View All Items

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.
Show less
Date Issued: 2002
PURL: http://purl.flvc.org/fcla/dt/12914
Subject Headings: Underwater acoustics, Signal processing--Digital techniques
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.
Show less
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: Real time method for remote measurement of compressional wave attenuation.
Creator: DeBruin, Darryl L., Florida Atlantic University, Schock, Steven G.
Abstract/Description: An acoustic measurement system is developed to estimate the compressional wave attenuation of marine sediments in real time. A chirp sonar transmits filtered digital reflection data to a signal processing computer that processes the data on an AT&T DSP32C chip. The signal processing computer estimates and displays the center frequency of the processed pulse as it is attenuated by the ocean sediments. Wavelet modelling establishes the relationship between the center frequency shift and...
Show moreAn acoustic measurement system is developed to estimate the compressional wave attenuation of marine sediments in real time. A chirp sonar transmits filtered digital reflection data to a signal processing computer that processes the data on an AT&T DSP32C chip. The signal processing computer estimates and displays the center frequency of the processed pulse as it is attenuated by the ocean sediments. Wavelet modelling establishes the relationship between the center frequency shift and relaxation time, from which the sediment type and compressional wave attenuation are determined. Frequency contours from two different data sites demonstrate that the system is able to reliably estimate sediment type and compressional wave attenuation. Error introduced by noise is below 1% for noise levels less than 0.1 of the normalized processed signal. Random error in the estimates is minimized by determining reliable frequency values and by ensemble averaging the values.
Show less
Date Issued: 1992
PURL: http://purl.flvc.org/fcla/dt/14824
Subject Headings: Marine sediments--Acoustic properties, Signal processing--Computer simulation
Format: Document (PDF)

Title: Sediment layer tracking using neural networks.
Creator: Freyermuth, Vincent Nicolas., Florida Atlantic University, Schock, Steven G.
Abstract/Description: The detection of sediment layer interfaces in normal incidence acoustic reflection data is a requirement for automatic classification and geologic mapping of subsurface layers. The detection is difficult because of the constructive and destructive interference caused by the impedance changes in the sediment column and high scattering noise levels. The purpose of this work is to implement a procedure using neural networks that automatically detects the sediment layers from the envelope of...
Show moreThe detection of sediment layer interfaces in normal incidence acoustic reflection data is a requirement for automatic classification and geologic mapping of subsurface layers. The detection is difficult because of the constructive and destructive interference caused by the impedance changes in the sediment column and high scattering noise levels. The purpose of this work is to implement a procedure using neural networks that automatically detects the sediment layers from the envelope of acoustic reflections. The data was collected using a sub-bottom profiler that transmits a 2 to 10 kHz FM pulse. The detection procedure is a three step method: a first neural network removes most of the reflections due to random scatterers, a second neural network tracks the layers and a third algorithm recognizes the segments of detected layers corresponding to the same sediment interface Applied on different sub-bottom images, the procedure detects more than 80% of the layers correctly.
Show less
Date Issued: 1998
PURL: http://purl.flvc.org/fcla/dt/15561
Subject Headings: Neural networks (Computer science), Marine sediments--Acoustic properties
Format: Document (PDF)

Title: An investigation of the influence of surface roughness on reflection coefficients measured by a chirp sonar using a laser profiling of the seafloor.
Creator: Hache, Nicolas., Florida Atlantic University, Beaujean, Pierre-Philippe, Schock, Steven G.
Abstract/Description: This research investigates the validity of an acoustic propagation model by comparing theoretical reflection coefficients, function of frequency, to FAU chirp sonar measurements (chirp sub-bottom profiler). An acoustic model has been implemented to estimate the spectrum of energy reflected from sandy sediments in the presence of surface scattering. The surface roughness being the dominant reverberation part, the volume scattering has been neglected in this model. A laser scanning system...
Show moreThis research investigates the validity of an acoustic propagation model by comparing theoretical reflection coefficients, function of frequency, to FAU chirp sonar measurements (chirp sub-bottom profiler). An acoustic model has been implemented to estimate the spectrum of energy reflected from sandy sediments in the presence of surface scattering. The surface roughness being the dominant reverberation part, the volume scattering has been neglected in this model. A laser scanning system involving an image-processing algorithm has been designed to measure the seafloor bottom roughness using 1D Fourier transforms. In the case of anisotropic roughness, an estimation of the sand ripples dominant direction is provided involving 2D Fourier transforms. Measurements of acoustic data using a chirp sonar and estimation of bottom roughness from video data of the scanner over an artificial bottom are provided to compare the reflection coefficients obtained from the data actually measured with those from the acoustical model.
Show less
Date Issued: 2005
PURL: http://purl.flvc.org/fcla/dt/13212
Subject Headings: Underwater acoustics--Measurement, Marine sediments--Acoustic properties, Oceanography, Seawater--Acoustic properties
Format: Document (PDF)

