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Title: Array processing techniques for frequency hopping multiple frequency shift keying long-range communications.
Creator: Bernault, Emmanuel Pierre., Florida Atlantic University, Schock, Steven G.
Abstract/Description: Underwater communication is an important component of Autonomous Underwater Vehicle (AUV) operations. Communicating underwater is limited to very low communication rates without the use of processing techniques that mitigate the influence of the acoustic channel. This thesis develops array processing techniques for frequency hopping and multiple frequency shift keying to achieve long range, reliable high speed communications. The thesis makes the comparison between two techniques for...
Show moreUnderwater communication is an important component of Autonomous Underwater Vehicle (AUV) operations. Communicating underwater is limited to very low communication rates without the use of processing techniques that mitigate the influence of the acoustic channel. This thesis develops array processing techniques for frequency hopping and multiple frequency shift keying to achieve long range, reliable high speed communications. The thesis makes the comparison between two techniques for calculating beamforming coefficients: a coherent Least Mean Square (LMS) adaptive filter and a non-coherent LMS. An Equal Gain Combiner (EGC) and a Maximum Likelihood (ML) were used to determine the performance of the coherent and non-coherent LMS. The results show that by using the coherent LMS, the ML or the EGC, communications at rates of 493 bit per second (bps) and 370bps can be achieved with no frame error at 5km in 40 feet of water using 16.3kHz of bandwidth centered at 25kHz.
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Date Issued: 2002
PURL: http://purl.flvc.org/fcla/dt/12914
Subject Headings: Underwater acoustics, Signal processing--Digital techniques
Format: Document (PDF)

Title: Design and development of a high-speed underwater acoustic modem.
Creator: Alleyne, Jochen Raoul, Florida Atlantic University, LeBlanc, Lester R.
Abstract/Description: The design, development and performance of an acoustic modem using spread spectrum modulation techniques in order to reduce multipath interference is detailed in this thesis. The design also includes a method to correct for Doppler shifts in the received data. Finally, error detection and correction are utilized in order to improve the robustness of the transmitted data. The results of field experiments with the modem are used to analyze the performance of the modem under a variety of...
Show moreThe design, development and performance of an acoustic modem using spread spectrum modulation techniques in order to reduce multipath interference is detailed in this thesis. The design also includes a method to correct for Doppler shifts in the received data. Finally, error detection and correction are utilized in order to improve the robustness of the transmitted data. The results of field experiments with the modem are used to analyze the performance of the modem under a variety of conditions. These results are then used as a basis from which to draw conclusions about the spread spectrum technique.
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Date Issued: 1997
PURL: http://purl.flvc.org/fcla/dt/15520
Subject Headings: Modems, Underwater acoustics
Format: Document (PDF)

Title: Design of a frequency shift keying array receiver for the acoustic modem.
Creator: Boubli, Cecile., Florida Atlantic University, LeBlanc, Lester R.
Abstract/Description: Currently, our acoustic modems are used to communicate underwater to Autonomous Underwater Vehicles AUVs. These modems have only one sensor and can transmit at low data rates (from 200 to 1200 bits per second) using Frequency Shift Keying (FSK) modulation. A two-dimensional array receiver (MillsCross) has been developed to receive underwater signals with more reliability, at a higher data rate (about 30,000 bits per second). This array has been designed to operate with Phase Shift Keying...
Show moreCurrently, our acoustic modems are used to communicate underwater to Autonomous Underwater Vehicles AUVs. These modems have only one sensor and can transmit at low data rates (from 200 to 1200 bits per second) using Frequency Shift Keying (FSK) modulation. A two-dimensional array receiver (MillsCross) has been developed to receive underwater signals with more reliability, at a higher data rate (about 30,000 bits per second). This array has been designed to operate with Phase Shift Keying modulated signals. The purpose of this thesis is to design and implement a signal processing software to demodulate and decode FSK signals acquired by the MillsCross. By taking advantage of the spatial gain of the MillsCross receiver array, higher reliability and longer ranges are expected using FSK, in addition to achieving compatibility between the two systems. This software includes a robust synchronization scheme, a spatial and an equalizing filter, a time-window self-adjusting process and the error control decoding.
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Date Issued: 2000
PURL: http://purl.flvc.org/fcla/dt/15788
Subject Headings: Underwater acoustics, Modems, Signal processing--Digital techniques
Format: Document (PDF)

