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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.

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.

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 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.

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

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.

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.

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.

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.

This volume contains the collection of papers from the second workshop on Experimental Acoustic Inversion Techniques for Exploration of the Shallow Water Environment. Acoustic techniques provide the most effective means for remote sensing of ocean and sea floor processes, and for probing the structure beneath the sea floor. No other energy propagates as efficiently in the ocean: radio waves and visible light are severely limited in range because the ocean is a highly conductive medium. However, sound from breaking waves and coastal shipping can be heard throughout the ocean, and marine mammals communicate acoustically over basin scale distances. The papers in this book indicate a high level of research interest that has generated significant progress in development and application of experimental acoustic inversion techniques. The applications span a broad scope in geosciences, from geophysical, biological and even geochemical research. The list includes: estimation of geotechnical properties of sea bed materials; navigation and mapping of the sea floor; fisheries, aquaculture and sea bed habitat assessment; monitoring of marine mammals; sediment transport; and investigation of natural geohazards in marine sediments. Audience This book is primarily intended for physicists and engineers working in underwater acoustics and oceanic engineering. It will also be of interest to marine biologists, geophysicists and oceanographers as potential users of the methodologies and techniques described in the book contributions.

Providing a wealth of information on fundamental topics in the areas of linear air and underwater acoustics, as well as space-time signal processing, this book provides real-world design and analysis equations. As a consequence of the interdisciplinary nature of air and underwater acoustics, the book is divided into two parts: Acoustic Field Theory and Space-Time Signal Processing. It covers the fundamentals of acoustic wave propagation as well as the fundamentals of aperture theory, array theory, and signal processing. Starting with principles and using a consistent, mainly standard notation, this book develops, in detail, basic results that are useful in a variety of air and underwater acoustic applications. Numerous figures, examples, and problems are included.