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The textbook “Principles of Hydroacoustics” is devoted to the study of the equations of liquid and solid elastic (isotropic and anisotropic). The textbook provides the main characteristics of the reflectivity of ideal and elastic bodies as the simple forms (sphere, infinite cylinder, prolate and oblate spheroids) and bodies of non-analytical shape (finite cylinder with hemispheres at the ends). Moreover, in the textbook, along with classical methods of diffraction theory, such numerical methods as the finite element method and the boundary element method are used. The textbook also studies the theory of synthesis of hydroacoustic antennas and criteria for acoustic diffraction measurements in a hydroacoustic basin.

A comprehensive review of the sources and impacts of different types of marine noise Measuring devices such as ocean bottom seismometers and hydrophones designed to detect earthquakes pick up many other signals. These were previously ignored as background noise from unknown sources, but advanced technology now allows insights into the noise created from icebergs, ships, hydrothermal vents, whales, rain, marine engineering, and more. Noisy Oceans: Monitoring Seismic and Acoustic Signals in the Marine Environment is a comprehensive guide to non-tectonic marine noise originating from different environmental, biological, and anthropogenic sources. Volume highlights include: Overview of marine soundscapes and their sources Existing and new methods for studying acoustic signals Case studies from around the world Spans disciplines from geology and geophysicists to biology Explores the impacts and implications of marine noise The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals.

A captivating exploration of how underwater animals tap into sound to survive, and a clarion call for humans to address the ways we invade these critical soundscapes—from an award-winning science writer“Sing Like Fish is that rare book that makes you see the world differently.”—Mark Kurlansky, New York Times bestselling author of Salt and CodLONGLISTED FOR THE ANDREW CARNEGIE MEDAL FOR EXCELLENCE IN NONFICTIONFor centuries, humans ignored sound in the “silent world” of the ocean, assuming that what we couldn't perceive, didn't exist. But we couldn't have been more wrong. Marine scientists now have the technology to record and study the complex interplay of the myriad sounds in the sea. Finally, we can trace how sounds travel with the currents, bounce from the seafloor and surface, bend with the temperature and even saltiness; how sounds help marine life survive; and how human noise can transform entire marine ecosystems. In Sing Like Fish, award-winning science journalist Amorina Kingdon synthesizes historical discoveries with the latest scientific research in a clear and compelling portrait of this sonic undersea world. From plainfin midshipman fish, whose swim-bladder drumming is loud enough to keep houseboat-dwellers awake, to the syntax of whalesong; from the deafening crackle of snapping shrimp, to the seismic resonance of underwater earthquakes and volcanoes; sound plays a vital role in feeding, mating, parenting, navigating, and warning—even in animals that we never suspected of acoustic ability. Meanwhile, we jump in our motorboats and cruise ships, oblivious to the impact below us. Our lifestyle is fueled by oil in growling tankers and furnished by goods that travel in massive container ships. Our seas echo with human-made sound, but we are just learning of the repercussions of anthropogenic noise on the marine world's delicate acoustic ecosystems—masking mating calls, chasing animals from their food, and even wounding creatures, from plankton to lobsters. With intimate and artful prose, Sing Like Fish tells a uniquely complete story of ocean animals'submerged sounds, envisions a quieter future, and offers a profound new understanding of the world below the surface.

Underwater acoustics is important in all underwater sonar systems for object detection, classification, surveillance and for communications links for military and civilian purposes. Sound is also a major tool for studying the ocean environment and the interaction of sound and marine life in general. Understanding Ocean Acoustics emphasises such applications and issues relevant to studies of the ocean environment and aquatic life. Its focus is therefore environmental research and development using low frequencies relevant to fish and sea mammals. For such frequencies, the geoacoustic properties of the bottom cannot be ignored, which requires knowledge about waves in solids, which is missing in most books on underwater acoustics.

This textbook on Underwater Acoustics has a structure that is more organic than logical. It thereby unifies diverse areas of research, including topics of signal processing, the sonar equation, sources and receivers, scattering and reverberation, wave propagation, propagation models, and inverse problems. It also provides code fragments written in Python which complement the discussion. This is a book written for both beginners and specialists, as well as for biologists, oceanographers, computer engineers, physicists, and mathematicians, and for civilian and naval personnel who are looking for a introductory overview of the topic.

