- Email: [email protected]
Underwater acoustics
Book Reviews
399
Mathematks for ecologists, I. CHASTON,1971. Butterworths, London, 132 pp. £2-20. MANYmOLOOISTSfind the conceptual jump from observed data to mathematical abstractions beyond them. They discover that what mathematics they once knew has been so little exercised that it is too rusty to be used. Text-books are all too often of little help. The first page or so is comprehensible, but suddenly the text takes a leap into a symbolismapparently of utter fantasy. If you are such a biologist then this is the mathematical book for you. Its purpose" is to provide an introduction to some of the basic principles of advanced mathematics by illustratinghow the basic concepts of calculns and linear algebra can be used to solve simplified biological problems". The biological examples that Dr. Chasten uses range from insects being swept from the substrate of a stream by the current, to the optimum hunting behaviour for predators. They help to make the biologist feel at home amongst the symbols. The reader is lead step by step through differential and integral calculus, first order differential equations, difference equations, matrices and their uses in solving simultaneouslinear equations, regression analysis and in some of the basic techniques of operations research. Each step is straightforward and easily followed, except for the matrices on pages 95 and 112 which include some errors worked into them. I am sure that there are many biologists for whom this little book will fulfil and satisfy a very definite need.
National Institute of Oceanography, Wormley, Godalming, Surrey, U.K.
M. V. ANGEL
Undeewat~ aenestics. Edited by R. W. B. SrePHeSS, Wiley-Interscience, London, 1970, 269 pp. 135s £6.75. Ttm E0eLDof underwater acoustics is not covered comprehensively as the title of this book might imply, rather it is a coliecflon of subjects given as a course at Imperial College, London, in 1967 by eight lecturers, each having chosen his own topic. The first chapter contributed by the Editor, introduces the underwater environment, discussing briefly the constituency, shape and dynamics of the sea and in slightly more detail the physical acoustics of water and air/water mixtures. It seems rather misleading to discuss fluctuations in signal transmission due to internal waves, turbulence and inhomogeneities under a section on 'noise', and there are many published examples of Lloyd mirror fringes at frequencies above 10 kHz, but these are minor blemishes on this general scene. The chapter entitled "Introduction to Acoustic Exploration" logically might have followed next since it introdtwes the fundamental sonar equation and discusses its parameters and their limitations in a refreshing manner. It has useful reminders of the importance of displays and various forms of noise. There are four chapters on specialized areas of underwater acoustics. That on normal mode methods in underwater sound is quite the best on the subject which this reviewer has seen, striking a happy balance between the mathematical development and physical reasoning, and in particular by making clear the approximations and how the model may be improved to approach the real ocean and its boundaries. The pr~is of relevant bibliographicmaterial at the end of this chapter is a valuable guide to further reading on this subject. Forward and back-scattering of sound from the sea surface is thoroughly reviewed in a chapter in which the theoretical approaches are compared with measurements; their divergence at low grazing angles is discussed. The theoretical importance of near surface bubbles is emphasized along with the lack of adequate data on their existence and persistence. The non-linearinteraction of acoustic waves is a mainly theoretical chapter using the 'quasi-linear' or 'source density" approach and three possible applications are given. By far the largest chapter and nearly 30~o of the book concerns acoustic echoes from targets of various geometrical shapes and materials and fish. Calculations and results of scale model and full size experiments are given at length with a large section on the scattering of sound from a fish. Despite the considerable detail on the high frequency and angular dependence of fish scattering, there is little or no discussion of the practical applications of the work in fi~h;ng, or scattering from fish shoals, nor of the deep scattering layers in the ocean or fish swimbladder resonance. Two chapters are concerned with the applications of underwater acoustics. One is an adequate review of the fundamental aspects of audio communicationbetween free divers. The other chapter, on
400
Book Reviews
underwater instrumentation, is frankly so bad as almost to defy review. As an example one figure, used incidentally without acknowledgement, is a long out-of-date pinger drive circuit operating from a 400 V d.c. supply, but is labelled and discussed in the text as a sparker discharge circuit operating from 10 kV. Practically every paragraph has something to which one could object, so that readers are advised to ignore this chapter or at best treat it with extreme caution. The book is well produced on good quality paper with generally clear figures, an author and a subject index and bibliographies after each chapter. A few editorial points have been missed, for example 'Kolmogorov' is spelled two other ways.
National Institute of Oceanography, Wormley, Godalming, Surrey, England.
