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Oceanic Engineering, IEEE Journal of

Issue 2 • Date April 2007

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Displaying Results 1 - 24 of 24
  • Table of contents

    Page(s): C1
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    Freely Available from IEEE
  • IEEE Journal of Oceanic Engineering publication information

    Page(s): C2
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    Freely Available from IEEE
  • Editorial: IEEE-JOE Peer-Reviewed Contributions

    Page(s): 285
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    Freely Available from IEEE
  • In Situ Alignment Calibration of Attitude and Doppler Sensors for Precision Underwater Vehicle Navigation: Theory and Experiment

    Page(s): 286 - 299
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1795 KB) |  | HTML iconHTML  

    This paper reports the development and experimental evaluation of two in situ least squares techniques for estimating the alignment matrix of Doppler sonars commonly used for precision navigation of oceanographic submersibles. Most previously reported methods addressed the problem of single degree-of-freedom heading alignment using bottom-lock Doppler sonar data and global positioning system (GPS) navigation data. This paper reports and evaluates two techniques for three degree-of-freedom calibration of attitude and Doppler sonar sensors using sensor data available to vehicles at full ocean depth. The first technique provides a general linear least squares estimate of the alignment matrix. The second technique results in a least squares alignment matrix estimate constrained to the group of rotation matrices. The performance of these estimates is evaluated with a laboratory remotely operated vehicle (ROV) and a field-deployed autonomous underwater vehicle (AUV). Experimental results are reported which demonstrate that Doppler navigation employing the reported alignment calibration techniques significantly improves navigation precision. The experiments show that the latter technique provides calibration estimates that improve Doppler navigation precision not only on the calibration data set itself, but also provide improved precision over a wide variety of vehicle trajectories other than the calibration data set. View full abstract»

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  • On the Use of Adaptive/Integral Actions for Six-Degrees-of-Freedom Control of Autonomous Underwater Vehicles

    Page(s): 300 - 312
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (908 KB) |  | HTML iconHTML  

    In this paper, the control of autonomous underwater vehicles (AUVs) in six-degrees-of-freedom (6-DOFs) is analyzed in a comparison study among several controllers. At steady state, the vehicle needs to compensate for two dynamic effects, the ocean current and the restoring forces; the appropriateness of the adaptive/integral action designed with respect to the persistent effects is discussed. Moreover, for each controller, an adaptive/integral proportional derivative (PD) plus gravity compensation-like version is derived and eventually modified so as to achieve null steady-state error under modeling uncertainty and presence of ocean current. Numerical simulations are presented to better illustrate the controllers' behavior. View full abstract»

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  • Underwater Vehicle Navigation Using Diffusion-Based Trajectory Observers

    Page(s): 313 - 326
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1275 KB) |  | HTML iconHTML  

    This paper addresses the issue of estimating underwater vehicle trajectories using gyro-Doppler (body-fixed velocities) and acoustic positioning signals (earth-fixed positions). The approach consists of diffusion-based observers processing a whole trajectory segment at a time, allowing the consideration of important practical problems such as different information update rates, outages, and outliers in a very simple framework. Results of contraction theory are used to prove that the observers are convergent, i.e., stable in the incremental sense. Simulation and experimental results are presented to illustrate the potential of application of the method. View full abstract»

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  • Simulation of an Inertial Acoustic Navigation System With Range Aiding for an Autonomous Underwater Vehicle

    Page(s): 327 - 345
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2432 KB) |  | HTML iconHTML  

    This paper presents an integrated navigation system for underwater vehicles to improve the performance of a conventional inertial acoustic navigation system by introducing range measurement. The integrated navigation system is based on a strapdown inertial navigation system (SDINS) accompanying range sensor, Doppler velocity log (DVL), magnetic compass, and depth sensor. Two measurement models of the range sensor are derived and augmented to the inertial acoustic navigation system, respectively. A multirate extended Kalman filter (EKF) is adopted to propagate the error covariance with the inertial sensors, where the filter updates the measurement errors and the error covariance and corrects the system states when the external measurements are available. This paper demonstrates the improvement on the robustness and convergence of the integrated navigation system with range aiding (RA). This paper used experimental data obtained from a rotating arm test with a fish model to simulate the navigational performance. Strong points of the navigation system are the elimination of initial position errors and the robustness on the dropout of acoustic signals. The convergence speed and conditions of the initial error removal are examined with Monte Carlo simulation. In addition, numerical simulations are conducted with the six-degrees-of-freedom (6-DOF) equations of motion of an autonomous underwater vehicle (AUV) in a boustrophedon survey mode to illustrate the effectiveness of the integrated navigation system. View full abstract»

