Download or read book Geoacoustic Inversion Using Direct Methods on Ambient Noise and Explosive Acoustic Data in a Shallow Water Waveguide written by and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fundamental goal of this thesis is to determine the geoacoustic parameters of a shallow water seabed using direct analysis methods on ambient noise and broadband explosive acoustic data. All data considered are from the Mid-Atlantic Bight shelf break experiment that was conducted from 19 July to 9 August 1996. Simple, theoretical treatments of acoustic propagation in a shallow water waveguide are applied to specific, measurable quantities in the data which can be inverted directly to produce estimates of bottom compressional sound speed, density, and attenuation. Shear influences are neglected throughout. Specifically, vertical coherence of the ambient noise is used to determine the sound speed contrast at the water bottom interface, mode travel times extracted from spectrograms of explosive data are used to estimate bottom density based on the concept of an ideal waveguide effective depth, and mode attenuation as a function of range extracted from similar spectrograms are employed to estimate attenuation. These direct inversion methods are less accurate than sophisticated matched field processing techniques or direct core measurements, but they do provide a relatively simple means of obtaining reasonable estimates of ocean bottom parameters from minimal information.

Download or read book Geoacoustic Inversion Using Direct Methods of Ambient Noise and Explosive Acoustic Data in a Shallow Water Waveguide written by Jose G. Rojas and published by . This book was released on 1998 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fundamental goal of this thesis is to determine the geoacoustic parameters of a shallow water seabed using direct analysis methods on ambient noise and broadband explosive acoustic data. All data considered are from the Mid-Atlantic Bight shelf break experiment that was conducted from 19 July to 9 August 1996. Simple, theoretical treatments of acoustic propagation in a shallow water waveguide are applied to specific, measurable quantities in the data which can be inverted directly to produce estimates of bottom compressional sound speed, density, and attenuation. Shear influences are neglected throughout. Specifically, vertical coherence of the ambient noise is used to determine the sound speed contrast at the water bottom interface, mode travel times extracted from spectrograms of explosive data are used to estimate bottom density based on the concept of an ideal waveguide effective depth, and mode attenuation as a function of range extracted from similar spectrograms are employed to estimate attenuation. These direct inversion methods are less accurate than sophisticated matched field processing techniques or direct core measurements, but they do provide a relatively simple means of obtaining reasonable estimates of ocean bottom parameters from minimal information.

Download or read book Acoustic Sensing Techniques for the Shallow Water Environment written by Andrea Caiti and published by Springer. This book was released on 2017-04-30 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thisvolume contains thecollection of papers from the second workshop on Expe- mental Acoustic Inversion Techniques for Exploration of theShallow Water Environment. Theworkshopthemefollowedtheoriginalconceptofthe rstworkshop, heldinCarvoeiro, Portugal, in 1999, i.e., to focus on experiments and experimental techniques for acoustic sensing in the shallow ocean. More than forty leading international scientists were invited to meet in the picturesque town of St. Angelo on the island of Ischia, in June 2004, to discuss progress in the application of new experimental techniques for exploration and assessment of shallowwater environments. Acoustic techniques provide the most effective means for remote sensing of ocean and sea oor processes, and for probing the structure beneath the sea oor. No other energy propagates as ef ciently in the ocean: radio waves and visible light are severely limited in range because the ocean is a highly conductive medium. However, sound from bre- ing waves and coastal shipping can be heard throughout the ocean, and marine mammals communicate acoustically over basin scale distances.