Title: Model experiments for the acoustic field in a water column which includes the effects of shear in marine sediments.
Creator: Hundley, Allen John., Florida Atlantic University, Glegg, Stewart A. L.
Abstract/Description: A scaled, horizontally stratified shallow water marine acoustic model is constructed for the purpose of investigating the sound field resulting from long range propagation. The characteristics of this sound field in the water column are strongly dependent upon properties of the surficial sediment. One effect is the conversion from compressional waves in the water column to shear waves in the sediment at grazing angles less than the critical. To model a shallow marine environment, concrete is...
Show moreA scaled, horizontally stratified shallow water marine acoustic model is constructed for the purpose of investigating the sound field resulting from long range propagation. The characteristics of this sound field in the water column are strongly dependent upon properties of the surficial sediment. One effect is the conversion from compressional waves in the water column to shear waves in the sediment at grazing angles less than the critical. To model a shallow marine environment, concrete is used as a substrate rock and laminating epoxy is used to model a surficial sediment. Preliminary tests of the effects of the model's environment are performed, and the range dependent sound field as a function of depth is measured for several CW frequencies. These sound field profiles are compared with an approximate predictive theory, and with a numerical solution which treats the sediment properties exactly.
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Date Issued: 1990
PURL: http://purl.flvc.org/fcla/dt/14618
Subject Headings: Underwater acoustics, Marine sediments--Acoustic properties
Format: Document (PDF)

Title: Multi-aspect imaging of cylindrical targets using a wide aperture FM sonar.
Creator: Rivalan, Gregory., Florida Atlantic University, Schock, Steven G.
Abstract/Description: The purpose of the thesis is to investigate a multi-aspect reflection technique to generate 3D images of buried cylinders using the Buried Object Scanning Sonar (BOSS). Target imagery is constructed using a sequence of acoustic echoes generated as the sonar approaches and passes the buried target. However, for the sake of simplicity, the influence of the sediment on the scattering field will not be considered. This thesis investigates the multi-aspect technique by generating synthetic images...
Show moreThe purpose of the thesis is to investigate a multi-aspect reflection technique to generate 3D images of buried cylinders using the Buried Object Scanning Sonar (BOSS). Target imagery is constructed using a sequence of acoustic echoes generated as the sonar approaches and passes the buried target. However, for the sake of simplicity, the influence of the sediment on the scattering field will not be considered. This thesis investigates the multi-aspect technique by generating synthetic images of cylindrical targets to determine both the best method and the sonar parameters for reconstructing the shape of an elastic cylinder. Recommendations for deploying BOSS-252 and setting sonar parameters are provided based on quantitative measurements of the simulated images of cylindrical targets.
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Date Issued: 2005
PURL: http://purl.flvc.org/fcla/dt/13268
Subject Headings: Three-dimensional display systems, Sonar, Sound-waves--Scattering, Underwater acoustics, Underwater exploration
Format: Document (PDF)

