Chapter I

The Nerves and Sensation—Production and Propagation of
Sonorous Motion—Experiments on Sounding Bodies placed
in Vacuo—Deadening of Sound by Hydrogen—Action of
Hydrogen on the Voice—Propagation of Sound through Air
of Varying Density—Reflection of Sound—Echoes—Refraction
of Sound—Diffraction of Sound; Case of Erith Village and
Church—Influence of Temperature on Velocity—Influence
of Density on Elasticity—Newton’s Calculation of
Velocity—Thermal Changes Produced by the Sonorous
Wave—Laplace’s Correction of Newton’s Formula—Ratio of
Specific Heats at Constant Pressure and at Constant
Volume deduced from Velocities of Sound—Mechanical
Equivalent of Heat deduced from this Ratio—Inference that
Atmospheric Air Possesses no Sensible Power to Radiate
Heat—Velocity of Sound in Different Gases—Velocity in
Liquids and Solids—Influence of Molecular Structure on
the Velocity of Sound. 31

SUMMARY OF CHAPTER I 77

CHAPTER II

Physical Distinction between Noise and Music—A
Musical Tone Produced by Periodic, Noise Produced
by Unperiodic, Impulses—Production of Musical
Sounds by Taps—Production of Musical Sounds by
Puffs—Definition of Pitch in Music—Vibrations of a
Tuning-Fork; their Graphic Representation on Smoked
Glass—Optical Expression of the Vibrations of a
Tuning-Fork—Description of the Siren—Limits of the
Ear; Highest and Deepest Tones—Rapidity of Vibration
Determined by the Siren—Determination of the Lengths
of Sonorous Waves—Wave-Lengths of the Voice in Man and
Woman—Transmission of Musical Sounds through Liquids and
Solids. 82

SUMMARY OF CHAPTER II 117

CHAPTER III

Vibration of Strings—How employed in Music—Influence of
Sound-Boards—Laws of Vibrating String—Combination of
Direct and Reflected Pulses—Stationary and Progressive
Waves—Nodes and Ventral Segments—Application of Results
to the Vibrations of Musical Strings—Experiments of
Melde—Springs set in Vibration by Tuning-Forks—Laws
of Vibration thus demonstrated—Harmonic Tones of
Strings—Definitions of Timbre or Quality, or Overtones
and Clang—Abolition of Special Harmonies—Conditions
which affect the Intensity of the Harmonic Tones—Optical
Examination of the Vibrations of a Piano-Wire 120

SUMMARY OF CHAPTER III 161

CHAPTER IV

Vibrations of a Rod fixed at Both Ends: its Subdivisions
and Corresponding Overtones—Vibrations of a Rod fixed
at One End—The Kaleidophone—The Iron Fiddle and Musical
Box—Vibrations of a Rod free at Both Ends—The Claque-bois
and Glass Harmonica—Vibrations of a Tuning-Fork:
its Subdivisions and Overtones—Vibrations of Square
Plates—Chladni’s Discoveries—Wheatstone’s Analysis of
the Vibrations of Plates—Chladni’s Figures—Vibrations of
Disks and Bells—Experiments of Faraday and Strehlke. 165

SUMMARY OF CHAPTER IV 196

CHAPTER V

Longitudinal Vibrations of a Wire—Relative Velocities of
Sound in Brass and Iron—Longitudinal Vibrations of Rods
fixed at One End—Of Rods free at Both Ends—Divisions and
Overtones of Rods vibrating longitudinally—Examination
of Vibrating Bars by Polarized Light—Determination of
Velocity of Sound in Solids—Resonance—Vibrations of
Stopped Pipes: their Divisions and Overtones—Relation
of the Tones of Stopped Pipes to those of Open
Pipes—Condition of Column of Air within a Sounding
Organ-Pipe—Reeds and Reed-Pipes—The Voice—Overtones of
the Vocal Chords—The Vowel Sounds—Kundt’s Experiments—New
Methods of determining the Velocity of Sound. 200

SUMMARY OF CHAPTER V 254

CHAPTER VI

Singing Flames—Influence of the Tube surrounding
the Flame—Influence of Size of Flame—Harmonic Notes
of Flames—Effect of Unisonant Notes on Singing
Flames—Action of Sound on Naked Flames—Experiments with
Fish-Tail and Bat’s-Wing Burners—Experiments on Tall
Flames—Extraordinary Delicacy of Flames as Acoustic
Reagents—The Vowel-Flame—Action of Conversational
Tones upon Flames—Action of Musical Sounds on
Smoke-Jets—Constitution of Water-Jets—Plateau’s Theory
of the Resolution of a Liquid Vein into Drops—Action of
Musical Sounds on Water-Jets—A Liquid Vein may compete in
Point of Delicacy with the Ear 260

SUMMARY OF CHAPTER VI 301

CHAPTER VII

_PART I_

RESEARCHES ON THE ACOUSTIC TRANSPARENCY OF THE ATMOSPHERE
IN RELATION TO THE QUESTION OF FOG-SIGNALLING

Introduction—Instruments and Observations—Contradictory
Results from the 19th of May to the 1st of July
inclusive—Solution of Contradictions—Aërial Reflection
and its Causes—Aërial Echoes—Acoustic Clouds—Experimental
Demonstration of Stoppage of Sound by Aërial Reflection
305

_PART II_

INVESTIGATION OF THE CAUSES WHICH HAVE HITHERTO BEEN
SUPPOSED EFFECTIVE IN PREVENTING THE TRANSMISSION OF
SOUND THROUGH THE ATMOSPHERE

Action of Hail and Rain—Action of Snow—Action of Fog;
Observations in London—Experiments on Artificial
Fogs—Observations on Fogs at the South Foreland—Action of
Wind—Atmospheric Selection—Influence of Sound-Shadow 341

SUMMARY OF CHAPTER VII 374

CHAPTER VIII

Law of Vibratory Motions in Water and
Air—Superposition of Vibrations—Interference of
Sonorous Waves—Destruction of Sound by Sound—Combined
Action of Two Sounds nearly in Unison with each
other—Theory of Beats—Optical Illustration of the
Principle of Interference—Augmentation of Intensity
by Partial Extinction of Vibrations—Resultant
Tones—Conditions of their Production—Experimental
Illustrations—Difference-Tones and
Summation-Tones—Theories of Young and Helmholtz 377

SUMMARY OF CHAPTER VIII 407

CHAPTER IX

Combination of Musical Sounds—The smaller the Two
Numbers which express the Ratio of their Rates of
Vibration, the more perfect is the Harmony of Two
Sounds—Notions of the Pythagoreans regarding Musical
Consonance—Euler’s Theory of Consonance—Theory of
Helmholtz—Dissonance due to Beats—Interference of Primary
Tones and of Overtones—Mechanism of Hearing—Schultze’s
Bristles—The Otoliths—Corti’s Fibres—Graphic
Representation of Consonance and Dissonance—Musical
Chords—The Diatonic Scale—Optical Illustration of
Musical Intervals—Lissajous’s Figures—Sympathetic
Vibrations—Various Modes of illustrating the Composition
of Vibrations 410

Summary of Chapter IX 450

APPENDIX I

ON THE INFLUENCE OF MUSICAL SOUNDS ON THE FLAME OF A JET OF
COAL-GAS. BY JOHN LE CONTE, M.D. 454

APPENDIX II

ON ACOUSTIC REVERSIBILITY 461

INDEX 471

ILLUSTRATION—FOG-SIREN _Frontispiece_