Title: Fuzzy auto-detection of bottom mines.
Creator: Bauer, Eric John., Florida Atlantic University, Schock, Steven G.
Abstract/Description: An automatic mine detection method has been designed for the purpose of locating mine-like objects on the seabed in real time using a high frequency, high resolution side scan sonar. The processing flow includes a calculation of the average scattering function of the local environment, shadow detection, and a fuzzy logic clustering/fuzzy logic detection procedure for identifying mine-like shadows. An Autonomous Underwater Vehicle (AUV) equipped with a fuzzy detection system gives the Navy the...
Show moreAn automatic mine detection method has been designed for the purpose of locating mine-like objects on the seabed in real time using a high frequency, high resolution side scan sonar. The processing flow includes a calculation of the average scattering function of the local environment, shadow detection, and a fuzzy logic clustering/fuzzy logic detection procedure for identifying mine-like shadows. An Autonomous Underwater Vehicle (AUV) equipped with a fuzzy detection system gives the Navy the capability of rapidly locating bottom mines in littoral underwater environments during over-the-horizon operations.
Show less
Date Issued: 2000
PURL: http://purl.flvc.org/fcla/dt/12705
Subject Headings: Submarine mines, Sonar, Fuzzy systems
Format: Document (PDF)

Title: The normal incidence reflection coefficient of a sandy seabed as a function of frequency.
Creator: Arizzi, Ernest Allen., Florida Atlantic University, Schock, Steven G.
Abstract/Description: A thesis investigates the measured and theoretical pressure reflection coefficients of the seabed at normal incidence. The theoretical reflection coefficient is calculated using a physics-based model developed by Maurice Biot. The model describes sound propagation in saturated porous media and interrelationships between the acoustic properties of the media and the physical properties of the pore fluid and the porous solid. Stoll modified the Biot model for the case of ocean sediments and...
Show moreA thesis investigates the measured and theoretical pressure reflection coefficients of the seabed at normal incidence. The theoretical reflection coefficient is calculated using a physics-based model developed by Maurice Biot. The model describes sound propagation in saturated porous media and interrelationships between the acoustic properties of the media and the physical properties of the pore fluid and the porous solid. Stoll modified the Biot model for the case of ocean sediments and developed an expression for calculating the reflection coefficient as a function of frequency. This thesis tests the model by comparing the reflection coefficient measured with chirp sonar to the reflection coefficient calculated using the Biot model. An experiment was conducted off Fort Walton Beach, Florida where chirp sonar transmitted FM pulses at normal incidence to a sandy seabed. Sediment properties measured during SAX-99 are used to calculate the theoretical reflection coefficient using the Biot-Stoll model. The agreement of the measured reflection coefficients with the theoretical calculations over the band of 1500 to 16000 Hz varies as much as 70%. The plotted results show a reduction of the reflection coefficient with frequency but the large deviations from the trend prevent any further conclusions.
Show less
Date Issued: 2004
PURL: http://purl.flvc.org/fcla/dt/13191
Subject Headings: Marine sediments--Acoustic properties, Underwater acoustics--Measurement, Sedimentation analysis
Format: Document (PDF)

Title: Broadband measurements of compressional wave attenuation.
Creator: Reeder, Angela Christine., Florida Atlantic University, Schock, Steven G., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: An in situ acoustic measurement system was developed to estimate the compressional wave attenuation of marine sediments. The system uses acoustic probes to measure a wideband acoustic pulse traveling horizontally though various sediments. The system transmits a 20 millisecond frequency-modulated (FM) pulse swept from 3 to 50 kHz and match filters the received signals. A special ratio of data collected at two horizontal ranges from the source is used to estimate attenuation as a function of...
Show moreAn in situ acoustic measurement system was developed to estimate the compressional wave attenuation of marine sediments. The system uses acoustic probes to measure a wideband acoustic pulse traveling horizontally though various sediments. The system transmits a 20 millisecond frequency-modulated (FM) pulse swept from 3 to 50 kHz and match filters the received signals. A special ratio of data collected at two horizontal ranges from the source is used to estimate attenuation as a function of frequency. Data is collected with the in situ system and a chirp subbottom profiling sonar at two offshore sites to compare the attenuation of horizontally and vertically traveling waves in sediment. The collected data is also used to determine the feasibility of remotely estimating in situ attenuation using a chirp sonar. In situ and chirp sonar estimates agree and fall within the range of attenuation measurements made by other investigators in similar sediments.
Show less
Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/15327
Subject Headings: Marine sediments--Acoustic properties--Measurement, Signal processing
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.
Show less
Date Issued: 2003
PURL: http://purl.flvc.org/fcla/dt/13084
Subject Headings: Underwater acoustics, Marine sediments--Acoustic properties
Format: Document (PDF)

