Fundamentals of shallow water acoustics

Series Preface......Page 5
Preface and Acknowledgments......Page 7
Contents......Page 11
1.1 Deep Versus Shallow......Page 16
1.2 Past and Present of Shallow Water Acoustics......Page 19
1.3 The Future of Shallow Water Acoustics......Page 25
1.4 Some ``Old Favorite´´ Research Areas Revisited and Updated......Page 29
2.1 The Coast as Acoustic Waveguide......Page 32
2.2 Properties of Sea Water: Vertical Stratification and Its Seasonal Variability......Page 33
2.3 Horizontal Stratification and Its Variability: Fronts and Eddies, Surface Ducts, and Storm Surges......Page 38
2.4 Dynamics of the Ocean Surface: Surface Waves......Page 47
2.5 Dynamical Processes Inside the Ocean: Tides and Internal Waves......Page 49
2.6 Experimental Studies of Coastal Internal Waves......Page 58
2.7 Coastal Geology and Geophysics......Page 66
2.8 Acoustics of Sediments......Page 70
2.9 Bottom Roughness......Page 78
2.10 Solid and Multicomponent Layered Bottom Models......Page 80
2.11 Acoustics of Biological Objects in a Coastal Area......Page 85
3.1 Field of a Point Source in a Layered Waveguide with Absorbing Boundaries......Page 93
3.2 The Pekeris Model......Page 100
3.3 Perturbation Theory and WKB Methods......Page 108
3.4.1 Ray Theory......Page 116
3.4.2 Rays as Interfering Modes......Page 119
3.4.3 Modes as Interfering Rays......Page 121
3.4.4 Distinguishing Between Ray and Mode Arrivals......Page 123
3.5 Mode Coupling in a Shallow Water Waveguide with Small Inhomogeneities......Page 127
3.6 Mode Coupling in Shallow Water with Smooth Inhomogeneities......Page 132
3.7 Horizontal Refraction in Shallow Water (The 3D Problem)\r......Page 138
3.8 Parabolic Equation......Page 152
4.1 A General Transmission Loss Example, Including a Simplified Theory of Shallow Water Attenuation......Page 159
4.2 Simplified Description of Solid, Multicomponent, Poro-Elastic, and Layered Bottom Models......Page 171
4.3 Optimum Frequency......Page 175
4.4 Interference Structure and Interference Invariant of the Sound Field......Page 179
4.5 Waveguide Dispersion of Sound Signals in Shallow Water......Page 185
4.6 Averaged Description of the Sound Field in a Waveguide......Page 195
4.6.1 Channel with Constant Sound Speed and Variable Depth......Page 198
4.6.2 Irregular Near-Bottom Sound Channel......Page 201
5.1 Structure and Models of Different Kinds of Random Inhomogeneities......Page 206
5.2 Description of a Random Sound Field by Coherent and Incoherent Parts......Page 209
5.3 Equations for Mode Interactions......Page 211
5.4 Equations for Intensity......Page 217
5.5 The Diffusion Equation and Averaged Decay Laws......Page 222
5.6.1 Waveguide of Constant Depth......Page 225
5.6.2 Irregular Waveguide......Page 229
5.6.3 Dependence of the Intensity on Depth......Page 232
5.7 Sound Field Fluctuations in the Presence of Background Internal Waves......Page 235
5.8 Models and Statistics of Intensity Fluctuations......Page 243
5.8.1 Intensity Fluctuations: Stochastic Modeling......Page 244
5.8.2 Experimental Measurements and the Statistics of Intensity Fluctuations......Page 245
5.8.3 Broadband Fluctuations......Page 249
6.1 Introduction: Sound Backscattering by the Sea Bottom......Page 251
6.2 Mode Theory of Bottom Reverberation in a Regular Waveguide......Page 256
6.3 Numerical Simulation of Low-Frequency Bottom Reverberation......Page 262
6.4 Long-Range Reverberation Studies Using Extended Arrays......Page 265
6.5 Long-Range Reverberation in a Randomly Inhomogeneous Waveguide......Page 271
