Mitigating the Impact of Ocean Ambient Noise in an Underwater Acoustic Communication System

Mitigating the Impact of Ocean Ambient Noise in an Underwater Acoustic Communication System

Author: Afolarin Egbewande

Publisher:

Published: 2022

Total Pages: 0

ISBN-13:

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In wireless communication links, receivers are typically designed to mitigate the variability in the propagation channel in presence of arbitrary white Gaussian noise. However, the variations in the instantaneous channel properties introduce high statistical variability in the communication link reliability. In fact, the underwater acoustic channel in the ocean is particularly sensitive to the changes in environmental conditions. Extensive research has been done on the propagation but it is typically assumed that ocean noise compares with terrestrial noise in the design of underwater acoustic receivers. This assumption does not accurately represent the impact of ocean ambient noise on the performance of underwater acoustic communication systems, particularly when using receiver arrays. This dissertation studies the unique properties of oceanic ambient noise, particularly the variability in its directional properties. The application developed in this work focuses on both anthropogenic noise due to vessels and naturally occurring ambient noise within the channel bandwidth. To this end, the characteristics of these noise sources and their impact on the underwater acoustic link are discussed in this dissertation. Firstly, using a compact receiver array, an acoustic source tracking procedure is designed to characterize the directional properties of vessel noise. This is achieved using a maximum-likelihood beamformer to estimate the bearing and a coherence-based matched-field processor to estimate the range of a vessel over its travel duration. Although the performance of most methodologies developed for characterizing vessel noise in literature are evaluated using computer simulations, the algorithm applied in this dissertation are tested with actual measurements of vessel noise from ocean experiments. It is observed that the noise directionality can be estimated accurately using a compact array but relies on the geometry of the array. Secondly, noise models are developed to characterize the unique properties of naturally occurring ambient noise at a compact array of acoustic receivers. Synthetic ambient noise is generated with defined properties and validated against measured ambient noise. Thirdly, the performance of a space-time receiver for signals processed in measured ambient noise is validated against signals processed in synthetic noise processes. It is observed that the variations in the space-time properties of ambient noise do not compare with the usual uncorrelated noise assumption in the design of an underwater acoustic receiver. Also, the bit-error rate of the space-time filter depends on optimizing the training and payload duration in the received signal to adapt to the time-varying property of ocean ambient noise.


Effects of Anthropogenic Noise on Animals

Effects of Anthropogenic Noise on Animals

Author: Hans Slabbekoorn

Publisher: Springer

Published: 2018-08-20

Total Pages: 322

ISBN-13: 1493985744

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Over the past several years, many investigators interested in the effects of man-made sounds on animals have come to realize that there is much to gain from studying the broader literature on hearing sound and the effects of sound as well as data from the effects on humans. It has also become clear that knowledge of the effects of sound on one group of animals (e.g., birds or frogs) can guide studies on other groups (e.g., marine mammals or fishes) and that a review of all such studies together would be very useful to get a better understanding of the general principles and underlying cochlear and cognitive mechanisms that explain damage, disturbance, and deterrence across taxa. The purpose of this volume, then, is to provide a comprehensive review of the effects of man-made sounds on animals, with the goal of fulfilling two major needs. First, it was thought to be important to bring together data on sound and bioacoustics that have implications across all taxa (including humans) so that such information is generally available to the community of scholars interested in the effects of sound. This is done in Chaps. 2-5. Second, in Chaps. 6-10, the volume brings together what is known about the effects of sound on diverse vertebrate taxa so that investigators with interests in specific groups can learn from the data and experimental approaches from other species. Put another way, having an overview of the similarities and discrepancies among various animal groups and insight into the “how and why” will benefit the overall conceptual understanding, applications in society, and all future research.