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  • Adaptive Autopilot Design of Time-Varying Uncertain Ships With Completely Unknown Control Coefficient

    Page(s): 346 - 352
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (726 KB) |  | HTML iconHTML  

    This paper develops an adaptive course controller for time-varying parametric uncertain nonlinear ships with completely unknown time-varying bounded control coefficient. The proposed design method does not require any a priori knowledge of the sign of the unknown time-varying control coefficient. The designed adaptive autopilot can guarantee the regulation of the ship course to any prescribed accuracy and the global uniform ultimate boundedness of all signals in the closed-loop system. The effectiveness of the presented autopilot has been demonstrated in a simulation involving a ship of 45 m in length. View full abstract»

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  • A Small Autonomous Surface Vehicle for Ocean Color Remote Sensing

    Page(s): 353 - 364
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1708 KB) |  | HTML iconHTML  

    This paper provides a study on the development and the use of a small autonomous surface vehicle (ASV) that automatically follows programmed mission transects, while measuring sensor outputs along the tracks. It discusses the mechanical construction of the ASV, the distributed architecture of controller area network (CAN)-based nodes for science and vehicle payloads, high-speed radio-frequency (RF) communications, the performance of the heading autopilot, global positioning system (GPS)-based guidance algorithm, and the mission programming technique. The field trials of the ASV, performed off the coast of Goa, India, are focused on retrieving the 2-D spatial distribution of surface chlorophyll, which is one of the useful parameters in characterizing the nature of calibration-validation (CALVAL) sites for ocean remote sensing needs. A further benefit of ASVs is that they can be built at a low cost and used in monitoring applications of diverse coastal ecosystems. View full abstract»

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  • Unmanned Underwater Vehicle Fuel Cell Energy/Power System Technology Assessment

    Page(s): 365 - 372
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (811 KB) |  | HTML iconHTML  

    This paper provides a technology assessment for an unmanned underwater vehicle (UUV) fuel cell energy/power system (FCEPS), including design methodology and design concepts. The design concepts are based on the polymer electrolyte membrane fuel cell (FC) operating on hydrogen and oxygen. The technology assessment method presented is a holistic approach which combines alternative hydrogen and oxygen storage [and fuel cell system (FCS)] options to provide the highest specific energy and energy density-within the constraints of the UUV application. Using this method, some surprising combinations appear as the theoretical ldquowinnersrdquo for maximum energy storage within the application constraints of the UUV. View full abstract»

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  • In Situ Underwater Electronic Holographic Camera for Studies of Plankton

    Page(s): 373 - 382
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2418 KB) |  | HTML iconHTML  

    In this paper, we describe an underwater electronic holographic camera (eHoloCam) that has been developed for in situ studies of the distribution and dynamics of plankton and other marine organisms and particles. The eHoloCam uses an Nd-YAG pulsed laser to freeze-frame fast moving particles and a complementary metal-oxide-semiconductor (CMOS) sensor for high-resolution image capture. Digital holograms and holographic videos are recorded at rates from 5 to 25 Hz over a period of several hours. Data is stored locally on an embedded computer. The eHoloCam is capable of recording all organisms and particles located in a water volume of 36.8 cm3 in a single hologram frame. The recorded holographic videos may subsequently be reconstructed numerically at a desired image plane. The main optical and mechanical specifications for eHoloCam are also described. To record electronic holographic videos of marine organisms, the eHoloCam was deployed from a towed sampling frame [autorecording instrumented environmental sampler (ARIES)] on the research vessel RV Scotia at speeds up to 4 kn (about 2 mldrs-1) in the North Sea off the Shetland Isles. Various images of marine organisms obtained from this deployment are shown, together with preliminary measurements on the distribution of Calanus copepods. View full abstract»

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  • Nonmetric Camera Calibration for Underwater Laser Scanning System

    Page(s): 383 - 399
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2824 KB) |  | HTML iconHTML  