Title: Visualization of buried objects in three-dimensional acoustic data acquired by a buried object scanning sonar.
Creator: Tellier, Arnaud Marc., Florida Atlantic University, Schock, Steven G., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The common approach for finding objects buried under the seabed is to use a single channel chirp reflection profiler. Reflection profiles lack information on target location, geometry and size. This thesis investigates methods for visualizing buried objects in noisy 3D acoustic data acquired by a small aperture scanning sonar. Various surface and volume rendering methods are tested with synthetic datasets containing fluid loaded spheres and with experimental data acquired with a 4-by-8 planar...
Show moreThe common approach for finding objects buried under the seabed is to use a single channel chirp reflection profiler. Reflection profiles lack information on target location, geometry and size. This thesis investigates methods for visualizing buried objects in noisy 3D acoustic data acquired by a small aperture scanning sonar. Various surface and volume rendering methods are tested with synthetic datasets containing fluid loaded spheres and with experimental data acquired with a 4-by-8 planar hydrophone array towed over buried objects with various aspects and size. The Maximum Intensity Projection is the best of the tested methods for real-time visualization of the data where a global overview of the targets is needed. A surface rendering technique such as the Marching Cubes is useful for offline measurement of the geometry and size of buried objects selected by the operator.
Show less
Date Issued: 1999
PURL: http://purl.flvc.org/fcla/dt/15682
Subject Headings: Three-dimensional display systems, Sonar, Sound-waves--Scattering, Computer graphics
Format: Document (PDF)

Title: The development and application of a numerical model for predicting the frequency response of the seabed from vertical profiles of sediment impedance.
Creator: Zhang, Jian Long., Florida Atlantic University, Schock, Steven G., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Interaction of normal incidence, wideband acoustic pulses with seabed is investigated to determine the acoustic frequency ranges that provide the most information about the sediment structure. An exact numerical model is developed for calculating the frequency response and impulse response of the seabed from an impedance profile of a sediment core. A database of impedance profiles from several ocean environments were studied to describe the shapes of commonly found impedance changes. The...
Show moreInteraction of normal incidence, wideband acoustic pulses with seabed is investigated to determine the acoustic frequency ranges that provide the most information about the sediment structure. An exact numerical model is developed for calculating the frequency response and impulse response of the seabed from an impedance profile of a sediment core. A database of impedance profiles from several ocean environments were studied to describe the shapes of commonly found impedance changes. The impulse response of the seabed is convolved with acoustic pulses to generate synthetic acoustic returns. The synthetic profiles are studied to determine the effect of operating frequency and bandwidth on resolution and on the accuracy of measuring impedance changes. This thesis explains why inversion procedures have failed to generate vertical impedance profiles of the seabed from normal incidence reflection data. The results of this work provide guidelines for selecting subbottom profiler array sizes and operating frequencies for quantitative sediment studies, and for subsampling cores.
Show less
Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/15293
Subject Headings: Marine sediments--Acoustic properties, Seismic reflection method
Format: Document (PDF)

