Master Handbook of Acoustics

529 Pages·2009·6.53 MB·English

by  David McMahon

Master Handbook
of Acoustics
About the Authors
F. Alton Everest was a leading acoustics consultant.
He was cofounder and director of the Science Film
Production division of the Moody Institute of Science,
and was also section chief of the Subsea Sound
Research section of the University of California.
Ken C. Pohlmann is well known as an audio educator,
consultant, and author. He is professor emeritus at the
University of Miami in Coral Gables, consultant for
many audio manufacturers and car makers, and author
of numerous articles and books including Principles of
Digital Audio.
Contributions are included from Peter D’Antonio,
Geoff Goacher and Doug Plum.
Master Handbook
of Acoustics
F. Alton Everest
Ken C. Pohlmann
Fifth Edition
New York Chicago San Francisco
Lisbon London Madrid Mexico City
Milan New Delhi San Juan
Seoul Singapore Sydney Toronto
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Dedicated to the memory of F. Alton Everest
This page intentionally left blank
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
1 Fundamentals of Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
The Sine Wave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Sound in Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Particle Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Propagation of Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Speed of Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Wavelength and Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Complex Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Harmonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Partials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Octaves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Electrical, Mechanical, and Acoustical Analogs . . . . . . . . . . . . . . . . . . . 17
2 Sound Levels and the Decibel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Ratios versus Differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Expressing Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Logarithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Decibels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Reference Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Logarithmic and Exponential Forms Compared . . . . . . . . . . . . . . . . . . 24
Acoustic Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Using Decibels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Example 1: Sound-Pressure Level . . . . . . . . . . . . . . . . . . . . . . . . 28
Example 2: Loudspeaker SPL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Example 3: Microphone Specifi cations . . . . . . . . . . . . . . . . . . . . 28
Example 4: Line Amplifi er . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Example 5: General-Purpose Amplifi er . . . . . . . . . . . . . . . . . . . 29
Example 6: Concert Hall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Example 7: Combining Decibels . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Measuring Sound-Pressure Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Sine-Wave Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3 Sound in the Free Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
The Free Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Sound Divergence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Sound Intensity in the Free Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
vii
viii Contents
Sound Pressure in the Free Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Examples: Free-Field Sound Divergence . . . . . . . . . . . . . . . . . . 36
Sound Fields in Enclosed Spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Hemispherical Field and Propagation . . . . . . . . . . . . . . . . . . . . . 38
4 The Perception of Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Sensitivity of the Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Ear Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
The Outer Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Directional Cues: An Experiment . . . . . . . . . . . . . . . . . . . . . . . . . 41
The Ear Canal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
The Middle Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
The Inner Ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Stereocilia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Loudness versus Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Loudness Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Area of Audibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Loudness versus Sound-Pressure Level . . . . . . . . . . . . . . . . . . . . . . . . . 49
Loudness and Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Loudness of Impulses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Audibility of Loudness Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Pitch versus Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
An Experiment in Pitch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
The Missing Fundamental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Timbre versus Spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Localization of Sound Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Binaural Localization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Law of the First Wavefront . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
The Franssen Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
The Precedence Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Perception of Refl ected Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
The Cocktail-Party Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Aural Nonlinearity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Subjective versus Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Occupational and Recreational Deafness . . . . . . . . . . . . . . . . . . . . . . . . 65
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
5 Signals, Speech, Music, and Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Sound Spectrograph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Speech . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Vocal Tract Molding of Speech . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Formation of Voiced Sounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Formation of Unvoiced Sounds . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Frequency Response of Speech . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Directionality of Speech . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Contents ix
Music . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
String Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Wind Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Nonharmonic Overtones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Dynamic Range of Speech and Music . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Power in Speech and Music . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Frequency Range of Speech and Music . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Auditory Area of Speech and Music . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Noise Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Random Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
White and Pink Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Signal Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Harmonic Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Resonance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Audio Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
6 Refl ection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Specular Refl ections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Flutter Echoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Doubling of Pressure at Refl ection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Refl ections from Convex Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Refl ections from Concave Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Refl ections from Parabolic Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Whispering Galleries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Standing Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
The Corner Refl ector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Mean Free Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Perception of Sound Refl ections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
The Effect of Single Refl ections . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Perception of Spaciousness, Images,
and Echoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Effect of Angle of Incidence, Signal Type, and Spectrum on
Audibility of Refl ection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
7 Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Wavefront Propagation and Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . 107
Wavelength and Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Diffraction of Sound by Obstacles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Diffraction of Sound by Apertures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Diffraction of Sound by a Slit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Diffraction by the Zone Plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Diffraction around the Human Head . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Diffraction by Loudspeaker Cabinet Edges . . . . . . . . . . . . . . . . . . . . . . 113
Diffraction by Various Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115