Acoustic propagation in a channel with range-dependent sound speed PDF Download

Author: M. J. Jacobson
Publisher:
ISBN:
Category :
Languages : en
Pages : 12

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Author: J. Potter
Publisher: Springer Science & Business Media
ISBN: 9401133123
Category : Science
Languages : en
Pages : 599

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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.

Author: Thomas Neighbors
Publisher: Elsevier
ISBN: 0128112476
Category : Science
Languages : en
Pages : 982

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Book Description
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

Author: Lewis A. Stallworth
Publisher:
ISBN:
Category :
Languages : en
Pages : 136

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The effects of current on the ray geometry, spreading loss, boundary loss and phase shift, and travel time of individual continuous-wave (CW) arrivals, as well as the effects on the total acoustic field, are analyzed for three distinct ocean channels: one with constant sound speed and spatially uniform current, one with linear depth-dependent sound speed and spatially uniform current, and one with constant sound speed and linear depth-dependent current. When possible, the theory is compared with actual acoustic-field observations. (Author).

Author: Thomas Rossing
Publisher: Springer Science & Business Media
ISBN: 0387304460
Category : Science
Languages : en
Pages : 1179

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This is an unparalleled modern handbook reflecting the richly interdisciplinary nature of acoustics edited by an acknowledged master in the field. The handbook reviews the most important areas of the subject, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest research and applications are incorporated throughout, including computer recognition and synthesis of speech, physiological acoustics, diagnostic imaging and therapeutic applications and acoustical oceanography. An accompanying CD-ROM contains audio and video files.

Author: Felipe Lourenco
Publisher:
ISBN:
Category :
Languages : en
Pages :

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In an idealized shallow water propagation channel with smooth boundaries and range independent sound speed profiles, normal modes can accurately describe the entire sound field which can be predicted using normal mode models. We also know that fluctuations in the sound field can be caused by fluctuations in the sound speed profile or by source/receiver motion. These phenomena are deterministic and can be simulated by changes in the mode shape or by a combination of the motion of modes past the receiver. If the fluctuations are small then small changes will occur in mode shape or in the mode positions, hence the phase response will be approximately linear and our propagation is "phase coherent" relative to the background noise. Furthermore, spatial and temporal averaging is possible, which enhances the signal-to-noise ratio (SNR). But random fluctuations of the sound speed caused by multipath interactions with the boundaries can totally distort the acoustic modes reducing and sometimes annihilating phase coherence. In this work we seek to understand coherence in terms of the normal acoustic mode structure. This structure can be randomized by fluctuations of the sound field and fluctuations of the boundaries. The research proposed here emphasizes the temporal fluctuations of the sound speed profile and how they affect acoustic mode structures and coherence. To achieve that, the Monterey-Miami Parabolic Equation model will be used to predict the mode shapes in a range dependent channel and random fluctuations will be introduced to observe how the modes are distorted in space and time.

Author: Mark Lewis Grabb
Publisher:
ISBN:
Category :
Languages : en
Pages : 354

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Author: P.C. Etter
Publisher: CRC Press
ISBN: 9780419201908
Category : Architecture
Languages : en
Pages : 364

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Book Description
Underwater Acoustic Modeling provides the only comprehensive source on how to translate our physical understanding of sound in the sea into mathematical formulas solvable by computers.

Author: James Thomas Warfield
Publisher:
ISBN:
Category : Acoustics
Languages : en
Pages : 198

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Author: Denis Makarov
Publisher: World Scientific
ISBN: 981427318X
Category : Science
Languages : en
Pages : 412

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Book Description
1. Ray and wave propagation. 1.1. Underwater sound channel. 1.2. Basic equations. 1.3. Geometrical optics approximations and optical-mechanical analogy. The Hamiltonian formalism. 1.4. Ray travel times. 1.5. Range-dependent environments. 1.6. Acoustic ocean tomography. 1.7. Experiments on long-range sound propagation. 1.8. Summary -- 2. Ray chaos. 2.1. Hamiltonian chaos. 2.2. Lyapunov instability. 2.3. Ray-medium resonance. 2.4. Overlapping of resonances. 2.5. Vertical resonance. 2.6. Manifestation of regular and chaotic ray motion in distributions of ray travel times. 2.7. Summary -- 3. Wave chaos. 3.1. The problem of wave chaos. 3.2. Normal modes. 3.3. Mode coupling under chaotic conditions. 3.4. Influence of fine-scale inhomogeneities on wave dynamics. 3.5. Summary -- 4. Chaotic phenomena in random environment. 4.1. Ray chaos in a random medium. 4.2. Travel times of chaotic rays. 4.3. Modal structure of the sound field in a waveguide with random inhomogeneities. 4.4. Wave beam in an ocean acoustic waveguide. 4.5. Arrival times of sound pulses in the presence of internal waves and a mesoscale inhomogeneity. 4.6. Summary -- 5. Glossary of some concepts and notations in Hamiltonian chaos theory