    This paper describes the development of an underwater camera system with a laser line source to measure seafloor features at millimeter scales. The quality of underwater photography is limited by the visibility of the water column. In real underwater environments, there are always suspended particles in the water column and light is scattered by these particles. As a result, photographic images taken under such conditions will be blurred. The stronger the light source is, the more severe the blurring will be. Therefore, it is difficult to discern the features of the intended target directly from the underwater images. To overcome this problem, a laser stripe can be projected onto the target and the profile of the target can be inferred from the displacement of the laser scan lines relative to a reference baseline. With a calibrated camera, the displacement expressed in pixels can be converted into the dimensions of the target in engineering units. To obtain a broader view in a closer distance, a wide-angle lens is usually used. As a result, the image taken with the wide-angle lens is nonlinear and is strongly distorted at the edges of the image. Calibration of a camera involves finding the optical and geometrical parameters of the camera and the environment in which it works. In this paper, a modified coordinate mapping calibration procedure is used. We divide the scope of the camera into several regions and build linear mappings between the world coordinate system and the pixels in the regions. We lay vertical and horizontal grid lines separated by 50 mm on an acrylic board that is aligned with the laser scanning sheet. These grid lines serve as longitude and latitude lines of a map. On the captured image, we curve-fit the grid points in pixel coordinates. A pair of interpolated longitude and latitude lines which pass through the target point are used to estimate the location of the point in the world coordinate system. We assess the accuracy of this procedure with- test pieces (grooved blocks and seabed ripples) fabricated by a computer numerical control milling machine. Our measurements show that the error is less than 1.5 mm when the target is scanned from a distance of 1 m. View full abstract»

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  • Designing a Dependable and Fault-Tolerant Semiautonomous Distributed Control Data Collection Network With Opportunistic Hierarchy

    Page(s): 400 - 407
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (917 KB) |  | HTML iconHTML  

    This paper presents the satellite-linked data acquisition and photogrammetry (SLiDAP) network, designed to conduct shore-based, close-range 3-D imaging in remote areas. The lack of communications and power infrastructure and ability to service the system requires periodic, synchronous operations of multiple semiautonomous elements with a high degree of reliability. The SLiDAP system uses an opportunistic network architecture based on four distinct levels of control, to accommodate unpredictable operational constraints and failures. The synchronization of periodic tasks in a distributed control and remotely operable network are highlighted, and measures to increase the reliability of system operations are discussed, including hardware redundancy, intelligent watchdog timer, software error tolerance, self-repair, and remote update capability. The characteristics of the SLiDAP system within the concept of autonomic computing are discussed. View full abstract»

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  • Pressure Dependence of Cymbal Transducers

    Page(s): 408 - 415
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (877 KB) |  | HTML iconHTML  

    The hydrostatic pressure limit that a receiver can withstand without failure is of major importance in underwater sonar systems. In this paper, the hydrostatic pressure tolerance and sensitivity of cymbal receivers were investigated. The failure mode in cymbal transducers under hydrostatic pressure is described. Effects of cavity geometry and material selection on hydrostatic piezoelectric coefficients and pressure limits were evaluated using both experimental data and finite-element analysis (FEA). It was found that cavity depth has a very strong effect on the stability of underwater sensitivity and pressure tolerance of these devices. Cymbals made with soft piezoelectric transducers (PZTs) possess higher figures of merit and better pressure tolerance than those made with hard PZTs. Alternatively, the cymbal sensitivity and pressure tolerance can be improved by changing the cap material. View full abstract»

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  • A Custom Chip Set for a Frequency-Agile High-Resolution Sonar Array

    Page(s): 416 - 427
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3053 KB) |  | HTML iconHTML  

    This paper describes two custom-integrated circuits, which form the core building blocks of a versatile wideband sonar array. An analog 0.5-mum complementary metal-oxide-semiconductor (CMOS) chip houses a preamplifier, an antialias filter, and a high-resolution (14-16 b) data converter based on delta-sigma modulation techniques. A complementary 0.35-mum digital CMOS chip incorporates a four-stage multirate filter cascade, which provides a wideband and two narrowband outputs. The complex narrowband outputs are obtained via a subsampling mixer and span over the top 15% or the top 10%, respectively, of the original band. The system sampling clock can vary from 2 to 10 MHz to enable tuning to a specific frequency window located anywhere between 30 and 150 kHz. Both chips process four sonar channels in parallel and, when clocked at 10 MHz, dissipate a combined power of 416 mW (104 mW per channel). View full abstract»

