Author: C. A. BoylesPublisher:
ISBN:
Category : Hearing
Languages : en
Pages :
Book Description
Modeling Acoustic Propagation and Scattering in Littoral Areas
Author: C. A. BoylesImpact of Littoral Environmental Variability on Acoustic Predictions and Sonar Performance
Author: Nicholas G. PacePublisher: Springer Science & Business Media
ISBN: 9401006261
Category : Science
Languages : en
Pages : 592
Book Description
The limiting influence of the environment on sonar has long been recognised as a major challenge to science and technology. As the area of interest shifts towards the lit toral, environmental influences become dominant both in time and space. The manyfold challenges encompass prediction, measurement, assessment and adaptive responses to maximize the effectiveness of systems. Although MCM and ASW activities are dom inated in different ways and scales by the environment, both warfare areas have had to consider the significantly changing requirements posed by operations in the littoraL The fundamental scientific issues involved in developing models relating acoustics to the environment are matched in difficulty by the need for data for their validation and eventual practical use for prediction. In many instances the need is for on-line adaptation of systems to changing circumstances whilst other needs are for the Ionger term planning activities. This book and the attached full-color CD are the proceedings of a conference organ ised by the SACLANT Undersea Research Centre, held at Villa Marigola, Lerici, Italy, on 16-20 September 2002. The fundamental problems associated with environmental 1 variability and sonar were explored at a previous SACLANTCEN conference in 1990. These problems have not gone away but, on the one hand are exaggerated by the move to the littoral and on the other hand, are open to treatrnent in new ways that advances in technology and computer power allow.
Predicting the Effects of Sea Surface Scatter on Broadband Pulse Propagation with an Ocean Acoustic Parabolic Equation Model
Author: Richard M. EadPublisher:
ISBN: 9781423518464
Category :
Languages : en
Pages : 93
Book Description
Littoral waters when compared to the open ocean create an environment of greater reverberation with acoustic energy scattering from the sea surface, bottom, topographic features, and regions that lack homogeneity within the volume. If the ocean surface is rough on the scale of an acoustic wavelength, considerable scattering can occur that can significantly influence coherent propagation. Because the rough surface is also evolving dynamically such scattering can introduce Doppler shifting and spreading of the acoustic pulse spectrum. This thesis builds upon prior efforts in ocean acoustic modeling and is focused on examining surface scattering and its affect upon coherent propagation. The dynamics/physics associated with sea surface scattering are explored in detail and mathematical relationships are developed and employed in revisions to the Monterey Miami Parabolic Equation (MMPE) model. The thesis provides background information associated with the MMPE and highlights earlier work related to surface scattering. It presents a formal analysis of an exact surface scattering approach in the context of a continuous wave (CW) benchmark exercise and the Doppler shifts associated with a dynamic rough surface. It expands on prior rough sea surface work to include modeling based on an empirical fetch-limited ocean wave spectrum and compares modeling results with measured data. Interest in broadband pulse propagation in shallow water is increasing with the need for improved active sonar systems and with the growth of applications such as underwater acoustic communications.
A Simple Acoustic Scattering Model for Ensembles of Rocks and Seashells Lying on the Ocean Floor
Author: Christopher FeuilladePublisher:
ISBN:
Category :
Languages : en
Pages : 26
Book Description
This report describes a computer model for predicting levels of acoustic scattering at sonar frequencies from an important class of clutter objects, i.e., rocks and seashells lying on the ocean floor. A simplified modeling approach has been adopted that incorporates basic concepts and principles. Rocks are represented by either grid movable spheres or elastic spheres, a technique that has been previously used to model aqueous suspensions of sand over the equivalent frequency range. Seashells are represented by water-filled spherical shells. The model predicts scattering strength values for areas of the ocean floor covered by ensembles of rocks and shells of sizes, numbers, geologic type, and material compositions typically found in littoral and coastal regions. The results of the model show that ensembles of cobbles and pebbles may give rise to scattering strengths of sufficient magnitude to mask sonar targets or to appear as false sonar targets themselves.
