Fundamentals of Shallow Water Acoustics

'Table of Contents.- Preface.- 1. What is shallow water acoustics?.- 1.1. Deep versus shallow.- 1.2 Past and Present of shallow water acoustics.- 1.3 The future of shallow water acoustics.- 1.4 Some "old favorite" research areas revisited and updated.- 2. Coastal Oceanography, Geology, and Biology.- 2.1. The coast as acoustic waveguide.- 2.2. Properties of sea water: Vertical stratification and its seasonal variability.- 2.3. Horizontal stratification and its variability: Fronts and eddies, surface ducts and storm surges.- 2.4 Dynamics of the ocean surface: Surface waves.- 2.5. Dynamical processes inside the ocean: Tides and internal waves.- 2.6. Experimental studies of coastal internal waves.- 2.7. Coastal Geology and Geophysics.- 2.8. Acoustics of sediments.- 2.9. Bottom roughness.- 2.10 Solid and multi-component layered bottom models.- 2.11. Acoustics of biological objects in a coastal area.- 3. Foundations of the theory of the propagation of sound.- 3.1. Field of a point source in a layered waveguide with absorbing boundaries.- 3.2. The Pekeris Model.- 3.3 Perturbation theory and WKB methods.- 3.4. Ray description of the sound field and ray-mode connections.- 3.4.1 Ray theory.- 3.4.2 Rays as interfering modes.- 3.4.3 Modes as interfering rays.- 3.4.4 Distinguishing between ray and mode arrivals.- 3.5. Mode coupling in a shallow water waveguide with small inhomogeneities.- 3.6. Mode coupling in shallow water with smooth inhomogeneities.- 3.7. Horizontal refraction in shallow water (the 3D problem).- 3.8 Parabolic equation (PE).- 4. Examples Illustrating the Characteristics of Waveguide Propagation.- 4.1. A General Transmission Loss Example, including a simplified theory of shallow water attenuation.- 4.2. Simplified description of solid, multi-component, poro-elastic and layered bottom models.- 4.3. Optimum frequency.- 4.4. Interference structure and interference invariant of the sound field.- 4.5 Waveguide dispersion of sound signals in shallow water.- 4.6. Averaged description of the sound field in a waveguide.- 5. Sound field in shallow water with random inhomogeneities.- 5.1. Structure and models of different kinds of random inhomogeneities.- 5.2. Description of a random sound field by coherent and incoherent parts.- 5.3 Equations for mode interactions.- 5.4 Equations for intensity.- 5.5. The Diffusion equation and averaged decay laws.- 5.6. Some examples.- 5.6.1 Waveguide of constant depth.- 5.6.2 Irregular waveguide.- 5.6.3 Dependence of the intensity on depth.- 5.7. Sound field fluctuations in the presence of background internal waves.- 5.8 Models and statistics of intensity fluctuations.- 6. Low frequency bottom reverberation in shallow water.- 6.1 Introduction - Sound scattering by the sea bottom.- 6.2 Mode theory of bottom reverberation in a regular waveguide.- 6.3 Numerical simulation of low frequency bottom reverberation.- 6.4 Long range reverberation studies using extended arrays.- 6.5 Long range reverberation in a randomly inhomogeneous waveguide.- 7. The inverse problem.- 7.1 General considerations. The linear inverse problem.- 7.2 Bottom versus water column influences on the dq_l and inverse.- 7.3 The generalized inverse, its error, and an example from the Corpus Christi GEMINI experiment.- 7.4 Examples of nonlinear bottom property inversion using various data types.- 7.5 Broadband experiments and the frequency dependence of the bottom parameters.- 7.6 Bottom geoacoustic inversions using ambient noise sources.- 8. Signal processing.- 8.1 Fundamentals of data processing techniques.- 8.2 Matched field processing in shallow water.- 8.2.1 Conventional MFP, Bartlett Processor.- 8.2.2 Two (analytic) examples of the parameter ambiguity function.- 8.2.3 Maximum likelihood beamformer.- 8.2.4 Variable coefficient likelihood beamformer.- 8.3 Spatial coherence of the sound field in shallow water and array signal gain.- 8.4... Mehr