentioned. Furthermore, numerical examples of propagation predictions are given for both shallow and deep water cases, with and without bottom absorption, and for both range-dependent and range-independent environmental conditions.
Book Synopsis Application of the Beilis-Tappert Parabolic Equation Method to Sound Propagation Over Irregular Terrain by : Santosh Parakkal
Download or read book Application of the Beilis-Tappert Parabolic Equation Method to Sound Propagation Over Irregular Terrain written by Santosh Parakkal and published by . This book was released on 2012 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Generalized Earth-flattening Transformation for Sound Propagation Over Irregular Terrain by : Santosh Parakkal
Download or read book A Generalized Earth-flattening Transformation for Sound Propagation Over Irregular Terrain written by Santosh Parakkal and published by . This book was released on 2007 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A practical conformal mapping method is derived that is applicable to sound propagation over realistic irregular terrain. Coupled with a parabolic equation model, the mapping method predicts transmission loss that is in good agreement with data from the Joint Acoustic Propagation Experiment (JAPE). A useful aspect of the mapping method is that, in the mapped coordinates, the terrain is flat, but the effective sound speed is c/ j, where c is the sound speed derived from meteorology, and J is the Jacobian of the conformal mapping, Thus, the effect of irregular terrain can be represented within the same framework as for sound-speed gradients due to temperature and wind. In general, terrain-generated sound speed gradients are 50-200 times greater than those due to temperature and wind and hence are critical for accurately predicting sound propagation over realistic irregular terrain.
Book Synopsis Integral Equation Methods for Acoustic Scattering by Infinite Obstacles and Surfaces by : Andrew Tristan Peplow
Download or read book Integral Equation Methods for Acoustic Scattering by Infinite Obstacles and Surfaces written by Andrew Tristan Peplow and published by . This book was released on 1996 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is concerned with the mathematical and numerical modelling of sound propagation over infinite surfaces in two and three-dimensions. In particular we consider the prediction, in a homogeneous medium, of sound propagation from a source in a cutting out onto flat surrounding ground, and scattering by an infinite rigid obstacle in three dimensions. In Chapter 2 a boundary integral formulation for the two-dimensional Helmholtz equation in a locally-perturbed half-plane with impedance boundary condition is developed to calculate sound propagation out of a cutting onto the surrounding terrain. A main result in this chapter is to show that the integral equation is uniquely solvable. A simple but robust boundary element method is developed and experimental convergence rates and numerical predictions are presented. Chapter 3 is concerned with the asymptotic behaviour of solutions at infinity to multidimensional second kind integral equations. A general second kind integral equation set on an infinite cylindrical surface is analysed in Chapter 4. Under certain conditions it is shown that an approximate solution, obtained by solving an integral equation on a finite cylindrical surface of length 2a, converges to the original solution, as a tends to infinity. Uniform stability and convergence results for a piecewise constant boundary element method for the truncated equations are also obtained. A boundary integral equation, which models three-dimensional acoustic radiation from an infinite rigid cylinder, illustrating the results of Chapters 3 and 4, is examined in Chapter 5.
