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Title: Detection and classification of marine mammal sounds.
Creator: Esfahanian, Mahdi, Zhuang, Hanqi, Florida Atlantic University, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
Abstract/Description: Ocean is home to a large population of marine mammals such as dolphins and whales and concerns over anthropogenic activities in the regions close to their habitants have been increased. Therefore the ability to detect the presence of these species in the field, to analyze and classify their vocalization patterns for signs of distress and distortion of their communication calls will prove to be invaluable in protecting these species. The objective of this research is to investigate methods...
Show moreOcean is home to a large population of marine mammals such as dolphins and whales and concerns over anthropogenic activities in the regions close to their habitants have been increased. Therefore the ability to detect the presence of these species in the field, to analyze and classify their vocalization patterns for signs of distress and distortion of their communication calls will prove to be invaluable in protecting these species. The objective of this research is to investigate methods that automatically detect and classify vocalization patterns of marine mammals. The first work performed is the classification of bottlenose dolphin calls by type. The extraction of salient and distinguishing features from recordings is a major part of this endeavor. To this end, two strategies are evaluated with real datasets provided by Woods Hole Oceanographic Institution: The first strategy is to use contour-based features such as Time-Frequency Parameters and Fourier Descriptors and the second is to employ texture-based features such as Local Binary Patterns (LBP) and Gabor Wavelets. Once dolphin whistle features are extracted for spectrograms, selection of classification procedures is crucial to the success of the process. For this purpose, the performances of classifiers such as K-Nearest Neighbor, Support Vector Machine, and Sparse Representation Classifier (SRC) are assessed thoroughly, together with those of the underlined feature extractors.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00004282, http://purl.flvc.org/fau/fd/FA00004282
Subject Headings: Acoustic phenomena in nature, Marine mammals -- Effect of noise on, Marine mammals -- Vocalization, Signal processing -- Mathematics, Underwater acoustics, Wavelets (Mathematics)
Format: Document (PDF)

Title: Modeling the performance of a laser for tracking an underwater dynamic target.
Creator: Dill, Thomas J., von Ellenrieder, Karl, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Options for tracking dynamic underwater targets using optical methods is currently limited. This thesis examines optical reflectance intensities utilizing Lambert’s Reflection Model and based on a proposed underwater laser tracking system. Numerical analysis is performed through simulation to determine the detectable light intensities based on relationships between varying inputs such as angle of illumination and target position. Attenuation, noise, and laser beam spreading are included in...
Show moreOptions for tracking dynamic underwater targets using optical methods is currently limited. This thesis examines optical reflectance intensities utilizing Lambert’s Reflection Model and based on a proposed underwater laser tracking system. Numerical analysis is performed through simulation to determine the detectable light intensities based on relationships between varying inputs such as angle of illumination and target position. Attenuation, noise, and laser beam spreading are included in the analysis. Simulation results suggest optical tracking exhibits complex relationships based on target location and illumination angle. Signal to Noise Ratios are a better indicator of system capabilities than received intensities. Signal reception does not necessarily confirm target capture in a multi-sensor network.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00004279, http://purl.flvc.org/fau/fd/FA00004279
Subject Headings: Acoustic velocity meters, Intelligent control systems, Optical instruments -- Design and construction, Roving vehicles (Astronautics), Target acquisition, Underwater acoustics
Format: Document (PDF)

Title: Characterization of the acoustic signature of an Ocean Explorer class AUV.
Creator: Lambe, Frederic Lionel., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The radiated noise from Autonomous Underwater Vehicles (AUV's) can interfere with on-board sensors and with certain type of missions. It is thus important to understand the parameters controlling the AUV self noise. In this thesis, measurement techniques and analyses are developed to investigate the mechanisms contributing to the acoustic noise of an Ocean Explorer class AUV. Measurements of the AUV acoustic signature are performed in a reverberant tank, after the tank is qualified to...
