Book review: Fundamentals of Physical Acoustics D.T. Blackstock; Wiley & Sons Ltd, New York, 2000, 541 pages, ISBN 0-471-3197This book is an excellent piece of work. The text is extremely clear and goes a long way towards meeting the declared pedagogical target. The author has written a comprehensive text. The proportions of equations and explanations/interpretations are particularly well balanced. Throughout the book, the context and the validity domain for any equation derived are clearly stated. No doubt this book will be of invaluable help for students, academics and engineers. The structure of the book has a peculiar recursive pattern. Several topics are treated in each chapter, but these topics are the main subjects themselves of subsequent chapters (which can sometimes be found after several intermediate chapters).Althoughthismeans that the author returns to a subject more than once, no impression of redundancy comes out from the reading. This is due to a careful choice of the examples and the different angles from which the problems are viewed. The way in which the book is structured has a beneficial effect and undoubtedly participates in enhancing the pedagogical content. Essentially, each subject is treated in detail several times, thus giving the readerthe opportunity to assimilate the concepts while still progressing in their discovery. Moreover the presentation and the layout of the book are excellent

The crevice model for heterogeneous nucleation of bubbles in water in response to a decreasing liquid pressure is studied. The model neglects gas-diffusion effects and is therefore more suited for acoustic than for flow cavitation. It is argued that previous work has overlooked the essential requirement of unstable growth of the interface in the crevice. As a consequence, the available results are incorrect in some cases. Another feature of the model which is considered is the process by which the interface moves out of the crevice. It is concluded that, depending on circumstances, the conditions for this step may be more stringent than those for the initial expansion of the nucleus inside the crevice. Some numerical examples are given to illustrate the complex behavior of nuclei, depending of geometrical parameters, gas saturation, contact angles, and other quantities.

To address the question of the role of nonlinear effects in the propagation of noise radiated by high-power jet aircraft, extensive measurements were made of the F-22A Raptor during static engine run-ups. Data were acquired at low-, intermediate-, and high-thrust engine settings with microphones located 23-305 m from the aircraft along several angles. Comparisons between the results of a generalized-Burgers-equation-based nonlinear propagation model and the measurements yield favorable agreement, whereas application of a linear propagation model results in spectral predictions that are much too low at high frequencies. The results and analysis show that significant nonlinear propagation effects occur for even intermediate-thrust engine conditions and at angles well away from the peak radiation angle. This suggests that these effects are likely to be common in the propagation of noise radiated by high-power aircraft.

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Following the experimental method of Thompson and Atchley [J. Acoust. Soc. Am. 117, 1828-1838 (2005)] laser Doppler anemometry (LDA) is used to investigate the influences of a thermoacoustically induced axial temperature gradient and of fluid inertia on the acoustic streaming generated in a cylindrical standing-wave resonator filled with air driven sinusoidally at a frequency of 308 Hz. The axial component of Lagrangian streaming velocity is measured along the resonator axis and across the diameter at acoustic-velocity amplitudes of 2.7, 4.3, 6.1, and 8.6 m/s at the velocity antinodes. The magnitude of the axial temperature gradient along the resonator wall is varied between approximately 0 and 8 K/m by repeating measurements with the resonator either surrounded by a water jacket, suspended within an air-filled tank, or wrapped in foam insulation. A significant correlation is observed between the temperature gradient and the behavior of the streaming: as the magnitude of the temperature gradient increases, the magnitude of the streaming decreases and the shape of the streaming cell becomes increasingly distorted. The observed steady-state streaming velocities are not in agreement with any available theory.

Thermoacoustic heat transport and its applications, thermoacoustic engines, have been discussed in a number of articles over the past several years. Lacking from these articles is a thorough, quantitative experimental investigation of the basic theory underlying thermoacoustic heat transport. A logical starting point for such a study is to investigate the simplest class of thermoacoustic engine—a stack of short plates referred to as a ThermoAcoustic Couple (TAC). The utility of this choice is that the theory can be reduced to its simplest form for analysis of the results. The results of measurements of thermoacoustically generated temperature gradients in TACs subjected to acoustic standing waves are reported. The value of the temperature gradient, which results from an acoustically generated entropy flow in the gas in thermal contact with the TAC, is a function of the peak acoustic pressure amplitude, the mean gas pressure, the Prandtl number of the gas, the configuration of the TAC, and its position in the standing wave. Measurements were made with a computer-controlled apparatus for drive ratios (the ratio of the acoustic pressure amplitude to the mean pressure of the gas) from approximately 0.1%–2.0%, in argon and helium having mean pressures from approximately 100–368 kPa, for three different TACs as a function of their positions in the standing wave. The results are compared with predictions based on a theory by Wheatley et al. [J. Acoust. Soc. Am. 74, 153–170 (1983)]. The measurements agree well with theory for drive ratios less than approximately 0.4%. However, the agreement diminishes at higher drive ratios, where two regions of behavior are observed. Agreement is, in general, best in the vicinity of acoustic particle velocity nodes at all drive ratios investigated.

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