OceThe OFFiciaaL MaganZineog OF the Oceanographyra Spocietyhy CITATION Munk, W. 2006. Review of Sounds in the Sea: From Ocean Acoustics to Acoustical Oceanography, by H. Medwin. Oceanography 19(1):192–194, http://dx.doi.org/10.5670/oceanog.2006.106. DOI http://dx.doi.org/10.5670/oceanog.2006.106 COPYRIGHT This article has been published inOceanography , Volume 19, Number 1, a quarterly journal of The Oceanography Society. Copyright 2006 by The Oceanography Society. All rights reserved. USAGE Permission is granted to copy this article for use in teaching and research. Republication, systematic reproduction, or collective redistribution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The Oceanography Society. Send all correspondence to: [email protected] or The Oceanography Society, PO Box 1931, Rockville, MD 20849-1931, USA. downLoaded From www.tos.org/oceanography Sounds in the Sea From Ocean Acoustics to Acoustical Oceanography By Herman Medwin, Cambridge Our aim is to facilitate the integration University Press, 2005, 670 pages, of ocean acoustics into applied physics, en- ISBN 052182950X, Hardcover, $100 US gineering, and biology curricula. It is our hope that Sounds in the Sea will become REVIEWED BY WALTER MUNK a vital component of all college studies of the ocean sciences and ocean engineering, My review copy came with the following as well as a useful reference for practicing note attached: ocean scientists and ocean engineers. Sincerely, Dear Reviewers of Sounds in the Sea: H Medwin, author of Sounds of the Sea icebergs...”; whereas “Acoustical Ocean- Some of us have the audacity to believe ography” is devoted to probing diverse that ocean exploration is more important The letter states the author’s intentions ocean processes using acoustics as a tool. to mankind than space exploration. And more clearly than anything I could have (Medwin has fostered a similar distinc- we have the wisdom to understand that said; Medwin has admirably fulfilled his tion in the organization of the Acoustic current acoustical studies, which use fre- quoted intentions. Society of America.) But the two points quencies from a fraction of a hertz to sev- Medwin has previously published two of view are strongly interactive and the eral megahertz, and which include ranges graduate-level textbooks on this general distinction not always so clear.* up to half way around the world, are far subject: Clay and Medwin’s Acoustical Part I by Medwin, Fundamentals, starts more effective at sea than optical efforts Oceanography (1977), followed by Med- with principles of sound transmission, which operate over only a single octave win and Clay’s Fundamentals of Acoustic followed by ocean-oriented discussions (frequency ratio 2 to 1) and achieve ranges Oceanography (1988). When I turned of biological sounds, and their interac- of only a few meters. to acoustics rather late in my career as tions with the seafloor and the sea sur- The accompanying new book on under- physical oceanographer, it was with the face. Emphasis is on the interpretation of water sound written with 25 co-authors, help of the 1977 volume. Part I of Sounds experimental results guided by theoreti- from Australia, Canada, England and the in the Sea, written by Medwin, is on the cal considerations (rather than on sys- U.S. serves a dual-purpose: it is both a text fundamentals of ocean acoustics (311 tematic derivations) with careful atten- and a reference volume that starts with pages of the present volume) and has tion to the many illustrations. The reader fundamentals at the under-graduate level been extracted from the 1998 book. Part (student) is frequently warned that “this and moves on to 15 chapters that describe II (287 pages), written by twenty-five section contains some advanced analyti- current ocean acoustical research. Along authors, is on acoustical oceanography. cal material.” Medwin pays tribute to his the way, it makes predictions of activities Medwin makes the following distinction many naval officer students at the Naval for the next five years, and concludes with in “Ocean Acoustics” our “...knowledge of Postgraduate School who “went on to approximately 500 selected references to (assumptions about) the ocean ... allows become Admirals and Captains in the the most important and recent literature. one to use sound to find fish, submarines, Navies of the USA and Turkey and West * Note added in proof. Medwin was not the only, nor the first, acoustician to propose such a distinction: Igor Mikhaltsev (personal communication 2006) refers to the “birth of two new sci- ences ... in the late fifties, ‘Ocean Acoustics’ and ‘Acoustical Methods of Ocean Investigation.’” All of the former papers were classified. For a recent history, see Mikhaltsev I. E. 2002.Izvestiya Atmospheric and Oceanic Physics, 38: 738–743. 