Author: Santosh Parakkal
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
Book Description
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.
Theoretical Models to Investigate Sound Propagation Over Irregular Terrain
Author: Santosh Parakkal
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
Book Description
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.
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
Book Description
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.
Sound Propagation Over Uneven Ground and Irregular Topography
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722750305
Category :
Languages : en
Pages : 56
Book Description
Theoretical, computational, and experimental techniques were developed for predicting the effects of irregular topography on long range sound propagation in the atmosphere. Irregular topography is understood to imply a ground surface that: (1) is not idealizable as being perfectly flat, or (2) that is not idealizable as having a constant specific acoustic impedance. The focus is on circumstances where the propagation is similar to what might be expected for noise from low altitude air vehicles flying over suburban or rural terrain, such that rays from the source arrive at angles close to grazing incidence. Berthelot, Yves H. and Pierce, Allan D. and Kearns, James A. and Zhou, Ji-Xun Unspecified Center...
Publisher: Createspace Independent Publishing Platform
ISBN: 9781722750305
Category :
Languages : en
Pages : 56
Book Description
Theoretical, computational, and experimental techniques were developed for predicting the effects of irregular topography on long range sound propagation in the atmosphere. Irregular topography is understood to imply a ground surface that: (1) is not idealizable as being perfectly flat, or (2) that is not idealizable as having a constant specific acoustic impedance. The focus is on circumstances where the propagation is similar to what might be expected for noise from low altitude air vehicles flying over suburban or rural terrain, such that rays from the source arrive at angles close to grazing incidence. Berthelot, Yves H. and Pierce, Allan D. and Kearns, James A. and Zhou, Ji-Xun Unspecified Center...
Scientific and Technical Aerospace Reports
Sound Propagation Over Uneven Ground and Irregular Topography
On the Long Range Propagation of Sound Over Irregular Terrain
Author: M. S. Howe
Publisher:
ISBN:
Category : Acoustical engineering
Languages : en
Pages : 44
Book Description
Publisher:
ISBN:
Category : Acoustical engineering
Languages : en
Pages : 44
Book Description
A Generalized Earth-flattening Transformation for Sound Propagation Over Irregular Terrain
Author: Santosh Parakkal
Publisher:
ISBN:
Category : Acoustical engineering
Languages : en
Pages : 246
Book Description
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.
Publisher:
ISBN:
Category : Acoustical engineering
Languages : en
Pages : 246
Book Description
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.
Keywords Index to U.S. Government Technical Reports
Author:
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 1160
Book Description
Publisher:
ISBN:
Category : Government publications
Languages : en
Pages : 1160
Book Description
Applied Mechanics Reviews
Monthly Catalog of United States Government Publications, Cumulative Index
Author: United States. Superintendent of Documents
Publisher:
ISBN:
Category : United States
Languages : en
Pages : 1504
Book Description
Publisher:
ISBN:
Category : United States
Languages : en
Pages : 1504
Book Description
Issues in Acoustic and Ultrasound Technology: 2011 Edition
Author:
Publisher: ScholarlyEditions
ISBN: 1464965641
Category : Technology & Engineering
Languages : en
Pages : 704
Book Description
Issues in Acoustic and Ultrasound Technology: 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Acoustic and Ultrasound Technology. The editors have built Issues in Acoustic and Ultrasound Technology: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Acoustic and Ultrasound Technology in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Acoustic and Ultrasound Technology: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.
Publisher: ScholarlyEditions
ISBN: 1464965641
Category : Technology & Engineering
Languages : en
Pages : 704
Book Description
Issues in Acoustic and Ultrasound Technology: 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Acoustic and Ultrasound Technology. The editors have built Issues in Acoustic and Ultrasound Technology: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Acoustic and Ultrasound Technology in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Acoustic and Ultrasound Technology: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.