everest f.a. the master handbook of acoustics

THE MASTER HANDBOOK
OF ACOUSTICS


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THE MASTER HANDBOOK
OF ACOUSTICS
F. Alton Everest
FOURTH EDITION

McGraw-Hill
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DOI: 10.1036/0071399747


To Bonnie Gail, whose love of art, nature, and the author
now embraces acoustics.


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CONTENTS

Epigraph
Introduction

Chapter 1

xxi
xxiii

Fundamentals of Sound

1

The Simple Sinusoid

2

Sine-Wave Language
Propagation of sound
The dance of the particles
How a sound wave is propagated
Sound in free space
Wavelength and Frequency
Complex Waves
Harmonics
Phase
Partials
Octaves
The concept of spectrum
Electrical, Mechanical, and Acoustical Analogs

12
12
12

15
15
17
20

Sound Levels and the Decibel

23

Ratios vs. Differences
Handling numbers
Logarithms

23
25
26

Decibels

26

Reference Levels

28

Logarithmic and Exponential Forms Compared

30

Acoustic Power

Chapter 2

3
5
5
7
9
10

31

Copyright 2001 The McGraw-Hill Companies, Inc. Click Here for Terms of Use.


viii

CONTENTS
Using Decibels
Example: Sound-pressure level
Example: Loudspeaker SPL
Example: Microphone specifications
Example: Line amplifier
Example: General-purpose amplifier
Example: Concert hall
Example: Combining decibels
Ratios and Octaves
Measuring Sound-Pressure Level

Chapter 3

33
34
34
35
35
35
35
36
37
39

The Ear and the Perception of Sound

41

Sensitivity of the Ear

41

A Primer of Ear Anatomy
The pinna: Directional encoder of sound
Directional cues: An experiment
The ear canal
The middle ear
The inner ear
Stereocilia
Loudness vs. Frequency

42

43
44
44
45
48
49
50

Loudness Control

51

Area of Audibility

53

Loudness vs. Sound-Pressure Level

54

Loudness and Bandwidth

56

Loudness of Impulses

59

Audibility of Loudness Changes

61

Pitch vs. Frequency
An experiment
Timbre vs. Spectrum

61
63
63

Localization of Sound Sources

64

Binaural Localization
Aural harmonics: Experiment #1
Aural harmonics: Experiment #2
The missing fundamental
The Ear as an Analyzer

67
68
69
69
70

The Ear as a Measuring Instrument
An auditory analyzer: An experiment

70

71


CONTENTS
Meters vs. the Ear
The Precedence Effect

75

Occupational and Recreational Deafness

76

Summary

79

Sound Waves in the Free Field

83

Free Sound Field: Definition

83

Sound Divergence
Examples: Free-field sound divergence
Inverse square in enclosed spaces
Hemispherical propagation

Chapter 5

73

Perception of Reflected Sound

Chapter 4

72

84
84
87
88

Speech, Music, and Noise

89

The Voice System
Artificial larynx
Sound spectrograph
Sound sources for speech
Vocal tract molding of speech
Formation of voiced sounds
Formation of unvoiced sounds
Putting it all together
Synthesized speech
Digital speech synthesis
Directionality of speech

Music
Wind instruments
Nonharmonic overtones
Dynamic range of speech and music
Power in Speech and Music

89
89
90
92
92
94
95
95
96
97
98
99
101
101
101
103

Frequency Range of Speech and Music

104

Future Dynamic-Range Requirements

104

Auditory Area

104

Noise
Noise—The good kind
Random noise
White and pink noise
Signal Distortion

107
108
109
111
112

Harmonic Distortion

114

ix


x

CONTENTS

Chapter 6

119

Resonance

120

Filters
Active filters
Analog vs. digital filters
Digitization
Quantization
Digital filters
Application of Digital Signal Processing (DSP)

122
123
124
125
126
126
105

Application of DSP to Room Equalization

Chapter 7

Analog and Digital Signal Processing

106

Reverberation

129

Reverberation and Normal Modes

130

Growth of Sound in a Room

132

Decay of Sound in a Room

134

Idealized Growth and Decay of Sound

134

Reverberation Time

135

Measuring Reverberation Time

137

Impulse Sound Sources

137

Steady-State Sources

138

Equipment

138

Measurement Procedure
Analysis of decay traces
Mode Decay Variations
Writing speed
Frequency effect
Reverberation Time Variation with Position

140
140
142
143
144
145

Acoustically Coupled Spaces

146

Electroacoustically Coupled Spaces
Decay rate

Eliminating decay fluctuations
Influence of Reverberation on Speech

146
147
147
148

Influence of Reverberation on Music

149

Optimum Reverberation Time
Bass rise of reverberation time
Living room reverberation time

150
152
154


CONTENTS
Artificial Reverberation: The Past
Artificial Reverberation: The Future

157

The Sabine Equation
Reverberation calculation: Example 1
Reverberation calculation: Example 2