192 Oceanography Vol. 19, No. 1, Mar. 2006 Germany.” Medwin’s lifelong teaching ef- and temporal distributions, and species- and avoidance have motivated quieter fort has made a significant contribution specific biomass estimates. Bioacoustic platforms. Fish-distribution surveys con- to today’s existing capabilities in antisub- absorption due to fish with swim blad- ducted by autonomous underwater ve- marine warfare. Here the presentation of ders can have a large effect on transmis- hicles with broad-beam sonars may not the fundamentals provides the necessary sion loss. Absorption spectroscopy can be far off. background and structure for the second relate absorption lines to the dimensions The high sound levels emitted by part of the book. of swim bladders and provide estimates some marine animals can be detected In Part II, Studies of the Near-Surface of year classes. Studies of fish hearing at great ranges. This has led to highly Ocean, Medwin has made an excellent choice of co-authors. I doubt whether anyone else would have been able to as- semble so many leading investigators in such diverse fields. The distinction between active and passive sources in upcominG acoustic oceanography appears in many of the chapters. As David Farmer points BOOK Reviews out, “the ocean provides a natural acous- tic signal rich in frequency diversity, temporal variability, and directional- Aglow in the Dark: The Revolutionary Science ity, that can be exploited to learn about of Biofluorescence the air-sea interface... and the details of by Vincent Peribone and David F. Gruber wave breaking which play so important a Harvard University Press, 263 pages role in air-sea transfer of momentum....” Farmer discusses scattering from bubbles Chemical Oceanography (3rd Edition) as an example of active acoustics. There by Frank J. Millero are many aspects of bubble dynamics; CRC Press, 496 pages the role of bubbles as tracers offers par- ticular promise. Dynamics of Marine Ecosystems: Biological-Physical Precipitation at sea is one of the most Interactions in the Oceans (3rd Edition) difficult meteorological parameters to by K.H. Mann and J.R.N. Lazier measure. Jeffrey A. Nystuen has been Blackwell Publishing, 496 pages pioneer in using the underwater sound of rain to measure oceanic rainfall. The acoustic record can be inverted to quanti- HYDRO to NAVOCEANO: 175 Years of Ocean Survey tative measures of drop size distribution. and Prediction by the U.S. Navy The distinct roles of active and pas- by Charles C. Bates sive acoustics are particularly evident Corn Field Press, 329 pages in bioacoustics. Scattering of sound by zooplankton is making it possible to ob- The Turbulent Ocean serve animal behaviors on temporal and by Steve A. Thorpe spatial scales that impact individuals. Cambridge University Press, 439 pages Fishery acoustics is to convert returned acoustic energy into fish lengths, spatial Oceanography Vol. 19, No. 1, Mar. 2006 193 successful passive bioacoustic studies provides perhaps the greatest challenge. what to include and what to omit. I miss of marine mammals. Among the tech- There are many other applications of a reference to Computational Ocean niques being developed are matched acoustic methods to the study of ocean Acoustics (Jensen, Kuperman, Porter, field filters to detect and identify the processes. I end this brief account with Schmidt 1993, AIP), when so much of calls. Acoustic oceanography may pro- a method closest to my heart: ocean recent progress can be attributed to in- vide the clue of whether and how the acoustic tomography (aptly described creased computer power. The reference animals themselves exploit the acoustic by Robert Spindel). The speed of sound to Flatté’s Sound Transmission Through a information. Many species of fish are is a sensitive function of temperature Fluctuating Ocean is without the accent also vocal and contribute significantly to and pressure. Together they determine on the author’s name and without the the ambient ocean noise. the properties of an oceanic waveguide names of his four co-authors. Perhaps the earliest application of (the SOFAR channel), which has been On completing my reading of Sounds acoustic methods to ocean science was exploited since its discovery in the mid- in the Sea, my overall impression is one in the measurement of ocean depth by 1940s by Maurice Ewing and J. Lamar of rapid developments along a vast ar- fathometers. But there are many other Worzel. The arrival pattern is a good ray of subjects, none more daring than seafloor applications under develop- indicator of the mean temperature pro- in bioacoustics. (This is in stark contrast ment. Hydrothermal plumes have been file between source and receiver. Re- to the “cautionary principle” followed acoustically detected by the backscat- ciprocal transmissions yield the mean by some environmental groups, which tered intensity and Doppler of particles current profile (sound travels faster with has impeded progress in active acoustics. suspended in the plume. A low-flying the current). Acoustic tomography ex- There has been no real progress in fifteen aircraft provides a high-speed, low-fre- ploits these features.