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Acoustic remote sensing of the ocean environment has seen a remarkable progress in the last ten-fifteen year as a result of an increasing understanding of the experimental techniques and procedures and of the subtleties of the interaction of sound with complex physical and biological processes. This is particularly true in the shallow water environment, where acoustic methods have the potential to allow for a fast and accurate characterization and assessment of the environment. To review the state of the art and the research progress in the field, a workshop was held in the island of Ischia, Italy, in June 2004. Special emphasis has been placed on the experimental applications, to realistically assess their potential and capabilities of the methods proposed. This volume, based on the workshop presentations, include a range of diverse and innovative applications, as well as comparisons in the field among competing approaches and review papers.
The invited contributions range from ocean acoustic tomography to estimation of the seabed and subbottom properties, to marine biology; ambient noise in the ocean is increasingly being investigated as a replacement for traditional acoustic source, to make acoustic inversion even less invasive and more environmentally friendly as a methodology to probe the ocean.
This book is primarily intended for physicists and engineers working in underwater acoustics and oceanic engineering. It will also be of interest to marine biologists, geophysicists and oceanographers as potential users of the methodologies and techniques described in the book contributions.
On the assessment of geoacoustic parameters in shallow water environments.- Bayesian inversion of seabed reflection data.-Backpropagation techniques in ocean acoustic inversion: time reversal, retrogation and adjoint modelling - a review.- Acoustic inversion at low kHz frequencies using an active, vertical line array.- Dispersion of broadband acoustic normal modes in the context of long sediment tomography.- Characterization of local seabed properties using synthesized horizontal array data.-Characterization of a range-dependent environment from towed array data.- Accounting for bias in horizontal wavenumber estimates due to source motion.- Acoustic clutter from burried submarine mud volcanoes.- Nonlinear acoustical methods in the detection of gassy sediments.- Acoustic scattering from submerged and buried objects.- High-frequency bistatic scattering experiments using proud and buried targets.- A sediment probe for the rapid assessment of seabed characteristics.- Continuous acoustic monitoring of physiological and environmental processes in seagrass prairies with focus on photosynthesis.- Shallow water tomography in a highly variable scenario.- Inversion of reflection loss measurements of a smooth water/sand interface.-Estimation of transmissions loss and its uncertainty.- A forward model for geoacoustic inversion based on ray tracing and plane-wave reflection coefficients.- Inversion of the propeller harmonics from a light aircraft for the geoacoustic properties of marine sediments.- Inversion of shallow water ambient noise data by means of differential evolution as a global search method.- Reflection Loss and Sub-bottom Profiling with Ambient Noise.- Inversion of geoacoustic model parameters using ship radiated noise.- Matched-field processing of humpback whale song off eastern Australia.- Inversions of horizontal and vertical line array data for the estimation of geoacoustic model parameters.- Issues of environmental variability in inverse problems in ocean acoustics.
