BIBLIOGRAPHY

L. D. Rozenberg, “Acoustic Focusing Systems,”
Publishing House of the Academy of Sciences of the USSR, Moscow–Leningrad, 1949, 112 pp., price 5 rubles 50 kopecks.

Soviet acoustical literature has been enriched by yet another excellent book—the monograph by L. D. Rozenberg, “Acoustic Focusing Systems,” which summarizes the work of the author and his collaborators in recent years in the field of sound optics. This is still a little-developed, but very important, field for a number of special applications. The great significance of this field and the timeliness of its development may be judged if only from the fact that, following the appearance of L. D. Rozenberg’s monograph, a whole series of foreign articles on the same subject appeared. It is gratifying to see that in this branch of science, as in many others, Soviet science has outstripped foreign science.

The book opens with an introduction, in which the common features and differences between the wave concepts of optics and acoustics are established. The second chapter considers focusing systems in general. The author divides focusing systems that may be used in acoustics into reflectors (mirrors), refractors (lenses), and diffractors (zone plates), and gives a preliminary comparative evaluation of them. In Chapters 3, 4, 5, and 6 these systems are considered in detail; moreover, the investigation of lenses is preceded by a consideration of the action of a wedge, which makes it possible to clarify the essential features of the phenomena. These principal chapters give not only the theory of the corresponding focusing systems, but also elements of calculation in the form, for example, of a number of optimal relations, as well as the results of experiments made possible in our time by the highly developed technique of acoustic measurements. The last, seventh chapter is devoted to the concentration of sound energy.

One methodological remark: the book is probably intended mainly for acousticians. If so, then it would have been useful to give a summary of the terms and definitions used, borrowed from optics. Such a summary is all the more desirable because the author himself is not always consistent; thus, for example, by a long-focus system he means a system with a small relative aperture; on p. 22 the term “focusing distance” occurs; on p. 24 it is stated that refractors are free from chromatic aberration, but the essence is clarified only on p. 61.

A large part of the book consists of original material. Especially noteworthy are: the general method for calculating focusing systems with large aperture angles, based on a generalization of Debye’s reasoning; the discovery of a velocity null at the center of the focal spot of a paraboloid; the determination of the optimal aperture angle for a zonal plate; the averaging of lens transparency; the investigation of elliptical mirrors,

The book is written lightly, clearly, and concisely. A difficult subject appears, in the author’s presentation, quite simple (I know no higher praise for a scientific work).

As has already been said, the field of acoustic optics is being developed intensively; since the publication of the book under review, extensive new material has already appeared. It is therefore time to prepare a second edition.

A. Kharkevich