The book investigates acoustic cloaking for elliptical targets, starting from the development of a systematic approach to deal with such non-axisymmetrical shapes by adopting transformation acoustics in elliptic coordinates, and concluding with numerical and experimental validation of a microstructured cloak in the underwater environment. The book thus comprises all the steps from theory to practice that led to the first experimental validation of acoustic invisibility for non-cylindrical objects, whose results are presented in the last chapter. Indeed, despite Transformation Theory is now an established tool to design material distributions capable to unlock the design of invisibility devices, it is not trivial to apply it for shapes different than the sphere and the cylinder, which are thus the ones mainly addressed in the literature. This book paves the way for exploration of other shapes, demonstrating the effectiveness of a pentamode cloak in reducing the acoustic visibility of anelliptical target, and discussing design choices that can make the implementation of the required microstructure less cumbersome despite the lack of axial symmetry of the problem, from both the numerical and manufacturing point of views.

This book highlights the advantages of the vector-phase method in underwater acoustic measurements and presents results of theoretical and experimental studies of the deep open ocean and shallow sea based on vector-phase representations. Based on the physical phenomena discovered and compensation of counter streams of energy and vortices of the acoustic intensity vector, processes of transmitting acoustic energy of a tonal signal in the real ocean are described. The book also discusses the development of advanced detection tools based on vector-phase sonar. This book provides useful content for professionals and researchers working in various fields of applied underwater acoustics.

This book introduces sonar system and acoustic channel model, average energy channel, coherent multipath channel, the theoretical basis for the stochastic time-varying space-variant channel, slowly time-varying coherent multipath channel, and reverberation channel. Based on the basic theory of underwater acoustic channels and the various characteristics of the marine acoustic environment factor, this textbook aims to help students understand the impact of the marine acoustic channel on the sonar system. It helps students to grasp underwater acoustic signal processing principles and obtain the ability to solve practical problems in underwater acoustic channel engineering. Finally, it aims at laying a foundation for the further sonar system design. This textbook is recommended for graduate or undergraduate students in the field of sonar signal processing, underwater acoustic engineering, as well as some related subjects of marine technology.

Le développement de l'éolien en mer fait aujourd'hui débat. Les effets possiblement préjudiciables des pollutions sonores sur la vie marine font partie des préoccupations légitimes de la société civile, de l'industrie et des instances politiques. Ce livre, qui réunit des experts de diverses disciplines, fait le point sur les connaissances scientifiques relatives à l'impact acoustique des projets éoliens offshore sur la faune marine et aux méthodes permettant de les réduire. Il s'inscrit dans le contexte d'un développement attendu des projets d'énergies marines renouvelables (EMR) et met l'accent sur l'impact du bruit des travaux en mer utiles à la construction, au fonctionnement et au démantèlement des éoliennes offshore sur divers compartiments de la faune marine (mammifères marins, poissons, invertébrés, oiseaux et tortues).Cet ouvrage est destiné aux professionnels des études d'impacts, chercheurs, étudiants, industriels des EMR, ainsi qu'aux responsables territoriaux et membres d'association de protection de la nature. Consulter l'avant-propos d'Alain Schuhl, Directeur Général Délégué à la Science (CNRS)

The book presents a broad-scope analysis of piezoelectric electromechanical transducers and the related aspects of practical transducer design for underwater applications. It uses an energy method for analyzing transducer problems that provides the physical insight important for the understanding of electromechanical devices. Application of the method is first illustrated with transducer examples that can be modeled as systems with a single degree of freedom, (such as spheres, short cylinders, bars and flexural disks and plates made of piezoelectric ceramics). Thereupon, transducers are modeled as devices with multiple degrees of freedom. In all these cases, results of modeling are presented in the form of equivalent electromechanical circuits convenient for the calculation of the transducers'operational characteristics. Special focus is made on the effects of coupled vibrations in mechanical systems on transducer performance. The book also provides extensive coverage of acoustic radiation including acoustic interaction between the transducers. The book is inherently multidisciplinary. It provides essential background regarding the vibration of elastic passive and piezoelectric bodies, piezoelectricity, acoustic radiation, and transducer characterization. Scientists and engineers working in the field of electroacoustics and those involved in education in the field will find this material useful not only for underwater acoustics, but also for electromechanics, energy conversion and medical ultrasonics.

