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Acoustical oceanography — Principles and applications
Marine Geology, 30 (1979) 313--327 313 © Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands Book Reviews
Acoustical Oceanography ~ Principles and Applications. Clay and Medwin. Wiley, Chichester, 1977, 444 pp., £20.65 or U.S. $34.95. The title is misleading. Current oceanography is about internal waves, eddies, micro-structure, ocean fronts, etc. While most of these are mentioned, they are not developed and have very little to do with the contents. The book is about sound in the ocean and tends to concentrate on the background needed to understand sonar systems. It is similar in c o n t e n t to Urick's book (Principles o f Underwater Sound). They are both useful texts with Urick's book emphasizing engineering applications and Clay and Medwin writing more for the physical scientist. The first chapter is a very sketchy description of some ocean features. The existence of the sound channel is mentioned, but the physical reasons for it are not developed. Ocean micro-structure is mentioned b u t the concept is broadened to include fine-structure. Most oceanographers would say that fine-structure has vertical length scales down to ~ 10 cm and lateral homogeneity from 10's of m to 10's of km. Internal waves are discussed briefly, but no mention is made of the Garrett--Munk spectrum which has received general acceptance. Also the paragraph on internal waves is incorrect. These waves have maximum amplitude where the vertical density gradient is small. The first chapter is generally interesting, but it fails to provide an overview of major oceanographic fields or to show that acoustics can provide the connecting thread in their study. Development of acoustic theory begins in chapter 2 with an introduction to basic phenomena such as Huygen's principle, Fresnel zones, and plane wave reflection from plane boundaries. It would have been helpful to extend Huygen's principle just a little further (e.g. Baker and Copson, Huygen's Principle} to show the essential difference between spherical and plane waves. Chapter 3 begins with some basic power radiation relations. Then there is some simple ray theory to introduce the first unique effects o f the ocean on sound propagation. Because the ray theory is only for layers with a linear sound speed dependence, it cannot be used for realistic intensity calculations or for analysis of near axial rays. Also, in the chapter is an up-to-date t r e a t m e n t of volume absorption. The anomalous low frequency absorption, which is twice as large in the Atlantic Ocean as it is in the Pacific, is ascribed to a boric acid relaxation process. This may be true, but there are some acousticians who claim t h a t propagation effects have not been properly considered in the analysis o f the data. Chapter 4 is a standard introduction to signal processing. The material is available in any number of other sources. The next chapter introduces basic sonar concepts such as tranducer radiation and receiving patterns and simple array steering concepts. There is also a useful section on parametric arrays. Chapter 6 is on scattering. The treatment of the material rises above the
314 introductory level and there is development of scattering functions, multiple scattering, and resonant scattering. In Chapter 8 the scattering t h e o r y is used to calculate scattering strengths of fish and other marine life such as siphonophores. Chapter 8 is on sediment attenuation (essentially the results of Hamilton) and elementary seismic reflection theory. At this point it would have been desirable to introduce some of the modern seismic techniques such as wave front migration. Chapter 9 is a dated introduction to waveguide propagation. The authors spend some time showing the orthogonality of wave functions for an unlikely propagation model. In fact, all realistic sound channels have some boundary losses so the wave functions are not orthogonal. Chapter 10 is on scattering from rough surfaces and again the level is closer to current research. It is a good introduction to a difficult subject. A large part of the book (~30%) consists of 10 appendices which are generally useful and well written. Appendix 3 which uses Debye's method to solve for the sound field near a caustic does require some comment. The m e t h o d is not simple and the results are much less accurate than standard caustic expansions. Thus, it seems unfair to ask the reader to work through this material. In summary, the book is well written and should be useful for the undergraduate student or the manager who wants a gentle, but perceptive, introduction to underwater acoustics. HOMER P. BUCKER (San Diego, Calif.)