Title: Modeling the forward look sonar.
Creator: Barrault, Guillaume., Florida Atlantic University, Cuschieri, Joseph M.
Abstract/Description: A numerical model that simulates the operation of a Forward Look Scan Sonar (FLSS) has been developed in this thesis. The model discretizes the sonar-projected signal by a set of rays using a geometrical approach. Bending of the rays due to varying acoustic wave speed is neglected. Simulated raw sonar data are generated, and used as input in the sonar processing algorithms to generate sonar images. Using the model, the influence of, the most critical characteristics of the sonar, including...
Show moreA numerical model that simulates the operation of a Forward Look Scan Sonar (FLSS) has been developed in this thesis. The model discretizes the sonar-projected signal by a set of rays using a geometrical approach. Bending of the rays due to varying acoustic wave speed is neglected. Simulated raw sonar data are generated, and used as input in the sonar processing algorithms to generate sonar images. Using the model, the influence of, the most critical characteristics of the sonar, including phase variations among the channels, non-homogeneous channel amplitude, and the number of bad channels, on the quality of the sonar image is determined. The results of the model are compared to real data from a low frequency FLS sonar (250 KHz) and a high frequency FLS sonar (600 KHz). There is good matching between the simulation and the operation of the two sonars and the performance was markedly enhanced by using the modeling results.
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Date Issued: 2001
PURL: http://purl.flvc.org/fcla/dt/12733
Subject Headings: Sonar, Underwater acoustics, Remote submersibles
Format: Document (PDF)

Title: Modeling the acoustic signature of an Ocean Explorer class autonomous underwater vehicle.
Creator: Debiesme, Francois-Xavier., Florida Atlantic University, Cuschieri, Joseph M.
Abstract/Description: Autonomous Underwater Vehicles (AUV) rely on acoustics for a number of mission functions such as communications (Acoustic Modem) and vision (Forward and Side Looking Sonars). The AUV acoustic signature (self-noise and vibration) can thus interfere with AUV operations. Additionally, underwater measurements such as turbulence measurements can be contaminated by interference between the AUV generated acoustics pressures and the low pressures of the turbulence. In this thesis a Finite Element and...
Show moreAutonomous Underwater Vehicles (AUV) rely on acoustics for a number of mission functions such as communications (Acoustic Modem) and vision (Forward and Side Looking Sonars). The AUV acoustic signature (self-noise and vibration) can thus interfere with AUV operations. Additionally, underwater measurements such as turbulence measurements can be contaminated by interference between the AUV generated acoustics pressures and the low pressures of the turbulence. In this thesis a Finite Element and Boundary Element approach is developed to characterize the self-noise (vibration and radiated sound pressure) of a simplified FAU Ocean Explorer AUV. Mechanical excitation from the "podule", which contains the motors for the propulsion and motion control, is assumed in the analysis. The low frequency (less than 1Khz) results are dominated by two types of modes. One type associated with the motion of the "podule" as a rigid body on the vibration isolation supports that connects it to the rest of the AUV structure. The second type is associated with local structural deformations of the "podule", support frame, and AUV hull. Modifying the stiffness of the supports reduces the frequency of the rigid body modes of the "podule", but does not influence the frequencies of the local structural deformations of the "podule" and the rest of the AUV. Decreasing the stiffness of the supports should result in a reduced AUV acoustic signature.
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Date Issued: 2000
PURL: http://purl.flvc.org/fcla/dt/15764
Subject Headings: Oceanographic submersibles, Underwater acoustics, Acoustic models
Format: Document (PDF)

Title: Radius distribution of ocean near surface bubbles.
Creator: Auffret, Yvan., Florida Atlantic University, Glegg, Stewart A. L.
Abstract/Description: This study proposed to determine an ocean surface bubble radius distribution using theoretical noise models, experimental noise spectral data and a theoretical model for the bubble size distribution. The obtained distribution was compared to previous experimental distributions. A good agreement was found for the radius upper cut-off but the shape and the peak radius of the distribution are different from experimental observations. The most probable reasons for these differences were given....
Show moreThis study proposed to determine an ocean surface bubble radius distribution using theoretical noise models, experimental noise spectral data and a theoretical model for the bubble size distribution. The obtained distribution was compared to previous experimental distributions. A good agreement was found for the radius upper cut-off but the shape and the peak radius of the distribution are different from experimental observations. The most probable reasons for these differences were given. Moreover, the validity of recent theoretical bubble noise models was checked. Eventually, the main limitations of the study were pointed out and directions for future works were given.
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Date Issued: 1993
PURL: http://purl.flvc.org/fcla/dt/14922
Subject Headings: Underwater acoustics, Acoustic surface waves, Bubbles
Format: Document (PDF)

