Download or read book Acoustic Sources of Opportunity in the Marine Environment Applied to Source Localization and Ocean Sensing written by Christopher M. Verlinden and published by . This book was released on 2017 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: Controlled acoustic sources have typically been used for imaging the ocean. These sources can either be used to locate objects or characterize the ocean environment. The processing involves signal extraction in the presence of ambient noise, with shipping being a major component of the latter. With the advent of the Automatic Identification System (AIS) which provides accurate locations of all large commercial vessels, these major noise sources can be converted from nuisance to beacons or sources of opportunity for the purpose of studying the ocean. The source localization method presented here is similar to traditional matched field processing, but differs in that libraries of data-derived measured replicas are used in place of modeled replicas. In order to account for differing source spectra between library and target vessels, cross-correlation functions are compared instead of comparing acoustic signals directly. The library of measured cross-correlation function replicas is extrapolated using waveguide invariant theory to fill gaps between ship tracks, fully populating the search grid with estimated replicas allowing for continuous tracking. In addition to source localization, two ocean sensing techniques are discussed in this dissertation. The feasibility of estimating ocean sound speed and temperature structure, using ship noise across a drifting volumetric array of hydrophones suspended beneath buoys, in a shallow water marine environment is investigated. Using the attenuation of acoustic energy along eigenray paths to invert for ocean properties such as temperature, salinity, and pH is also explored. In each of these cases, the theory is developed, tested using numerical simulations, and validated with data from acoustic field experiments.
Download or read book Fundamentals of Acoustical Oceanography written by Herman Medwin and published by Academic Press. This book was released on 1997-11-05 with total page 739 pages. Available in PDF, EPUB and Kindle. Book excerpt: The developments in the field of ocean acoustics over recent years make this book an important reference for specialists in acoustics, oceanography, marine biology, and related fields. Fundamentals of Acoustical Oceanography also encourages a new generation of scientists, engineers, and entrepreneurs to apply the modern methods of acoustical physics to probe the unknown sea. The book is an authoritative, modern text with examples and exercises. It contains techniques to solve the direct problems, solutions of inverse problems, and an extensive bibliography from the earliest use of sound in the sea to present references.Written by internationally recognized scientists, the book provides background to measure ocean parameters and processes, find life and objects in the sea, communicate underwater, and survey the boundaries of the sea. Fundamentals of Acoustical Oceanography explains principles of underwater sound propagation, and describes how both actively probing sonars and passively listening hydrophones can reveal what the eye cannot see over vast ranges of the turbid ocean. This book demonstrates how to use acoustical remote sensing, variations in sound transmission, in situ acoustical measurements, and computer and laboratory models to identify the physical and biological parameters and processes in the sea.* Offers an integrated, modern approach to passive and active underwater acoustics* Contains many examples of laboratory scale models of ocean-acoustic environments, as well as descriptions of experiments at sea* Covers remote sensing of marine life and the seafloor* Includes signal processing of ocean sounds, physical and biological noises at sea, and inversions* resents sound sources, receivers, and calibration* Explains high intensities; explosive waves, parametric sources, cavitation, shock waves, and streaming* Covers microbubbles from breaking waves, rainfall, dispersion, and attenuation* Describes sound propagation along ray paths and caustics* Presents sound transmissions and normal mode methods in ocean waveguides
Download or read book Noisy Oceans written by Gaye Bayrakci and published by John Wiley & Sons. This book was released on 2023-12-19 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: Noisy Oceans 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.