International Regulation of Underwater Sound

International Regulation of Underwater Sound

Author: Elena McCarthy

Publisher: Springer Science & Business Media

Published: 2007-05-08

Total Pages: 295

ISBN-13: 1402080786

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Numerous incidents suggest that man-made sound injures and can kill marine mammals. This book offers an objective look at how ocean noise should be addressed given the lack of regulatory structure and the scientific uncertainty over the effects of noise on marine life. It is an essential text for policymakers, governments and NGOs, biologists, environmental activists, , oceanographers, and those in the shipping, engineering, and offshore oil and gas industries.


Ocean Noise and Marine Mammals

Ocean Noise and Marine Mammals

Author: National Research Council

Publisher: National Academies Press

Published: 2003-05-22

Total Pages: 220

ISBN-13: 0309133157

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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.


Digital Underwater Acoustic Communications

Digital Underwater Acoustic Communications

Author: Lufen Xu

Publisher: Academic Press

Published: 2016-09-16

Total Pages: 292

ISBN-13: 0128030291

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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


The Effects of Noise on Aquatic Life II

The Effects of Noise on Aquatic Life II

Author: Arthur N. Popper

Publisher: Springer

Published: 2015-11-26

Total Pages: 1243

ISBN-13: 149392981X

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The meeting of Aquatic Noise 2013 will introduce participants to the most recent research data, regulatory issues and thinking about effects of man-made noise and will foster critical cross-disciplinary discussion between the participants. Emphasis will be on the cross-fertilization of ideas and findings across species and noise sources. As with its predecessor, The Effects of Noise on Aquatic Life: 3rd International Conference will encourage discussion of the impact of underwater sound, its regulation and mitigation of its effects. With over 100 contributions from leading researchers, a wide range of sources of underwater sound will be considered.


Underwater Sound Propagation and Acoustic Communication in a Time-varying Shallow Estuarine Environment

Underwater Sound Propagation and Acoustic Communication in a Time-varying Shallow Estuarine Environment

Author: Zheguang Zou

Publisher:

Published: 2018

Total Pages: 132

ISBN-13: 9780355734898

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Estuaries are water regions that connect rivers and oceans, which are very important due to heavy traffic, fishery and other coastal engineering activities. Underwater acoustic technology offers a series of effective applications and technical supports for real-time monitoring and long-term preservation of the nature environment and ecosystem in these regions. However, estuaries are shallow waters with complicated temporal and spatial environmental variability, involving a variety of physical oceanographic processes, such as tidal water mixing and ocean winds/waves, which can significantly influence the underwater sound propagation and moreover, underwater acoustic communications. In order to perform reliably and effectively in such complex time-varying shallow-water ocean environments, next-generation underwater acoustic communication systems need an all new design based on the environmental variability of the physical ocean, which takes the environmental physics and time-varying variability into account and is able to adapt and switch to the optimal mode as the environment evolves. Therefore, a deep, comprehensive and thorough understanding of the link between the time-varying ocean environment, underwater acoustic channel, and underwater acoustic communication systems is highly required. ☐ This dissertation investigated the relationship between the shallow-water, time-varying environment of estuaries, the underwater sound propagation and underwater acoustic communications, which can help the design of underwater acoustic systems so that they can adapt the time-varying environment with wiser parameter configurations. In this dissertation, field data analysis, joint numerical modeling, together with a controllable laboratory experiment were used to study acoustic channel variability of a shallow estuary and its influence on the performance of underwater acoustic communications. This dissertation included four aspects: (a) Effect of water-column variation due to the tidal dynamics in an estuary on the underwater acoustic direct path; (b) Effect of time-varying surface roughness due to the wind-driven waves on underwater acoustic surface paths; (c) Numerically modeling the effect of time-varying wind-driven shallow-water waves on coherent underwater acoustic communications using a combined model; (d) Conducting a controllable laboratory experiment to investigate the time-varying wind-driven water waves on the performance of coherent and non-coherent underwater acoustic communications. ☐ The first two aspects focused on the link between the time-varying environment of an estuary and the underwater acoustic wave propagation. With field data analysis and joint numerical modeling, the time-varying variability of acoustic direct paths and surface-bounced paths from a high-frequency acoustic experiment conducted in the Delaware Bay estuary was explored. On one hand, periodical acoustic direct path fading was found in the tidal-straining Delaware Bay estuary, with the fading period as same as the semi-diurnal tide. Based on physical oceanography and ocean acoustics, the mechanism that causes the direct path fading and its link to the water dynamics of an estuary was investigated. On the other hand, the relationship between the acoustic surface paths and the surface wind speed was investigated, and the wind-influenced shallow-water time-varying channel was studied using field data analysis and a joint model combining physical oceanography and ocean acoustics. The joint numerical model, including a wind-wave model, a surface generation algorithm and a parabolic equation acoustic model, reproduced the relationship between the wind speed and surface reflection signals. ☐ The last two aspects applied the knowledge of underwater sound propagation in shallow estuaries into analyzing the performance of underwater acoustic communication systems, i.e., investigating how the fast fluctuation of a shallow-water environment (wind-driven waves) influences different fundamental modulation schemes for underwater acoustic communications. To better analyze the effect of environmental variability of the physical ocean on underwater acoustic communications, the surface condition was set as the only variation in the numerical modeling and the controllable laboratory experiment. On one hand, a combined model including physical oceanography, ocean acoustics, and underwater acoustic communication was used to study the time-varying underwater acoustic channel under different wind speeds, and the performance of the coherent acoustic communication (QPSK) system. On the other hand, a controllable laboratory experiment was conducted to investigate bit-error-rate (BER) performance of the MFSK (representing the non-coherent acoustic communication) and the QPSK (representing the coherent acoustic communication) acoustic modulations. ☐ The main conclusions of the dissertation are as follows. For the time-varying variability of underwater acoustic channel: (a) Due to the tidal-straining water dynamics of an estuary, periodical water column exchange between the seawater and the freshwater, up-refracting sound speed profile is more likely to form by the end of ebb tide, which redirects sound signal away from the deep receivers and creates shadow zone for the sound direct path; (b) In an open estuary, the acoustic pressure of surface-bounced paths decreases with increased wind speed, as a result of increased acoustic scattering due to the wind-driven surface roughness. For underwater acoustic communications: (c) Coherent acoustic communications are sensitive to the fast time-varying variability, and performance decrease significantly with increased wind speed, as a result of increased channel variability and decreased temporal coherence; (d) Non-coherent acoustic communications are less sensitive to the channel variability, and the reduced multipath signals due to wind-wave surface may improve the system performance. ☐ The key novelties of this dissertation include: (a) Using a joint model involving physical oceanography and ocean acoustics to study the effect of time-varying estuarine environment (water-column variations and wind-driven surface waves) on underwater sound propagation and the underwater acoustic channels. (b) Using an integrated model involving physical oceanography, ocean acoustics, and underwater acoustic communications to study the effect of time-varying estuarine environment (wind-driven surface waves) on underwater acoustic communications. (c) Using field experimental data, numerical modeling and controllable laboratory experiment to study the underwater sound propagation and underwater acoustic communications in a time-varying ocean environment.


Marine Mammals and Noise

Marine Mammals and Noise

Author: W. John Richardson

Publisher: Academic Press

Published: 2013-10-22

Total Pages: 593

ISBN-13: 0080573037

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Many marine mammals communicate by emitting sounds that pass through water. Such sounds can be received across great distances and can influence the behavior of these undersea creatures. In the past few decades, the oceans have become increasingly noisy, as underwater sounds from propellers, sonars, and other human activities make it difficult for marine mammals to communicate. This book discusses, among many other topics, just how well marine mammals hear, how noisy the oceans have become, and what effects these new sounds have on marine mammals. The baseline of ambient noise, the sounds produced by machines and mammals, the sensitivity of marine mammal hearing, and the reactions of marine mammals are also examined. An essential addition to any marine biologist's library, Marine Mammals and Noise will be especially appealing to marine mammalogists, researchers, policy makers and regulators, and marine biologists and oceanographers using sound in their research.