Physical and Applied Acoustics. An Introduction

420 Pages·1972·11.47 MB·English

by  Erwin Meyer (Eds.)

Physical and
A pplied Acoustics
AN INTRODUCTION
ERWIN MEYER ERNST-GEORG NEUMANN
I
University of Göttingen / Ruhr University of Bochum
Translated, by John M. Taylor, Jr.
UNDERWATER SOUND REFERENCE DIVISION
NAVAL RESEARCH LABORATORY
ORLANDO, FLORIDA
ACADEM IC PRESS New York and London 1972
Copyright © 1972, by Academic Press, Inc.
All rights reserved.
No part of this book may be reproduced in any form,
by photostat, microfilm, retrieval system, or any
other means, without written permission from
the publishers.
ACADEMIC PRESS, INC.
Ill Fifth Avenue, New York, New York 10003
United Kingdom Edition published by
ACADEMIC PRESS, INC. (LONDON) LTD.
24/28 Oval Road, London NW1
Library of Congress Catalog Card Number: 75-187239
Printed in the United States of America
Originally published in German under the title
PHYSIKALISCHE UND TECHNISCHE AKUSTIK
© 1967 by Friedr. Vieweg & Sohn GmbH, Verlag, Braunschweig
The senior author of this book, my highly esteemed
teacher} Professor Erwin Meyer, died at the age of 72
.
on 6th March 1972, shortly before the release of the book
Ernst-Georg Neumann
Preface to the English "Edition
This book was first published in German under the title Physikalische und
Technische Akustik in 1967. The English language edition incorporates
numerous revisions of and additions to the original text as well as two new
chapters (“Quantum Acoustics” and “Flow Acoustics”). The book belongs
to a four-part series on the physics of vibrations drawn from a 2-year course
of lectures and experiments on the same subject. The other three parts are
devoted to vibration theory, electronic measurement practice, and high-
frequency engineering.*
An essential characteristic of this book is emphasis on mechanical-
acoustical or acoustical-electrical analogies that are based on common
theoretical relationships and lead to similar results in the various fields.
Bringing these similarities to the fore seems to us to have great technical and
pedagogical value in these days when individual professional fields are
becoming increasingly divergent; developing the subject matter in this way
brings out clearly some easily recognizable and widely applicable physical
and engineering principles.
xi
Xll PREFACE TO THE ENGLISH EDITION
This book surveys the whole field of acoustics; theory, experiment, and
technological applications are intermingled. A knowledge of the fundamentals
of experimental physics is assumed on the one hand, and of differential and
integral calculus and differential equations on the other hand. Whenever
possible, complicated theoretical expositions are omitted in favor of intuitive
explanations. Technical applications are discussed at length. The center of
gravity of the presentation falls on the experimental side.
The many demonstration experiments described in the book are conceived,
even in their written form, to reinforce the accompanying text. Furthermore,
they form the basis for many experiments to determine numerical values of
acoustical quantities; they also are suitable for use as exercises, for practical
application, or for use in metrology laboratories.
These experiments are, to some extent, “idealized” for instructional
purposes, although the intent always is to concentrate attention on the
essential content of the experiment, not to mask it, by the experimental
technique. For example, the frequency characteristic of a quantity might be
plotted automatically in the lecture hall by using a storage oscilloscope and
displaying the results on a television screen, but obviously such experiments
could be carried out with less elaborate equipment.
The experimental results are used instead of idealized ones to elucidate the
text and to show at the same time the usefulness of the experiment, or even
its inadequacies. The important points of the experiments are described in
sufficient detail to permit them to be readily duplicated.
When it appears to be profitable, the “electrical” experiment analogous
to the “mechanical-acoustical” demonstration is added.
Available subject matter for the book is extensive. Small wonder, then,
that monographs exist on the subject matter of the individual chapters. As
is usual in German textbooks, no attempt has been made, in most cases, to
identify the various authors associated with the described facts and findings,
various pieces of apparatus, quantitative measurements, etc. Many of the
figures have been taken, gratefully, from existing literature.
As has already been mentioned, this book originated in a series of lecture-
experiments given by one of the authors (E. Meyer) for two decades in the
Third Institute of Physics of the University of Göttingen. To set up such a
course requires the interested and expert assistance of the Institute’s work­
shops. We were favored in having the services of Master Electronics Tech­
nician H. Henze, a tireless colleague of complete technical competence and
devotion to the cause. Our special thanks to him, therefore, although many
other co-workers in the Institute, including W. Ebrecht, also contributed in
large measure. During the course of the years, many suggestions for improv­
ing or expanding the “repertoire” of experiments have come from the
scientific staff of instructors and assistants.
PREFACE TO THE ENGLISH EDITION xiil
Finally, we would like to express our sincere thanks to Mr. John M. Taylor,