Download or read book Machine Learning in Passive Ocean Acoustics for Localizing and Characterizing Events written by Emma Ozanich and published by . This book was released on 2020 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: Passive acoustics, or the recording of pressure signals from uncontrolled sound sources, is a powerful tool for monitoring man-made and natural sounds in the ocean. Passive acoustics can be used to detect changes in physical processes within the environment, study behavior and movement of marine animals, or observe presence and motion of ocean vessels and vehicles. Advances in ocean instrumentation and data storage have improved the availability and quality of ambient noise recordings, but there is an ongoing effort to improve signal processing algorithms for extracting useful information from the ambient noise. This dissertation uses machine learning as a framework to address problems in underwater passive acoustic signal processing. Statistical learning has been used for decades, but machine learning has recently gained popularity due to the exponential growth of data and its ability to capitalize on these data with efficient GPU computation. The chapters within this dissertation cover two types of problems: characterization and classification of ambient noise, and localization of passive acoustic sources. First, ambient noise in the eastern Arctic was studied from April to September 2013 using a vertical hydrophone array as it drifted from near the North Pole to north of Fram Strait. Median power spectral estimates and empirical probability density functions (PDFs) along the array transit show a change in the ambient noise levels corresponding to seismic survey airgun occurrence and received level at low frequencies and transient ice noises at high frequencies. Noise contributors were manually identified and included broadband and tonal ice noises, bowhead whale calling, seismic airgun surveys, and earthquake T phases. The bowhead whale or whales detected were believed to belong to the endangered Spitsbergen population and were recorded when the array was as far north as 86°24'N. Then, ambient noise recorded in a Hawaiian coral reef was analyzed for classification of whale song and fish calls. Using automatically detected acoustic events, two clustering processes were proposed: clustering handpicked acoustic metrics using unsupervised methods, and deep embedded clustering (DEC) to learn latent features and clusters from fixed-length power spectrograms. When compared on simulated signals of fish calls and whale song, the unsupervised clustering methods were confounded by overlap in the handpicked features while DEC identified clusters with fish calls, whale song, and events with simultaneous fish calls and whale song. Both clustering approaches were applied to recordings from directional autonomous seafloor acoustic recorder (DASAR) sensors on a Hawaiian coral reef in February 2020. Next, source localization in ocean acoustics was posed as a machine learning problem in which data-driven methods learned source ranges or direction-of-arrival directly from observed acoustic data. The pressure received by a vertical linear array was preprocessed by constructing a normalized sample covariance matrix (SCM) and used as the input for three machine learning methods: feed-forward neural networks (FNN), support vector machines (SVM) and random forests (RF). The FNN, SVM, RF and conventional matched-field processing were applied to recordings from ships in the Noise09 experiment to demonstrate the potential of machine learning for underwater source localization. The source localization problem was extended by examining the relationship between conventional beamforming and linear supervised learning. Then, a nonlinear deep feedforward neural network (FNN) was developed for direction-of-arrival (DOA) estimation for two-source DOA and for K-source DOA, where K is unknown. With multiple snapshots, K-source FNN achieved resolution and accuracy similar to Multiple Signal Classification (MUSIC) and SBL for an unknown number of sources. The practicality of the deep FNN model was demonstrated on ships in the Swellex96 experimental data.
Download or read book Optimal Localization of Ocean Acoustic Sources in an Uncertain Environment written by Anthony M. Richardson and published by . This book was released on 1990 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Acoustic Sensing Techniques for the Shallow Water Environment written by Andrea Caiti and published by Springer Science & Business Media. This book was released on 2006-09-21 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Ocean Noise and Marine Mammals written by National Research Council and published by National Academies Press. This book was released on 2003-05-22 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: For the 119 species of marine mammals, as well as for some other aquatic animals, sound is the primary means of learning about the environment and of communicating, navigating, and foraging. The possibility that human-generated noise could harm marine mammals or significantly interfere with their normal activities is an issue of increasing concern. Noise and its potential impacts have been regulated since the passage of the Marine Mammal Protection Act of 1972. Public awareness of the issue escalated in 1990s when researchers began using high-intensity sound to measure ocean climate changes. More recently, the stranding of beaked whales in proximity to Navy sonar use has again put the issue in the spotlight. Ocean Noise and Marine Mammals reviews sources of noise in the ocean environment, what is known of the responses of marine mammals to acoustic disturbance, and what models exist for describing ocean noise and marine mammal responses. Recommendations are made for future data gathering efforts, studies of marine mammal behavior and physiology, and modeling efforts necessary to determine what the long- and short-term impacts of ocean noise on marine mammals.