Title: Target signature for a periodic structure using a low-frequency broadband side-scan simulator.
Creator: Dietz, Jerrold Edward Gilbert., Florida Atlantic University, LeBlanc, Lester R.
Abstract/Description: Many acoustic targets of interest contain features that are periodic in space. This thesis demonstrates that a chirp waveform, 2 kHz to 12 kHz, can detect repetitive structures with periods in the range of 0.125 m to 0.75 m. As aspect angle increases from 0 deg to 90 deg, a frequency shift in the range of 830 Hz to 4800 Hz will occur as the period decreases from 0.75 to 0.125 m. It follows that, spectral analysis can aid in target identification. A sonar propagation model has been developed...
Show moreMany acoustic targets of interest contain features that are periodic in space. This thesis demonstrates that a chirp waveform, 2 kHz to 12 kHz, can detect repetitive structures with periods in the range of 0.125 m to 0.75 m. As aspect angle increases from 0 deg to 90 deg, a frequency shift in the range of 830 Hz to 4800 Hz will occur as the period decreases from 0.75 to 0.125 m. It follows that, spectral analysis can aid in target identification. A sonar propagation model has been developed to simulate the acoustic backscattered energy of a target with periodic characteristics in the presence of seafloor scattering. Examining the spectral components, with appropriate time gating, can achieve a gain of 7 dB at 3100 m.
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Date Issued: 2001
PURL: http://purl.flvc.org/fcla/dt/12788
Subject Headings: Sidescan sonar, Underwater acoustics, Scattering (Physics)
Format: Document (PDF)

Title: A communication protocol for acoustic ad-hoc networks of autonomous underwater vehicles.
Creator: Baud, Bertrand., Florida Atlantic University, An, Edgar
Abstract/Description: This thesis presents the design and implementation of an underwater network communication protocol. The goal is to enable several autonomous underwater vehicles (AUVs) to form a communication network and to exchange information during at-sea missions. The focus of this work is on the upper layers of the protocol: Network and Transport layers. Routing is a critical issue since all the nodes forming the network are moving. A study and comparison of existing routing algorithms is presented. Two...
Show moreThis thesis presents the design and implementation of an underwater network communication protocol. The goal is to enable several autonomous underwater vehicles (AUVs) to form a communication network and to exchange information during at-sea missions. The focus of this work is on the upper layers of the protocol: Network and Transport layers. Routing is a critical issue since all the nodes forming the network are moving. A study and comparison of existing routing algorithms is presented. Two routing algorithms have been chosen and implemented in the network layer of the protocol: Flooding and Destination Sequence Distance Vector Routing. The protocol has been tested on several types of simulated missions. An analysis of the results is proposed for each mission.
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Date Issued: 2001
PURL: http://purl.flvc.org/fcla/dt/12774
Subject Headings: Underwater acoustics, Submersibles, Computer networks
Format: Document (PDF)

Title: The effects of sensor mislocation in vertical arrays.
Creator: Joy, David Raymond., Florida Atlantic University, Glegg, Stewart A. L.
Abstract/Description: Knowledge of the effects of sensor mislocation is necessary for interpreting the outputs from vertical acoustic receiver arrays deployed in the ocean. The first phase of this study consists of deriving a numerical method to determine the geometric shape of a flexible array cable, anchored at its upper end and displaced by horizontal ocean currents. Analytic methods to verify the numerical method are then derived. The second phase of this study considers measurements of a simple sound source...
Show moreKnowledge of the effects of sensor mislocation is necessary for interpreting the outputs from vertical acoustic receiver arrays deployed in the ocean. The first phase of this study consists of deriving a numerical method to determine the geometric shape of a flexible array cable, anchored at its upper end and displaced by horizontal ocean currents. Analytic methods to verify the numerical method are then derived. The second phase of this study considers measurements of a simple sound source by perturbed array cables. The results are compared with those from straight cables to ascertain the effect of the sensor mislocation. These effects are evaluated in terms of array cable curvature and tilt.
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Date Issued: 1990
PURL: http://purl.flvc.org/fcla/dt/14595
Subject Headings: Underwater acoustics
Format: Document (PDF)

