In recent years, research on acoustic remote sensing of the ocean has evolved considerably, especially in studying complex physical and biological processes in shallow water environments. To review the state of the art, an international workshop was held at Carvoeiro, Portugal, in March 1999, bringing together leading international researchers in the field. In contrast to much of the recent theoretical work, emphasis was placed on the experimental validation of the techniques. This volume, based on presentations at this workshop, summarizes a range of diverse and innovative applications. The invited contributions explore the use of acoustics to measure bottom properties and morphology, as well as to probe buried objects within the sediment. Within the water column, sound is applied to imaging of oceanographic features such as currents and tides or monitoring of marine life. Another key theme is the use of sound to solve geometric inverse problems for precise tracking of undersea vehicles. Audience: This volume should be useful both to the novice seeking an introduction to the field and to advanced researchers interested in the latest developments in acoustic sensing of the ocean environment. The workshop was sponsored by the Fundacao para a Ciecia e a Tecnologia (Portuguese Foundation for Science and Technology).

On the assessment of geoacoustic parameters in shallow water environments / Jean-Claude Le Gac, Yann Stéphan, Thierry Garlan, N. Weber.- Bayesian inversion of seabed reflection data / Stan E. Dosso, Charles W. Holland- Backpropagation techniques in ocean acoustic inversion: time reversal, retrogation and adjoint modelling - a review / Matthias Meyer, Jean-Pierre Hermand.- Acoustic inversion at low kHz frequencies using an active, vertical line array / Paul C. Hines, Matt Coffin.- Dispersion of broadband acoustic normal modes in the context of long range sediment tomography / Gopu Potty, James Miller- Characterization of local seabed properties using synthetized horizontal array data / Peter L. Nielsen, Mark Fallat, Christopher Harrison.- Characterization of a range-dependent environment from towed array data / Mark Fallat, Peter Nielsen, Stan E. Dosso, Martin Siderius.- Accounting for bias in horizontal wavenumber estimates due to source motion / Kyle M. Becker.- Acoustic clutter from buried submarine mud volcanoes / Charles W. Holland, Anthony L. Gerig, Piero Boni.- Nonlinear acoustical methods in the detection of gassy sediments / Jaroslaw Tegowski, Zygmunt Klusek, Jaromir Jakacki.- Acoustic scattering from submerged and buried objects / Ilkka Karasalo, Patrik Skogqvist.- High-frequency bistatic scattering experiments using proud and buried targets / Philippe Blondel, Peter F. Dobbins, Nic Jayasundere, Mario Cosci.- A sediment probe for the rapid assessment of seabed characteristics / John Osler, Arnold Furlong, Harold Christian.- Continuous acoustic monitoring of physiological and environmental processes in seagrass prairies with focus on photosynthesis / Jean-Pierre Hermand.- Shallow water tomography in a highly variable scenario / Cristiano Soares, Sergio M. Jesus, Emanuel Coelho.- Inversions of reflection loss measumements of a smooth water/sand interface / Marcia J. Isakson, Tracianne Neilsen, AndrewWorley.-Estimation of transmission loss and its uncertainty / Peter Gerstoft, Chen-Fen Huang, William Hodgkiss.- A forward model for geoacoustic inversion based on ray tracing and plane-wave refection coefficients / Jens M. Hovem, Hefeng Dong, Xiukun Li.- Inversion of the propeller harmonics from a light aircraft for the geoacoustic properties of marine sediments / Michael J. Buckingham, Eric M. Giddens, Fernardo Simonet.- Inversion of shallow water ambient noise data by means of differential evolution as a global search method / Dick G. Simons, Camiel van Moll, Chris H. Harrison.- Reflection Loss and Sub-bottom Profiling with Ambient Noise / Chris Harrison.- Inversion of geoacoustic model parameters using ship radiated noise / Ross N. Chapman, Reza M. Dizaji, R. Lyn Kirlin.- Matched-field processing of humpback whale song off eastern Australia / Aaron Thode, Peter Gerstoft, Melanie Guerra, M. Dale Stokes, Michael Noad, Douglas Cato.- Inversions of horizontal and vertical line array data for the estimation of geoacoustic model parameters / Dag Tollefsen, Michael J. Wilmut, Ross N. Chapman.- Issues of enrironment variability in inverse problems in ocean acoustics / David P. Knobles, M. Gray, Robert A. Koch, Adam Cook

In recent years, research on acoustic remote sensing of the ocean has evolved considerably, especially in studying complex physical and biological processes in shallow water environments. To review the state of the art, an international workshop was held at Carvoeiro, Portugal, in March 1999, bringing together leading international researchers in the field. In contrast to much of the recent theoretical work, emphasis was placed on the experimental validation of the techniques. This volume, based on presentations at this workshop, summarizes a range of diverse and innovative applications. The invited contributions explore the use of acoustics to measure bottom properties and morphology, as well as to probe buried objects within the sediment. Within the water column, sound is applied to imaging of oceanographic features such as currents and tides or monitoring of marine life. Another key theme is the use of sound to solve geometric inverse problems for precise tracking of undersea vehicles. Audience: This volume should be useful both to the novice seeking an introduction to the field and to advanced researchers interested in the latest developments in acoustic sensing of the ocean environment. The workshop was sponsored by the Fundacao para a Ciecia e a Tecnologia (Portuguese Foundation for Science and Technology).

Thisvolume contains thecollection of papers from the second workshop on Expe- mental Acoustic Inversion Techniques for Exploration of theShallow Water Environment. Theworkshopthemefollowedtheoriginalconceptofthe rstworkshop, heldinCarvoeiro, Portugal, in 1999, i.e., to focus on experiments and experimental techniques for acoustic sensing in the shallow ocean. More than forty leading international scientists were invited to meet in the picturesque town of St. Angelo on the island of Ischia, in June 2004, to discuss progress in the application of new experimental techniques for exploration and assessment of shallowwater environments. Acoustic techniques provide the most effective means for remote sensing of ocean and sea oor processes, and for probing the structure beneath the sea oor. No other energy propagates as ef ciently in the ocean: radio waves and visible light are severely limited in range because the ocean is a highly conductive medium. However, sound from bre- ing waves and coastal shipping can be heard throughout the ocean, and marine mammals communicate acoustically over basin scale distances.