Neighbors / Bradley Applied Underwater Acoustics

Leif Bjørnø
1. Auflage 2017
ISBN: 978-0-12-811247-2
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 980 Seiten

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

Autoren/Hrsg.

Neighbors, Thomas

Bradley, David

Inhaltsverzeichnis

1;Applied Underwater Acoustics;2
2;Applied Underwater Acoustics;4
3;Copyright;5
4;Dedication;6
5;Contents;8
6;List of Contributors;14
7;Preface;16
8;1 - General Characteristics of the Underwater Environment;18
8.1;1.1 INTRODUCTION;18
8.2;1.2 A BRIEF EXPOSITION OF THE HISTORY OF UNDERWATER ACOUSTICS;22
8.2.1;1.2.1 UNDERWATER ACOUSTICS BEFORE 1912;23
8.2.2;1.2.2 THE YEARS 1912 THROUGH 1918;25
8.2.3;1.2.3 THE YEARS 1919 THROUGH 1939;27
8.2.4;1.2.4 THE YEARS 1940 THROUGH 1946;29
8.2.5;1.2.5 THE YEARS AFTER 1946;29
8.3;1.3 INTERNATIONAL STANDARD UNITS;32
8.4;1.4 THE DECIBEL SCALES;33
8.5;1.5 FEATURES OF OCEANOGRAPHY;35
8.5.1;1.5.1 SOUND SPEED PROFILES;35
8.5.2;1.5.2 THERMOCLINES;39
8.5.3;1.5.3 ARCTIC REGIONS;41
8.5.4;1.5.4 DEEP ISOTHERMAL LAYERS;46
8.5.5;1.5.5 EXPRESSIONS FOR THE SPEED OF SOUND;50
8.5.6;1.5.6 SURFACE WAVES;53
8.5.7;1.5.7 INTERNAL WAVES;60
8.5.8;1.5.8 BUBBLES FROM WAVE BREAKING;63
8.5.9;1.5.9 OCEAN ACIDIFICATION;74
8.5.10;1.5.10 DEEP-OCEAN HYDROTHERMAL FLOWS;77
8.5.11;1.5.11 EDDIES, FRONTS, AND LARGE-SCALE TURBULENCE;80
8.5.12;1.5.12 DIURNAL AND SEASONAL CHANGES;82
8.6;1.6 SONAR EQUATIONS;83
8.6.1;1.6.1 DEFINITIONS OF THE SONAR EQUATION TERMS;84
8.6.2;1.6.2 SONAR EQUATIONS;88
8.7;1.7 ABBREVIATIONS;92
8.8;Acknowledgment;93
8.9;REFERENCES;93
9;2 - Sound Propagation;102
9.1;2.1 THE CONCEPT OF WAVES;102
9.1.1;2.1.1 THE WAVE EQUATION FOR AN INVISCID FLUID;103
9.1.2;2.1.2 THE HELMHOLTZ EQUATION;106
9.1.3;2.1.3 HARMONIC WAVES;108
9.1.4;2.1.4 PLANE WAVES;110
9.1.5;2.1.5 CYLINDRICAL WAVES;115
9.1.6;2.1.6 SPHERICAL WAVES;119
9.1.7;2.1.7 PLANE WAVE DECOMPOSITION OF A SPHERICAL WAVE;122
9.2;2.2 SOUND PROPAGATION IN A VISCOUS FLUID;124
9.2.1;2.2.1 DISPERSION FORMULAS;125
9.2.2;2.2.2 KRAMERS–KRONIG DISPERSION RELATIONS;127
9.2.3;2.2.3 CAUSALITY AND STOKES' EQUATION;129
9.2.4;2.2.4 PULSE PROPAGATION IN A VISCOUS FLUID;130
9.3;2.3 SOUND WAVES AND SHEAR WAVES IN MARINE SEDIMENTS;134
9.3.1;2.3.1 THE BIOT THEORY;135
9.3.2;2.3.2 THE GRAIN-SHEARING THEORY;137
9.4;2.4 SOURCE OR RECEIVER IN MOTION;145
9.4.1;2.4.1 DOPPLER FREQUENCY SHIFTS (SOURCE STATIONARY, OBSERVER IN MOTION);146
9.4.2;2.4.2 DOPPLER FREQUENCY SHIFTS (OBSERVER STATIONARY, SOURCE IN MOTION);148
9.4.3;2.4.3 ACOUSTIC FIELD FROM A MOVING SOURCE;149
9.5;2.5 SOUND REFLECTION AND TRANSMISSION AT A FLUID–FLUID BOUNDARY;153
9.5.1;2.5.1 STRUCTURE OF THE SOLUTION;154
9.5.2;2.5.2 THE STATIONARY PHASE APPROXIMATION;158
9.5.3;2.5.3 PLANE-WAVE REFLECTION;159
9.5.4;2.5.4 WESTON'S EFFECTIVE DEPTH;163
9.5.5;2.5.5 PLANE-WAVE REFRACTION;164
9.5.6;2.5.6 THE LATERAL WAVE;167
9.6;2.6 THE “IDEAL” WAVEGUIDE;173
9.6.1;2.6.1 PLANE WAVES AND NORMAL MODES;173
9.6.2;2.6.2 THE ACOUSTIC FIELD IN THE IDEAL WAVEGUIDE;176
9.6.3;2.6.3 INTERMODAL INTERFERENCE;178
9.7;2.7 THE PEKERIS CHANNEL;179
9.7.1;2.7.1 THE INTEGRAL-TRANSFORM SOLUTION FOR THE FIELD;180
9.7.2;2.7.2 THE NORMAL MODE SOLUTION;182
9.7.3;2.7.3 THE CHARACTERISTIC EQUATION;184
9.8;2.8 THREE-DIMENSIONAL PROPAGATION;187
9.8.1;2.8.1 HORIZONTAL REFRACTION;188
9.8.2;2.8.2 THE “IDEAL” WEDGE;189
9.8.3;2.8.3 THE SHADOW EDGE;192
9.8.4;2.8.4 INTRAMODAL INTERFERENCE;195
9.8.5;2.8.5 THE PENETRABLE WEDGE;196
9.9;Acknowledgment;197
9.10;REFERENCES;197
