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| Release | : 2006 |
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Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2009.
| Author | : Joseph J. Sikora (III.) |
| Publisher | : |
| Total Pages | : 242 |
| Release | : 2005 |
| Genre | : Seamounts |
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This thesis develops and utilizes a method for analyzing data from the North Pacific Acoustic Laboratory's (NPAL) Basin Acoustic Seamount Scattering Experiment (BASSEX). BASSEX was designed to provide data to support the development of analytical techniques and methods which improve the understanding of sound propagation around underwater seamounts. The depth-dependent sound velocity profile of typical ocean waveguides force sound to travel in convergence zones about a minimum sound speed depth. This ducted nature of the ocean makes modeling the acoustic field around seamounts particularly challenging, compared to an isovelocity medium. The conical shape of seamounts also adds to the complexity of the scatter field. It is important to the U.S. Navy to understand how sound is diffracted around this type of topographic feature. Underwater seamounts can be used to conceal submarines by absorbing and scattering the sound they emit. BASSEX measurements have characterized the size and shape of the forward scatter field around the Kermit-Roosevelt Seamount in the Pacific Ocean. Kermit-Roosevelt is a large, conical seamount which shoals close to the minimum sound speed depth, making it ideal for study. Acoustic sources, including M-sequence and linear frequency-modulated sources, were stationed around the seamount at megameter ranges. A hydrophone array was towed around the seamount to locations which allowed measurement of the perturbation zone. Results from the method developed in this thesis show that the size and shape of the perturbation zone measured coincides with theoretical and experimental results derived in previous work.
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| Release | : 2005 |
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Submitted in partial fulfillment of the requirements for Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2005.
| Author | : P. D. Koenigs |
| Publisher | : |
| Total Pages | : 16 |
| Release | : 1981 |
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A low frequency (50-800 Hz) sound-propagation experiment was conducted along a 1400-km path running eastward from Bermuda toward the Mid-Atlantic Ridge. SUS charges were detonated at depths of 18, 154, 615, and 1230 m. The receiver was located at the axis of the deep sound channel (125 m) at a maximum range of 1300 km. The acoustic path crossed several seamounts of the Corner Seamount Group. The highest of these peaks rose to the sound axis. This paper presents the relative enhancement of signal level of SOFAR propagation due to these seamounts as a function of source depth and frequency. The enhancement was minimal for the 1230-m shots, while the greatest enhnacement occurred for the 18-m shots at the 50-Hz filter band. This implies these seamounts and other topographic features such as the mid-Atlantic Ridge can significantly increase the coupling of low-frequency ship-generated noise into the deep sound channel. (Author).
| Author | : Robert Parish Spaudling (Jr) |
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| Total Pages | : 85 |
| Release | : 1979 |
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Propagation loss due to shadowing by seamounts is studied utilizing physical models in air. Dickens Seamount in the Gulf of Alaska is approximated by three models; A plane wedge, a contoured wedge, and a scaled three dimensional model. The forward diffraction over each is analyzed for a five octave frequency range. A new concept, the far-field 'diffraction scattering strength' is defined and used to predict frequency-dependent diffraction loss at sea. The total propagation loss is calculated by adding laboratory model values of upslope forward scatter and crest diffraction losses to computer-predicted ray refraction losses up to and away from the seamount. This predicted loss is then compared to long range ocean propagation loss measurements for the case in which rays are completely blocked by the Seamount. Close agreement is found. (Author).
| Author | : Herman Medwin |
| Publisher | : Academic Press |
| Total Pages | : 739 |
| Release | : 1997-11-05 |
| Genre | : Science |
| ISBN | : 0080532160 |
The developments in the field of ocean acoustics over recent years make this book an important reference for specialists in acoustics, oceanography, marine biology, and related fields. Fundamentals of Acoustical Oceanography also encourages a new generation of scientists, engineers, and entrepreneurs to apply the modern methods of acoustical physics to probe the unknown sea. The book is an authoritative, modern text with examples and exercises. It contains techniques to solve the direct problems, solutions of inverse problems, and an extensive bibliography from the earliest use of sound in the sea to present references.Written by internationally recognized scientists, the book provides background to measure ocean parameters and processes, find life and objects in the sea, communicate underwater, and survey the boundaries of the sea. Fundamentals of Acoustical Oceanography explains principles of underwater sound propagation, and describes how both actively probing sonars and passively listening hydrophones can reveal what the eye cannot see over vast ranges of the turbid ocean. This book demonstrates how to use acoustical remote sensing, variations in sound transmission, in situ acoustical measurements, and computer and laboratory models to identify the physical and biological parameters and processes in the sea.* Offers an integrated, modern approach to passive and active underwater acoustics* Contains many examples of laboratory scale models of ocean-acoustic environments, as well as descriptions of experiments at sea* Covers remote sensing of marine life and the seafloor* Includes signal processing of ocean sounds, physical and biological noises at sea, and inversions* resents sound sources, receivers, and calibration* Explains high intensities; explosive waves, parametric sources, cavitation, shock waves, and streaming* Covers microbubbles from breaking waves, rainfall, dispersion, and attenuation* Describes sound propagation along ray paths and caustics* Presents sound transmissions and normal mode methods in ocean waveguides
| Author | : L.M. Brekhovskikh |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 289 |
| Release | : 2003-03-18 |
| Genre | : Science |
| ISBN | : 0387954678 |
This book provides an up-to-date introduction to the theory of sound propagation in the ocean. The text treats both ray and wave propagation and pays considerable attention to stochastic problems such as the scattering of sound at rough surfaces and random inhomogeneities. An introductory chapter that discusses the basic experimental data complements the following theoretical chapters. New material has been added throughout for this third edition. New topics covered include: - inter-thermocline lenses and their effect on sound fields - weakly divergent bundles of rays - ocean acoustic tomography - coupled modes - sound scattering by anisotropic volume inhomogeneities with fractal spectra - Voronovich's approach to sound scattering from the rough sea surface. In addition, the list of references has been brought up to date and the latest experimental data have been included.
| Author | : John Lamar Worzel |
| Publisher | : Geological Society of America |
| Total Pages | : 256 |
| Release | : 1948 |
| Genre | : Deep-sea sounding |
| ISBN | : 0813710278 |