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 Acoustic Signal Processing for Ocean Exploration written by J.M.F Moura and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 671 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acoustic Signal Processing for Ocean Explortion has two major goals: (i) to present signal processing algorithms that take into account the models of acoustic propagation in the ocean and; (ii) to give a perspective of the broad set of techniques, problems, and applications arising in ocean exploration. The book discusses related issues and problems focused in model based acoustic signal processing methods. Besides addressing the problem of the propagation of acoustics in the ocean, it presents relevant acoustic signal processing methods like matched field processing, array processing, and localization and detection techniques. These more traditional contexts are herein enlarged to include imaging and mapping, and new signal representation models like time/frequency and wavelet transforms. Several applied aspects of these topics, such as the application of acoustics to fisheries, sea floor swath mapping by swath bathymetry and side scan sonar, autonomous underwater vehicles and communications in underwater are also considered.
Download or read book Model based Ocean Acoustic Passive Localization written by and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Passive Acoustic Techniques for Monitoring Ocean Dynamics written by Oleg A. Godin and published by . This book was released on 2009 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ambient noise in the ocean carries vast information about physical properties of the propagation medium, including sound speed and current velocity fields in the water column and geoacoustic parameters of the sea floor. Passive acoustic techniques utilize the ambient noise and sound sources of opportunity, such as shipping, to retrieve environmental information from measurements of acoustic pressure on hydrophone arrays without need for any controlled sound sources. Non-invasive nature of passive acoustic techniques and the types of the environmental characteristics these provide, combined with their low power requirements and the intrinsic needs for long observation times, near real-time access to data, and rather large data flows, make the passive acoustics ideally suited for incorporation into cabled ocean observatories. In this paper, we focus on retrieval of environmental parameters from the cross-correlation function of ambient noise. It is shown theoretically that, with the averaging time being sufficiently long, the two-point correlation function of diffuse ambient noise in an arbitrary inhomogeneous, moving medium contains as much information about the environment as can be obtained acoustically by placing transceivers in the two points. Thus, measurements of the noise cross-correlation allow one to quantify flow-induced acoustic non-reciprocity and evaluate both spatially averaged flow velocity and sound speed between the two points. Limitations are discussed which arise from the fact that ambient noise in the ocean is neither perfectly diffuse nor stationary. As an example of opportunities offered by coherent processing of ambient noise, we introduce the concept of a passive inverted echo sounder which would provide measurements of the heat content of the ocean and characterize the local internal gravity wave processes, much like conventional, active inverted echo sounders. Instead of radiating sound, the passive inverted echo sounder employs high-frequency acoustic noise generated by interaction and breaking of waves on the ocean surface as well as low-frequency noise from distant shipping to measure two-way acoustic travel times between near-bottom acoustic sensors and reflective ocean surface as well as scattering layers in the water column. The use of linear hydrophone arrays to decrease the necessary averaging times and improve accuracy of the correlation measurements of acoustic travel times will be discussed.
