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Author: Aaron Michael Gunderson
Publisher:
ISBN:
Category : Underwater acoustics
Languages : en
Pages : 306
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Book Description
Scattering by partially exposed objects breaking through an interface is profoundly different from scattering by the same objects in a free field environment. The presence of the interface both adds additional scattering paths, and can strongly modify or remove preexisting paths, depending upon the level of exposure and grazing angle. Acoustic scattering by partially exposed spheres and cylinders through an interface is considered in the time and frequency domains. Scattering from a handball (a rubber, hollow spherical shell) is also considered, and results are compared to those from solid spheres. Experimentally acquired results are compared to several theoretic models, including the Kirchhoff approximation, partial wave series solutions, ray theory, and finite element simulations. The Kirchhoff approximation has previously been applied to backscattering from a rigid cylinder at a free surface [K. Baik and P.L. Marston, IEEE Journal of Oceanic Engineering 33, 386-396 (2008)], and the analogous process for a rigid sphere is developed here. Scattering path contributions are identified based on timing models and frequency content, and target elastic resonances and interference phenomena are discussed. Two different interfaces are considered in experiments and models: an air-water interface (free surface) and a sand-water interface. Comparisons and distinctions are made between the results at the two interfaces, which are shown to become similar in the low grazing angle limit. Smooth, continuous transitions in scattering amplitude are shown to correlate with scattering path coupling points becoming exposed as the target is lowered through the interface. Scattering in the low target exposure limit is shown to be dominated by Franz wave contributions (surface-guided, nonelastic waves). This contrasts with high exposure and free field scattering signatures from spheres and cylinders, in which the Franz contribution is highly diminished and is not a significant contributor. Bistatic scattering from free field spheres and cylinders is also considered, in the context of understanding the bistatic scattering paths from these targets at partial exposure through an interface. Results from this work have direct applications to understanding the scattering from partially exposed objects resting on or buried within a seafloor environment. [Work supported by the Office of Naval Research.]
Author: Aaron Michael Gunderson
Publisher:
ISBN:
Category : Underwater acoustics
Languages : en
Pages : 306
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Book Description
Scattering by partially exposed objects breaking through an interface is profoundly different from scattering by the same objects in a free field environment. The presence of the interface both adds additional scattering paths, and can strongly modify or remove preexisting paths, depending upon the level of exposure and grazing angle. Acoustic scattering by partially exposed spheres and cylinders through an interface is considered in the time and frequency domains. Scattering from a handball (a rubber, hollow spherical shell) is also considered, and results are compared to those from solid spheres. Experimentally acquired results are compared to several theoretic models, including the Kirchhoff approximation, partial wave series solutions, ray theory, and finite element simulations. The Kirchhoff approximation has previously been applied to backscattering from a rigid cylinder at a free surface [K. Baik and P.L. Marston, IEEE Journal of Oceanic Engineering 33, 386-396 (2008)], and the analogous process for a rigid sphere is developed here. Scattering path contributions are identified based on timing models and frequency content, and target elastic resonances and interference phenomena are discussed. Two different interfaces are considered in experiments and models: an air-water interface (free surface) and a sand-water interface. Comparisons and distinctions are made between the results at the two interfaces, which are shown to become similar in the low grazing angle limit. Smooth, continuous transitions in scattering amplitude are shown to correlate with scattering path coupling points becoming exposed as the target is lowered through the interface. Scattering in the low target exposure limit is shown to be dominated by Franz wave contributions (surface-guided, nonelastic waves). This contrasts with high exposure and free field scattering signatures from spheres and cylinders, in which the Franz contribution is highly diminished and is not a significant contributor. Bistatic scattering from free field spheres and cylinders is also considered, in the context of understanding the bistatic scattering paths from these targets at partial exposure through an interface. Results from this work have direct applications to understanding the scattering from partially exposed objects resting on or buried within a seafloor environment. [Work supported by the Office of Naval Research.]
Author: Anthony Ryan Smith
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Receiver scans of the aluminum cylinder at the air-water interface showed the presence of Franz waves, which were stronger for lower exposure. Target scans of the cylinder at the interface for various grazing angles also showed Franz features.