The book presents a broad-scope analysis of piezoelectric electromechanical transducers and the related aspects of practical transducer design for underwater applications. It uses an energy method for analyzing transducer problems that provides the physical insight important for the understanding of electromechanical devices. Application of the method is first illustrated with transducer examples that can be modeled as systems with a single degree of freedom, (such as spheres, short cylinders, bars and flexural disks and plates made of piezoelectric ceramics). Thereupon, transducers are modeled as devices with multiple degrees of freedom. In all these cases, results of modeling are presented in the form of equivalent electromechanical circuits convenient for the calculation of the transducers'operational characteristics. Special focus is made on the effects of coupled vibrations in mechanical systems on transducer performance. The book also provides extensive coverage of acoustic radiation including acoustic interaction between the transducers. The book is inherently multidisciplinary. It provides essential background regarding the vibration of elastic passive and piezoelectric bodies, piezoelectricity, acoustic radiation, and transducer characterization. Scientists and engineers working in the field of electroacoustics and those involved in education in the field will find this material useful not only for underwater acoustics, but also for electromechanics, energy conversion and medical ultrasonics. Part I contains an introduction to the energy method illustrated with examples of one degree of freedom transducers. It is self-sufficient and can be read independently.

Le bruit en mer lié au développement des activités maritimes constitue une menace pour la protection de la faune marine, notamment des mammifères. Il représente une préoccupation croissante des administrations, françaises et étrangères, et des organisations internationales (Nations unies, Organisation maritime internationale, Union européenne, Sanctuaire Pelagos). La société civile s'est également emparée de la question (ONG oeuvrant pour la protection de l'environnement), de même que les acteurs économiques porteurs de solutions technologiques.Forte de ce constat, l'université de Toulon a souhaité réunir différents représentants de la « communauté » du bruit en mer le temps d'un colloque destiné à susciter des interactions interdisciplinaires entre chercheurs, autorités administratives, membres de la société civile et acteurs économiques en vue de dégager des solutions pour concilier développement des activités maritimes et protection de la faune marine. Cet ouvrage dresse un état de la recherche sur le bruit en mer — sous-marin et en surface — et ses effets sur la faune marine en vue de mesurer les efforts qui restent à déployer pour réduire les émissions acoustiques d'origine anthropique et limiter leurs impacts sur le milieu marin. Cette synthèse a mobilisé une trentaine de spécialistes reconnus pour leur expertise et formant une communauté d'acteurs issus d'horizons divers, mués par le souci de protéger le milieu marin de cette forme de pollution complexe à saisir.Ce livre est destiné aux scientifiques, chercheurs, étudiants et enseignants, ainsi qu'aux techniciens et acteurs, publics, privés et de la société civile, impliqués ou intéressés par la question du bruit en mer. Consulter la préface d'Annick Girardin, ministre de la Mer

This collection brings together studies of isotropic and anisotropic scatterers and waveguides, hydroacoustic antennas for echo sounders, frequency, pulse and transitional characteristics of loudspeakers, and oil residues in railway tanks. It also investigates numerical solutions of sound scattering problems by bodies of non-analytical forms using the boundary element method.

This book covers all small details about Underwater Sensor Networks (UWSN). Researchers can use this book as a prerequisite before starting any research on underwater networks or underwater applications. This book covers the introduction, challenges, different architectural models for UWSN, various attacks on UWSN, underwater applications, and networking layers. The target audience includes professors and students in engineering, and researchers and engineers working on marine applications. In academic level, the book is helpful for students having Networking and Information Security as elective subject and doing projects in Wireless Networks. It is also helpful for spostgraduates and Ph.D. researchers to learn basics of Underwater Sensor Networks.

This book presents a comprehensive overview of hydroacoustics and describes the physical basis of acoustic processes observed in the sea. In addition, it discusses the basic concepts and provides simplified models of sound propagation and acoustic phenomena at the boundary between environments. Lastly, the book examines in detail a number of applications of ocean acoustics and methods. The ocean is the last reserve of natural resources. It is also an essential element in the biosphere, ensuring the latter's balance, and plays a pivotal role in the Earth's climate system and global warming. Consequently, studying the ocean is one of humankind's most critical scientific tasks, but penetrating its mysteries is no mean feat. Acoustics (hydroacoustics) is one of the most powerful tools for examining the water layer and beyond, since sound waves are the only type of radiation that can propagate over distances of hundreds and even thousands of kilometers in the ocean.This unique resource appeals to specialists working in the fields of ocean and atmosphere physics, students and postgraduate students studying sea physics and oceanology, and anyone who is interested in the problems the ocean is currently facing.

