A workshop was held to introduce new developments in acoustics and signal processing in the field of ocean acoustics and tomography, laboratory ultrasonics, seismology and medical ultrasonics. The underlying theme is time reversal acoustics.

In this interdisciplinary book, leading experts in underwater acoustics, seismology, acoustic medical imaging and non-destructive testing present basic concepts as well as the recent advances in imaging. The different subjects tackled show significant similarities.

Recent advances in wave propagation in random media are certainly consequences of new approaches to fundamental issues, as well as of a strong interest in potential applications. A collective effort has been made to present in this book the state of the art in fundamental concepts, as well as in biomedical imaging techniques. As an example, the recent introduction of wave chaos, and more specifically random matrix theory - an old tool from nuclear physics - to the study of multiple scattering, has pointed the way to a deeper understanding of wave coherence in complex media. At the same time, efficient new approaches for retrieving information from random media promise to allow wave imaging of small tumors in opaque tissues. Review chapters are written by experts in the field, with the aim of making the book accessible to the widest possible scientific audience: graduate students and research scientists in theoretical and applied physics, optics, acoustics, and biomedical physics.

This book contains the technical papers presented at the 16th International Symposium on Acoustical Imaging which was held in Chicago, Illinois USA from June 10-12, 1987. This meeting has long been a leading forum for acoustic imaging scientists and engineers to meet and exchange ideas from a wide range of disciplines. As evidenced by the diversity of topical groups into which the papers are organized, participants at the meeting and readers of this volume can benefit from developments in medical imaging, materials testing, mathematics, microsocopy and seismic exploration. A common denominator in this field, as its name implies, is the generation, display, manipulation and analysis of images made with mechanical wave energy. Sound waves respond to the elastic properties of the medium through which they propagate, and as such, are capable of characterizing that medium; something that cannot be done by other means. It is astonishing to realize that acoustic wave imaging is commonly performed over about eight decades of frequency, with seismology and microscopy serving as lower and upper bounds, respectively. The physics is the same, but the implementations are quite different and there is much to learn. The conference chairman and editor wishes to express his appreciation to those who helped run the symposium - namely the Technical Review COIIII1ttee and Session Cbair:aen including Floyd Dunn, Gordon S.

Novel, accurate and computationally efficient methods for wave-based subsurface imaging in acoustic and elastic media are developed. The methods are based on Arbitrarily Wide-Angle Wave Equations (AWWE), which are highly-accurate space-domain one-way wave equations, formulated in terms of displacement components. Main contributions of this research are as follows. (I) Acoustic-AWWE Imaging, a new time-domain migration technique that is highly accurate for imaging steep dips in heterogeneous media. Similar in form to conventional 15 & deg; equation, the acoustic AWWE is implemented using an efficient double-marching explicit finite-difference scheme. Its accuracy and efficiency is studied both analytically and through numerical experiments. The method is able to achieve highly accurate images with only a few times the computational cost of the conventional low-order methods. (II) A new class of highly-accurate Absorbing Boundary Conditions (ABCs) for modeling and imaging with high-order one-way wave equations and parabolic equations. These ABCs, are developed using special imaginary-length finite elements. They effectively absorb the incident wave front and generate artifact-free images with as few as three absorbing layers. They are essential tools in imaging in truncated domains and underwater acoustics. (III) Elastic-AWWE imaging: The first high-order space-domain displacement-based elastic imaging method is developed in this research. The method, which is applicable to complex elastic media, is implemented using a unique downward continuation technique. At each depth step, a half-space is attached to the physical layer to simulate one-way propagation. The half-space is effectively approximated using special imaginary-length finite elements. The method is eventually implemented in frequency-space domain using a finite difference method. Numerical instabilities due to improper mapping of complex wave modes are suppressed by rotating the AWWE parameters in complex wav.

This book presents recent studies of acoustic wave propagation through different media including the atmosphere, Earth's subsurface, complex dusty plasmas, porous materials, and flexible structures. Mathematical models of the underlying physical phenomena are introduced and studied in detail. With its seven chapters, the book brings together important contributions from renowned international researchers to provide an excellent survey of recent computational and experimental studies of acoustic waves. The first section consists of four chapters that focus on computational studies, while the next section is composed of three chapters that center on experimental studies.