Author: Grant Carl Eastland
Publisher:
ISBN: 9781267671226
Category :
Languages : en
Pages :
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Book Description
Reversible SAS filtering of monostatic and bistatic data is used to identify different specular mechanisms involving the target and free surface, in addition to the corresponding elastic responses. Delayed multiple scattering features are also visible involving more than one reflection from the target. During the investigation, additional mechanisms were discovered and studied: Franz wave features, which are from diffracted acoustic surface waves and Rayleigh wave features, which are Surface Elastic Waves.
Author:
Publisher:
ISBN:
Category : Music
Languages : en
Pages : 764
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Book Description
Author: Steven L. Garrett
Publisher: Springer
ISBN: 3319499785
Category : Science
Languages : en
Pages : 913
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Book Description
This textbook provides a unified approach to acoustics and vibration suitable for use in advanced undergraduate and first-year graduate courses on vibration and fluids. The book includes thorough treatment of vibration of harmonic oscillators, coupled oscillators, isotropic elasticity, and waves in solids including the use of resonance techniques for determination of elastic moduli. Drawing on 35 years of experience teaching introductory graduate acoustics at the Naval Postgraduate School and Penn State, the author presents a hydrodynamic approach to the acoustics of sound in fluids that provides a uniform methodology for analysis of lumped-element systems and wave propagation that can incorporate attenuation mechanisms and complex media. This view provides a consistent and reliable approach that can be extended with confidence to more complex fluids and future applications. Understanding Acoustics opens with a mathematical introduction that includes graphing and statistical uncertainty, followed by five chapters on vibration and elastic waves that provide important results and highlight modern applications while introducing analytical techniques that are revisited in the study of waves in fluids covered in Part II. A unified approach to waves in fluids (i.e., liquids and gases) is based on a mastery of the hydrodynamic equations. Part III demonstrates extensions of this view to nonlinear acoustics. Engaging and practical, this book is a must-read for graduate students in acoustics and vibration as well as active researchers interested in a novel approach to the material.
Author: Trevor J. Cox
Publisher: CRC Press
ISBN: 0203893050
Category : Architecture
Languages : en
Pages : 495
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Book Description
Absorbers and diffusers are two of the main design tools for altering the acoustic conditions of rooms, semi-enclosed spaces and the outdoor environment. Their correct use is important for delivering high quality acoustics. Unique and authoritative, this book decribes how to effectively measure, model, design and apply diffusers and absorbers. It is a resource for new and experienced acousticians, seeking an understanding of the evolution, characteristics and application of modern diffusers. Absorption is a more established technology and so the book blends traditional designs with modern developments. The book covers practical and theoretical aspects of absorbers and diffusers and is well illustrated with examples of installations and case studies. This new edition brings Acoustic Absorbers and Diffusers up-to-date with current research, practice and standards. New developments in measurement, materials, theory and practice since the first edition (published in 2004) are included. The sections on absorbers are extended to include more about noise control.
Author: Harald Ibach
Publisher: Springer Science & Business Media
ISBN: 3540347100
Category : Science
Languages : en
Pages : 653
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Book Description
This graduate-level textbook covers the major developments in surface sciences of recent decades, from experimental tricks and basic techniques to the latest experimental methods and theoretical understanding. It is unique in its attempt to treat the physics of surfaces, thin films and interfaces, surface chemistry, thermodynamics, statistical physics and the physics of the solid/electrolyte interface in an integral manner, rather than in separate compartments. It is designed as a handbook for the researcher as well as a study-text for graduate students. Written explanations are supported by 350 graphs and illustrations.
Author: John Monteith
Publisher: Butterworth-Heinemann
ISBN: 9780713129311
Category : Nature
Languages : en
Pages : 308
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Book Description
Thoroughly revised and up-dated edition of a highly successful textbook.
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.
Author: Andre Guinier
Publisher:
ISBN:
Category : X-rays
Languages : en
Pages : 268
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Book Description