Download or read book Experimental Acoustic Inversion Methods for Exploration of the Shallow Water Environment written by Andrea Caiti and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, research on acoustic remote sensing of the ocean has evolved considerably, especially in studying complex physical and biological processes in shallow water environments. To review the state of the art, an international workshop was held at Carvoeiro, Portugal, in March 1999, bringing together leading international researchers in the field. In contrast to much of the recent theoretical work, emphasis was placed on the experimental validation of the techniques. This volume, based on presentations at this workshop, summarizes a range of diverse and innovative applications. The invited contributions explore the use of acoustics to measure bottom properties and morphology, as well as to probe buried objects within the sediment. Within the water column, sound is applied to imaging of oceanographic features such as currents and tides or monitoring of marine life. Another key theme is the use of sound to solve geometric inverse problems for precise tracking of undersea vehicles. Audience: This volume should be useful both to the novice seeking an introduction to the field and to advanced researchers interested in the latest developments in acoustic sensing of the ocean environment. The workshop was sponsored by the Fundação para a Ciêcia e a Tecnologia (Portuguese Foundation for Science and Technology).

Download or read book Geoacoustic Inversion in Laterally Varying Shallow water Environments Using High resolution Wavenumber Estimation written by Kyle M. Becker and published by . This book was released on 2002 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental method for extracting horizontal wavenumber spectra for point-source acoustic fields in laterally varying shallow water waveguides is discussed. The experiment was designed to provide input data for a perturbative inversion method for inferring the geoacoustic properties of the bottom. The input data are discrete values of horizontal wavenumbers that correspond the propagating modes in a shallow-water waveguide. Based on the asymptotic Hankel transform pair relationship between the complex pressure field and the depth-dependent Green's function, a high-resolution autoregressive (AR) spectral estimator is applied to extract wavenumber content. The estimator is characterized in terms of it performance on short-aperture noisy data. The estimator is then used on short-aperture synthetic acoustic data for extracting local horizontal wavenumber content for doing range-dependent geoacoustic inversion. Results are discussed in terms of discrete and continuous changes in the waveguide environment. The estimator is then applied to real data for a fixed receiver and towed source. For a source speed of 2 m/s, a shift was observed in the measured wavenumbers. Based on this observation, a method for measuring modal group velocity is presented from measurements of the shifted wavenumbers for a source towed out and back along the same track.

Download or read book Inverting for Geoacoustic Seabed Parameters Using Ambient Noise written by Nicholas Michael Carbone and published by . This book was released on 1996 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Full Field Inversion Methods in Ocean and Seismo Acoustics written by Orest Diachok and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent advances in the power of inversion methods, the accuracy of acoustic field prediction codes, and the speed of digital computers have made the full field inversion of ocean and seismic parameters on a large scale a practical possibility. These methods exploit amplitude and phase information detected on hydrophone/geophone arrays, thereby extending traditional inversion schemes based on time of flight measurements. Full field inversion methods provide environmental information by minimising the mismatch between measured and predicted acoustic fields through a global search of possible environmental parameters. Full Field Inversion Methods in Ocean and Seismo-Acoustics is the formal record of a conference held in Italy in June 1994, sponsored by NATO SACLANT Undersea Research Centre. It includes papers by NATO specialists and others. Topics covered include: · speed and accuracy of acoustic field prediction codes · signal processing strategies · global inversion algorithms · search spaces of environmental parameters · environmental stochastic limitations · special purpose computer architectures · measurement geometries · source and receiving sensor technologies.

Download or read book Acoustic Modeshape Inversion Using Deep Water Ambient Noise Measurements written by Khalid A. AlMuhanna and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ocean acoustic tomography is a powerful method that uses sound to study ocean properties such as temperature, which is directly related to sound speed in water. This thesis focuses on using ambient noise to infer the normal modes of the ocean waveguide. The modes are a set of orthogonal functions that are solutions to the depth dependent wave equation, which depends on sound speed and thus on the temperature. Assuming that noise signals received by a vertical array consist of a sum of uncorrelated modes, the modeshapes can be determined from an eigenvector decomposition of the measured cross-spectral density matrix. Several authors have applied this technique to estimate the modes of shallow water waveguides, but there have been few opportunities to apply this technique in deep water waveguides. In this thesis the modeshapes of a deep water environment in the North Pacific are estimated using ambient noise data measured during the SPICE04 experiment. Although noise measurements were not the primary focus of SPICE04, the experiment provided a large data set for this analysis. In addition to acoustic measurements, the experiment also included extensive sampling of the environmental parameters. This thesis summarizes some of the noise statistics measured during 2004-2005. The measured modeshapes derived from the data are compared with the true modes derived from the measured environmental data.