Title: A comparison of shallow water sound propagation measurements and computer model predictions.
Creator: Cichock, Joseph Arnold., Florida Atlantic University, Glegg, Stewart A. L.
Abstract/Description: High-resolution sound propagation measurements were made on a 1/10000 th-scale model of the Santa Lucia Escarpment, located off the Southern California coast. The tank was modified from previous experiments using a rubber coating on the tank bottom. High frequency, high resolution, Transmission Loss measurements were made on the SFTF range, Dania Florida. The Parabolic Equation Model RAM was used to validate these measurement sets. A new approach to account for shear wave effects on the...
Show moreHigh-resolution sound propagation measurements were made on a 1/10000 th-scale model of the Santa Lucia Escarpment, located off the Southern California coast. The tank was modified from previous experiments using a rubber coating on the tank bottom. High frequency, high resolution, Transmission Loss measurements were made on the SFTF range, Dania Florida. The Parabolic Equation Model RAM was used to validate these measurement sets. A new approach to account for shear wave effects on the Transmission Loss for the RAM model was developed. Using this new approach, the scaled low frequency Santa Lucia measurements showed excellent agreement with the RAM calculated TL, but there were discrepancies in the predictions of the high frequency at sea measurements at ranges greater than 1 km.
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Date Issued: 2000
PURL: http://purl.flvc.org/fcla/dt/12706
Subject Headings: Underwater acoustics, Sound--Transmission
Format: Document (PDF)

Title: Low-frequency source height measurements.
Creator: Armstrong, Joseph., Florida Atlantic University, Glegg, Stewart A. L.
Abstract/Description: The Federal Highway Administration's development of a new highway noise prediction model (TNM) necessitated the collection of equivalent source height data on moving highway vehicles as a function of frequency. An original method developed by Glegg and Yoon was used in the initial collection of this data. Analysis of this data indicated the measured source height was overestimated at frequencies below 500 Hz. In order to improve the equivalent source height estimates below this frequency two...
Show moreThe Federal Highway Administration's development of a new highway noise prediction model (TNM) necessitated the collection of equivalent source height data on moving highway vehicles as a function of frequency. An original method developed by Glegg and Yoon was used in the initial collection of this data. Analysis of this data indicated the measured source height was overestimated at frequencies below 500 Hz. In order to improve the equivalent source height estimates below this frequency two alternative methods were investigated. The first method made use of the coherence function to remove noise from the autospectral density estimate for an array element through the cross spectra of two other elements. This method is called the noise extraction method and was found to be ineffective for this application. However, the second method used matched-field processing, and a significant improvement in the estimated equivalent source heights was achieved for frequencies below 500 Hz.
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Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/15333
Subject Headings: Noise barriers--Evaluation, Underwater acoustics
Format: Document (PDF)

Title: Experimental analysis of the AUV acoustic signature.
Creator: Frandsen, Susan Eileen., Florida Atlantic University, Cuschieri, Joseph M.
Abstract/Description: This thesis presents an experimental analysis of the acoustic signature of an Ocean Explorer class AUV. The experimental analysis consists of three parts. The first part reports the measurements performed in an open water environment at NSWC in Lake Pend Oreille, Idaho. The second part reports on measurements performed at the FAU test tank on a mock model of the AUV and the third part reports the measurements also in the FAU test tank of the AUV under typical operating conditions. The model...
Show moreThis thesis presents an experimental analysis of the acoustic signature of an Ocean Explorer class AUV. The experimental analysis consists of three parts. The first part reports the measurements performed in an open water environment at NSWC in Lake Pend Oreille, Idaho. The second part reports on measurements performed at the FAU test tank on a mock model of the AUV and the third part reports the measurements also in the FAU test tank of the AUV under typical operating conditions. The model measurement results were also used to verify the prediction capabilities of a numerical FE model of the AUV using the reciprocity method. The measurements in the FAU tank considered different operating conditions and different mounting of the podule inside the AUV. The podule contains the main mechanical components of the AUV, which are the propulsion motor and the control surface motors. Also considered in these measurements is the influence of the propeller and the influence of covering the aft section of the AUV with a compliant layer. The results of this analysis show that the type of mounting of the podule is not very significant and that significant energy is transferred through the water trapped in between the podule and the hull. Furthermore, the propeller has a significant influence on the acoustic signature since it generates distinct tones. These tones were also observed in the results of the open water measurements.
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Date Issued: 2001
PURL: http://purl.flvc.org/fcla/dt/12768
Subject Headings: Underwater acoustics, Oceanographic submersibles
Format: Document (PDF)

