Bibliography

New Books on Acoustics

Corrado Crescini, Principii fondamentali di elettroacustica theorica ed applicata, Milano, 1939.
Corrado Crescini, Fundamentals of Theoretical and Applied Electroacoustics, Milan, 1939, 396 pp.

C. Crescini’s course in electroacoustics is the first textbook on technical acoustics in the Italian language known to us, and for that reason its appearance deserves attention. Work on acoustics in Italy is comparatively little developed, and in Crescini’s book we do not find anything original either in the theoretical or in the technical part. For the most part the author uses material from the German, English, and American literature in compiling the book. However, approaching the book from the standpoint of its usefulness as a textbook, it should be regarded as quite successful. All the material is carefully worked through by the author and is presented successfully.

The book is divided into 14 chapters. Chapter I contains the general theory of the sound field (plane and spherical waves, standing waves, wave energy). Chapter II contains information on oscillations of systems with 1 and 2 degrees of freedom, on electromechanical oscillatory systems, and also on the simplest acoustic radiators (pulsating and oscillating sphere, oscillating diaphragm). Chapter III contains the theory of horns in the usual form, with some additions from recent works by Stenzel, Ballantine, Olson, and others. Chapters IV, V, and VI analyze the theory, calculation, and construction of loudspeakers, and also set out questions concerning the measurement of the basic characteristics of loudspeakers. In considerable detail the methods of calculating electrodynamic, diffuse-field, and horn loudspeakers are presented; moreover, in the appendices to the book the author gives a number of useful nomograms that facilitate the technique of calculation.

A short Chapter VII is devoted to the construction of a headphone. Chapter VIII deals with the calculation and design of permanent magnetic fields for electrodynamic instruments. In Chapter IX, the problems of constructing modern types of microphones are set out in rather considerable detail; the author pays particular attention to questions of the directional action of microphones. Chapter X is devoted to sound recording; it analyzes the basic devices for gramophone and magnetic sound recording, as well as for recording on film, and also considers the corresponding methods of reproducing sound from recordings. This chapter is presented very compactly and at the same time clearly; it should be considered successful.

Chapter XI examines piezoelectric acoustic instruments made of Rochelle salt, which in recent years have found wide application in technology. The details of manufacturing Rochelle-salt crystals, cutting plates, and producing bimorph elements are given. Designs of microphones, adapters, and loudspeakers are described.

Chapter XII gives the fundamentals of physiological acoustics. Chapter XIII is devoted to questions of the sound reinforcement of rooms and open spaces.

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Interesting data are presented on the power required for sound reinforcement of various rooms; questions of the placement of microphones and loudspeakers for the purpose of obtaining a uniform field are discussed; basic information on architectural acoustics is given. Chapter XIV contains supplements concerning various details of the calculations.

Assessing the book as a whole, it should be said that the author has succeeded in presenting in a concise and clear form extensive material on electroacoustics and its applications. The exposition is at a modern level. No serious oversights or errors were noticed. It is very good that the book is supplied with a large number of illustrations, drawings, graphs, and nomograms. A fairly complete bibliography is provided.

There is no need to raise the question of translating the book as a whole into Russian, since most of the material presented is already well set forth in books that have appeared in our country. The translation of individual chapters—for example, Chapters IV, V, and VI (in part), on loudspeakers, and Chapter XIII, on sound reinforcement—would undoubtedly be desirable, even if in a small print run.

S. N. Rzhevkin, Moscow

F. Trendelenburg, Einführung in die Akustik, Berlin, 1939.

Ф. Тренделенбург, Введение в акустику, Berlin, 1939, 277 pp.

F. Trendelenburg’s book consists of seven chapters. Chapter I covers general questions of the theory of vibrations and the theory of waves. Chapter II is devoted to the measurement of the basic quantities in a sound field. Chapter III concerns sound sources, Chapter IV the propagation of sound. Chapter V is devoted to questions of sound reception (microphones), its perception by the ear, and sound recording. Chapter VI concerns the analysis of sound and, in particular, the analysis of the human voice. Chapter VII contains an acoustic terminology (German standard), a list of the most important formulas, and tabular material.

The title “Introduction to Acoustics” fits this book only to a very small extent. The author does not in fact provide a systematic approach to the analysis of a definite field of phenomena, as is usually done in books that constitute an introduction to the scientific and limited survey of modern methods of physical and technical acoustics. As an introductory course for persons beginning their study, this book is completely unsuitable. From the very first pages the author uses, without justification, such complex concepts as the wave equation (for gas, membranes, and plates), the natural oscillations of a three-dimensional continuum, questions in the theory of nonlinear oscillations, and the Fourier integral. This compels one to conclude that the book will be within the powers only of persons who already have a solid physical and mathematical education and who are beginning the study of acoustics as a special discipline.

Judging the book as a survey manual, one should give it a very high evaluation. In previous years the author had already published a number of books of a survey character on acoustics (Fortschritte der Akustik; Klänge und Geräusche) and has considerable experience in writing manuals of this kind. The book is excellently illustrated and produced. The author is able briefly and intelligibly to explain complex techniques of modern experimental and technical acoustics, selecting the most interesting fundamental features of phenomena or methods of measurement and not burdening the exposition with technical details. Having read the book, the reader obtains a clear picture of the broad development of modern acoustics. However, after reading it he will not be able to penetrate sufficiently deeply into the essence of the matter.

It should be noted that the survey of measurement methods and technical applications is carried out almost exclusively using examples from German works and German technology. This is, of course, a defect for a book of survey character, since in other countries, especially in America, very many fundamentally new and important investigations in acou-

Thanks to such a narrow approach, the author fails, for example, to give a complete picture of the development of modern microphone and loudspeaker technology, since the most interesting new American works have appeared in this field. There is likewise nothing about new work on synthetic speech and a number of other interesting and important studies and technical applications.

I believe that Trendelenburg’s book may be recommended to students of senior courses in the physics departments of universities, as well as to engineers working in acoustics. A translation of the book into Russian does not seem especially necessary.

S. N. Rzhevkin, Moscow