Stratigraphic Micropalaeontology of Atlantic Basin and Borderlands. F.M. Swain (Editor). Elsevier, Amsterdam, 1977, 603 pp., Dfl. 122.00 or U.S. $49.95. The title of this volume, based on the contributions to a symposium held at the UniverSity of Delaware in June 1976, is somewhat misleading. Approximately the first third of the book is devoted to Palaeozoic and earliest Mesozoic ostracods, foraminifers, conodonts, radiolaria and palynomorphs of preAtlantic times. The remaining two thirds deal with Mesozoic and Cenozoic foraminifers, oatracods, radiolaria, palynomorphs and silicoflagellates, partly from Atlantic Basin (i.e. deep-sea) sites, but also extensively from epicontinental occurrences. The papers do not hang together very well as a study of the micropalaeontology of an ocean basin and its surroundings, but they provide useful reviev(s~of the stratigraphic occurrence of particular taxonomic groups. .: Thus, n o t surprisingly, ostracod workers will be rewarded with reviews of Early Palaeozoic ostracods (by:Copeland and Swain), of Late Palaeozoic (by Sanchez de Posada), Jurassic and Cretaceous (by Bate, Neale and Bertels) and Cenozoic (by Keen and Van den Bold). Smaller Foraminifera are reviewed
Acoustical Oceanography ~ Principles and Applications. Clay and Medwin. Wiley, Chichester, 1977, 444 pp., £20.65 or U.S. $34.95. The title is misleading. Current oceanography is about internal waves, eddies, micro-structure, ocean fronts, etc. While most of these are mentioned, they are not developed and have very little to do with the contents. The book is about sound in the ocean and tends to concentrate on the background needed to understand sonar systems. It is similar in c o n t e n t to Urick's book (Principles o f Underwater Sound). They are both useful texts with Urick's book emphasizing engineering applications and Clay and Medwin writing more for the physical scientist. The first chapter is a very sketchy description of some ocean features. The existence of the sound channel is mentioned, but the physical reasons for it are not developed. Ocean micro-structure is mentioned b u t the concept is broadened to include fine-structure. Most oceanographers would say that fine-structure has vertical length scales down to ~ 10 cm and lateral homogeneity from 10's of m to 10's of km. Internal waves are discussed briefly, but no mention is made of the Garrett--Munk spectrum which has received general acceptance. Also the paragraph on internal waves is incorrect. These waves have maximum amplitude where the vertical density gradient is small. The first chapter is generally interesting, but it fails to provide an overview of major oceanographic fields or to show that acoustics can provide the connecting thread in their study. Development of acoustic theory begins in chapter 2 with an introduction to basic phenomena such as Huygen's principle, Fresnel zones, and plane wave reflection from plane boundaries. It would have been helpful to extend Huygen's principle just a little further (e.g. Baker and Copson, Huygen's Principle} to show the essential difference between spherical and plane waves. Chapter 3 begins with some basic power radiation relations. Then there is some simple ray theory to introduce the first unique effects o f the ocean on sound propagation. Because the ray theory is only for layers with a linear sound speed dependence, it cannot be used for realistic intensity calculations or for analysis of near axial rays. Also, in the chapter is an up-to-date t r e a t m e n t of volume absorption. The anomalous low frequency absorption, which is twice as large in the Atlantic Ocean as it is in the Pacific, is ascribed to a boric acid relaxation process. This may be true, but there are some acousticians who claim t h a t propagation effects have not been properly considered in the analysis o f the data. Chapter 4 is a standard introduction to signal processing. The material is available in any number of other sources. The next chapter introduces basic sonar concepts such as tranducer radiation and receiving patterns and simple array steering concepts. There is also a useful section on parametric arrays. Chapter 6 is on scattering. The treatment of the material rises above the
314 introductory level and there is development of scattering functions, multiple scattering, and resonant scattering. In Chapter 8 the scattering t h e o r y is used to calculate scattering strengths of fish and other marine life such as siphonophores. Chapter 8 is on sediment attenuation (essentially the results of Hamilton) and elementary seismic reflection theory. At this point it would have been desirable to introduce some of the modern seismic techniques such as wave front migration. Chapter 9 is a dated introduction to waveguide propagation. The authors spend some time showing the orthogonality of wave functions for an unlikely propagation model. In fact, all realistic sound channels have some boundary losses so the wave functions are not orthogonal. Chapter 10 is on scattering from rough surfaces and again the level is closer to current research. It is a good introduction to a difficult subject. A large part of the book (~30%) consists of 10 appendices which are generally useful and well written. Appendix 3 which uses Debye's method to solve for the sound field near a caustic does require some comment. The m e t h o d is not simple and the results are much less accurate than standard caustic expansions. Thus, it seems unfair to ask the reader to work through this material. In summary, the book is well written and should be useful for the undergraduate student or the manager who wants a gentle, but perceptive, introduction to underwater acoustics. HOMER P. BUCKER (San Diego, Calif.)
Stratigraphic Micropalaeontology of Atlantic Basin and Borderlands. F.M. Swain (Editor). Elsevier, Amsterdam, 1977, 603 pp., Dfl. 122.00 or U.S. $49.95. The title of this volume, based on the contributions to a symposium held at the UniverSity of Delaware in June 1976, is somewhat misleading. Approximately the first third of the book is devoted to Palaeozoic and earliest Mesozoic ostracods, foraminifers, conodonts, radiolaria and palynomorphs of preAtlantic times. The remaining two thirds deal with Mesozoic and Cenozoic foraminifers, oatracods, radiolaria, palynomorphs and silicoflagellates, partly from Atlantic Basin (i.e. deep-sea) sites, but also extensively from epicontinental occurrences. The papers do not hang together very well as a study of the micropalaeontology of an ocean basin and its surroundings, but they provide useful reviev(s~of the stratigraphic occurrence of particular taxonomic groups. .: Thus, n o t surprisingly, ostracod workers will be rewarded with reviews of Early Palaeozoic ostracods (by:Copeland and Swain), of Late Palaeozoic (by Sanchez de Posada), Jurassic and Cretaceous (by Bate, Neale and Bertels) and Cenozoic (by Keen and Van den Bold). Smaller Foraminifera are reviewed