Download or read book Shallow Water Acoustics written by Boris G. Katsnelson and published by Springer Science & Business Media. This book was released on 2002-05-01 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this book is to present the main theoretical approaches and models in shallow water acoustics as well as different experimental results. The focus is primarily concentrated on physical results describing the sound field in wave length. The authors show dynamic phenomena (tides, internal waves) from the perspective of acoustic influence as well as the scattering of sound over the macroscopic body in shallow water waveguide. The method of acoustic probing can be used by physicists, geophysicists, geologists and oceanographers.

Download or read book Geoacoustic Inversions in a Very Shallow Water Environment written by Katherine Megan McArthur and published by . This book was released on 2002 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Matched Field Processing Based Geo acoustic Inversion in Shallow Water written by Lin Wan and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Shallow water acoustics is one of the most challenging areas of underwater acoustics; it deals with strong sea bottom and surface interactions, multipath propagation, and it often involves complex variability in the water column. The sea bottom is the dominant environmental influence in shallow water. An accurate solution to the Helmholtz equation in a shallow water waveguide requires accurate seabed acoustic parameters (including seabed sound speed and attenuation) to define the bottom boundary condition. Direct measurement of these bottom acoustic parameters is excessively time consuming, expensive, and spatially limited. Thus, inverted geo-acoustic parameters from acoustic field measurements are desirable.