B, S. MCCARTNEY
Research in the Antarctic. Edited by Louis O. QUAM, 1971. American Association for the Advancement of Science, Washington, D.C. 768 pp. $19.95 to AAAS members, $24.95 to others. THis COMPENDIUM is compiled mainly from papers read at the AAAS symposium on Antarctic research held at Dallas in 1968, but several new chapters have been added to extend its scope. These are not distinguished from those that have had to wait some time for publication. It begins with reproductions of papers by James Eights who sailed to the South Shetland Islands in 1829-31, on what was probably the first USA officially sponsored exploring expedition, and for which the papers by Eights seem to be the principal remaining record. He was the first to find plant fossils in the Antarctic, and his accounts of the birds and animals have been shown to be accurate. He tends to dramatize when writing about sweeping currents, exploding icebergs and shooting spray. Dr. Hedgpeth has not been able to add to the bibliography compiled by the late W. T. Caiman who summar~ed what is known about Eights in 1937, so that we cart be fairly certain that there can be no more to find. A general introductory section gives useful information about SCAR, the Scientific Committee on Antarctic Research, its activities and relations with other bodies. There is also an account of the Antarctic Treaty which gives Antarctic scientists the freedom of movement to pursue scientific programmes that marine scientists are in danger of losing in the world oceans. The introduction to the section on biology skips from Eights to the Second Byrd Expedition doing no justice to men like J. D. Dana, who included an account of the Antarctic krill in his systematic study of the Cr t a, or Louis Agassiz, who made extensive studies of the fishes collected by Wilkes, though most unfortunately he was not able to publish his work. It seems rather facile to say that Eights established USA traditions in Antarctic biology (p. 69) when there have been so few past references to his work. El Sayed summarizes what has been done on trophic relationships in the Antarctic Ocean. He emphasizes the need for overall estimates of rates of production, storage and release of organic material, but recognizes the difficulties of sampling active forms of plankton or micronekton such as krill. Hedgpeth focuses attention o n pivotal problems in benthic biography and ecology. Miiller-Schwarze reviews recent contributions to study of the behaviour of penguins and seals. Feeney and Osuga consider the physiology and bio-chemistry of the cold-adapted fishes. The remaining chapters are by authorities on land plants, lichens, microbiology and medical research. In the section on Ocean Dynamics, Gordon describes the currents and water masses. Using reasonable figures for evaporation, heat exchange and radiation, he makes estimates of vertical exchanges as well as zonal and meridonal transports. He questions the applicability of geostrophic calculations where the density gradients are so small. Since the paragraph on the formation of Antarctic Bottom Water under the interior of the Ross Ice Shelf was written there is perhaps growing opposition to the idea of extensive bottom freezing below ice shelves (see, for example, R. H. Thomas and P.H. Coslett, Nature,Lend.,228,47-49,1970). Warrenwrites on thewidespread effect of Antarctic water in the oceans to the north, describing the pattern of flow, particularly the western boundary currents. Stommel and Bowen give careful consideration to repeated observations across the circumpolar current made by the Discovery H in 1938-39. They show that the 3 ° to 4 ° spacing of the stations, the best that a small team keeping pace with the sampling and analysis could then do, is not sufficiently close to give statistically significant information on variability. Elder and Seabrook use the observa-
399
Mathematks for ecologists, I. CHASTON,1971. Butterworths, London, 132 pp. £2-20. MANYmOLOOISTSfind the conceptual jump from observed data to mathematical abstractions beyond them. They discover that what mathematics they once knew has been so little exercised that it is too rusty to be used. Text-books are all too often of little help. The first page or so is comprehensible, but suddenly the text takes a leap into a symbolismapparently of utter fantasy. If you are such a biologist then this is the mathematical book for you. Its purpose" is to provide an introduction to some of the basic principles of advanced mathematics by illustratinghow the basic concepts of calculns and linear algebra can be used to solve simplified biological problems". The biological examples that Dr. Chasten uses range from insects being swept from the substrate of a stream by the current, to the optimum hunting behaviour for predators. They help to make the biologist feel at home amongst the symbols. The reader is lead step by step through differential and integral calculus, first order differential equations, difference equations, matrices and their uses in solving simultaneouslinear equations, regression analysis and in some of the basic techniques of operations research. Each step is straightforward and easily followed, except for the matrices on pages 95 and 112 which include some errors worked into them. I am sure that there are many biologists for whom this little book will fulfil and satisfy a very definite need.
National Institute of Oceanography, Wormley, Godalming, Surrey, U.K.