This book provides comprehensive coverage of the detection and processing of signals in underwater acoustics. Background material on active and passive sonar systems, underwater acoustics, and statistical signal processing makes the book a self-contained and valuable resource for graduate students, researchers, and active practitioners alike. Signal detection topics span a range of common signal types including signals of known form such as active sonar or communications signals; signals of unknown form, including passive sonar and narrowband signals; and transient signals such as marine mammal vocalizations. This text, along with its companion volume on beamforming, provides a thorough treatment of underwater acoustic signal processing that speaks to its author's broad experience in the field.

Loin du monde du silence, le milieu marin doit se concevoir comme un environnement sonore. L'océan est porteur de bruits d'origine physique (vagues, pluie, glace, séismes) et biologiques (chant des baleines, clics des dauphins, claquements de crevettes ou d'oursins). Ce paysage acoustique est essentiel pour la faune marine. Il participe, entre autres, à l'orientation des larves, à la communication des animaux entre eux, à la détection de prédateurs. Toutefois, depuis un peu plus d'un siècle, les activités humaines modifient grandement ce paysage acoustique. Les bruits d'origine anthropique proviennent des navires, des installations posées en mer, des sonars et plus récemment de l'utilisation des énergies marines renouvelables. La faune marine perçoit-elle ces nouveaux sons? La question de l'impact des sons anthropiques sur la faune marine se révèle un enjeu écologique et économique majeur pour les années à venir. Les auteurs montrent la diversité de leurs effets sur la faune grâce à une approche multidisciplinaire associant la physique, la réglementation, la biologie et l'étude d'impact ; une place particulière est donnée aux premiers retours d'expérience de production d'énergies marines renouvelables (EMR) en Europe. Cet ouvrage se veut un premier état des lieux d'un champ de recherche qui ne fait que commencer.

Applied Underwater Acoustics meets the needs of scientists and engineers working in underwater acoustics and graduate students solving problems in, and preparing theses on, topics in underwater acoustics. The book is structured to provide the basis for rapidly assimilating the essential underwater acoustic knowledge base for practical application to daily research and analysis. Each chapter of the book is self-supporting and focuses on a single topic and its relation to underwater acoustics. The chapters start with a brief description of the topic's physical background, necessary definitions, and a short description of the applications, along with a roadmap to the chapter. The subtopics covered within individual subchapters include most frequently used equations that describe the topic. Equations are not derived, rather, assumptions behind equations and limitations on the applications of each equation are emphasized. Figures, tables, and illustrations related to the sub-topic are presented in an easy-to-use manner, and examples on the use of the equations, including appropriate figures and tables are also included. - Provides a complete and up-to-date treatment of all major subjects of underwater acoustics - Presents chapters written by recognized experts in their individual field - Covers the fundamental knowledge scientists and engineers need to solve problems in underwater acoustics - Illuminates, in shorter sub-chapters, the modern applications of underwater acoustics that are described in worked examples - Demands no prior knowledge of underwater acoustics, and the physical principles and mathematics are designed to be readily understood by scientists, engineers, and graduate students of underwater acoustics - Includes a comprehensive list of literature references for each chapter