Download or read book Important Elements In Geoacoustic Inversion Signal Processing and Reverberation in Underwater Acoustics written by Alex Tolstoy and published by . This book was released on 2008-01-01 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains a number of papers by leading researchers discussing their work on either geoacoustic inversion (GI), signal processing (SP), or reverberation. It is intended for scientists entering these fields as well as for experienced researchers. Chapter 1 (Tolstoy) begins the section on GI. It is a review article covering the main topics of GI and mentions such subjects as matched field processing (MFP), improved source localization and tracking, array element localization, propagation and parameter modeling, search methods, the nature of the search spaces, improving efficiency, sensitivities and uncertainty, benchmarking, and applications to simulated and test data. It is intended as a resource for understanding the GI area as well as for locating key references. Chapter 2 (Dosso) describes one of the most successful and most applied methods for GI: a Bayesian approach using a hybrid simulated annealing (SA) variant for optimization and Gibbs sampling to characterize the posterior probability density. The formulation is discussed here in mathematical detail. The emphasis in this chapter is on rigorous uncertainty estimation where the unknowns are considered to be random variables constrained by the data and prior information. Errors are assumed to be Gaussian distributed for the derivation of some key equations, and statistical tests are presented to support this assumption. Data from the PROSIM 97 experiment at numerous frequencies are analyzed. Chapter 3 (Chapman & Jiang) discusses the interpretation of matched field inversion results, particularly their limitations, and illustrates their analysis using multifrequency experimental data from the New Jersey continental shelf site that was selected on the basis of high spatial and temporal coherence across the array. They are concerned with the impact of data errors due to parameter correlations in Bayesian inversions, and the effect of the bottom slope in three dimensions (they conclude that only two dimensions are needed for their inversions). Chapter 4 (Michalopoulou & Nolte) begins as a review of Bayesian source localization methods but is primarily concerned with one such approach which the authors developed: the Optimum Uncertain Field Processor (OUFP). This is an approach used for target localization and tracking which reduces sensitivity to environmental mismatch by incorporating prior information. The method also produces posterior distributions permitting the quantification of uncertainty and error estimation of calculated parameters including environmental properties. Moving and multiple sources are discussed. Chapter 5 (Taroudakis) discusses modal inversion techniques in shallow water. Modal observables such as modal phase, modal arrivals, and dispersion curves using both the time and frequency domains are incorporated into linear and non-linear inversion procedures. The methods are based on geophysical analysis using normal mode propagation. Good separation of modes is required which is affected by the nature of the array and the frequencies used for the inversions in a given scenario. Chapter 6 (Baxley) is a review of the use of GI primarily to: (1) show results of simplified approaches to GI, (2) review the SWellEX experiments of 1993-1999 as a good testbed of GI, and (3) perform inversion using horizontal as well as vertical line arrays. The intention was the optimization of system performance for the localization and tracking of undersea targets using a variety of arrays and the Bartlett processor. Range-independence was assumed so that a simple normal mode model could be used. A number of parameters were estimated using a number of frequencies (less than 200Hz) assuming a simplified bottom. Chapter 7 (Rajan et al.) is a complete and mathematical discussion of modal inverse techniques. The chapter presents a formulation of the inverse problem, an estimation of the modal eigenvalue, demonstrations in RI and RD waveguides with discussions of error sources, spectral estimation, modal attenuation coefficients, sediment characteristics determined from modal dispersion data, integral equations, matrix inversion, resolution and variation of estimates, further demonstrations of inversion success for simulated and test data, and more. A complete coverage of modal issues is presented here. Chapter 8 (Tolstoy) is the final chapter on GI and concerns a volumetric (tomographic) GI method. This approach combines individual 2-D (range and depth slice) inversions on multiple arrays and for distributed sources into a full consistent 3-D (range, depth, and azimuth) image of the region bottom. It is discussed within the context of the Haro Strait test and concludes that information about array geometry (phone depths and shape) is essential for successful inversion where success is defined as high MFP values (at any and all frequencies with good signal-to-noise) at a unique set of parameters. Additionally, 3-D resolution may be improved via regularization to counter scarcity of resources. Chapter 9 (Arvelo) starts the section on signal processing with a detailed discussion of the factors affecting system performance, particularly at low frequencies (below 1 kHz). These include noise, especially as it affects coherence (temporal and spatial), waveguide variability (such as bathymetry), and scattering processes. A review of low-frequency coherence modeling and measurements is presented, and examples are provided to illustrate key points. Methods to circumvent the hard limits imposed by spatial coherence include the exploitation of multiple dimensions, such as the design of planar and volumetric arrays. Seismic coherence is also discussed. Chapter 10 (Sullivan & Candy) is a review of passive synthetic aperture processing (PASA). This approach to array processing utilizes the (towed) array motion to enhance its performance by explicitly incorporating this motion into the signal model. Historically, its name is based on the idea that the improved performance is equivalent to effectively having a longer array (the array appears to be larger when multiple phone locations can be combined coherently, and this approach is most effective for short aperture arrays). It is unique in that it treats the problem as a recursive estimation process rather than a beamforming process. Again, the primary interest here is system performance. Since it recursive in time, its application is limited to continuous signals (such as radiated noise) as opposed to short-term signals (such as pulses). The authors present the PASA development in mathematical detail (narrowband and broadband, single and multiple sources) including both simulated and experimental data. Chapter 11 (Zurk) completes the section on signal processing where concerns about waveguide mismatch are addressed by the development of more robust processing methods. Rather than attempting to determine ocean properties, many signal processors concentrate on the goal of devising techniques less dependent on the channel nature with the intent of improving system performance in uncertain environments. This can involve incorporating the statistics of the environment, using a calibration source, or developing invariant (robust) processors. These approaches are discussed here. Chapter 12 (Gauss) is the only chapter to concentrate on reverberation and presents a review of active sonar components coupled with signal processing for the purpose of detecting, localizing, and tracking undersea targets. Incomplete knowledge of the environment and clutter (reverberation from non-targets) are the primary limits on system performance. Clutter mechanisms include: bathymetry, the ocean surface roughness, fish, bubbles, and more. These mechanisms and methods to control their influence using frequencies 50 Hz to 5 kHz (single frequency and broadband), in deep and shallow water scenarios, are discussed. Deconvolution is critical to all reverberation efforts. Additionally, Doppler effects can be also used to separate signal contributions. The chapter concludes with a summary of contemporary issues and future trends. Finally, the observant reader will notice that this text is dedicated to Leon Sibul. Leon died quite unexpectedly early in 2007 with the intention of contributing a chapter to this book. We in the research community miss his mathematical insights and contributions to signal processing. We miss the chapter he would have given to us in this book. But most of all, we miss him.