10;3 - Sound Propagation Modeling;202
10.1;3.1 RAY MODELS;205
10.1.1;3.1.1 A PARTICULAR TYPE OF ANALYTIC 2-D RAY TRACING;206
10.1.1.1;3.1.1.1 Kinematic Ray Tracing;207
10.1.1.2;3.1.1.2 Dynamic Ray Tracing;207
10.1.1.3;3.1.1.3 Caustics;209
10.1.1.4;3.1.1.4 Coherent Computation of Propagation Loss and Propagation Time Series;209
10.1.2;3.1.2 EXAMPLE;211
10.2;3.2 WAVE NUMBER INTEGRATION OR SPECTRAL METHODS;213
10.2.1;3.2.1 SOLUTION OF THE DEPTH-DEPENDENT ODE SYSTEMS;215
10.2.1.1;3.2.1.1 Recursive Computation of Reflection-Coefficient Matrices for the Solid Bottom;216
10.2.1.2;3.2.1.2 Propagator Matrices for the Fluid Region;219
10.2.1.3;3.2.1.3 Alternative Treatment of the Fluid Region;220
10.2.1.4;3.2.1.4 Final Remarks;221
10.2.2;3.2.2 ADAPTIVE INTEGRATION;222
10.2.3;3.2.3 EXAMPLE;223
10.3;3.3 NORMAL MODE PROPAGATION MODELS;225
10.3.1;3.3.1 MODAL WAVE NUMBERS;226
10.3.2;3.3.2 MODE FUNCTIONS;227
10.3.3;3.3.3 EXCITATION COEFFICIENTS;229
10.3.4;3.3.4 RANGE-DEPENDENT MEDIA;230
10.3.4.1;3.3.4.1 Equations Relating the Modal Expansion Coefficients;231
10.3.4.2;3.3.4.2 Solution in Terms of Reflection-Coefficient Matrices;233
10.3.4.3;3.3.4.3 Final Remarks;234
10.3.5;3.3.5 EXAMPLES;235
10.3.5.1;3.3.5.1 Range-Invariant Media;235
10.3.5.2;3.3.5.2 Range-Dependent Media;239
10.4;3.4 PARABOLIC EQUATION METHODS;242
10.4.1;3.4.1 INTERFACE CONDITIONS AT THE VERTICAL RANGE-SEGMENT INTERFACES;244
10.4.2;3.4.2 NUMERICAL SOLUTION METHODS;245
10.4.2.1;3.4.2.1 Start Solution;245
10.4.2.2;3.4.2.2 Rational-Function Approximations for the Relevant Operators;247
10.4.2.3;3.4.2.3 Depth Discretization and Range Integration;249
10.4.3;3.4.3 EXTENDED AND ALTERNATIVE PE APPROACHES;250
10.4.3.1;3.4.3.1 Extension to Media That Vary Regionwise Smoothly With Range and Depth;250
10.4.3.2;3.4.3.2 Coordinate Transformation Techniques;251
10.4.3.3;3.4.3.3 Two-Way PE Approaches;252
10.4.3.4;3.4.3.4 Extension to Fluid-Solid Media;252
10.4.4;3.4.4 EXAMPLES;253
10.5;3.5 FINITE-DIFFERENCE AND FINITE-ELEMENT METHODS;256
10.5.1;3.5.1 ONE-DIMENSIONAL FEM AND FDM FOR PARABOLIC AND NORMAL-MODE EQUATIONS;257
10.5.1.1;3.5.1.1 Application to Normal Modes;258
10.5.2;3.5.2 TWO-DIMENSIONAL FEM AND FDM FOR THE HELMHOLTZ EQUATION;259
10.5.2.1;3.5.2.1 FEM Discretization;260
10.5.2.2;3.5.2.2 FDM Discretization;261
10.5.2.3;3.5.2.3 Methods to Solve the Linear Equation System and Possibilities to Reduce Its Size;262
10.5.3;3.5.3 TIME-DOMAIN MODELING;263
10.5.3.1;3.5.3.1 FEM Discretization;263
10.5.3.2;3.5.3.2 FDM Discretization;263
10.5.3.3;3.5.3.3 Numerical Dispersion, Time Integration, and Stability;264
10.5.3.4;3.5.3.4 Including Absorption;265
10.5.3.5;3.5.3.5 Some Recent Developments;265
10.5.4;3.5.4 EXAMPLES;266
10.6;3.6 3-D SOUND PROPAGATION MODELS;268
10.6.1;3.6.1 MODELING HORIZONTAL REFRACTION BY A SLOPING BOTTOM OR CHANGING SOUND-SPEED PROFILE;270
10.6.1.1;3.6.1.1 Fourier Transformation With Respect to the y-Coordinate;271
10.6.1.2;3.6.1.2 Equations Relating the Modal Expansion Coefficients;272
10.6.1.3;3.6.1.3 Solution in Terms of Reflection-Coefficient Matrices;273
10.6.1.4;3.6.1.4 Final Remarks;273
10.6.2;3.6.2 MODELING DIFFRACTION AROUND A CYLINDRICALLY SYMMETRIC ANOMALY;274
10.6.2.1;3.6.2.1 Fourier Series With Respect to the ? Coordinate;274
10.6.2.2;3.6.2.2 Equations Relating the Modal Expansion Coefficients;276
10.6.2.3;3.6.2.3 Solution in Terms of Reflection-Coefficient Matrices;277
10.6.2.4;3.6.2.4 Final Remarks;278
10.6.3;3.6.3 EXAMPLES;278
10.7;LIST OF ABBREVIATIONS AND SYMBOLS;280