Download or read book Localization of Acoustic Transients in Shallow Water Environments written by Charles Louis Nicholson and published by . This book was released on 1992 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Challenges and Innovations in Ocean In Situ Sensors written by Eric Delory and published by Elsevier. This book was released on 2018-09-21 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt: Challenges and Innovations in Ocean In-Situ Sensors: Measuring Inner Ocean Processes and Health in the Digital Age highlights collaborations of industry and academia in identifying the key challenges and solutions related to ocean observations. A new generation of sensors is presented that addresses the need for higher reliability (e.g. against biofouling), better integration on platforms in terms of size and communication, and data flow across domains (in-situ, space, etc.). Several developments are showcased using a broad diversity of measuring techniques and technologies. Chapters address different sensors and approaches for measurements, including applications, quality monitoring and initiatives that will guide the need for monitoring. Integrates information across key marine and maritime sectors and supports regional policy requirements on monitoring programs Offers tactics for enabling early detection and more effective monitoring of the marine environment and implementation of appropriate management actions Presents new technologies driving the next generation of sensors, allowing readers to understand new capabilities for monitoring and opportunities for another generation of sensors Includes a global vision for ocean monitoring that fosters a new perspective on the direction of ocean measurements
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 1052 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Algorithms for Localization and Tracking of Acoustic Sources with Widely Separated Sensors written by and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiple sensor arrays distributed over a region provide the means for accurate localization of the (x, y) position of a source. When microphone arrays are used to measure aeroacoustic signals from ground vehicles, random fluctuations in the air lead to frequency-selective coherence of the signals that arrive at widely-separated arrays. We have shown previously that even in cases of imperfect spatial coherence, improvements in source localization accuracy are possible when the data from widely-separated arrays are processed jointly by a fusion center. Further, we have shown that a distributed processing scheme involving bearing estimation at individual arrays and time-delay estimation between pairs of widely-separated sensors performs nearly as well as the optimum scheme, with significantly lower communication bandwidth. These results were obtained by studying the Cramer-Rao bound (CR13) on source localization accuracy based on a statistical model for the data measured at the sensors. The contributions of this paper include the presentation of more accurate performance bounds (Ziv-Zakai), and the development of a narrowband subspace algorithm for source localization with distributed arrays and partially coherent signals. We demonstrate through analysis, simulation, and processing of measured data that the performance of both algorithms is limited by ambiguities that arise from the narrowband signals and the large spacing between arrays.
Download or read book Passive Acoustic Localization and Tracking Using Arrays and Directional Sensors written by Ludovic Tenorio-Hallé and published by . This book was released on 2021 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: In bioacoustics, passive acoustic localization and tracking plays an important role in studying marine mammals and other organisms that produce underwater sounds. However, the implementation of such techniques faces many practical challenges, such as lack of environmental data for accurately modeling acoustic propagation, uncertainties in sensor position, time-synchronization of autonomous instruments, and logistical constraints due to large arrays. The three research chapters of this dissertation cumulatively address these hurdles. Chapter 2 develops a reformulation of the "double-difference" method for long-range tracking of acoustic sources. Originally developed for high-resolution localization of earthquakes across a network of widely distributed sensor, the double-difference approach is here adapted to exploit acoustic multipath on a vertical array, deployed in a deep-water waveguide. Results are shown to provide high-precision relative depth and range tracks of sources on the order of 50 km away, by compensating for biases caused by underdetermined array tilt and sound speed model. The method is demonstrated on both a towed acoustic source and a sperm whale (Physeter macrocephalus). Chapter 3 presents a passive time-synchronization technique for independent autonomous acoustic recorders. This approach relies on the coherent ambient noise sources maintaining the same statistical angular distribution around the instruments. Under this assumption, the temporal evolution of the cross-correlation function between sensor pairs reveals their relative time drift. This method enables continuous measurements of clock offset, including small-scale non-linear fluctuations of the drift, otherwise unobservable with standard time-synchronization techniques. Data from a field study in San Ignacio Lagoon, Mexico, is used to demonstrate this technique which is here applied to low frequency pulses, most likely originating from croaker fish (Sciaenidae family). Chapter 4 uses acoustic vector sensor data to track multiple sources simultaneously. The method is demonstrated on singing humpback whales (Megaptera novaeangliae) off western Maui. Here, the directional capabilities of vector sensors are exploited to identify and match azimuthal tracks from multiple sources between sensors, yielding localized whale tracks in terms of latitude and longitude over time. This approach shows potential for further applications such as tracking boats and analyzing the directional properties of ambient noise field.
Download or read book Listening in the Ocean written by Whitlow W. L. Au and published by Springer. This book was released on 2019-03-20 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