Show moreThe radiated noise from Autonomous Underwater Vehicles (AUV's) can interfere with on-board sensors and with certain type of missions. It is thus important to understand the parameters controlling the AUV self noise. In this thesis, measurement techniques and analyses are developed to investigate the mechanisms contributing to the acoustic noise of an Ocean Explorer class AUV. Measurements of the AUV acoustic signature are performed in a reverberant tank, after the tank is qualified to establish a reliable procedure to measure the AUV source levels. The measurement results are compared that obtained in an anechoic tank and in open-water. Acoustic measurements are correlated with vibration measurements performed on various components of the AUV, in order to identify the dominant components. From the results, some preliminary mitigation procedures to reduce the AUV acoustic signature are developed.
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Date Issued: 1999
PURL: http://purl.flvc.org/fcla/dt/15618
Subject Headings: Oceanographic submersibles, Underwater acoustics
Format: Document (PDF)

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: Docking the Ocean Explorer Autonomous Underwater Vehicle using a low-cost acoustic positioning system and a fuzzy logic guidance algorithm.
Creator: Kronen, David Mitchell., Florida Atlantic University, Smith, Samuel M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Having the ability to dock an Autonomous Underwater Vehicle (AUV) can significantly enhance the operation of such vehicles. In order to dock an AUV, the vehicle's position must be known precisely and a guidance algorithm must be used to drive the AUV to its dock. This thesis will examine and implement a low cost acoustic positioning system to meet the positioning requirements. At-sea tests will be used as a method of verifying the systems specifications and proper incorporation into the AUV....
Show moreHaving the ability to dock an Autonomous Underwater Vehicle (AUV) can significantly enhance the operation of such vehicles. In order to dock an AUV, the vehicle's position must be known precisely and a guidance algorithm must be used to drive the AUV to its dock. This thesis will examine and implement a low cost acoustic positioning system to meet the positioning requirements. At-sea tests will be used as a method of verifying the systems specifications and proper incorporation into the AUV. Analyses will be run on the results using several methods of interpreting the data. The second portion of this thesis will develop and test a fuzzy logic docking algorithm which will guide the AUV from a location within the range of the sonar system to the docking station. A six degree of freedom simulation incorporating the Ocean Explorer's hydrodynamic coefficients will be used for the simulation.
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Date Issued: 1997
PURL: http://purl.flvc.org/fcla/dt/15502
Subject Headings: Oceanographic submersibles, Acoustical engineering, Underwater acoustics, Fuzzy algorithms
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: Fatigue crack growth rate of short cracks for high strength steels in sea water.
Creator: Kim, Kijoon., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Experiments have been performed which determined the fatigue crack growth rate (FCGR) of short cracks (a > 0.1mm) for five high strength steels (yield stress 370-570 MPa) in air and in natural seawater with and without cathodic protection. Attention was focused upon Regions I and Il of the classical FCGR-stress intensity range(Delta K) curve with particular consideration of the near-threshold behavior for short cracks. Single edge notch (SEN) three-point bend specimens and a direct current...
Show moreExperiments have been performed which determined the fatigue crack growth rate (FCGR) of short cracks (a > 0.1mm) for five high strength steels (yield stress 370-570 MPa) in air and in natural seawater with and without cathodic protection. Attention was focused upon Regions I and Il of the classical FCGR-stress intensity range(Delta K) curve with particular consideration of the near-threshold behavior for short cracks. Single edge notch (SEN) three-point bend specimens and a direct current potential drop (DCPD) crack monitoring system were employed, and test parameters simulated offshore structure conditions. The results indicated enhanced FCGR for short cracks compared to macrocracks by 3-20 times in air and 2-6 in seawater free-corroding(FC). Also, the Delta Kth for short cracks was apparently lower than for long ones in both environments. The transition from short to long crack behavior occurred at constant $\Delta$K in each environment (15.6 MPa m in air and 10.0 MPa m in seawater(FC)) irrespective of initial Delta K (Delta K(0)). The transition crack length ranged from 0.25 to 1.6 mm and was inversely proportional to $\Delta$K(0). Scanning electron microscope fractography showed that the mechanism of enhanced crack growth rate was associated with secondary crack (SC) formation in air and SC or inter-granular cracking (or both) in seawater (FC). The enhanced FCGR for short cracks was minimized by polarization to -950 mV(SCE). Through an elastic-plastic fracture mechanics analysis using the J-integral parameter it was found that the influence of plastic deformation at the crack tip was approximately independent of crack length (short versus long), and the linear-elastic fracture mechanics analysis gave a realistic representation for fatigue behavior.