Jr., who has translated our German text into English with great insight and
thorough knowledge of the subject matter. We are especially indebted to
Academic Press for their fine work on the book.
* The other three parts of this series are, respectively,
E. Meyer and D. Guicking. “Schwingungslehre.” Vieweg, Braunschweig, Germany. In
preparation.
E. Meyer and K.-H. Zimmermann. “Elektronische Messtechnik.” Vieweg, Braunschweig,
Germany. In preparation.
E. Meyer and R. Pottel. “Physikalische Grundlagen der Hochfrequenztechnik.” Vieweg,
Braunschweig, Germany, 1969.
Translator's Preface
In the book Physikalische und Technische Akustik, Dr. Erwin Meyer, with
his colleague Dr. E.-G. Neumann, has presented in straightforward, frugal
German the content of the remarkable acoustics course that he brought to a
high level of pedagogical excellence over a period of some 20 years at the
University of Göttingen. It was a pleasure to read the book in German and
a joy to translate it into English. Because of the excellence of the original
writing, it was possible to be fairly literal in the translation and, I hope,
retain in English the virtues of the original.
With few exceptions, the text has not been amplified, revised, or adapted
especially for readers of English. The exceptions are a few changes in
mathematical symbols and symbols for physical quantities, some added notes
about vowel sounds in English, and a brief mention of the American National
Standard reference level for sound pressure. To tamper further with the
original seemed presumptuous and to try to make the reader forget that this
is a translation did not appear to be a worthy aim. Indeed, the definite
German orientation of much of the book is one of its great merits! Those
XV
xvi translator’s preface
who read only English will find here a somewhat different historical per­
spective and a different approach to many topics. They will become acquainted
with several concepts not prevalent in the English-language literature.
The only difficulties encountered in the translation concerned names for
quantities and concepts that do not have direct English equivalents. In some
instances the German term has been retained without apology; in others,
new English expressions have been introduced.
I am grateful to the authors for supplying in advance the German manu­
script for Chapters 10 and 11 (newly written for the second German edition)
as well as some revisions and additions to the first nine chapters (unchanged
in the second German edition). This English edition, then, is more complete
and up to date than the second German edition is.
Both authors have kindly reviewed the English text and supplied comments
and corrections. Dr. Meyer graciously spent considerable time in personal
conference with me over the English manuscript. Nevertheless, the authors
are not to be blamed for any mistranslations or infelicities of English style.
The responsibility for such faults is mine alone.
Several of my colleagues in the Underwater Sound Reference Division,
Naval Research Laboratory, have read the manuscript and offered suggestions
regarding English terminology and clarification of awkward renderings. I am
especially grateful to R. J. Bobber and D. T. Hawley.
Finally, I thank the German publisher Friedr. Vieweg & Sohn and the
American publisher Academic Press for the privilege of translating this
outstanding textbook into English.
Figure Credits
The following figures were adapted from the sources listed below:
Fig. 3.7 C. M. Harris, J. Acoust. Soc. Amer. 40,1 48 (1966).
Fig. 3.8 C. M. Harris, J. Acoust. Soc. Amer. 35, 11 (1963).
Figs. 5.38, 5.39, 5.40, 5.41 H. Stenzel and O. Brosze, “Leitfaden zur Berechnung von
Schall Vorgängen.” Springer Verlag, Berlin, Göttingen, Heidelberg 1958.
Figs. 7.4, 7.5 G. v. Bekesy, J. Acoust. Soc. Amer. 19, 452 (1947).
Fig. 7.10 E. Zwicker, Acustica 10, 185 (1960).
Fig. 7.11 D. Maiwald, Acustica 18, 69 (1967).
Fig. 7.18 J. D. Foulkes, J. Acoust. Soc. Amer. 33, 7 (1961).
Fig. 7.32 J. C. Steinberg and N. R. French, J. Acoust. Soc. Amer. 18, 4 (1946).
Fig. 8.20 W. Gohlke, “Einführung in die piezoelektrische Messtechnik.” Akad. Verlags-
ges. Geest & Portig, Leipzig, 1954.
Fig. 8.30 L. Bergmann, “Der Ultraschall.” S. Hirzel Verlag, Stuttgart, 1954.
Fig. 9.2 H. Brauns, “Stereotechnik.” Frankh’scheV erlagshandlung, Stuttgart, 1961.
Figs. 9.21, 9.23, 9.24 S. J. Begun, “Magnetic Recording.” Murray Hill Books Inc.,
New York, Toronto, 1949.
Figs. 10.8, 10.9, 10.10, 10.11 E. Bernstein and S. Lundquist, “Tunneling Phenomena
in Solids.” Plenum Press, New York, 1969.
xvii
1
Theory of Sound Fields
Mechanical oscillations can be propagated as sound waves in gaseous,
liquid, or solid mediums. How well they are transmitted depends on the nature
of the medium. Sound waves behave similarly in liquids and gases; therefore,
their propagation in these two mediums can be discussed together. Because
extended liquids and gases cannot support shear stresses, only longitudinal
waves in which the particle displacements are parallel to the direction of
propagation can occur in them. A much greater variety of waveforms is possible
in solids.
1.1. Sound in Liquids and Gases
1.1.1. The Three Basic Equations
A sound wave involves space and time variations of the density, the pres­
sure, and the temperature of the medium, as well as variation of the position
and the velocity of the particles of the medium from their mean values in the
1