The International Symposium on Acoustical Imaging is a unique forum for advanced research, covering new technologies, developments, methods and theories in all areas of acoustics. This interdisciplinary Symposium has been taking place continuously since 1968. In the course of the years the proceedings volumes in the Acoustical Imaging Series have become a reference for cutting-edge research in the field. In 2011 the 31st International Symposium on Acoustical Imaging was held in Warsaw, Poland, April 10-13. Offering both a broad perspective on the state-of-the-art as well as in-depth research contributions by the specialists in the field, this Volume 31 in the Series contains an excellent collection of papers in six major categories: Biological and Medical Imaging Physics and Mathematics of Acoustical Imaging Acoustic Microscopy Transducers and Arrays Nondestructive Evaluation and Industrial Applications Underwater Imaging

Surface Acoustic Waves in Inhomogeneous Media covers almost all important problems of the interaction of different types of surface acoustic waves with surface inhomogeneities. The problems of surface acoustic wave interaction with periodic topographic gratings widely used in filters and resonators are under careful consideration. The most important results of surface wave scattering by local defects such as grooves, random roughness, elastic wedges are given. Different theoretical approaches and practical rules for solving the surface wave problems are presented.

Rapid growth of the mobile communication market has triggered extensive research on the bulk as well as surface acoustic wave devices in the last decade. Quite a few important results on the modeling and simulation of Film Bulk Acoustic Resonator (FBAR) and Layered SAW devices were reported recently. The other recent advance of acoustic waves in solids is the so-called phononic crystals or phononic band-gap materials. Analogous to the band-gap of light in photonic crystals, acoustic waves in periodic elastic structures also exhibit band-gap. Important applications of phononic band gap materials can potentially be found with creating a vibration free environment in microstructures, and design of advanced acoustic frequency filter, etc. In addition to the wave electronics and phononic crystals, to facilitate the emerging needs in the quantitative nondestructive evaluation of materials, waves in anisotropic solids and/or electro-, magneto- interaction problems also regained much attention recently. Topics treated include: Waves in piezoelectric crystals; Simulation of advanced BAW and SAW devices; Analysis of band gaps in phononic structures; Experimental investigation of phononic structures; Waves in multilayered media;Waves in anisotropic solids and/or electro-, magneto- interaction problems.

This volume contains forty-six of the papers presented at the Ninth International Symposium on Acoustical Imaging held December 3-6, 1979, in Houston, Texas. The theme of the confer ence was the integration of applications technology. The major objective of the conference was to promote interaction among researchers working on different applications of acoustical imaging. In addition to serving as a state-of-the-art research ref erence, this volume includes six tutorial review papers. For convenience, all the papers are grouped under the following headings: methods, transducers, processing and display, phased array considerations, acoustic microscopy/non-destructive evalu ation, reconstructive tomography and inversion techniques, tissue characterization and impediography, nedica1 applications, under water applications, and seismic applications. The editor would like to thank the authors and the confer ence participants. The editor would also like to express his appreciation for the assistance in evaluating the abstracts from the following members of the Program Committee: Mahfuz Ahmed, University of California Irvine l:1edica1 Center; Pierre A1ais, Paris University, France; C.B. Burckhardt, Hoffman-Laroche, Basel, Switzerland; B.P. Hildebrand, Spectron Development Labora tories, Inc., Costa Mesa, California; Larry W. Kessler, Sonoscan, Inc., Bensenville, Illinois; Rolf Uue11er, University of Hinnesota, l1inneapo1is, Uinnesota; John P. Powers, Naval Post Graduate School, J:1onterey, California; Jerry L. Sutton, Naval Ocean Systems Center, San Diego, California; F.L. Thurstone, Duke University, Durham, North Carolina; Robert C. Waag, University of Rochester, Rochester, New York; and Glen Wade, University of California, Santa Barbara, California.