This book contains 17 invited papers and 80 communicated papers presented at the International Symposium on Physical Acoustics, held at the University Campus of Kortrijk, Belgium, from 19-22 June 1990. The twenty-fifth anniversary of the Campus was celebrated with special activi ties such as concerts, exhibitions and scientific meetings. This symposium was a part of the celebration. The 120 participants came from 18 different countries. Among the largest groups we mention 32 French contributions and 19 contributions from the U.S.S.R. We especially thank Prof. V.V. Proklov from Moscow and Prof. S.V. Kulakov from Leningrad who helped us with the distribution of invitations in the U.S.S.R. We also thank Prof. G. Quentin and Ir B. Poiree from Paris who endeav oured to inform all French acousticians. We thank all the lecturers for their effort in producing the material for the book in time. The invited lectures have been collected and retyped by Prof. M. Breazeale (U.S.A.), while the contributed papers were collec ted by Prof. O. Leroy and retyped in Belgium. The first 200 pages of the book comprise the invited lectures, not classified by topic, but are in alphabetical order with reference to the first author. The second part of the book contains the contributed papers and posters also classified in alphabetical order according to the first author.

Most dialogues are multimodal. When people talk, they use not only their voices, but also facial expressions and other gestures, and perhaps even touch. When computers communicate with people, they use pictures and perhaps sounds, together with textual language, and when people communicate with computers, they are likely to use mouse gestures almost as much as words. How are such multimodal dialogues constructed? This is the main question addressed in this selection of papers of the second Venaco Workshop, sponsored by the NATO Research Study Group RSG-10 on Automatic Speech Processing, and by the European Speech Communication Association (ESCA).

The up-to-date review articles in this book on modern developments in the field of sonic and ultra sonic power transducers present various aspects, applications, and possible future developments that are of interest to engineers and researchers.

To place this book in perspective it is useful for the reader to be aware of the recent history of the topic of underwater sound generation at the ocean surface by natural mechanisms. A meeting in Lerici, Italy in 1987 was convened within the NATO Advanced Research Workshop series, to bring together underwater acousticians and ocean hydrodynamicists to examine various mechanisms which generate sound naturally at the ocean surface. A record of that meeting was published in the NATO scientific publication series in 1988 under the title 'Sea Surface Sound'. That meeting was successful in inspiring and co ordinating both participants and non-attending colleagues to examine some key issues which were raised during the course of presentations and discussions. The understanding among those present was that another meeting should be convened 3 years hence to report and review progress in the subject. Accordingly the second conference was convened in Cambridge in 1990, whose proceedings are presented here. This volume represents a very gratifying increase in only a 3 year interval in our understanding of a number of physical processes which generate sound at the peripheries of oceans. In fact it represents both the acceleration of singular effort as well as the development of interdisciplinary sophistication and co-operation. The enthusiasm, goodwill, and intense scientific curiosity which characterized the Lerici meeting carried through to Cambridge. The collegial atmosphere established by the participants was perfectly timed to foster another major advance in studies of ocean surface sound.