10.8;Acknowledgments;281
10.9;REFERENCES;281
11;4 - Absorption of Sound in Seawater;290
11.1;4.1 PHYSICS AND PHENOMENA;290
11.2;4.2 EXPERIMENTAL DATA;292
11.2.1;4.2.1 ABSORPTION PRESSURE DEPENDENCE;295
11.2.2;4.2.2 ABSORPTION TEMPERATURE DEPENDENCE;297
11.2.3;4.2.3 PH DEPENDENCE OF ABSORPTION;299
11.2.4;4.2.4 SALINITY DEPENDENCE;299
11.3;4.3 SOUND ABSORPTION MECHANISMS;300
11.3.1;4.3.1 SOUND ABSORPTION IN FRESHWATER;300
11.3.2;4.3.2 MOLECULAR CHEMICAL RELAXATION PROCESSES;301
11.3.2.1;4.3.2.1 Temperature Dependence;303
11.3.2.2;4.3.2.2 Pressure Effects;305
11.4;4.4 FORMULAS AND EXPRESSIONS;305
11.4.1;4.4.1 FRANCOIS AND GARRISON EQUATION FOR SOUND ABSORPTION IN SEAWATER;305
11.4.1.1;4.4.1.1 Boric Acid Coefficients;306
11.4.1.2;4.4.1.2 Magnesium Sulfate Coefficients;307
11.4.1.3;4.4.1.3 Pure Water Contribution;307
11.4.2;4.4.2 AINSLIE AND MCCOLM SIMPLIFIED EQUATION FOR SOUND ABSORPTION IN SEAWATER;307
11.5;4.5 SYMBOLS AND ABBREVIATIONS;308
11.6;REFERENCES;309
12;5 - Scattering of Sound;314
12.1;5.1 PHYSICS AND PHENOMENA;314
12.2;5.2 SCATTERING FROM POINT-LIKE OBJECTS;320
12.2.1;5.2.1 SINGLE OBJECTS;320
12.2.1.1;5.2.1.1 Rigid and Elastic Spheres;320
12.2.1.2;5.2.1.2 Gas Bubbles;322
12.2.1.3;5.2.1.3 Single Fish;324
12.2.1.4;5.2.1.4 Canonically Shaped Objects;325
12.2.1.5;5.2.1.5 Submarines;327
12.2.2;5.2.2 MULTIPLE OBJECTS;330
12.2.2.1;5.2.2.1 Fish Schools;331
12.2.2.2;5.2.2.2 Bubble Clouds;331
12.2.2.3;5.2.2.3 Deep Scattering Layer;334
12.2.2.4;5.2.2.4 Suspended Sediments;335
12.3;5.3 SCATTERING FROM EXTENDED, NEARLY PLANE, ROUGH SURFACES;335
12.3.1;5.3.1 BRAGG SCATTERING;337
12.3.2;5.3.2 REFLECTION FROM FACETS;337
12.3.3;5.3.3 LAMBERT'S LAW;338
12.3.4;5.3.4 SCATTERING FROM THE SEA SURFACE;339
12.3.5;5.3.5 SCATTERING FROM THE SEABED;343
12.4;5.4 THEORETICAL BASIS FOR SCATTERING CALCULATIONS;349
12.4.1;5.4.1 THE PERTURBATION APPROXIMATION;349
12.4.2;5.4.2 THE HELMHOLTZ–KIRCHHOFF METHOD;352
12.4.3;5.4.3 SCATTERING FROM SURFACES WITH TWO SCALES OF ROUGHNESS;354
12.5;5.5 SCATTERING FROM CURVED, ROUGH SURFACES;357
12.6;5.6 REVERBERATION;363
12.7;5.7 SYMBOLS AND ABBREVIATIONS;370
12.8;REFERENCES;375
13;6 - Ambient Noise;380
13.1;6.1 PHYSICS AND PHENOMENA;380
13.2;6.2 SOURCES OF AMBIENT NOISE;381
13.2.1;6.2.1 TIDES AND HYDROSTATIC EFFECTS OF WAVES;381
13.2.2;6.2.2 SEISMIC ACTIVITIES;383
13.2.3;6.2.3 TURBULENCE;384
13.2.4;6.2.4 SURFACE PHENOMENA;384
13.2.4.1;6.2.4.1 Breaking Waves;385
13.2.4.2;6.2.4.2 Nonlinear Wave–Wave Interaction;386
13.2.4.3;6.2.4.3 Bubbles;387
13.2.5;6.2.5 PRECIPITATION;389
13.2.6;6.2.6 BIOLOGICAL ACTIVITY;391
13.2.7;6.2.7 ICE NOISE;392
13.2.8;6.2.8 SHIPPING;392
13.2.9;6.2.9 OTHER MAN-MADE (ANTHROPOGENIC) SOURCES;396
13.2.10;6.2.10 SEDIMENT FLOW–GENERATED NOISE;397
13.2.11;6.2.11 THERMAL NOISE;397
13.3;6.3 SPECTRA OF AMBIENT NOISE;398
13.3.1;6.3.1 DEEP-WATER SPECTRA;399
13.3.2;6.3.2 SHALLOW-WATER SPECTRA;400
13.4;6.4 DIRECTIVITY OF AMBIENT NOISE;401
13.4.1;6.4.1 NOISE PROPAGATION;401
13.5;6.5 COHERENCE OF AMBIENT NOISE;405
13.6;6.6 SELF-NOISE;407
13.7;6.7 AMPLITUDE DISTRIBUTIONS FOR UNDERWATER NOISE;409
13.8;6.8 SYMBOLS AND ABBREVIATIONS;414
13.9;REFERENCES;416
14;7 - Shallow-Water Acoustics;420
14.1;7.1 WHAT IS SHALLOW-WATER ACOUSTICS?;420
14.1.1;7.1.1 MILITARY APPLICATIONS;421
14.1.2;7.1.2 DUAL-USE APPLICATIONS;422
14.1.3;7.1.3 OCEAN SCIENCES APPLICATIONS;422
14.1.4;7.1.4 COMMERCIAL APPLICATIONS;423
14.2;7.2 PHYSICS AND PHENOMENA;423
14.2.1;7.2.1 SOURCE LEVEL TERM;423