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  • Qualitative Analysis of Old and New Sea Level Measuring Techniques and Their Data Consistency

    Page(s): 428 - 435
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1119 KB) |  | HTML iconHTML  

    This paper encompasses the analyses of sea level data measured at four tide gauges situated in the city of Split, Croatia. Two old long-term stations comprise float-type instruments in stilling wells, with analog recording on a chart, while two modern stations were installed in 1999 and 2000, calculating sea level height from the measured sea and air pressure. Although analog recording devices with a drum may suffer from inaccuracy in timing and drum rotation speed, clock errors, and vertical pencil position, the largest errors in the data came from the digitizing process, which is subjected to the individual work of a technician. Although, the data collected with pressure systems are supposed to be more homogeneous and accurate, after several years of work, the sensors usually have a drift in time. This problem turned out to be accompanied with lower quality sensors being part of wider automatic measuring systems, whereas the station which has been specially designed for sea level measurements showed no drifts in four years of operating. Therefore, one should be careful in choosing measuring equipment between various manufacturers. In addition, the equipment should be regularly checked since the malfunction in global positioning system (GPS) clock resulted in time drift of sea level data of more than an hour. View full abstract»

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  • Winter PRIMER Ocean-Acoustic Solitary Wave Modeling Studies

    Page(s): 436 - 452
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2486 KB) |  | HTML iconHTML  

    In this paper, we present results from a joint oceanographic-acoustic study of solitary waves and their effects during the 1997 winter PRIMER4 experiment on the shelfbreak south of Cape Cod, MA. The study addresses the acoustic effects induced by solitary waves and associated oceanographic phenomena. Solitary wave generation and propagation simulations are produced by the Lamb model [J. Geophys. Res., vol. 99, pp. 848-864, 1994]. The model is nonhydrostatic and is formulated in 2.5 dimensions using terrain following coordinates. Acoustic field calculations are performed with a parabolic equation acoustic model along the path of solitary wave train propagation. The oceanographic model is initialized from density profiles derived from conductivity-temperature-depth (CTD) casts using analytical functions. The model is forced with a prescribed semidiurnal tidal velocity. An ocean background current is introduced. Simulations based on parameters derived from measurements show the following: 1) internal solitary waves of elevation propagate onto the shelfbreak region; 2) opposing ocean currents enhance the formation of solitary waves at the shelfbreak; 3) deepening of the winter mixed layer results in less penetration of the solitary waves on to the shelf; 4) density structure, mixed-layer depth, tidal forcing, and ocean currents control the formation of solitary waves of elevation at the shelfbreak; 5) energy conversion, from semidiurnal barotropic to semidiurnal barcoclinic tides and to internal solitary waves, occurs; 6) amplitudes and periods of modeled solitary waves are in the range of thermistor chain measurements; and 7) lower mixed-layer densities increase the phase speed of simulated solitary waves. Acoustic field calculations are coupled to the propagation of the solitary wave packets through the sound-speed changes that are derived from the oceanographic simulations. Acoustic model predictions show signal intensity fluctuations similar to the anomalous loses i- n acoustic energy observed in the Yellow Sea data taken by Zhou [J. Acoust. Soc. Amer., vol. 90, pp. 2042-2054, 1991]. In some cases, the presence of solitary waves on the shelf enhances the propagation of acoustic energy onto the shelf. This was observed for acoustic simulations where the acoustic source was located beyond the shelfbreak and at a depth greater than the shelf depth. View full abstract»

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  • Sensitivity of Satellite Altimetry Data Assimilation on a Weapon Acoustic Preset

    Page(s): 453 - 468
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2351 KB) |  | HTML iconHTML  