Title: High-Speed High-Frequency Acoustic Communications in Ports and Shallow Water.
Creator: Blue, Patrick Michael, Beaujean, Pierre-Philippe, Florida Atlantic University
Abstract/Description: A detailed study of a novel method for high-speed acoustic communications in ports and shallow water is presented. A series of field experiments, coupled with simulated results using an acoustic channel model have been conducted to outline the optimal modulation schemes for use in the highly reverberant and Doppler dominated shallow water acoustic channel. Field experiments were conducted in the vicinity of the SeaTech marina and the Port Everglades turning basin in water depths of 2 to 15...
Show moreA detailed study of a novel method for high-speed acoustic communications in ports and shallow water is presented. A series of field experiments, coupled with simulated results using an acoustic channel model have been conducted to outline the optimal modulation schemes for use in the highly reverberant and Doppler dominated shallow water acoustic channel. Field experiments were conducted in the vicinity of the SeaTech marina and the Port Everglades turning basin in water depths of 2 to 15 meters and ranges of between 25 and 75 meters. An automated FAU acoustic modem transmitted BPSK and QPSK modulated messages centered at 300 kHz, with a source level of 173 dB re 1pPa and a symbol bandwidth of 25, 50 or 75 kHz. The coded rate varied from 25000 to 150000 bits per second. These high data rates are made possible using a high resolution Decision Feedback Equalizer with an efficient Doppler compensation process. The results of this study demonstrate the ability of such a system to transmit video images in a shallow water environment.
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Date Issued: 2007
PURL: http://purl.flvc.org/fau/fd/FA00012504
Subject Headings: Underwater acoustics, Deep-sea sounding, Seawater--Acoustic properties
Format: Document (PDF)

Title: A three-dimensional forward-look sonar simulation model.
Creator: Gazagnaire, Julia., Florida Atlantic University, Cuschieri, Joseph M., Beaujean, Pierre-Philippe
Abstract/Description: The aim of this thesis is to develop a simulation tool, The 3-D Forward-Look Sonar Simulation Model (3-D-FLSSM), for the 3-D Forward Look Sonar or equivalent that provides insight to the defining characteristics of the sonar system that affect the image quality and the data processing. The simulator includes a representation of the acoustic environment, which incorporates a flat seafloor and spherical target, both of which are assumed to a have small-scale roughness (much less than the...
Show moreThe aim of this thesis is to develop a simulation tool, The 3-D Forward-Look Sonar Simulation Model (3-D-FLSSM), for the 3-D Forward Look Sonar or equivalent that provides insight to the defining characteristics of the sonar system that affect the image quality and the data processing. The simulator includes a representation of the acoustic environment, which incorporates a flat seafloor and spherical target, both of which are assumed to a have small-scale roughness (much less than the acoustic wavelength) associated with them. The backscatter from the target and the seafloor are calculated using the Rayleigh-Rice approximation implementing Kuo's backscattering cross section. The simulator is capable of modeling targets of various shapes and sizes. The 3-D-FLSSM assumes a plane wave approximation and a constant sound velocity throughout the water column. The final product is a simulation tool with a focus on shallow water littoral acoustics, which can be used to define the sonar hardware and processing software necessary to meet various operational requirements.
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Date Issued: 2003
PURL: http://purl.flvc.org/fcla/dt/13002
Subject Headings: Sonar--Computer simulation, Underwater acoustics, Remote submersibles
Format: Document (PDF)