Modeling of Sound Propagation in the Sea
Author: Aleksandr Nikolaevich BarkhatovPublisher: Springer
ISBN:
Category : Science
Languages : en
Pages : 116
Book Description
The book is concerned with the application of modeling techniques and procedures to the investigation of sound propagation in the sea. The modeling method affords a means for studying the laws governing the sound fields in the sea and in other, similar media under controlled laboratory conditions and can be used in underwater acoustics as a coroHary to field experiments. The method has a number of advantages, principal of which are the relative simplicity and low cost of model tests by com parison with fuH-scale tests under oceanic conditions, the high accuracy of acoustical mea surements, excellent reproducibility of the measurement results, and the capability of rapidly varying the experimental conditions, which, unlike the conditions of field experiments, are under complete control. For the modeling of sound propagation in the sea the latter is treated, depending on the problem to be solved, either as a volume-homogeneous medium or as a medium possessing regular and randomly-distributed inhomogeneities. We direct our primary attention in the book to the modeling of layered-inhomogeneous media, but we also discuss separate problems bearing on the study of sound propagation in the sea. It is demonstrated in examples how modeling is employed to investigate the sound field in the ocean for certain typical vertical distributions of the velocity of sound in the ocean.
Fundamentals of Shallow Water Acoustics
Author: Boris KatsnelsonPublisher: Springer Science & Business Media
ISBN: 1441997776
Category : Science
Languages : en
Pages : 549
Book Description
Shallow water acoustics (SWA), the study of how low and medium frequency sound propagates and scatters on the continental shelves of the worlds oceans, has both technical interest and a large number of practical applications. Technically, shallow water poses an interesting medium for the study of acoustic scattering, inverse theory, and propagation physics in a complicated oceanic waveguide. Practically, shallow water acoustics has interest for geophysical exploration, marine mammal studies, and naval applications. Additionally, one notes the very interdisciplinary nature of shallow water acoustics, including acoustical physics, physical oceanography, marine geology, and marine biology. In this specialized volume the authors, all of whom have extensive at-sea experience in US and Russian research efforts, have tried to summarize the main experimental, theoretical, and computational results in shallow water acoustics, with an emphasis on providing physical insight into the topics presented.
Ukraïnsʹke Barokko
Author: Proceedings of the National Symposium on Ocean Electronics
Author: V. ChanderPublisher: Allied Publishers
ISBN: 9788177645576
Category : Science
Languages : en
Pages : 248
Book Description
Papers presented at the conference.
Sound Propagation in the Sea
Author: Robert J. UrickPublisher:
ISBN:
Category : Sound
Languages : en
Pages : 272
Book Description
Two Dimensional Acoustic Propagation Through Oceanic Internal Solitary Waves
Author: Publisher:
ISBN:
Category : Hydrodynamics
Languages : en
Pages : 65
Book Description
Internal solitary waves, or solitons, are often generated in coastal or continental shelf regions when tidal currents advect stratified water over bathymetric relief, creating an internal tide which non-linearly evolves into one or more solitons. A major consequence of solitons in a stratified environment is the vertical displacement of water parcels which can lead to sound speed variability of order 10m/s with spatial scales of order 100 meters and timescales of order minutes. Thus significant variations in sonar performance on both surface based ships and submarines can be expected. An understanding into the nature of acoustic propagation through these waves is vital for future development of sonar prediction systems. This research investigates acoustic normal mode propagation through solitons using a 2D parabolic equation simulation and weak acoustic scattering theory whose primary physics is a single scatter Bragg mechanism. To simplify the theory, a Gaussian soliton model is developed that compares favorably to the results from a traditional sech2 soliton model. The theory of sound through a Gaussian soliton was then tested against the numerical simulation under conditions of various acoustic frequency, source depths, soliton position relative to the source and soliton number. The theoretical results compare favorably with numerical simulations at 75, 150 and 300-Hz. Higher frequencies need to be tested to determine the limits of the first order theory. Higher order theory will then be needed to address even higher frequencies and to deal with weakly excited modes. This research is the first step in moving from a state of observing acoustic propagation through solitons, to one of predicting it.