An Experimental Model Study Of Underwater Acoustic Scattering From A Wind Driven Surface
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An Experimental Model Study Of Underwater Acoustic Scattering From A Wind Driven Surface
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Author : F. John Kingsbury
language : en
Publisher:
Release Date : 1970
An Experimental Model Study Of Underwater Acoustic Scattering From A Wind Driven Surface written by F. John Kingsbury and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1970 with categories.
The results of an experimental investigation into the characteristics of acoustic energy reflected from rough, time-varying surfaces are presented. Theory pertinent to the study of acoustic scattering is also presented to form a predictive base for the experimental work. The experimentally derived amplitude, slope, spectral, and spatial correlation characteristics of the rough surfaces are presented. Measurement results are shown which describe the spatial distribution characteristics of energy scattered from the rough surfaces. Experiments performed to determine the modulation effects imposed on the reflected acoustic energy by the time-varying surfaces are also presented. For all the measurements, the effects on the scattered energy characteristics of shadowing and changes in acoustic frequency, grazing angle, and the direction of acoustic propagation relative to the wave motion are discussed. (Author).
Scientific And Engineering Studies Underwater Acoustic Scattering
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Author :
language : en
Publisher:
Release Date : 1987
Scientific And Engineering Studies Underwater Acoustic Scattering written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with Underwater acoustics categories.
Underwater Scattering And Radiation
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Author : Allan D. Pierce
language : en
Publisher: Academic Press
Release Date : 2013-10-22
Underwater Scattering And Radiation written by Allan D. Pierce and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-10-22 with Technology & Engineering categories.
Underwater Scattering and Radiation describes the relevant theoretical foundations of underwater scattering and radiation. Acoustic scattering from elastic solids is discussed, and variational formulations in acoustic radiation and scattering are presented. Surface waves and quasi-cylindrical modes are also explored, along with the Helmholtz-Kirchhoff integral corollaries. Comprised of two chapters, this volume begins with a comprehensive account of scattering by elastic objects, focusing on the classic idealized shapes of spheres and infinite cylinders. The reader is introduced to important concepts such as normal modes, the S-matrix, and the T-matrix as well as resonances, whispering gallery modes, Franz modes, and Stoneley waves. Subsequent sections describe methods for treating scattering by elastic bodies of more general shapes. The T-matrix formalism is discussed and then applied to spheroidal scatterers and finite cylinders. The second chapter analyzes how variational principles can be used in acoustics, with the choice of topics directed toward applications to underwater acoustic radiation and scattering. This book will be of interest to physicists.
Sound Propagation In The Sea
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Author : Robert J. Urick
language : en
Publisher:
Release Date : 1979
Sound Propagation In The Sea written by Robert J. Urick and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1979 with Sound categories.
Scattering Of Underwater Acoustic Signals From A Rough Moving Surface
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Author : Franz B. Tuteur
language : en
Publisher:
Release Date : 1977
Scattering Of Underwater Acoustic Signals From A Rough Moving Surface written by Franz B. Tuteur and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1977 with Doppler effect categories.
The research dealt with surface scattering and consisted of an experimental as well as a theoretical component. The experimental work was conducted in a model tank equipped with a wind tunnel to produce a wind-driven surface. The tank is very well instrumented and interfaced to a computer so that the experimental results can be accepted with considerable confidence. Four separate projects are included in the work covered by this report. These are: (1) Calculation and Measurement of first and second-order moments of the channel transfer function; (2) Spatial correlation between two receivers; (3) Power scattered in directions other than forward; and (4) Asymmetric Doppler amplitudes in forward scatter. Each one of these projects is briefly discussed and summarized.
Hyrdoacoustic Ocean Exploration
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Author : Iftikhar B. Abbasov
language : en
Publisher: John Wiley & Sons
Release Date : 2016-09-14
Hyrdoacoustic Ocean Exploration written by Iftikhar B. Abbasov and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-09-14 with Science categories.
The only book that offers a comprehensive and fully up-to-date coverage of hydroacoustic ocean exploration, this work deals with the diagnostics of non-uniformities in a water medium using the hydroacoustic parametric antenna. The non-uniformities of the water medium in the study are of geometrically regular shape, i.e., the shape of a sphere, a cylinder, and a spheroid. An account is given of theoretical and experimental studies of wave processes that occur in the event of the scattering of non-linearly interacting acoustic waves at a sphere, a cylinder, and a spheroid. Scattering problems are formulated; solutions to the inhomogeneous wave equation are found in the first and second approximations using the successive approximations method. For the first time, high-frequency asymptotic expressions of acoustic pressure for all spectral components of the secondary field are obtained for the nonlinear scattering problem. The scattering diagrams are calculated and plotted, and then analyzed and compared. Results of experimental studies of the parametric acoustic antenna field scattering at solid steel spheres are presented. Experimental scattering diagrams both for the parametric antenna pump waves and for the secondary field waves including the difference frequency wave, the sum frequency wave, and the second harmonic wave are presented. 3D modeling of wave processes is also considered. A must have for researchers and specialists in nonlinear hydroacoustics and ocean acoustics; it also may be of use for postgraduates and students specializing in hydroacoustics and ocean exploration.