14.2.1.1;7.2.1.1 Example: Integrating Pseudorandom Noise Sequences and Frequency Modulation Sweeps for Signal Gain;426
14.2.2;7.2.2 ARRAY GAIN TERM;428
14.2.2.1;7.2.2.1 Examples: Mode Filtration Techniques in Shallow Water;430
14.2.2.1.1;7.2.2.1.1 Time Resolution of Modes;430
14.2.2.1.2;7.2.2.1.2 Amplitude-Shaded Vertical Array Mode Resolution;430
14.2.2.1.3;7.2.2.1.3 Vertical Array Steering;432
14.2.2.1.4;7.2.2.1.4 Horizontal Array Steering;432
14.2.2.1.5;7.2.2.1.5 Focused Array Mode Filtration;433
14.2.3;7.2.3 TRANSMISSION LOSS TERM;433
14.2.3.1;7.2.3.1 Simple Geometric Spreading Intensity Arguments;433
14.2.3.2;7.2.3.2 Popular Propagation Theories and Their Application(s) to Shallow Water;434
14.2.3.2.1;7.2.3.2.1 Ray Theory;434
14.2.3.2.2;7.2.3.2.2 Normal Modes and Shallow Water;441
14.2.3.2.3;7.2.3.2.3 Vertical Modes and Horizontal Rays;448
14.2.3.2.3.1;7.2.3.2.3.1 Example: Ducting Between Nonlinear Internal Waves;449
14.2.3.2.4;7.2.3.2.4 Parabolic Equation;451
14.2.3.2.5;7.2.3.2.5 Wave Number Integration;453
14.2.4;7.2.4 AMBIENT NOISE TERM;454
14.2.5;7.2.5 REVERBERATION TERM;459
14.2.5.1;7.2.5.1 The Bottom Boundary Layer;462
14.2.5.2;7.2.5.2 Water Column Reverberation;463
14.2.5.3;7.2.5.3 Sea Surface Scattering and Reverberation;463
14.2.5.4;7.2.5.4 The Sea Surface Plus Bubble Scattering and Reverberation;463
14.3;7.3 SOME ADDITIONAL TOPICS OF INTEREST IN SHALLOW-WATER ACOUSTICS;465
14.3.1;7.3.1 ONE- AND TWO-LAYER WATER COLUMN SOUND SPEED PROFILES IN SHALLOW-WATER ACOUSTICS;465
14.3.2;7.3.2 THE OPTIMUM FREQUENCY;466
14.3.3;7.3.3 ARRIVAL STRUCTURES IN SHALLOW-WATER AND RAY/MODE RESOLUTION;467
14.3.4;7.3.4 WAVEGUIDE INVARIANT;468
14.3.5;7.3.5 INTENSITY FLUCTUATION STATISTICS;469
14.4;7.4 SOME NEWER TOPICS;472
14.4.1;7.4.1 THE SHELF BREAK, SLOPE, AND CANYON REGIONS AND THE TRANSITION TO DEEP WATER;472
14.4.2;7.4.2 ARCTIC SHALLOW-WATER ACOUSTICS;473
14.4.3;7.4.3 CLIMATE CHANGE AND SHALLOW-WATER ACOUSTICS;474
14.5;LIST OF ACRONYMS;475
14.6;LIST OF SYMBOLS IN EQUATIONS;476
14.7;REFERENCES;477
14.8;APPENDIX 7.A1;480
15;8 - The Seafloor;486
15.1;8.1 BACKGROUND AND HISTORY;487
15.2;8.2 THE ORIGIN AND NATURE OF SEAFLOOR SEDIMENTS;488
15.3;8.3 ACOUSTICS OF SEDIMENTS;488
15.3.1;8.3.1 FLUID MODEL;489
15.3.2;8.3.2 ELASTIC MODEL;491
15.3.3;8.3.3 POROELASTIC MODEL;494
15.4;8.4 MODEL FOR SOUND SCATTERING BY THE SEAFLOOR;499
15.4.1;8.4.1 MODEL PARAMETERS;500
15.4.2;8.4.2 SCATTERING BY SEAFLOOR ROUGHNESS;501
15.4.3;8.4.3 SCATTERING BY SEAFLOOR HETEROGENEITY;503
15.4.4;8.4.4 SCATTERING MODEL EXAMPLES;505
15.5;8.5 SEDIMENT PHYSICAL PROPERTIES;511
15.5.1;8.5.1 GRAIN SIZE DISTRIBUTION;512
15.5.2;8.5.2 SEDIMENT BULK DENSITY AND POROSITY;516
15.5.3;8.5.3 PORE FLUID AND PORE SPACE PROPERTIES;518
15.5.4;8.5.4 PERMEABILITY;519
15.5.5;8.5.5 GRAIN PROPERTIES;520
15.5.6;8.5.6 SEDIMENT TYPE;520
15.5.7;8.5.7 SUMMARY OF SEDIMENT PROPERTIES;524
15.6;8.6 SEDIMENT GEOACOUSTIC PROPERTIES;524
15.6.1;8.6.1 SOUND SPEED AND ATTENUATION;526
15.6.2;8.6.2 SHEAR WAVE MEASUREMENTS;529
15.6.3;8.6.3 INDEX OF IMPEDANCE;532
15.7;8.7 SEAFLOOR ROUGHNESS;534
15.7.1;8.7.1 MEASUREMENT OF SEAFLOOR ROUGHNESS;535
15.7.2;8.7.2 STATISTICAL CHARACTERIZATION OF SEAFLOOR ROUGHNESS;537
15.7.3;8.7.3 PREDICTION OF SEAFLOOR ROUGHNESS FROM SEDIMENT PHYSICAL PROPERTIES;537
15.8;8.8 SEAFLOOR HETEROGENEITY;539
15.8.1;8.8.1 MEASUREMENTS OF SEDIMENT VOLUME HETEROGENEITY;540
15.8.2;8.8.2 GAS IN SEDIMENTS;541
15.9;8.9 SEAFLOOR IDENTIFICATION AND CHARACTERIZATION BY USE OF SONAR;543
15.9.1;8.9.1 FEATURE CLUSTERING;546