A new approach to body detection and control based on its unavoidable ultra-low frequency (ULF) oscillation related to its motion in media (mainly, in the ocean) is presented. The main concept of this approach lies in enriching the list of moving body control enabling factors by influence of ULF oscillations on the body's outer fields. It is shown that ULF oscillation of a moving body could be detected in the atmosphere or in the ocean directly with the aid of ambient fluid ULF pressure or velocity changes, say, observed inside an oceanic layer or on the ocean's surface. But ULF oscillation's indirect appearance is demonstrated to be the most important for submerged moving body detection. This appearance comprises an additional ULF modulation (distortion) of outer natural sound fields related to ocean wind noise and distant shipment noise in forward scattering. The physical analogy an indirect moving body ULF oscillation is justified in the book and could be partly compared to the recent universe gravity waves detection discovery in 2016 with the aid of electromagnetic wave distortion that is provided by gravity wave propagation. Specifics of sound scattering by flow inhomogeneity generated by a moving body were demonstrated in Acoustics of Moving Inhomogeneities, which was published recently by Nova Science Publishers. However, this very book is devoted in particular to the modulation of forward scattered sound fields of the ULF field provided by a moving body and the application of corresponding results to its control in the ocean, as well as mainly to submerged submarine control. Proposed detection methods are independent of a moving body's self-noise level. Their application requires consideration of the ambient flow (including surface gravity wave flows) contribution to sound diffraction by the finite size moving body, mainly in forward scattering. A lot of known diffraction problem results should be revised in the light of a moving body ULF field. Examples of practical applications are presented, showing that moving body detection (especially in deep water ocean regions with the aid of natural outer field ULF modulation) is successfully achieved. Detection in shallow water regions is slightly worse due to a smaller wave inhomogeneity scale and when the natural ULF hydrodynamics'noise field level increased. It is shown that body detection distances being thought as unachievable are realized in light of these new moving body ULF field effects. The book is aimed at providing a new approach to external fields of a moving body, mainly submarines. This version of submarine detection is practically substantiated and proven to be effective in Russia for various ocean regions with the aid of various types of arrays. Conclusions substantiated in the book are recommended for practical application. At the same time, additional efforts of scientists, hydroacoustics and naval equipment specialists related to various ULF field applications based on theory predictions are necessary.

This title brings to light the discoveries and insights into the lives of many marine species made possible over the last decade by passive acoustic recorders (PAR). Pop-ups, ARF, HARP, EAR, Bprobe, C-POD Atag, and Dtag are the acronyms of some of the many PARs that have changed our understanding of how marine animals live and strive in the ocean. Various types of PARs are used by different investigators in different areas of the world. These recorders have accumulated copious amounts of very important data, unveiling previously unknown information about large marine animals. Temporal, seasonal and spatial distribution patterns have been uncovered for many marine species. There have been many discoveries, new understandings and insights into how these animals live in and utilize the ocean and the importance of acoustics in their lives. Listening Within the Ocean summarizes these important discoveries, providing both a valuable resource for researchers and enjoyable reading for non-professionals interested in marine life.

The only book that offers a comprehensive and fully up-to-date coverage of hydroacoustic ocean exploration, this work deals with the diagnostics of non-uniformities in a water medium using the hydroacoustic parametric antenna. The non-uniformities of the water medium in the study are of geometrically regular shape, i.e., the shape of a sphere, a cylinder, and a spheroid. An account is given of theoretical and experimental studies of wave processes that occur in the event of the scattering of non-linearly interacting acoustic waves at a sphere, a cylinder, and a spheroid. Scattering problems are formulated; solutions to the inhomogeneous wave equation are found in the first and second approximations using the successive approximations method. For the first time, high-frequency asymptotic expressions of acoustic pressure for all spectral components of the secondary field are obtained for the nonlinear scattering problem. The scattering diagrams are calculated and plotted, and then analyzed and compared. Results of experimental studies of the parametric acoustic antenna field scattering at solid steel spheres are presented. Experimental scattering diagrams both for the parametric antenna pump waves and for the secondary field waves including the difference frequency wave, the sum frequency wave, and the second harmonic wave are presented. 3D modeling of wave processes is also considered. A must have for researchers and specialists in nonlinear hydroacoustics and ocean acoustics; it also may be of use for postgraduates and students specializing in hydroacoustics and ocean exploration.

Digital Underwater Acoustic Communications focuses on describing the differences between underwater acoustic communication channels and radio channels, discusses loss of transmitted sound in underwater acoustic channels, describes digital underwater acoustic communication signal processing, and provides a comprehensive reference to digital underwater acoustic communication equipment. This book is designed to serve as a reference for postgraduate students and practicing engineers involved in the design and analysis of underwater acoustic communications systems as well as for engineers involved in underwater acoustic engineering. - Introduces the basics of underwater acoustics, along with the advanced functionalities needed to achieve reliable communications in underwater environment - Identifies challenges in underwater acoustic channels relative to radio channels, underwater acoustic propagation, and solutions - Shows how multi-path structures can be thought of as time diversity signals - Presents a new, robust signal processing system, and an advanced FH-SS system for multimedia underwater acoustic communications with moderate communication ranges (above 20km) and rates (above 600bps) - Describes the APNFM system for underwater acoustic communication equipment (including both civil and military applications), to be employed in active sonar to improve its performance