Title: A passive platform for tracking underwater vehicles.
Creator: Dufour, Emmanuel R., Florida Atlantic University, Glegg, Stewart A. L.
Abstract/Description: Over recent years, the trend in Autonomous Underwater Vehicle (AUV) design has been to reduce vehicle size and cost. On board navigation systems are both large and expensive so alternate solutions for vehicle positioning are required. The thesis explores the performance of a passive platform, the Ambient Noise Sonar (ANS), in remotely detecting, localizing and tracking submersible vessels. This task is achieved by exploiting communication signatures emitted by the moving submersible. The...
Show moreOver recent years, the trend in Autonomous Underwater Vehicle (AUV) design has been to reduce vehicle size and cost. On board navigation systems are both large and expensive so alternate solutions for vehicle positioning are required. The thesis explores the performance of a passive platform, the Ambient Noise Sonar (ANS), in remotely detecting, localizing and tracking submersible vessels. This task is achieved by exploiting communication signatures emitted by the moving submersible. The utility modem integrated on the AUV can be operated in a PSK and a MFSK mode. It was demonstrated that the ANS successfully tracks AUVs in both cases. First, the thesis presents the sonar beamformer and shows its potential for tracking by using the AUV communication signals. It describes a scheme developed to enhance the processor performance in a multi-target configuration and clutter. Then, it discusses promising tracking results from experiments conducted in summer and fall 1998, off the coast of South Florida.
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Date Issued: 1999
PURL: http://purl.flvc.org/fcla/dt/15671
Subject Headings: Oceanographic submersibles--Automatic control, Underwater acoustics, Acoustical engineering
Format: Document (PDF)

Title: A volume scattering model for sediment classification through acoustic means.
Creator: Jenkins, Michael Gerard., Florida Atlantic University, LeBlanc, Lester R.
Abstract/Description: A simple model is developed to evaluate the acoustic scattering environment of sediments based on the envelope function of digital sub-bottom sonar data. Scattering pressure and intensity histograms are produced from model results. These histograms are compared to the theoretical distributions expected for scattering event pressure and intensity. Sediment composition is inferred from the determined acoustic scattering environment. The model has been applied to X-Star digital sub-bottom data...
Show moreA simple model is developed to evaluate the acoustic scattering environment of sediments based on the envelope function of digital sub-bottom sonar data. Scattering pressure and intensity histograms are produced from model results. These histograms are compared to the theoretical distributions expected for scattering event pressure and intensity. Sediment composition is inferred from the determined acoustic scattering environment. The model has been applied to X-Star digital sub-bottom data taken in the vicinity of St. John's Harbor, New Brunswick. Model results are compared to ground truth (Borehole logs) taken within the survey area. This comparison indicates general trends within the sediment scattering environment which may be linked to sediment composition. Distinct differences in model results were noted over areas of differing sediment types.
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Date Issued: 1993
PURL: http://purl.flvc.org/fcla/dt/14945
Subject Headings: Sedimentation analysis, Underwater acoustics, Sound--Reverberation
Format: Document (PDF)

Title: Sound generated due to vortical flow past a forward facing step.
Creator: Gundlapalli, Ravishankar., Florida Atlantic University, Dhanak, Manhar R.
Abstract/Description: The sound field associated with the motion of 2-dimensional finite core vortex past a forward facing step is obtained. A numerical scheme using Contour Dynamics technique and incompressible, inviscid equations of motion is developed to determine the evolution of the structure of the vortex, its path over the step and the radiated sound. An appropriate low-frequency Green's function is derived and the expression for the far field acoustic pressure as formulated by Mohring is used. The vortex...
Show moreThe sound field associated with the motion of 2-dimensional finite core vortex past a forward facing step is obtained. A numerical scheme using Contour Dynamics technique and incompressible, inviscid equations of motion is developed to determine the evolution of the structure of the vortex, its path over the step and the radiated sound. An appropriate low-frequency Green's function is derived and the expression for the far field acoustic pressure as formulated by Mohring is used. The vortex structure evolves in the non-uniform flow in the vicinity of the step and under certain conditions is found to undergo significant deformation of its core structure. The far field acoustic pressure is found to be a strong function of vortex motion in the vicinity of the step. Results for the vortex trajectory and the associated acoustic pressure are presented for a variety of flow parameters.
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Date Issued: 1992
PURL: http://purl.flvc.org/fau/fd/FADT14825
Subject Headings: Underwater acoustics, Vortex-motion, Eddies, Hydrodynamics
Format: Document (PDF)