15.9.2;8.9.2 IMAGE SEGMENTATION;548
15.9.3;8.9.3 REFLECTION;548
15.9.4;8.9.4 SCATTERING STRENGTH;549
15.9.5;8.9.5 MODEL FITTING TO ECHO TIME SERIES;554
15.10;LIST OF SYMBOLS;557
15.11;REFERENCES;560
16;9 - Inverse Methods in Underwater Acoustics;570
16.1;9.1 INTRODUCTION;570
16.2;9.2 SOME BASIC MATHEMATICAL RELATIONSHIPS;572
16.3;9.3 SOURCE LOCALIZATION BY MATCHED FIELD PROCESSING;573
16.4;9.4 GEOACOUSTIC INVERSION;576
16.4.1;9.4.1 GEOACOUSTIC MODELS;576
16.4.2;9.4.2 LINEAR INVERSIONS FOR GEOACOUSTIC PROFILES;578
16.4.3;9.4.3 GEOACOUSTIC INVERSION BY BAYESIAN INFERENCE;580
16.4.4;9.4.4 BAYESIAN MATCHED FIELD INVERSION;584
16.4.4.1;9.4.4.1 Bayesian Matched Field Inversion by Optimization;584
16.4.4.2;9.4.4.2 Bayesian Matched Field Inversion by Integration of the a Posteriori Probability Density;589
16.5;9.5 OCEAN ACOUSTIC TOMOGRAPHY;593
16.5.1;9.5.1 INVERSION OF TRAVEL TIMES;594
16.5.2;9.5.2 ACOUSTIC THERMOMETRY;595
16.5.3;9.5.3 ACOUSTIC TOMOGRAPHY IN SHALLOW WATER;597
16.6;REFERENCES;598
17;10 - Sonar Systems;604
17.1;10.1 SONAR SYSTEM APPLICATIONS;605
17.2;10.2 SONAR SYSTEM TYPES;608
17.2.1;10.2.1 TRANSDUCER MATERIALS;608
17.2.2;10.2.2 PROJECTORS AND HYDROPHONES;613
17.2.3;10.2.3 PARAMETERS OF PIEZOCERAMICS;618
17.2.4;10.2.4 TRANSDUCER GEOMETRIES;623
17.2.4.1;10.2.4.1 Plates;624
17.2.4.2;10.2.4.2 Cylindrical Elements;624
17.2.4.3;10.2.4.3 Spherical Elements;628
17.2.4.4;10.2.4.4 Tonpilz Transducers;630
17.2.4.5;10.2.4.5 Flextensional Transducers;633
17.2.4.6;10.2.4.6 Flexural Transducers;635
17.2.5;10.2.5 ACOUSTIC FIELD QUALITIES OF TRANSDUCERS;638
17.2.5.1;10.2.5.1 Single-Element Transducers;639
17.2.5.1.1;10.2.5.1.1 The Pole Concept;639
17.2.5.1.2;10.2.5.1.2 Piston Sources;643
17.2.5.1.3;10.2.5.1.3 Hydrophones;654
17.2.5.2;10.2.5.2 Arrays;661
17.2.5.2.1;10.2.5.2.1 Array Types;662
17.2.5.2.2;10.2.5.2.2 Array Qualities;669
17.2.5.2.3;10.2.5.2.3 Towed Arrays;677
17.3;10.3 SINGLE-BEAM ECHO SOUNDERS;681
17.4;10.4 MULTIBEAM ECHO SOUNDERS;689
17.4.1;10.4.1 MULTIBEAM ECHO SOUNDER STRUCTURE;696
17.4.1.1;10.4.1.1 Projector Unit;697
17.4.1.2;10.4.1.2 Receiver Unit;698
17.4.1.3;10.4.1.3 Sonar Processor Unit;699
17.4.1.4;10.4.1.4 Auxiliary Equipment;701
17.4.2;10.4.2 MULTIBEAM ECHO SOUNDER APPLICATIONS;702
17.4.2.1;10.4.2.1 Bathymetry;702
17.4.2.2;10.4.2.2 Snippets;705
17.4.2.3;10.4.2.3 Side-Scan Data;705
17.4.3;10.4.3 MULTIBEAM ECHO SOUNDER PERFORMANCE LIMITATIONS;705
17.5;10.5 SIDE-SCAN SONAR;706
17.5.1;10.5.1 SINGLE-ROW SSS;706
17.5.2;10.5.2 MULTIROW SSS;712
17.6;10.6 SYNTHETIC APERTURE SONAR;713
17.7;10.7 OTHER SONAR TYPES;718
17.8;10.8 TRANSDUCER CALIBRATION;723
17.8.1;10.8.1 DEFINITIONS;723
17.8.2;10.8.2 RECIPROCITY CALIBRATIONS;725
17.8.3;10.8.3 OTHER CALIBRATION METHODS;729
17.9;10.9 SONAR SYSTEM EXAMPLE CALCULATIONS;734
17.10;10.10 SONAR DESIGN CALCULATIONS;740
17.10.1;10.10.1 TONPILZ TRANSDUCER AND HYDROPHONE CALCULATIONS;741
17.10.2;10.10.2 EQUIVALENT CIRCUITS;745
17.10.3;10.10.3 FINITE-ELEMENT TECHNIQUES;749
17.11;10.11 SYMBOLS AND ABBREVIATIONS;753
17.12;REFERENCES;755
18;11 - Signal Processing;760
18.1;11.1 BACKGROUND AND DEFINITIONS;760
18.1.1;11.1.1 SIGNALS AND NOISE IN UNDERWATER ACOUSTICS;760
18.1.2;11.1.2 WHAT IS “SIGNAL PROCESSING” AND WHY DO WE DO IT?;761
18.1.3;11.1.3 STRUCTURE OF THIS CHAPTER;763
18.1.4;11.1.4 OTHER RESOURCES;763
18.1.5;11.1.5 MATHEMATICAL NOTATION;764
18.1.6;11.1.6 LIST OF SYMBOLS AND NOTATION;764
18.1.7;11.1.7 LIST OF ABBREVIATIONS;765
18.2;11.2 CHARACTERIZING THE SIGNAL AND NOISE;766