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Date Issued: 1992
PURL: http://purl.flvc.org/fcla/dt/12313
Subject Headings: Steel--Fatigue--Environmental aspects, Underwater acoustics, Seawater--Acoustic properties
Format: Document (PDF)

Title: Impact of noise on seafloor property estimation using Biot model parameters obtained through an inversion of chirp sonar data.
Creator: Munro, Lachlan I., Florida Atlantic University, Schock, Steven G., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This thesis describes the development and testing of an inversion method, based on the Biot-Stoll acoustic wave propagation model, for estimating sediments properties from acoustic reflection measurements of the seabed. The Biot-Stoll model is a physics-based model which describes the propagation of compressional and shear waves through porous media. Given the physical sediment properties of the seabed, the pressure reflection coefficient of the seabed is calculated using the Biot-Stoll model...
Show moreThis thesis describes the development and testing of an inversion method, based on the Biot-Stoll acoustic wave propagation model, for estimating sediments properties from acoustic reflection measurements of the seabed. The Biot-Stoll model is a physics-based model which describes the propagation of compressional and shear waves through porous media. Given the physical sediment properties of the seabed, the pressure reflection coefficient of the seabed is calculated using the Biot-Stoll model. The proposed inversion procedure varies sediment properties until a least squares fit is obtained between the output of the model and the measured reflection coefficient. Random errors are introduced into the reflection coefficient measurement to determine the effect of measurement error in the estimation of seabed properties such as permeability, porosity, mean grain diameter, and sediment type.
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Date Issued: 2003
PURL: http://purl.flvc.org/fcla/dt/13084
Subject Headings: Underwater acoustics, Marine sediments--Acoustic properties
Format: Document (PDF)

Title: HELIUM SPEECH PROCESSING BY LINEAR PREDICTION METHOD.
Creator: LEE, HYUN JICK., Florida Atlantic University, Erdol, Nurgun, College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
Abstract/Description: The human speech production system is reviewed through general acoustic theory. Based upon that, the characteristics of helium speech is compared to normal speech. The Linear Prediction algorithm is derived for computer implementation by recursive formulas. The correction factors for the vocal tract area functions are found from simulated helium speech and normal speech data for four vowels. By the correction factors, new corrected area functions are applied to the Linear Prediction algorithm...
Show moreThe human speech production system is reviewed through general acoustic theory. Based upon that, the characteristics of helium speech is compared to normal speech. The Linear Prediction algorithm is derived for computer implementation by recursive formulas. The correction factors for the vocal tract area functions are found from simulated helium speech and normal speech data for four vowels. By the correction factors, new corrected area functions are applied to the Linear Prediction algorithm so that new synthesis filters can be built. The output of the algorithm is enhanced helium speech.
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Date Issued: 1985
PURL: http://purl.flvc.org/fcla/dt/14244
Subject Headings: Acoustical engineering, Underwater acoustics
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: Validation of numerical modelling for long range acoustic propagation.
Creator: Riley, Joseph M., Florida Atlantic University, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Laboratory scale measurements were conducted to validate numerical prediction models used to predict the acoustic field in a shallow water ocean environment. Experimental measurements were conducted in a range independent environment which included the effects of shear in marine sediments and in a depth varying range dependent environment. Good agreement between the experimental measurements and the numerical prediction codes were obtained using optimized values for the input parameters of...