    The purpose of this research is to assess the benefit of assimilating satellite altimeter data for naval undersea warfare. To accomplish this, sensitivity of the weapon acoustic preset program (WAPP) for the Mk 48 variant torpedo to changes in the sound-speed profile (SSP) is analyzed with SSP derived from the modular ocean data assimilation system (MODAS). The MODAS fields differ in that one uses altimeter data assimilated from three satellites while the other uses no altimeter data. The metric used to compare the two sets of outputs is the relative difference in acoustic coverage area generated by WAPP. Output presets are created for five different scenarios, two anti surface warfare (ASTJW) scenarios, and three antisubmarine warfare (ASW) scenarios, in each of three regions: the East China Sea, Sea of Japan, and an area south of Japan that includes the Kuroshio currents. Analysis of the output reveals that, in some situations, WAPP output is very sensitive to the inclusion of the altimeter data because of the resulting differences in the subsurface predictions. The change in weapon presets can be so large that the effectiveness of the weapon may be affected. View full abstract»

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  • Visual and Passive Acoustic Marine Mammal Observations and High-Frequency Seismic Source Characteristics Recorded During a Seismic Survey

    Page(s): 469 - 483
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4420 KB) |  | HTML iconHTML  

    In this paper, we present marine mammal observation statistics, high-frequency seismic source characteristics, and example denoising of marine mammal acoustical recordings using data collected during the mitigation and monitoring program for a 3-D seismic survey by EnCana Corporation, Calgary, AB, Canada, in the Northwest Atlantic during 2003. Marine mammals were observed both visually and acoustically. No marine mammal incidents or adverse reactions were observed during the survey. Acoustical observations were made by the Sea map Passive Acoustic Cetacean Monitoring System (SPACMS), consisting of two hydrophones placed 50 m apart, towed ahead of and to one side of the seismic source. Visual and acoustical detections were uncorrelated, indicating the complementary nature of the two observational techniques. Visual detections were more common per hour of effort than acoustical detections. Acoustical detection rates showed no significant day-night difference. Marine mammals appeared to have avoided very close ranges (100 m) from the seismic array during seismic acquisition, but the overall number of marine mammals in the observable radius (1-2 km) did not change significantly when the seismic source was ldquoonrdquo compared to ldquooff.rdquo Marine mammals were observed in larger groups and appeared to have become less vocal when the seismic source was active. It should be noted however, that the results from this data gathering effort may be affected by potential sources of bias (such as the combination of data from toothed and baleen whales). Signal processing of seismic source signatures indicated some high-frequency energy content consistent with expectations from earlier work. This analysis confirmed that most of the seismic energy was concentrated at lower frequencies (500 Hz). No low-frequency comparisons with near-field data could be made due to the geometry of the SPACMS recording hydrophones and seismic source, which resulted in the Lloyd's mirror effect o- bliterating low-frequency components in the SPACMS records. A wavelet-based denoising method was applied to improve the visibility of marine mammal vocalizations on a spectrogram display. View full abstract»

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  • Measurement of the In Situ Compressional Wave Properties of Marine Sediments

    Page(s): 484 - 496
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1577 KB) |  | HTML iconHTML  

    Geoacoustic inversion requires a generic knowledge of the frequency dependence of compressional wave properties in marine sediments, the nature of which is still under debate. The use of in situ probes to measure sediment acoustic properties introduces a number of experimental difficulties that must be overcome. To this end, a series of well-constrained in situ acoustic transmission experiments were undertaken on intertidal sediments using a purpose-built in situ device, the Sediment Probing Acoustic Detection Equipment (SPADE). Compressional wave speed and attenuation coefficient were measured from 16 to 100 kHz in medium to fine sands and coarse to medium silts. Spreading losses, which were adjusted for sediment type, were incorporated into the data processing, as were a thorough error analysis and an examination of the repeatability of both the acoustic wave emitted by the source and the coupling between probes and sediment. Over the experimental frequency range and source-to-receiver (S-R) separations of 0.99-8.1 m, resulting speeds are accurate to between 1.1% and 4.5% in sands and less than 1.9% in silts, while attenuation coefficients are accurate to between 1 and 7 dBm in both sands and silts. Preliminary results indicate no speed dispersion and an attenuation coefficient that is proportional to frequency. View full abstract»

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  • Ambient Noise Analysis of Deep-Ocean Measurements in the Northeast Pacific

    Page(s): 497 - 512
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2656 KB) |  | HTML iconHTML  