Underwater Sound Propagation And Acoustic Communication In A Time Varying Shallow Estuarine Environment
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Author : Zheguang Zou
language : en
Publisher:
Release Date : 2018
Underwater Sound Propagation And Acoustic Communication In A Time Varying Shallow Estuarine Environment written by Zheguang Zou and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Estuaries are water regions that connect rivers and oceans, which are very important due to heavy traffic, fishery and other coastal engineering activities. Underwater acoustic technology offers a series of effective applications and technical supports for real-time monitoring and long-term preservation of the nature environment and ecosystem in these regions. However, estuaries are shallow waters with complicated temporal and spatial environmental variability, involving a variety of physical oceanographic processes, such as tidal water mixing and ocean winds/waves, which can significantly influence the underwater sound propagation and moreover, underwater acoustic communications. In order to perform reliably and effectively in such complex time-varying shallow-water ocean environments, next-generation underwater acoustic communication systems need an all new design based on the environmental variability of the physical ocean, which takes the environmental physics and time-varying variability into account and is able to adapt and switch to the optimal mode as the environment evolves. Therefore, a deep, comprehensive and thorough understanding of the link between the time-varying ocean environment, underwater acoustic channel, and underwater acoustic communication systems is highly required. ☐ This dissertation investigated the relationship between the shallow-water, time-varying environment of estuaries, the underwater sound propagation and underwater acoustic communications, which can help the design of underwater acoustic systems so that they can adapt the time-varying environment with wiser parameter configurations. In this dissertation, field data analysis, joint numerical modeling, together with a controllable laboratory experiment were used to study acoustic channel variability of a shallow estuary and its influence on the performance of underwater acoustic communications. This dissertation included four aspects: (a) Effect of water-column variation due to the tidal dynamics in an estuary on the underwater acoustic direct path; (b) Effect of time-varying surface roughness due to the wind-driven waves on underwater acoustic surface paths; (c) Numerically modeling the effect of time-varying wind-driven shallow-water waves on coherent underwater acoustic communications using a combined model; (d) Conducting a controllable laboratory experiment to investigate the time-varying wind-driven water waves on the performance of coherent and non-coherent underwater acoustic communications. ☐ The first two aspects focused on the link between the time-varying environment of an estuary and the underwater acoustic wave propagation. With field data analysis and joint numerical modeling, the time-varying variability of acoustic direct paths and surface-bounced paths from a high-frequency acoustic experiment conducted in the Delaware Bay estuary was explored. On one hand, periodical acoustic direct path fading was found in the tidal-straining Delaware Bay estuary, with the fading period as same as the semi-diurnal tide. Based on physical oceanography and ocean acoustics, the mechanism that causes the direct path fading and its link to the water dynamics of an estuary was investigated. On the other hand, the relationship between the acoustic surface paths and the surface wind speed was investigated, and the wind-influenced shallow-water time-varying channel was studied using field data analysis and a joint model combining physical oceanography and ocean acoustics. The joint numerical model, including a wind-wave model, a surface generation algorithm and a parabolic equation acoustic model, reproduced the relationship between the wind speed and surface reflection signals. ☐ The last two aspects applied the knowledge of underwater sound propagation in shallow estuaries into analyzing the performance of underwater acoustic communication systems, i.e., investigating how the fast fluctuation of a shallow-water environment (wind-driven waves) influences different fundamental modulation schemes for underwater acoustic communications. To better analyze the effect of environmental variability of the physical ocean on underwater acoustic communications, the surface condition was set as the only variation in the numerical modeling and the controllable laboratory experiment. On one hand, a combined model including physical oceanography, ocean acoustics, and underwater acoustic communication was used to study the time-varying underwater acoustic channel under different wind speeds, and the performance of the coherent acoustic communication (QPSK) system. On the other hand, a controllable laboratory experiment was conducted to investigate bit-error-rate (BER) performance of the MFSK (representing the non-coherent acoustic communication) and the QPSK (representing the coherent acoustic communication) acoustic modulations. ☐ The main conclusions of the dissertation are as follows. For the time-varying variability of underwater acoustic channel: (a) Due to the tidal-straining water dynamics of an estuary, periodical water column exchange between the seawater and the freshwater, up-refracting sound speed profile is more likely to form by the end of ebb tide, which redirects sound signal away from the deep receivers and creates shadow zone for the sound direct path; (b) In an open estuary, the acoustic pressure of surface-bounced paths decreases with increased wind speed, as a result of increased acoustic scattering due to the wind-driven surface roughness. For underwater acoustic communications: (c) Coherent acoustic communications are sensitive to the fast time-varying variability, and performance decrease significantly with increased wind speed, as a result of increased channel variability and decreased temporal coherence; (d) Non-coherent acoustic communications are less sensitive to the channel variability, and the reduced multipath signals due to wind-wave surface may improve the system performance. ☐ The key novelties of this dissertation include: (a) Using a joint model involving physical oceanography and ocean acoustics to study the effect of time-varying estuarine environment (water-column variations and wind-driven surface waves) on underwater sound propagation and the underwater acoustic channels. (b) Using an integrated model involving physical oceanography, ocean acoustics, and underwater acoustic communications to study the effect of time-varying estuarine environment (wind-driven surface waves) on underwater acoustic communications. (c) Using field experimental data, numerical modeling and controllable laboratory experiment to study the underwater sound propagation and underwater acoustic communications in a time-varying ocean environment.
