SOUND WAVES THEIR SHAPE AND SPEED 1 I 3 1 o OQ O . 1 o H PREFACE
THE question of the influence of the material of which a wind
musical instrument is made has not been settled after more than a
century of widespread discussion. Is the tone quality of a flute,
the tube of which is made of gold, superior to that of a similar
flute made of silver or wood If there is a difference, what is the
explanation It was this specific question that, in 1900, started
the investigations which, having passed much beyond the original
inquiry, have furnished the material for the reports here
presented. The desire to investigate the physical nature of musical
sounds, and the sound-producing characteristics of musical
instruments, led to a study of all available methods for recording
the forms of sound waves. No device was found which was
sufficiently sensitive and free from disturbing in fluences for the
proposed investigations, and a new instru ment, the Phonodeik, was
developed. Part I of this work describes the phonodeik, and the
methods of using it, to gether with illustrations of phonodeik
records of sounds of various types, such as voices, musical
instruments, bells, fog horns, and the explosive sounds from large
guns in action. A chapter is included explaining the photography of
sound waves by the electric-spark method, as applied to the study
of projectiles in flight and to the acoustics of auditoriums. In
1918 and 1919 the writer organized, and carried out at Sandy Hook
Proving Ground an extended series of experi ments on the pressure
developed in the sound waves pro PREFACE duced by the discharge of
large guns, and for the determina tion of the velocity of the
explosive sounds and of the normalvelocity of sound in the free
air. Preliminary re ports have been presented to various scientific
societies, but the reduction of the large amount of observational
material has only recently been completed. A final report covering
the several phases of these investigations is now presented as Part
II of this work. In the reduction of the observations, a least -
squares method of solving the exponential equations involved was
prepared by Dean T. M. Focke, Head of the Department of
Mathematics, Case School of Applied Science. The first
calculations, extending over a period of a year, were made by the
writers Research Assistant, Mr. Ralph F, Hovey. The authors
Research Associates, Professor John R. Mar tin, 1928, and Dr.
Robert S. Shankland, 1932-33, have made the principal calculations
relating to the final analysis and determination of the velocity of
sound, and have assisted in the preparation of the manuscript.
Professor R. S. Buring ton has given valuable aid. The author is
especially in debted to Professor J. J. Nassau for advice and
suggestions. The author is under obligation to the Chief of
Ordnance of the War Department and to the Commanding Officers of
Sandy Hook Proving Ground for many privileges and courtesies
extended in connection with the experimental work and the
preparation of these reports. The Chief of Ordnance has given
approval of the free use of all the scientific data obtained at the
Proving Ground, and has provided the photographs reproduced in
Figures 37, 57, and 63. CASE SCHOOL OP APPLIED SCIENCE, DAYTON C.
MILLER. CLEVELAND, OHIO, MABCH, 1937. vi CONTENTS PART I THE
PHONODEIK SOUND WAVES AND THEIR SHAPES CHAPTER PAGE I. Sound and
Tone Quality Sound Waves 3 TheAnalysis of Complex Sounds 6 II. The
Phonodeik Recording Sound Waves 9 Mechanical Principles of the
Phonodeik 13 Optical Principles of the Phonodeik 22 Auxiliary
Records Time Signals and Axis .... 24 The Phonodeik Laboratory 26
The Projection Phonodeik 30 The Portable Phonodeik 33 Corrections
for Resonance Effects 39 III. The Shapes of Sound Waves
Interpreting Phonodeik Records 47 Photographs of Sound Waves from
Voices and Instru ments 50 IV...
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