    During the late 1960s and throughout the 1970s, the U.S. Navy conducted a series of ocean acoustic measurement exercises to support development of systems and techniques to detect nuclear submarines. The exercises and most of the technical documentation were classified. In 2003, a project was sponsored by the U.S. Office of Naval Research (ONR, Arlington, VA) to declassify documentation and demonstrate the capability to recover acoustic data recorded on magnetic tape. One of the exercises, known as CHURCH OPAL, was selected for demonstration of acoustic data recovery. The record on magnetic tape spanned a period of ten days in September 1975 from a vertical assembly of hydrophones at a site midway between Hawaii and California. This paper presents selected excerpts from a key report (Wittenborn, 1976) on ambient noise that previously was unpublished and unavailable for general distribution. The earlier work is augmented with more complete and detailed analyses of the recovered digital data using modern analytical techniques. Data acquired from the hydrophones below critical depth enabled isolation of ambient noise due to distant shipping and local wind. The frequency band of the acoustic analyses was 30-500 Hz. The wind component of the ambient noise was evaluated at frequencies lower than reported by Wenz (1962). View full abstract»

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  • Acoustic Propagation Through Clustered Bubble Clouds

    Page(s): 513 - 523
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (622 KB) |  | HTML iconHTML  

    One of the underlying assumptions in the effective medium theory describing the propagation of acoustic waves through bubble clouds is that the probability of an individual bubble being located at some position in space is independent of the locations of other bubbles. However, bubbles within naturally occurring clouds may be influenced by the dynamics of the fluids in which they are entrained so that they become preferentially concentrated, or clustered, leading to statistical dependence in their positions. For bubble clouds in which the important scattering terms include those with interactions between at least two bubbles, statistical dependence between bubble positions leads to a reduction in the attenuation of the coherent acoustic pressure field from that which would be predicted for a nonclustered bubble cloud. Bubble clustering can be accommodated in effective medium theories using correlation functions describing the relationship between the positions of the bubbles. For double scattering, the two-bubble correlation (i.e., the pair correlation function) must be used, for triple scattering, the three bubble correlation must be used, and so on. In contrast to the three attenuation of the coherent field, making the assumption of independent bubble positions leads to an underestimate of the incoherent field. Both the coherent and incoherent acoustic fields for bubble clouds exhibiting correlated bubble positions are explored in this paper with the use of numerical simulations. View full abstract»

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  • Continuous Reverberation Response and Comb Spectra Waveform Design

    Page(s): 524 - 532
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (311 KB) |  | HTML iconHTML  

    A model for the matched filter response to continuous reverberation from the transmission of broadband waveforms is developed. The application is for reverberation from a rough interface, based on perturbation theory. The model is developed for both the stationary rough bottom and the moving ocean surface interfaces. The mean reverberation is predicted as a function of the Doppler speed of the matched filter replica. Application is made to the design of waveforms with comb-like spectra. A uniform train of impulses produces a comb spectrum that is shown to significantly reject reverberation for a certain range of Doppler speeds. A similar low-reverberation response is produced from a continuous source emitting a wavetrain composed of adjacent hyperbolic-frequency-modulated (HFM) pulses. A waveform design technique is demonstrated to ensure continuity of the entire HFM wavetrain. Finally, waveforms with geometrically spaced comb spectra are considered. A new geometric comb waveform with constant amplitude is specified. However, this waveform requires a large bandwidth which may be difficult to obtain with practical high-power sources. Hard and soft-clipped versions of the comb spectra waveform are considered which provide useful compromises between the amount of reverberation suppression, the transmitted energy efficiency, and the utilization of available bandwidth. View full abstract»

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  • IEEE Oceanic Engineering Society Information

    Page(s): C3
    Save to Project icon | Request Permissions | PDF file iconPDF (35 KB)  
    Freely Available from IEEE

Aims & Scope

The IEEE Journal of Oceanic Engineering (ISSN 0364-9059) is published quarterly by the IEEE Oceanic Engineering Society (IEEE OES). The scope of the Journal is the field of interest of the IEEE OES, which encompasses all aspects of science, engineering, and technology that address research, development, and operations pertaining to all bodies of water. This includes the creation of new capabilities and technologies from concept design through prototypes, testing, and operational systems to sense, explore, understand, develop, use, and responsibly manage natural resources.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
N. Ross Chapman
School of Earth & Ocean Sciences
University of Victoria
3800 Finnerty Road
Victoria, BC V8P 5C2 Canada
chapman@uvic.ca