Sonochemistry and the Acoustic Bubble provides an introduction to the way ultrasound acts on bubbles in a liquid to cause bubbles to collapse violently, leading to localized'hot spots'in the liquid with temperatures of 5000° celcius and under pressures of several hundred atmospheres. These extreme conditions produce events such as the emission of light, sonoluminescence, with a lifetime of less than a nanosecond, and free radicals that can initiate a host of varied chemical reactions (sonochemistry) in the liquid, all at room temperature. The physics and chemistry behind the phenomena are simply, but comprehensively presented. In addition, potential industrial and medical applications of acoustic cavitation and its chemical effects are described and reviewed. The book is suitable for graduate students working with ultrasound, and for potential chemists and chemical engineers wanting to understand the basics of how ultrasound acts in a liquid to cause chemical and physical effects. - Experimental methods on acoustic cavitation and sonochemistry - Helps users understand how to readily begin experiments in the field - Provides an understanding of the physics behind the phenomenon - Contains examples of (possible) industrial applications in chemical engineering and environmental technologies - Presents the possibilities for adopting the action of acoustic cavitation with respect to industrial applications

The ocean is opaque to electromagnetic radiation and transparent to low frequency sound, so acoustical methodologies are an important tool for sensing the undersea world. Stochastic sound-speed fluctuations in the ocean, such as those caused by internal waves, result in a progressive randomisation of acoustic signals as they traverse the ocean environment. This signal randomisation imposes a limit to the effectiveness of ocean acoustic remote sensing, navigation and communication. Sound Propagation through the Stochastic Ocean provides a comprehensive treatment of developments in the field of statistical ocean acoustics over the last 35 years. This will be of fundamental interest to oceanographers, marine biologists, geophysicists, engineers, applied mathematicians, and physicists. Key discoveries in topics such as internal waves, ray chaos, Feynman path integrals, and mode transport theory are addressed with illustrations from ocean observations. The topics are presented at an approachable level for advanced students and seasoned researchers alike.

This Technical Report presents the outcome of a Working Group that was established to determine broadly applicable sound exposure guidelines for fishes and sea turtles. After consideration of the diversity of fish and sea turtles, guidelines were developed for broad groups of animals, defined by the way they detect sound. Different sound sources were considered in terms of their acoustic characteristics and appropriate metrics defined for measurement of the received levels. The resultant sound exposure guidelines are presented in a set of tables. In some cases numerical guidelines are provided, expressed in appropriate metrics. When there were insufficient data to support numerical values, the relative likelihood of effects occurring was evaluated, although the actual likelihood of effects depends on the received level. These sound exposure guidelines, which are based on the best scientific information at the time of writing, should be treated as interim. The expectation is that with more research the guidelines can be refined and more cells in the tables completed. Recommendations are put forward defining the research requirements of highest priority for extending these interim exposure guidelines.

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.

As man turns his attention from the overcrowded continents of this planet and explores the spaciousness of the ocean, the applications of ocean acoustics become increasingly numerous and important. This book pro- vides an up-to-date introduction to the theory of sound propagation in the ocean, with much new material having been added throughout the second edition. It includes both ray and wave treatments and considerable attention is paid to stochastic problems such as the scattering of sound at rough surfaces and random inhomogeneties. An introductory chapter that discusses the basic experimental data complements the following theoretical chapters.

Shallow water acoustics (SWA), the study of how low and medium frequency sound propagates and scatters on the continental shelves of the worlds oceans, has both technical interest and a large number of practical applications. Technically, shallow water poses an interesting medium for the study of acoustic scattering, inverse theory, and propagation physics in a complicated oceanic waveguide. Practically, shallow water acoustics has interest for geophysical exploration, marine mammal studies, and naval applications. Additionally, one notes the very interdisciplinary nature of shallow water acoustics, including acoustical physics, physical oceanography, marine geology, and marine biology. In this specialized volume the authors, all of whom have extensive at-sea experience in US and Russian research efforts, have tried to summarize the main experimental, theoretical, and computational results in shallow water acoustics, with an emphasis on providing physical insight into the topics presented.