M. V. ANGEL
Undeewat~ aenestics. Edited by R. W. B. SrePHeSS, Wiley-Interscience, London, 1970, 269 pp. 135s £6.75. Ttm E0eLDof underwater acoustics is not covered comprehensively as the title of this book might imply, rather it is a coliecflon of subjects given as a course at Imperial College, London, in 1967 by eight lecturers, each having chosen his own topic. The first chapter contributed by the Editor, introduces the underwater environment, discussing briefly the constituency, shape and dynamics of the sea and in slightly more detail the physical acoustics of water and air/water mixtures. It seems rather misleading to discuss fluctuations in signal transmission due to internal waves, turbulence and inhomogeneities under a section on 'noise', and there are many published examples of Lloyd mirror fringes at frequencies above 10 kHz, but these are minor blemishes on this general scene. The chapter entitled "Introduction to Acoustic Exploration" logically might have followed next since it introdtwes the fundamental sonar equation and discusses its parameters and their limitations in a refreshing manner. It has useful reminders of the importance of displays and various forms of noise. There are four chapters on specialized areas of underwater acoustics. That on normal mode methods in underwater sound is quite the best on the subject which this reviewer has seen, striking a happy balance between the mathematical development and physical reasoning, and in particular by making clear the approximations and how the model may be improved to approach the real ocean and its boundaries. The pr~is of relevant bibliographicmaterial at the end of this chapter is a valuable guide to further reading on this subject. Forward and back-scattering of sound from the sea surface is thoroughly reviewed in a chapter in which the theoretical approaches are compared with measurements; their divergence at low grazing angles is discussed. The theoretical importance of near surface bubbles is emphasized along with the lack of adequate data on their existence and persistence. The non-linearinteraction of acoustic waves is a mainly theoretical chapter using the 'quasi-linear' or 'source density" approach and three possible applications are given. By far the largest chapter and nearly 30~o of the book concerns acoustic echoes from targets of various geometrical shapes and materials and fish. Calculations and results of scale model and full size experiments are given at length with a large section on the scattering of sound from a fish. Despite the considerable detail on the high frequency and angular dependence of fish scattering, there is little or no discussion of the practical applications of the work in fi~h;ng, or scattering from fish shoals, nor of the deep scattering layers in the ocean or fish swimbladder resonance. Two chapters are concerned with the applications of underwater acoustics. One is an adequate review of the fundamental aspects of audio communicationbetween free divers. The other chapter, on
400
Book Reviews
underwater instrumentation, is frankly so bad as almost to defy review. As an example one figure, used incidentally without acknowledgement, is a long out-of-date pinger drive circuit operating from a 400 V d.c. supply, but is labelled and discussed in the text as a sparker discharge circuit operating from 10 kV. Practically every paragraph has something to which one could object, so that readers are advised to ignore this chapter or at best treat it with extreme caution. The book is well produced on good quality paper with generally clear figures, an author and a subject index and bibliographies after each chapter. A few editorial points have been missed, for example 'Kolmogorov' is spelled two other ways.
National Institute of Oceanography, Wormley, Godalming, Surrey, England.
B, S. MCCARTNEY
Research in the Antarctic. Edited by Louis O. QUAM, 1971. American Association for the Advancement of Science, Washington, D.C. 768 pp. $19.95 to AAAS members, $24.95 to others. THis COMPENDIUM is compiled mainly from papers read at the AAAS symposium on Antarctic research held at Dallas in 1968, but several new chapters have been added to extend its scope. These are not distinguished from those that have had to wait some time for publication. It begins with reproductions of papers by James Eights who sailed to the South Shetland Islands in 1829-31, on what was probably the first USA officially sponsored exploring expedition, and for which the papers by Eights seem to be the principal remaining record. He was the first to find plant fossils in the Antarctic, and his accounts of the birds and animals have been shown to be accurate. He tends to dramatize when writing about sweeping currents, exploding icebergs and shooting spray. Dr. Hedgpeth has not been able to add to the bibliography compiled by the late W. T. Caiman who summar~ed what is known about Eights in 1937, so that we cart be fairly certain that there can be no more to find. A general introductory section gives useful information about SCAR, the Scientific Committee on Antarctic Research, its activities and relations with other bodies. There is also an account of the Antarctic Treaty which gives Antarctic scientists the freedom of movement to pursue scientific programmes that marine scientists are in danger of losing in the world oceans. The introduction to the section on biology skips from Eights to the Second Byrd Expedition doing no justice to men like J. D. Dana, who included an account of the Antarctic krill in his systematic study of the Cr t a, or Louis Agassiz, who made extensive studies of the fishes collected by Wilkes, though most unfortunately he was not able to publish his work. It seems rather facile to say that Eights established USA traditions in Antarctic biology (p. 69) when there have been so few past references to his work. El Sayed summarizes what has been done on trophic relationships in the Antarctic Ocean. He emphasizes the need for overall estimates of rates of production, storage and release of organic material, but recognizes the difficulties of sampling active forms of plankton or micronekton such as krill. Hedgpeth focuses attention o n pivotal problems in benthic biography and ecology. Miiller-Schwarze reviews recent contributions to study of the behaviour of penguins and seals. Feeney and Osuga consider the physiology and bio-chemistry of the cold-adapted fishes. The remaining chapters are by authorities on land plants, lichens, microbiology and medical research. In the section on Ocean Dynamics, Gordon describes the currents and water masses. Using reasonable figures for evaporation, heat exchange and radiation, he makes estimates of vertical exchanges as well as zonal and meridonal transports. He questions the applicability of geostrophic calculations where the density gradients are so small. Since the paragraph on the formation of Antarctic Bottom Water under the interior of the Ross Ice Shelf was written there is perhaps growing opposition to the idea of extensive bottom freezing below ice shelves (see, for example, R. H. Thomas and P.H. Coslett, Nature,Lend.,228,47-49,1970). Warrenwrites on thewidespread effect of Antarctic water in the oceans to the north, describing the pattern of flow, particularly the western boundary currents. Stommel and Bowen give careful consideration to repeated observations across the circumpolar current made by the Discovery H in 1938-39. They show that the 3 ° to 4 ° spacing of the stations, the best that a small team keeping pace with the sampling and analysis could then do, is not sufficiently close to give statistically significant information on variability. Elder and Seabrook use the observa-