18.2.1;11.2.1 SAMPLING AND QUANTIZING ANALOG SIGNALS;766
18.2.2;11.2.2 TIME AND FREQUENCY CHARACTERIZATION;767
18.2.2.1;11.2.2.1 Signal Consistency: Deterministic and Random Signals;768
18.2.2.2;11.2.2.2 Temporal Characterization;768
18.2.2.3;11.2.2.3 Spectral Content: The Fourier Transform and Spectral Density;769
18.2.3;11.2.3 DISCRETE FOURIER TRANSFORM;772
18.2.4;11.2.4 RANDOM PROCESSES: SPECTRA AND CORRELATION FUNCTIONS;773
18.2.5;11.2.5 CROSS-SPECTRA AND COHERENCE;775
18.2.6;11.2.6 CEPSTRUM;775
18.3;11.3 FILTERING;776
18.3.1;11.3.1 FILTER TYPES;776
18.3.2;11.3.2 PERFORMANCE METRICS, DESIGN, AND IMPLEMENTATION;777
18.3.2.1;11.3.2.1 Filtering Performance Metrics;777
18.3.2.2;11.3.2.2 Digital Filter Design and Implementation;777
18.3.3;11.3.3 BAND-PASS SIGNALS: DIGITAL DOWN-CONVERSION;781
18.3.4;11.3.4 WINDOWING FOR SIDE-LOBE SUPPRESSION;781
18.3.5;11.3.5 DATA-DEPENDENT OR ADAPTIVE FILTERING;784
18.4;11.4 DETECTION;784
18.4.1;11.4.1 PERFORMANCE METRICS, DESIGN, IMPLEMENTATION, AND ANALYSIS PROCEDURE;786
18.4.1.1;11.4.1.1 Detection Performance Metrics;786
18.4.1.2;11.4.1.2 Required SNR and Detection Threshold;787
18.4.1.3;11.4.1.3 Detector Design and Implementation;788
18.4.1.4;11.4.1.4 Analysis of Detection Performance;790
18.4.2;11.4.2 STRUCTURED DESIGN APPROACHES;791
18.4.3;11.4.3 DETECTING SIGNALS OF KNOWN FORM: CORRELATION PROCESSING;794
18.4.3.1;11.4.3.1 Example: Doppler Filter Bank;794
18.4.3.2;11.4.3.2 Pulse Compression, Matched Filtering, and the Ambiguity Function;796
18.4.3.3;11.4.3.3 Example: LFM Pulse Compression;797
18.4.3.4;11.4.3.4 Other Applications in Underwater Acoustics;798
18.4.4;11.4.4 DETECTING RANDOM OR UNKNOWN SIGNALS: ENERGY DETECTOR;798
18.4.5;11.4.5 DETECTING UNKNOWN SIGNAL ONSET: PAGE'S TEST;799
18.4.6;11.4.6 NORMALIZING FOR CONSTANT FALSE ALARM RATE;801
18.5;11.5 ESTIMATION;803
18.5.1;11.5.1 PERFORMANCE METRICS, DESIGN, IMPLEMENTATION, AND ANALYSIS PROCEDURE;804
18.5.1.1;11.5.1.1 Estimation Performance Metrics;804
18.5.1.2;11.5.1.2 Estimator Design and Implementation Process;805
18.5.1.3;11.5.1.3 Estimator Analysis Procedure and the Cramer-Rao Lower Bound;805
18.5.2;11.5.2 STRUCTURED DESIGN APPROACHES;806
18.5.2.1;11.5.2.1 Maximum Likelihood Estimation;806
18.5.2.2;11.5.2.2 Method of Moments Estimation;808
18.5.2.3;11.5.2.3 Other Approaches;809
18.5.3;11.5.3 SPECTROGRAM, PERIODOGRAM, AND POWER SPECTRAL DENSITY ESTIMATION;809
18.5.3.1;11.5.3.1 Periodogram for Spectral Density Estimation;811
18.5.3.2;11.5.3.2 Zero-Padding the DFT;814
18.5.4;11.5.4 TIME-DELAY ESTIMATION;815
18.5.5;11.5.5 BEAMFORMING AND ANGLE OF ARRIVAL ESTIMATION;818
18.6;REFERENCES;821
19;12 - Bio- and Fishery Acoustics;826
19.1;12.1 INTRODUCTION;826
19.2;12.2 MARINE LIFE: FROM WHALES TO PLANKTON;827
19.3;12.3 ACOUSTIC SCATTERING BY MARINE LIFE;828
19.3.1;12.3.1 ZOOPLANKTON SCATTERING;830
19.3.2;12.3.2 SWIM BLADDER SCATTERING;832
19.3.3;12.3.3 FISH BODY SCATTERING;834
19.3.4;12.3.4 LARGE-BODY SCATTERING;835
19.3.5;12.3.5 MANY-BODY SCATTERING;838
19.4;12.4 ACTIVE IMAGING SYSTEMS;841
19.4.1;12.4.1 SINGLE-BEAM ECHO SOUNDERS;841
19.4.2;12.4.2 SIDE-SCAN SONARS;845
19.4.3;12.4.3 MULTIBEAM ECHO SOUNDERS;846
19.4.4;12.4.4 COMBINING SENSORS;849
19.5;12.5 MARINE LIFE AND SOUND;852
19.5.1;12.5.1 GENERAL POINTS;852
19.5.2;12.5.2 MARINE MAMMALS;853
19.5.3;12.5.3 FISH, TURTLES, AND INVERTEBRATES;855
19.6;12.6 PASSIVE ACOUSTIC MONITORING;857
19.7;12.7 SELECTED PRACTICAL APPLICATIONS;860
19.7.1;12.7.1 ACTIVE ACOUSTICS: FISH SURVEY;860