Title: Synchronous spatial array processing for underwater vehicle tracking.
Creator: Normand, Olivier., Florida Atlantic University, Schock, Steven G., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Navigation of Unmanned Underwater Vehicles (UUVs) is commonly assisted in confined areas by acoustic positioning systems. The Department of Ocean Engineenng at Florida Atlantic University is developing an altemative system based on submerged modems. This thesis describes an optimal target location estimation technique using a multi-channel spatial receiver array (Millscross) used as a development tool combined with a synchronous modem and transponder network mounted on buoys and UUVs. The...
Show moreNavigation of Unmanned Underwater Vehicles (UUVs) is commonly assisted in confined areas by acoustic positioning systems. The Department of Ocean Engineenng at Florida Atlantic University is developing an altemative system based on submerged modems. This thesis describes an optimal target location estimation technique using a multi-channel spatial receiver array (Millscross) used as a development tool combined with a synchronous modem and transponder network mounted on buoys and UUVs. The Millscross provides a reference to evaluate the performance of the navigation estimator. Spatial array principles are used to develop decoding and beamforming techniques to process modem messages, enabling the end user (the UUV) to estimate in real-time its own position and navigate in space. A simulation was used to compare actual results with theory and determine the processing and decoding algorithms. These algorithms were then applied to real data to estimate the target position (direction of arrival and geodetic coordinates).
Show less
Date Issued: 2002
PURL: http://purl.flvc.org/fcla/dt/12917
Subject Headings: Underwater navigation, Underwater acoustics, Signal processing--Digital techniques
Format: Document (PDF)

Title: Simulation of reflection tomographic images of underwater targets with the effect of vehicle motion sensing errors.
Creator: Quentin, Gwendoline., Florida Atlantic University, Schock, Steven G., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The Buried Object Scanning Sonar (BOSS) is being developed at Florida Atlantic University to image targets buried under the seabed. Tomographic images are constructed using a sequence of sonar transmissions while the vehicle is moving. This motion causes image distortion and should be measured and removed by mapping the echoes received to an absolute coordinate system. The aim of this thesis is to develop and simulate a technique for generating BOSS images that provide an accurate...
Show moreThe Buried Object Scanning Sonar (BOSS) is being developed at Florida Atlantic University to image targets buried under the seabed. Tomographic images are constructed using a sequence of sonar transmissions while the vehicle is moving. This motion causes image distortion and should be measured and removed by mapping the echoes received to an absolute coordinate system. The aim of this thesis is to develop and simulate a technique for generating BOSS images that provide an accurate representation of target shape and size, by removing vehicle motion while mapping the image pixels. Synthetic acoustic data sets are generated by convolving the auto-correlated FM transmission pulse with the impulse response of an elastic sphere. Synthetic outputs of a Doppler velocity log and a 3-axis inertial measurement unit are generated to simulate vehicle motion. Noise is added to the sensor data to show the effects of motion sensor errors on image quality.
Show less
Date Issued: 2003
PURL: http://purl.flvc.org/fcla/dt/13040
Subject Headings: Ocean tomography, Sonar, Underwater navigation
Format: Document (PDF)

Marine sediments--Acoustic properties (6)	+ -
Sonar (4)	+ -
Underwater acoustics (4)	+ -
Signal processing--Digital techniques (2)	+ -
Sound-waves--Scattering (2)	+ -

Three-dimensional display systems (2)	+ -
Underwater acoustics--Measurement (2)	+ -
Underwater navigation (2)	+ -
Computer graphics (1)	+ -
Fuzzy systems (1)	+ -
Marine sediments--Acoustic properties--Measurement (1)	+ -
Neural networks (Computer science) (1)	+ -
Ocean tomography (1)	+ -
Oceanography (1)	+ -
Seawater--Acoustic properties (1)	+ -
Sedimentation analysis (1)	+ -
Seismic reflection method (1)	+ -
Signal processing (1)	+ -
Signal processing--Computer simulation (1)	+ -
Submarine mines (1)	+ -
Underwater exploration (1)	+ -

Florida Atlantic University (13)	+ -
Schock, Steven G. (13)	+ -
College of Engineering and Computer Science (6)	+ -
Department of Ocean and Mechanical Engineering (6)	+ -
Arizzi, Ernest Allen. (1)	+ -

Bauer, Eric John. (1)	+ -
Beaujean, Pierre-Philippe (1)	+ -
Bernault, Emmanuel Pierre. (1)	+ -
DeBruin, Darryl L. (1)	+ -
Freyermuth, Vincent Nicolas. (1)	+ -
Hache, Nicolas. (1)	+ -
Munro, Lachlan I. (1)	+ -
Normand, Olivier. (1)	+ -
Quentin, Gwendoline. (1)	+ -
Reeder, Angela Christine. (1)	+ -
Rivalan, Gregory. (1)	+ -
Tellier, Arnaud Marc. (1)	+ -
Zhang, Jian Long. (1)	+ -

Search In

Sort Results By:

Narrow results by:

Collection

Topical Subject

Genre

Type of Resource

Language

Creator

Format

Owner