The nonlinear interaction between two surface acoustic waves can be used in a number of signal processing devices. In this report the principles which underlie this interaction are developed both theoretically and experimentally. In the signal processing devices it is demonstrated that both convolution and fourier transformations can be carried out in real time. In the imaging work it is shown that acoustic surface waves can be used to scan optical images which are projected onto a semiconducting layer of silicon. This scanning process transfers spatial image pattern into a temporal pattern which can be transmitted electrically to a remote display station. (Modified author abstract).

The work consists of two projects - one on the digital control of acoustic signals from an imaging array and the second on the use of acoustic signals to interrogate thermal images formed on an array of silicon bolometers. In the first project it has been shown that in contrast to the present systems where analog systems are used to control the arrays in acoustic imaging multilevel digital processing systems can be employed to provide for the scanning and focusing of these arrays. The net result is an increase in performance and flexibility of these systems with images in real time. In the second part of the program we have shown that propagating acoustic signals can be used to interrogate an array of silicon bolometers which contain a thermal image. The theoretical and experimental results comprise a foundation for the construction of the thermal imaging device of the type described. The device should outperform existing uncooled thermal imaging devices over a practical range of frequencies. (Author).

The comprehensive research activity around the World in the fields of Underwater Acoustics and Signal Processing being strongly supported by new experimental technique and equipment and by the parallel fast developments in computer technology and solid state devices, which has led to a rapidly reducing cost of digital processing thus enabling more complex processing to be carried out economically, emphasize how necessary it is at intervals of a few years through a NATO Advanced Study Institute (NATO ASI) and guided by leading experts to study the conquests in the fields of Underwater Acoustics and Signal Processing. This need of study is moreover stressed by the interdisciplina rity of Underwater Acoustics and Signal Processing, where a strong impact from other branches of science, - Geophysics, Radioastronomy, Bioengineering, Telecommunication, Seismology, Space Research etc. - is taking place, which makes it an extre mely difficult task for scientists to follow-up the development in all its phases and to preserve the general view of its rapid ly increasing number of possibilities. The present Proceedings of the NATO ASI held in Copenhagen during August 1980 join the series of proceedings of NATO summer schools on Underwater Acoustics and Signal Processing held during the past 20 years. The equality and the fusion of the individual research fields of Underwater Acoustics and Signal Processing and the separate introduction of advanced research results from other scientific areas related to underwater acoustics such as transducers characterize the subject matter of this NATO ASI.

This textbook provides a unified approach to acoustics and vibration suitable for use in advanced undergraduate and first-year graduate courses on vibration and fluids. The book includes thorough treatment of vibration of harmonic oscillators, coupled oscillators, isotropic elasticity, and waves in solids including the use of resonance techniques for determination of elastic moduli. Drawing on 35 years of experience teaching introductory graduate acoustics at the Naval Postgraduate School and Penn State, the author presents a hydrodynamic approach to the acoustics of sound in fluids that provides a uniform methodology for analysis of lumped-element systems and wave propagation that can incorporate attenuation mechanisms and complex media. This view provides a consistent and reliable approach that can be extended with confidence to more complex fluids and future applications. Understanding Acoustics opens with a mathematical introduction that includes graphing and statistical uncertainty, followed by five chapters on vibration and elastic waves that provide important results and highlight modern applications while introducing analytical techniques that are revisited in the study of waves in fluids covered in Part II. A unified approach to waves in fluids (i.e., liquids and gases) is based on a mastery of the hydrodynamic equations. Part III demonstrates extensions of this view to nonlinear acoustics. Engaging and practical, this book is a must-read for graduate students in acoustics and vibration as well as active researchers interested in a novel approach to the material.

Includes brief descriptions of projects, listings of contracts and grant support, and listings of publications.