19.7.2;12.7.2 PASSIVE ACOUSTICS: AMBIENT NOISE MONITORING;861
19.7.3;12.7.3 ACOUSTIC TELEMETRY: FISH BEHAVIOR;863
19.8;12.8 CONCLUSIONS: FUTURE DEVELOPMENTS;864
19.9;REFERENCES;866
20;13 - Finite-Amplitude Waves;874
20.1;13.1 PHYSICS AND NONLINEAR PHENOMENA;875
20.1.1;13.1.1 HARMONIC DISTORTION;875
20.1.2;13.1.2 FOCUSED SOUND FIELDS;878
20.1.3;13.1.3 CAVITATION;880
20.1.4;13.1.4 ACOUSTIC RADIATION PRESSURE AND ACOUSTIC STREAMING;882
20.2;13.2 NONLINEAR UNDERWATER ACOUSTICS;883
20.2.1;13.2.1 PARAMETRIC ACOUSTIC TRANSMITTING ARRAYS;884
20.2.2;13.2.2 PARAMETRIC ACOUSTIC RECEIVING ARRAYS;889
20.2.3;13.2.3 APPLICATIONS OF THE PARAMETRIC ACOUSTIC ARRAY;890
20.3;13.3 UNDERWATER EXPLOSIONS;895
20.3.1;13.3.1 THE SHOCK WAVE;895
20.3.2;13.3.2 THE GAS BUBBLE;897
20.3.3;13.3.3 OTHER SOURCES OF HIGH-INTENSITY SOUND;898
20.4;13.4 LIST OF SYMBOLS AND ABBREVIATIONS;901
20.5;REFERENCES;903
21;14 - Underwater Acoustic Measurements and Their Applications;906
21.1;14.1 INTRODUCTION;906
21.2;14.2 ACOUSTICS AND MARINE RENEWABLE ENERGY DEVELOPMENTS;907
21.2.1;14.2.1 NOISE DURING THE CONSTRUCTION PHASE;908
21.2.2;14.2.2 NOISE DURING OPERATION;910
21.3;14.3 UNDERWATER ACOUSTICS IN NUCLEAR-TEST-BAN TREATY MONITORING;911
21.3.1;14.3.1 THE HYDROACOUSTIC NETWORK OF THE CTBTO;913
21.3.2;14.3.2 INSTALLATION AND PERFORMANCE OF THE NEWEST IMS HYDROACOUSTIC STATION: HA03, ROBINSON CRUSOE ISLAND, JUAN FERNÁNDEZ ARCHIPEL ...;914
21.4;14.4 CHARACTERIZATION OF NOISE FROM SHIPS;916
21.4.1;14.4.1 GENERAL CHARACTERIZATION OF NOISE PRODUCED BY SHIPS;916
21.4.2;14.4.2 NOISE GENERATED BY A PROPULSION SYSTEM;918
21.4.3;14.4.3 NOISE GENERATED BY A PROPELLER;919
21.4.4;14.4.4 IDENTIFICATION OF ACOUSTIC WAVES EMITTED BY A MOVING SHIP;919
21.4.5;14.4.5 SUMMARY;920
21.5;14.5 UNDERWATER SOUNDSCAPES;921
21.6;14.6 UNDERWATER ACOUSTIC COMMUNICATIONS;925
21.7;14.7 UNDERWATER ARCHAEOLOGY;930
21.7.1;14.7.1 THE WORKING CYCLE OF FIELD MARINE ARCHAEOLOGISTS;930
21.7.1.1;14.7.1.1 Large Area Search;931
21.7.1.2;14.7.1.2 Local Surveying and Mapping;932
21.7.1.3;14.7.1.3 Evolving Trends: A Technological Future for the Exploration of Deep Water Archaeological Sites;933
21.8;14.8 APPLICATIONS OF UNDERWATER ACOUSTICS IN POLAR ENVIRONMENTS;934
21.8.1;14.8.1 INTRODUCTION;934
21.8.2;14.8.2 ARCTIC;935
21.8.3;14.8.3 ANTARCTIC;938
21.9;14.9 TANK EXPERIMENTS;940
21.9.1;14.9.1 INTRODUCTION;940
21.9.2;14.9.2 DESCRIPTION OF DIFFERENT CATEGORIES OF TANKS USED FOR UNDERWATER APPLICATIONS;941
21.9.3;14.9.3 CONCLUSION;944
21.10;14.10 ACOUSTIC POSITIONING AT SEA;944
21.10.1;14.10.1 LBL POSITIONING DEVELOPMENT;945
21.10.2;14.10.2 ULTRASHORT BASELINE (USBL) POSITIONING;946
21.10.3;14.10.3 EFFECTS OF NOISE;947
21.10.4;14.10.4 IMPROVED CODING;947
21.10.5;14.10.5 COORDINATION WITH INERTIAL SENSORS;947
21.11;14.11 OCEAN OBSERVING SYSTEMS AND OCEAN OBSERVATORIES, OCEANOGRAPHERS, AND ACOUSTICIANS—A PERSONAL PERSPECTIVE;948
21.11.1;14.11.1 INTRODUCTION;948
21.11.2;14.11.2 OCEANOGRAPHERS;949
21.11.3;14.11.3 ACOUSTICIANS;950
21.11.4;14.11.4 FUTURE DIRECTIONS;950
21.12;14.12 APPLICATIONS OF UNDERWATER ACOUSTICS TO MILITARY PURPOSES;951
21.12.1;14.12.1 PASSIVE SONAR;952
21.12.2;14.12.2 ACTIVE SONAR;955
21.13;REFERENCES;957
22;Index;966
22.1;A;966
22.2;B;967
22.3;C;968
22.4;D;968
22.5;E;969
22.6;F;969
22.7;G;970
22.8;H;970
22.9;I;970
22.10;J;971
22.11;K;971
22.12;L;971
22.13;M;971
22.14;N;972
22.15;O;972
22.16;P;973
22.17;Q;974
22.18;R;974
22.19;S;974
22.20;T;979
22.21;U;980
22.22;V;981
22.23;W;981
22.24;Y;981
22.25;Z;981