Chapter 1 - Introduction to Underwater Acoustics Chapter 2 - Applications of Underwater Acoustics Chapter 3 - Ocean Acoustic Tomography Chapter 4 - SOFAR Channel and Echo Sounding Chapter 5 - Speed of Sound

Fifteen years ago NATO organised a conference entitled'Ocean Acoustic Modelling'. Many of its participants were again present at this variability workshop. One such participant. in concluding his 1975 paper, quoted the following from a 1972 literature survey:'... history presents a sad lack of communications between acousticians and oceanographers'Have we done any better in the last 15 years? We believe so, but only moderately. There is still a massive underdeveloped potential for acousticians and oceanographers to make significant progress together. Currently, the two camps talk together insufficiently even to avoid simple misun­ derstandings. such as those in Table 1. Table 1 Ocsanographic and acoustic jargon (from an idea by Pol/ardi Jargon Oceanographic use Acoustic use dbordB decibar (depth in m) decibel (energy level) PE primitive equations parabolic equations convergence zone converging currents converging rays (downwelling water) (high energy density) front thermohaline front wave, ray or time front speed water current speed sound propagation speed 1 The list goes on.

During the past decade there has been a renewed interest in active sonar systems at both low and medium frequencies. More recently this interest has been extended to very high frequencies in shallow water. Reverberation often limits the detection performance of these systems, and there is a need to understand the underlying mechanisms that cause the scattering. With more emphasis being given to reverberation phenomena in the Scientific Program of Work at the SACLANT Undersea Research Centre, it was considered an opportune time to host a meeting, bringing together scientists from NATO countries to foster cross-disciplinary dialogue and generate ideas for new research directions. Consequently the Ocean Reverberation Symposium was held 25-29 May 1992 in La Spezia, Italy. Over 60 presentations were made on a diverse selection of topics, of which ten papers will be published as a SACLANTCEN Conference Proceedings. The papers in this volume are grouped into 8 sections, usually in the same order as presented at the corresponding session of the Symposium: Section 1 - Scattering Mechanisms Section 2 - High Frequency Measurements and Mechanisms Section 3 - Reverberation Modelling Section 4 - ARSRP Mid-Atlantic Ridge Experiment Section 5 - Low Frequency Measurements Section 6 - Volume Scattering Section 7 - Signal Processing Issues Section 8 - Applications Taken together the papers show some emerging trends in the research.

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).

Chapter 1 - Acid Chapter 2 - Base Chapter 3 - Acid Dissociation Constant Chapter 4 - Acid–base Reaction and Acid–base Extraction Chapter 5 - Buffer Solution and Acidity Function Chapter 6 - pH Chapter 7 - Proton Affinity and Self–ionization of Water Chapter 8 - Equilibrium Chemistry Chapter 9 - Dynamic Equilibrium and Reaction Quotient Chapter 10 - Equilibrium Constant Chapter 11 - Stability Constants of Complexes Chapter 12 - Determination of Equilibrium Constants Chapter 13 - Chromatography

This literature study presents an overview of underwater acoustic networking. It provides a background and describes the state of the art of all networking facets that are relevant for underwater applications. This report serves both as an introduction to the subject and as a summary of existing protocols, providing support and inspiration for the development of network architectures.

This monograph develops the theory of noise mechanisms and measurements, and describes general noise characteristics and computational methods. The vast ambient noise literature is concisely summarized using theory combined with key representative results. The air sea boundary interaction zone is described in terms of nondimensional variables requisite for future experiments. Noise field coherency, rare directional measurements, and unique basin scale computations and methods are presented. The use of satellite measurements in these basin scale models is demonstrated. A series of appendices provides in-depth mathematical treatments which will be of interest to graduate students and active researchers.

Offering complete and comprehensive coverage of modern sonar spectrum system analysis, Underwater Acoustics: Analysis, Design and Performance of Sonar provides a state-of-the-art introduction to the subject and has been carefully structured to offer a much-needed update to the classic text by Urick. Expanded to included computational approaches to the topic, this book treads the line between the highly theoretical and mathematical texts and the more populist, non-mathematical books that characterize the existing literature in the field. The author compares and contrasts different techniques for sonar design, analysis and performance prediction and includes key experimental and theoretical results, pointing the reader towards further detail with extensive references. Practitioners in the field of sonar design, analysis and performance prediction as well as graduate students and researchers will appreciate this new reference as an invaluable and timely contribution to the field. Chapters include the sonar equation, radiated, self and ambient noise, active sonar sources, transmission loss, reverberation, transducers, active target strength, statistical detection theory, false alarms, contacts and targets, variability and uncertainty, modelling detections and tactical decision aids, cumulative probability of detection, tracking target motion analysis and localization, and design and evaluation of sonars