Title: Transducer design for underwater acoustic communications using the finite element method.
Creator: Jacquemin, Jean-Philippe M. J., Florida Atlantic University, LeBlanc, Lester R.
Abstract/Description: The behavior of radially polarized free-flooded ring (FFR) transducers is studied for application in underwater acoustic communications. Theoretical models are first presented. Then the finite element method (FEM) is introduced and a FEM model for the FFR transducer is proposed. Experimental data are collected and compared to the simulation results with good correspondence. A series of FEM simulations lead then to optimum geometrical parameters for a fine-tuned FFR transducer dedicated to...
Show moreThe behavior of radially polarized free-flooded ring (FFR) transducers is studied for application in underwater acoustic communications. Theoretical models are first presented. Then the finite element method (FEM) is introduced and a FEM model for the FFR transducer is proposed. Experimental data are collected and compared to the simulation results with good correspondence. A series of FEM simulations lead then to optimum geometrical parameters for a fine-tuned FFR transducer dedicated to underwater acoustic communications. Finally, stack transducers models and the piezocomposite technology are presented as possible improvement of the present transducer.
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Date Issued: 2001
PURL: http://purl.flvc.org/fcla/dt/12758
Subject Headings: Underwater acoustics, Finite element method, Transducers, Interdigital
Format: Document (PDF)

Acoustical engineering (4)	+ -
Oceanographic submersibles (4)	+ -
Acoustic surface waves (3)	+ -
Signal processing--Digital techniques (3)	+ -
Acoustic imaging (2)	+ -

Marine sediments--Acoustic properties (2)	+ -
Modems (2)	+ -
Remote submersibles (2)	+ -
Seawater--Acoustic properties (2)	+ -
Sonar (2)	+ -
Wavelets (Mathematics) (2)	+ -
Acoustic models (1)	+ -
Acoustic phenomena in nature (1)	+ -
Acoustic velocity meters (1)	+ -
Bubbles (1)	+ -
Computer networks (1)	+ -
Deep-sea sounding (1)	+ -
Eddies (1)	+ -
Finite element method (1)	+ -
Fuzzy algorithms (1)	+ -
Hydrodynamics (1)	+ -
Intelligent control systems (1)	+ -
Local area networks (Computer network) (1)	+ -
Marine mammals -- Effect of noise on (1)	+ -
Marine mammals -- Vocalization (1)	+ -
Marine sediments (1)	+ -
Noise barriers--Evaluation (1)	+ -
Noise--Measurement (1)	+ -
Oceanographic submersibles--Automatic control (1)	+ -

Florida Atlantic University (36)	+ -
College of Engineering and Computer Science (16)	+ -
Department of Ocean and Mechanical Engineering (13)	+ -
Glegg, Stewart A. L. (11)	+ -
LeBlanc, Lester R. (6)	+ -

Cuschieri, Joseph M. (5)	+ -
Schock, Steven G. (4)	+ -
Department of Computer and Electrical Engineering and Computer Science (3)	+ -
Beaujean, Pierre-Philippe (2)	+ -
Erdol, Nurgun (2)	+ -
Olivieri, Marc P. (2)	+ -
Smith, Samuel M. (2)	+ -
Alleyne, Jochen Raoul (1)	+ -
An, Edgar (1)	+ -
Armstrong, Joseph. (1)	+ -
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