Leseproben

Chapter 1

General Characteristics of the Underwater Environment

L. Bjørnø1,†, and M.J. Buckingham2     1UltraTech Holding, Taastrup, Denmark     2Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, United States

Abstract

This chapter provides a framework and roadmap for the book. It starts with a brief history of underwater acoustics from the time of the Greek philosopher Aristotle (384–322BC) up to the post–World War II era. This is followed by a discussion of the international system of units used in the book and a discussion on the use of the decibel scale. Next, the chapter deals with the features of oceanography including sound speed profiles, thermoclines, arctic regions, deep isothermal layers, expressions for the speed of sound, surface waves, internal waves, bubbles from wave breaking, ocean acidification, deep-ocean hydrothermal flows, eddies, fronts and large-scale turbulence, and diurnal and seasonal changes. This is followed by a discussion of the sonar equation that is fundamental to underwater acoustics.

Keywords

Arctic regions; Breaking waves; Bubbles; Deep isothermal layers; Deep-ocean hydrothermal flows; Detection probability; Detection threshold; Directivity index; Eddies; False alarm probability; Francois and Garrison equation; Fronts and large-scale turbulence; Internal waves; Noise level; Ocean acidification; Oceanography; Receiver-operating characteristic curves; Reverberation level; Sonar equations; Sound speed profiles; Source level; Speed of sound; Surface waves; Target strength; Thermoclines; Transmission loss; Underwater acoustics history

1.1. Introduction

Over the past about 100years the exploitation of the seas and their resources has continuously increased. Acoustic waves have turned out to be a very useful tool for detecting resources and objects in the water column and on the seafloor. Other methods have been used with varying degrees of success depending on the objects to be detected or investigated. These methods include magnetics, magnetic anomaly detection, where minor changes in the earth's magnetic field due to presence of an object can be measured; optical methods; electric field changes; hydrodynamics such as pressure changes; thermal methods; and electromagnetic waves. While radar is very useful for detection of objects above water, electromagnetic radar waves are strongly absorbed in seawater. While electromagnetic waves in the visible frequency band from 4 to 8·1014Hz are much less absorbed, with a minimum absorption coefficient of 3·10-3cm-1 in the green-blue light near 455nm wavelength (i.e., 6.59·1014Hz), electromagnetic wave absorption in the normally used radar bands is several orders of magnitude higher than in the visible band. Seawater salt contains magnesium that makes the water conduct electricity since the 2+ cation constitutes 3.7% of seawater salt. A 1GHz radar wave in the ultra-high frequency (UHF) band with a 0.3m wavelength has a 1400dB/m absorption coefficient while the same wavelength in the 5kHz sound wave has a 3·10-4dB/m absorption coefficient. Therefore, radar systems are not useful for detecting objects under water.

Underwater sound is used in many applications, such as hydrography, off-shore activities, dredging, defense and security, marine research, and fishery. Hydrography includes harbor and river surveys, bathymetric surveys, flood damage assessment, engineering inspection, pipeline and cable route surveys, exclusive economic zone (EEZ) mapping, breakwater mapping, and so on. Off-shore activities include pipeline and cable installation and inspection, leakage detection, route and site surveys, subsea structure installation support, renewables, remotely operated vehicle (ROV) intervention guidance, decommissioning, reconnaissance surveys, search and recovery, oil and gas prospecting, and prospecting for minerals and resources on and in the seafloor. Dredging includes sonars used by rock and stone dump vessels, excavator and trailing suction hopper dredgers, cutter suction and bucket dredgers, clamshell grab cranes and underwater plow vessels, and placement support. Defense and security includes mine counter measures, submarine and torpedo detection, obstacle avoidance, search and recovery, underwater communication, vessel and fleet protection, waterside security, diver detection, and so on. Marine research includes environmental monitoring, ambient noise measurements, marine archeology, marine mammal research, and fishery research. Fishery includes fishery operations, fish school detection, catch monitoring and control, trawl position control, phytoplankton and zooplankton investigations, communication between monitoring sensors on fishing gear and the fishing vessel, seabed mapping, bottom discrimination, and so on.

The counterpart to radar above water is sonar under water. SONAR is the acronym for sound navigation and ranging. It was originally used during World War II as an analog to the name “radar” and as a replacement for the name “asdics” for underwater detection systems using sound, which were used by the British Royal Navy during World War I. The two most common sonar types are passive and active. In a passive sonar system, the acoustic signal originates at a target and propagates to a receiver, where the acoustic signal is converted to an electrical signal for processing. In an active sonar system, an electrical signal is converted to an acoustical signal by a transmitter and the sound waves propagate from the transmitter to a target and back to a receiver, where conversion from acoustical to electrical signal takes place followed by electronic signal processing. Signal processing is aimed at enhancing the return signal from the target or reducing the noise in which the return signal may be embedded, as discussed in Chapter 11. The transmitter is normally called the projector and the receiver is called the hydrophone, as discussed in Chapter 10. If the return signal—the echo—from a target is detected, the position and the potential target movement are determined by the time delay of the echo from the target and the direction of the echo, respectively. The speed of a moving target can be estimated from the frequency shift—the Doppler shift—in the echo from the target, as discussed in Chapter 2.

When a sound wave is produced in water it propagates from the site where it is produced. Sound sources can be natural, such as breaking waves, rain falling on the water surface, seismic activities in the seafloor, and so on, or man-made such as sonar signals, underwater explosions, ship noise, and so on, as discussed in Chapter 6. During propagation the sound signal is exposed to a number of processes which may change the sound signal and its propagation, such as sound signal amplitude attenuation due to absorption, divergence, and scattering, as discussed in Chapter 4. Scattering takes place during the sound wave's interaction with the sea surface, seafloor, and inhomogeneities in the water column, as discussed in Chapter 5. These inhomogeneities can be natural, such as plankton, fish and sea mammals, and variations in the sea temperature and salinity. Scattering and reflection of sound signals may cause sound waves to follow different paths, producing multi-path sound propagation, which can make detection of objects in the water column and on the seafloor difficult. The scattering of underwater sound may lead to reverberation which limits detection. Use of advanced signal processing on the transmitted and received signal opens up the possibility to avoid or reduce the degradation of the propagated sound signal, as discussed in Chapter 11. Ambient noise in the sea can also become a limiting factor for signal detection. The sound signal received by a hydrophone carries information about the signal source and what the signal has encountered while propagating from the source to the hydrophone. The signal received by the hydrophone is processed to extract information of value to the user. This complicated “underwater world,” where sound propagation is influenced by many individual sources with effect on the sound signal's amplitude, phase, and spectral composition, is the basis for this book, “Applied Underwater Acoustics.”

Each chapter is introduced with a section giving the necessary definitions and describing the physical background for the subsequent sections of the chapter. The man-made sources of sound from sonar systems of various types are described in Chapter 10. This chapter also describes the different transducer types, their charge forming elements, and their geometries. Chapter 10 illuminates the sonar types available today, characteristic features, as well as their design, calculation, and calibration. Hydrophones, including array types, and their characteristics are also a part of Chapter 10.

The sound wave propagation through the water and the different factors which influence the propagation path are discussed in...