Acoustic Scattering From A Wind Driven Water Surface
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Author : Peter M. Schultheiss
language : en
Publisher:
Release Date : 1976
Acoustic Scattering From A Wind Driven Water Surface written by Peter M. Schultheiss and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1976 with categories.
A very substantial fraction of the effort was devoted to improving the experimental facility. A partly automated hydrophone positioning system was installed in order to facilitate measurement of scattered power for a variety of transmitter and receiver locations. Improved hydrophone amplifiers now furnish the required signal to noise ratios for reliable measurements with receiver placement varying all the way from the forward-scatter to the back-scatter postion. A greatly improved waveheight probe will permit characterization of surface statistics at a level of detail not previously accessible. Such a level of detail appears to be essential to any effort to reconcile experiment with theory. The construction process is now largely complete and measurements are in progress. The first azimuthal surveys of scattered power have been carried out and are included in this report. It is clear from this limited data set that some key features of the scattering process (e.g. back scattered power level) are poorly predicted by existing theory. A major portion of this report is therefore devoted to a review of theoretical background. The standard analytical approaches are examined to see what changes in the usual assumptions might lead to results more compatible with experimental observations.
Characterization Of Active Underwater Acoustic Channels Part Ii Scattering In An Isovelocity Ocean
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Author :
language : en
Publisher:
Release Date : 1974
Characterization Of Active Underwater Acoustic Channels Part Ii Scattering In An Isovelocity Ocean written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1974 with categories.
The general approach to scattering phenomena developed here is now applied specifically to underwater acoustic scattering problems in an isovelocity medium, for the present without absorption and inhomogeneous properties other than the various possible scattering mechanisms themselves. Among the principal new results are (1) the explicit inclusion of doppler, which is shown to produce a nonstationary frequency-modulation of the injected signal; (2) the presence and effects of two orders of inhomogeneities in the second-order media statistics, e.g., poisson, or specular point scatterers (k=1) and continuous scattering elements (k=2); (3) the coherence properties and spectrum of the specular component (k=0); (4) necessary and sufficient conditions for the applicability of the poisson model alone (and of the earlier poisson models cited in the literature); (5) conditions that the medium be a WSSUS medium; (6) for weak scattering interactions, the wave number spectra of surfaces and volumes, including the interaction of surface displacement and motion; (7) various experimental programs for the measurement and underwater remote sensing of the medium; (8) an extensive development of wave surface statistics, particularly point and directional covariances, spectra, and wave number spectra for a variety of sea surface models, including the author's recent model; (9) strong-scattering results; and (10) channel characterizations by means of the local bicovariance and cospreading functions, with specific examples
Characterization Of Active Underwater Acoustic Channels Part I A New Formulation For Scattering By Random Media And Interfaces
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Author :
language : en
Publisher:
Release Date : 1974
Characterization Of Active Underwater Acoustic Channels Part I A New Formulation For Scattering By Random Media And Interfaces written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1974 with categories.
A general approach to scattering phenomena is developed and applied specifically to underwater acoustic scattering situations involving the medium and its interfaces. The fundamental elements of the method are the development of the available scattering elements into a hierarchy of independent scatter processes, based on the scatterers activated, at any given instant. This, with the governing class of Langevin equation (e.g., forms of the (scalar) wave equation here) permits a corresponding development, in linear superposition, of the received, scattered field x sub m as a hierarchy of independent processes, x sub m(k), k=0,1,2., representing different scales of inhomogeneity which may be present in the medium, or upon its interfaces. First- and second-order moments (covariances and generalized spectra) are obtained in canonical form, representing global properties of the channel and the local properties of the medium itself. A number of probability densities are also obtained in important limiting cases, e.g. various (conditional) normal p.d.f.'s. Part I concludes with some remarks on an experimental program, designed to test and quantify various aspects of the general model, both for studies of the medium itself (and its associated interfaces), and for the broad class of statistical communication applications, such as detection, extraction, classification, communications per se, as well as signal and aperture design problems