7.1 General Considerations: The Linear Inverse Problem......Page 279
7.2 Bottom Versus Water Column Influences on the deltaql and Inverse......Page 284
7.3.1 GEMINI Experiment......Page 290
7.4 Examples of Nonlinear Bottom Property Inversion Using Various Data Types......Page 296
7.4.1 Horizontal Interference Structure and Bottom Parameters Estimation......Page 297
7.4.2 Using the Vertical Interference Pattern for Bottom Parameter Estimation......Page 300
7.5 Broadband Experiments and the Frequency Dependence of the Bottom Parameters......Page 302
7.6 Bottom Geoacoustic Inversions Using Ambient Noise Sources......Page 310
7.6.1 Inversion for Bottom Properties from Ship Self-Noise......Page 311
7.6.2 Inversion for Bottom Properties from Random ``Ship of Opportunity´´ Noise......Page 313
7.6.3 Inversion for Bottom Properties from Random Surface Noise......Page 316
8.1 Fundamentals of Data Processing Techniques......Page 317
8.2 Matched Field Processing in Shallow Water......Page 325
8.2.1 Conventional MFP, Bartlett Beamformer......Page 328
8.2.2 Two (Analytic) Examples of the Parameter Ambiguity Function......Page 329
8.2.3 Maximum Likelihood Beamformer......Page 331
8.2.4 Variable Coefficient Likelihood Beamformer......Page 332
8.2.5 Comparison of Processors for Simple Examples......Page 333
8.3 Spatial Coherence of the Sound Field in Shallow Water and Array Signal Gain......Page 336
8.4 Mode Filtration......Page 346
8.5 Time-Reversal Mirror of the Sound Field in Shallow Water\r......Page 360
8.6 Acoustic Uncertainty......Page 370
9.1 Introduction. Model of a Noise Source: General Equations\r......Page 375
9.2 Relationship Between the Continuous and the Discrete Components of the Field of Surface Noise Sources in a Waveguide......Page 386
9.3 Effect of the Frequency Dependence of the Bottom Absorption Coefficient on the Noise Spectrum......Page 389
9.4 Vertical Directivity of the Sound Field and the Effect of Random Inhomogeneities......Page 393
9.5 Effect of the Sound Speed Profile on the Vertical Distribution of the Noise Field Intensity......Page 403
10.1 The Frequency Band Used for Large-Scale Acoustic Monitoring......Page 408
10.2 Low-Frequency Sources of Sound......Page 410
10.3 Receiving Acoustic Arrays and the Design of Large-Scale Acoustic Monitoring Experiments on the Shelf......Page 424
11.2 Physical Oceanography......Page 435
11.3 Bottom Acoustic Properties......Page 438
11.4.2 Interference Invariant......Page 440
11.5 Physical Phenomena, Concerned with Stochastic Effects\r......Page 441
11.6.1 Water Layer......Page 442
11.6.2 Bottom Layer......Page 443
11.7 Signal Processing......Page 444
11.8.1 AUV, Gliders, Etc. and the Construction of Detailed Oceanographic Models......Page 445
Analytic Signals and Waves......Page 448
Surface Waves......Page 455
Nonlinear Corrections for Surface Waves......Page 461
Internal Waves......Page 464
Case of Constant Brunt-Vaisala Frequency......Page 469
Two-Layered Water Column......Page 470
Acoustic Waves......Page 474
Appendix B: Modal Decomposition of the Sound Field from a Point Source (Green Function)......Page 481
Appendix C: Mode Coupling Equations......Page 489
Appendix D: Empirical Orthogonal Functions......Page 495
Appendix E: Scattering at Localized Inhomogeneities in the Waveguide. Approximate Description......Page 501
Appendix F: Reflection of a Plane Wave from Half-Space......Page 507
Main Provisional Notation......Page 511
References......Page 517
Abbreviations......Page 541
Index......Page 543