Download or read book Geo acoustic Stratification Deep in the Sea Bed from Ambient Noise in Shallow Water written by M. Buckingham and published by . This book was released on 1997 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The long-term objective is to develop a reliable ambient-noise inversion technique for obtaining the geo-acoustic parameters, including the stratification, of the sea bed from measurements of the broadband vertical coherence of the noise in shallow water. The method would be implemented in a free-floating instrument, self navigated with GPS, and consisting of a pair of vertically aligned hydrophones, to provide a cost-effective sensor system for collecting the required noise data over extensive areas of shallow water. The resultant bottom information would provide essential input to navy propagation loss models.

Download or read book Advances in Noise Reduction and Feature Extraction of Acoustic Signal written by Govind Vashishtha and published by Frontiers Media SA. This book was released on 2023-10-11 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acoustic signal is one of the hot topics of research in physics and has been studied by many engineers and scientists in various real-world fields, including underwater acoustics, architectural acoustics, engineering acoustics, physical acoustics, environmental acoustics, psychological acoustics, and so on. Noise reduction is the foundation of acoustic signal pre-processing, and the feature extraction for noise reduction signals can obtain useful information from the acoustic signal, which is the linchpin for pattern recognition, target detection, tracking, and localization.

Download or read book The Journal of the Acoustical Society of America written by Acoustical Society of America and published by . This book was released on 2006 with total page 988 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Modal WKB Inversion Method for Determining Sound Speed Profiles in the Ocean and Ocean Bottom written by Kevin D. Casey and published by . This book was released on 1988 with total page 770 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two approaches to determining the ocean sound profile using measured acoustic modal eigenvalues are examined. Both methods use measured eigenvalues and mode dependent assumed values of the WKB phase integral as input data and use the WKB phase integral as a starting point for relating the index of refraction to depth. Inversion method one is restricted to monotonic or symmetric sound speed profiles and requires a measurement of the sound speed at one depth to convert the index of refraction profile to a sound speed profile. Inversion method two assumes that the sound speed at the surface and the minimum sound speed in the profile are known and is applicable to monotonic profiles and to general single duct sound speed profiles. For asymmetric profiles, inversion method two gives the depth difference between two points of equal sound speed in the portion of the profile having two turning points, and in the remainder of the profile it gives sound speed versus depth directly. A numerical implementation of the methods is demonstrated using idealized ocean sound speed profiles numerical experiments used to test the performance of the inversions using noisy data. The two methods are used to determine the sediment sound speed profiles in two shallow water waveguide models, and inversion method one is used to find the sediment sound speed profile using data from an experiment performed in the Gulf of Mexico. Theses. (edc).

Download or read book Geoacoustic Inversion of Subbottom Channels Using Mulitple Frequency Input Parameters written by Rebecca Weeks and published by . This book was released on 2010 with total page 611 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates inversion techniques used to determine the geoacoustic properties of a shallow-water waveguide. The data used were obtained in the Shallow Water '06 Modal Mapping Experiment in which four buoys drifted over a system of subbottom channels. The method used was perturbative inversion using modal eigenvalues as input parameters, which were found using an autoregressive spectral estimator. This work investigates the differences between a "channel" region and a "no channel" region based on an inferred stratigraphic model. Inversions were performed on data from a single buoy both at individual frequencies and multiple frequencies simultaneously. Since the use of multiple frequencies and a certain set of constraints proved to be an effective method of inversion, the method was applied to data from the other three buoys as well. It is shown that the "channel" and "no channel" regions have significantly different sound speed profiles.