Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 84 for “"Underwater Acoustics"”.
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Underwater acoustics in arctic environments
Includes bibliographical references (leaves 46-47).
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Efficient inversion methods in underwater acoustics
… inverse problem of parameter estimation in underwater acoustics. These techniques take into account properties of the ocean environment and are accurate in their estimation results without being prohibitively computationally intensive. For the inversion, select ray paths are taken into …
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Optimization for source localization and geoacoustic inversion in underwater acoustics
Matched-field inversion techniques are widely used for source localization and geoacoustic parameter estimation. These inversion methods correlate the received data with modeled data and find the model parameters which provide the maximum correlation. However, when a large number of unknown …
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Acoustic interference fields in the ocean
Two areas of underwater acoustics are investigated: ocean-bottom scattering and acoustic fields in geometrically dispersive sound channels. The purpose is to describe and provide an understanding of the physical mechanisms in these two areas by comparing analyzed results from ocean experiments with …
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Single mode excitation in the shallow water acoustic channel using feedback control
… incorporating elements of adaptive estimation, underwater acoustics, array processing and control theory to generate a high-fidelity single mode is presented. This approach also yields a cohesive framework for evaluating the feasibility of generating a single mode with given array geometries, …
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THE EFFECT OF TROPICAL CYCLONE PASSAGE ON UNDERSEA ACOUSTIC PARAMETERS IN THE EAST CHINA SEA
… for more accurate ocean predictions, to include underwater acoustics, in an operationally relevant region.
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Automatic baleen whale detection and 2D localization using a network of unsynchonized passive acoustic sensors
Underwater acoustics is a powerful tool for learning about the ocean’s soniferous marine life. However, most modern acoustic sensing systems consist of expensive arrays of timesynchronized recorders which require a crewed research vessel and significant expertise to deploy, operate, and recover. …
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Sequential bayesian filtering for spatial arrival time estimation
… propagation medium is of utmost importance in underwater acoustics. Matched field processing is often the method of choice for the estimation of such parameters. This approach, based on full field calculations, is computationally intensive and sensitive to assumptions on the structure of the …
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Automatic Baleen Whale Detection and 2D Localization Using a Network of Unsynchronized Passive Acoustic Sensors
Underwater acoustics is a powerful tool for learning about the ocean's soniferous marine life. However, most modern acoustic sensing systems consist of expensive arrays of time-synchronized recorders which require a crewed research vessel and significant expertise to deploy, operate, and recover. …
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Low-Frequency Emission Enhancement by Resonant Acoustic Metamaterials
… demanded in audio, medical ultrasonics, and underwater acoustics. Emission enhancement and controlling the directivity of an acoustic source is however restricted to the properties of the source. In particular, the size of the source, in comparison with the wavelength of the sound, plays a …
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Acoustic source localization
Many technologies rely on underwater acoustics. Most of these applications are able to denoise Gaussian noise from the surrounding, but have trouble removing impulse like noises. One source of impulse-like noise is the snapping shrimps. The acoustic signals they emit from snapping their claws …
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Ocean acoustic applications of an autonomous underwater vehicle at the New England Shelfbreak
… contributing to a dynamic ocean environment. Underwater acoustics is a valuable tool for studying these oceanographic processes, as environmental variability greatly influences acoustic propagation and scattering. The work in this dissertation follows an interdisciplinary approach to explore …
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An experimental study of air entrainment by breaking waves
… an important role in air-sea gas transfer and in underwater acoustics near the ocean surface. This work reports on a series of laboratory and field experiments on the measurement on air entrainment by breaking waves. The first part of this thesis addresses the measurement of high volumetric …
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Acoustic scattering by axisymmetric finite-length bodies with application to fish : measurement and modeling
… data, are crucial to the quantitative use of acoustics in the ocean.
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Estimation and tracking of rapidly time-varying broadband acoustic communication channels
This thesis develops methods for estimating wideband shallow-water acoustic communication channels. The very shallow water wideband channel has three distinct features: large dimension caused by extensive delay spread; limited number of degrees of freedom (DOF) due to resolvable paths and …
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An inverse method for obtaining the attenuation profile and small variations in the sound speed and density profiles of the ocean bottom
The acoustic properties of marine sediments have a direct effect on the propagation of sound in the ocean. In the frequency range of interest (50 - 500 Hz) the sediment can be modelled as a fluid. Assuming horizontal stratification of the ocean bottom, the acoustic parameters of interest are the …
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Design and testing of an acoustic ultra-short baseline navigation system
An ultra-short baseline acoustic navigation system has been developed which is capable of determining bearing to a sound source with an error of less than 1° in typical operational conditions. The system has a demonstrated ability to operate in an environment in which multipath interference is …
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Inversion for subbottom sound velocity profiles in the deep and shallow ocean
This thesis investigates the application of acoustic measurements in the deep and shallow ocean to infer the sound velocity profile (svp) in the seabed. For the deep water ocean, an exact method based on the Gelfand-Levitan integral equation is evaluated. The input data is the complex plane-wave …
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A matched field processing approach to long range acoustic navigation
This thesis presents the design and simulation of an acoustic listen-only navigation system for use in a time-varying high-multipath environment. The system uses a ray tracing model of sound propagation in a horizontally stratified ocean to associate each multipath arrival with a particular ray …
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