Show moreLaboratory scale measurements were conducted to validate numerical prediction models used to predict the acoustic field in a shallow water ocean environment. Experimental measurements were conducted in a range independent environment which included the effects of shear in marine sediments and in a depth varying range dependent environment. Good agreement between the experimental measurements and the numerical prediction codes were obtained using optimized values for the input parameters of the environmental model. In comparing experimental measurements to the numerical prediction codes it became apparent that the codes were very sensitive to the input parameters describing the bottom boundary of the ocean waveguide.
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Date Issued: 1992
PURL: http://purl.flvc.org/fcla/dt/14819
Subject Headings: Acoustical engineering, Underwater acoustics, Marine sediments
Format: Document (PDF)

Title: A broadband signal processor for acoustic imaging using ambient noise.
Creator: Olivieri, Marc P., Florida Atlantic University, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Buckingham et al. (Nature Vol. 356, p 327) first introduced the concept of acoustic imaging using ambient noise as a method for passively detecting objects in the ocean. Several analytical studies followed, and it was shown that a two dimensional acoustic image could be obtained based on this approach, and that at least 900 pixels are necessary to restitute the details of spherical objects placed in an underwater sound channel. The alternative approach described in this paper is based on a...
Show moreBuckingham et al. (Nature Vol. 356, p 327) first introduced the concept of acoustic imaging using ambient noise as a method for passively detecting objects in the ocean. Several analytical studies followed, and it was shown that a two dimensional acoustic image could be obtained based on this approach, and that at least 900 pixels are necessary to restitute the details of spherical objects placed in an underwater sound channel. The alternative approach described in this paper is based on a signal processing which uses the broadband nature of the ambient noise in the ocean, and therefore, optimizes the use of available sound energy scattered by the object. Images with thousands of pixels can be obtained using a relatively small number of transducers. This method has been validated using simple experiments in air, scaled to represent an ocean application, and results showing images of various objects will be presented.
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Date Issued: 1994
PURL: http://purl.flvc.org/fcla/dt/15065
Subject Headings: Acoustic imaging, Signal processing, Underwater acoustics
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: A feasibility study on using LonWorks Power Line Transceivers for underwater communications.
Creator: Powell, Jennifer Cairns., Florida Atlantic University, Smith, Samuel M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This project consisted of a feasibility study to ascertain whether or not an inexpensive acoustic modem for an Autonomous Underwater Vehicle (AUV) could be developed using low cost commercially available products. Our AUV's at Florida Atlantic University currently use LonWorks for their internal control networks, so we have plenty of experience with their parts. The LonWorks Power Line Transceivers are capable of generating a signal that can be sent to a transducer for communication through...
Show moreThis project consisted of a feasibility study to ascertain whether or not an inexpensive acoustic modem for an Autonomous Underwater Vehicle (AUV) could be developed using low cost commercially available products. Our AUV's at Florida Atlantic University currently use LonWorks for their internal control networks, so we have plenty of experience with their parts. The LonWorks Power Line Transceivers are capable of generating a signal that can be sent to a transducer for communication through the water. The PLT-30 Power Line Transceiver generates a direct sequence spread spectrum signal (DSSS) that offers many useful operating features; such as anti-jam, interference rejection and covert communications, low intercept probability, and most importantly, multipath protection. After numerous tests, however, the system was incapable of establishing reliable acoustic communications. We conclude that the PLT-30 Power Line Transceiver use as an underwater acoustic modem is not a viable approach. As an alternative method, communication through an electric current field was tested in a salt-water pool. The initial test produced a 100% success rate.
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Date Issued: 2000
PURL: http://purl.flvc.org/fcla/dt/12695
Subject Headings: Local area networks (Computer network), Underwater acoustics
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)	+ -
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