Reverberant Field

159
160
162
162

Control of Interfering Noise

165

Noise Sources and Some Solutions
Airborne noise
Noise carried by structure
Noise transmitted by diaphragm action
Sound-insulating walls
Porous materials
Sound Transmission Classification (STC)

166
167
167
168
168
169
170

Comparison of Wall Structures

171

Double Windows

173

Sound-Insulating Doors
Noise and room resonances
Active noise control

Chapter 9

156

Arrival Time Gap

Chapter 8

155

175
176
177

Absorption of Sound

179

Dissipation of Sound Energy

179

Evaluation of Sound Absorption

181

Reverberation Chamber Method

182

Impedance Tube Method

182

Tone-Burst Method

185

Mounting of Absorbents

186

Mid/High Frequency Absorption by Porosity
Glass fiber: Building insulation
Glass fiber: Boards
Acoustical tile
Effect of Thickness of Absorbent

187
189
190

190
190

Effect of Airspace behind Absorbent

191

Effect of Density of Absorbent

192

xi


xii

CONTENTS
Open-Cell Foams
Drapes as Sound Absorbers

193

Carpet as Sound Absorber
Effect of carpet type on absorbance
Effect of carpet underlay on absorbance
Carpet absorption coefficients
Sound Absorption by People

196
199

200
200
200

Absorption of Sound in Air

203

Low-Frequency Absorption by Resonance

203

Diaphragmatic Absorbers

205

Polycylindrical Absorbers

209

Poly Construction

212

Membrane Absorbers

213

Helmholtz Resonators

215

Perforated Panel Absorbers

218

Slat Absorbers

224

Placement of Materials

225

Reverberation Time of Helmholtz Resonators
Taming room modes
Increasing Reverberation Time

225
226
229

Modules

Chapter 10

192

229

Reflection of Sound

235

Reflections from Flat Surfaces

235

Doubling of Pressure at Reflection

237

Reflections from Convex Surfaces

237

Reflections from Concave Surfaces

237

Reflections from Parabolic Surfaces

238

Reflections inside a Cylinder

240

Standing Waves

240

Reflection of Sound from Impedance
Irregularities

240

The Corner Reflector

243

Echo-Sounding

243

Perceptive Effects of Reflections

244


CONTENTS

Chapter 11

245

Diffraction and Wavelength

246

Diffraction of Sound by Large and Small Apertures

247

Diffraction of Sound by Obstacles

248

Diffraction of Sound by a Slit

249

Diffraction by the Zone Plate

250

Diffraction around the Human Head

251

Diffraction by Loudspeaker Cabinet Edges

253

Diffraction by Various Objects

254

Refraction of Sound

257

Refraction of Sound
Refraction of sound in solids
Refraction of sound in the atmosphere
Refraction of sound in the ocean
Refraction of sound in enclosed spaces

Chapter 13

245

Rectilinear Propagation

Chapter 12

Diffraction of Sound

258
258
260
263
265

Diffusion of Sound

267

The Perfectly Diffuse Sound Field

267

Evaluating Diffusion in a Room
Steady-state measurements
Decay Beats

268
268
269

Exponential Decay

270

Spatial Uniformity of Reverberation Time

271

Decay Shapes

275

Microphone Directivity

275

Room Shape

275

Splaying Room Surfaces
Nonrectangular rooms
Geometrical Irregularities

281
281
282

Absorbent in Patches

282

Concave Surfaces

286

Convex Surfaces: The Poly

286

Plane Surfaces

287

xiii


xiv

CONTENTS

Chapter 14

289

Schroeder’s First Acoustic Diffusor

290

Maximum-Length Sequences

292

Reflection Phase-Grating Diffusors

292

Quadratic-Residue Diffusors

293

Primitive-Root Diffusors

296

Quadratic-Residue Applications

298

Performance of Diffraction-Grating Diffusors

Expansion of the QRD line
Solving flutter problems
Application of fractals
Diffusion in three dimensions
Acoustic concrete blocks
Measuring diffusion efficiency
Comparison of Gratings with Conventional
Approaches

Chapter 15

The Schroeder Diffusor

298
304
304
306
308
309
311
312

Modal Resonances in Enclosed Spaces

317

Resonance in a Pipe

318

Bathroom Acoustics

319

Reflections Indoors

320

Two-Wall Resonance

322

Waves vs. Rays

322

Frequency Regions

323

Dividing the Audio Spectrum

325

Wave Acoustics
Mode calculations—An example
Experimental Verification

326
328

331

Mode Identification

331

Mode Decay

333

Mode Bandwidth

334

Mode Pressure Plots

339

Modal Density

341

Mode Spacing and Coloration

342

Experiments with Colorations

344

Simplified Axial Mode Analysis

346


CONTENTS
The Bonello Criterion
Controlling Problem Modes

Reflections in Enclosed Spaces

353
353

Mean Free Path
The effect of single reflections
Perception of sound reflections
Perception of spaciousness
Image changes
Discrete echoes
Effect of angle of incidence on audibility
of reflection
Effect of signal type of audibility of reflection
Effect of spectrum on audibility of reflection
Using reflection data
Large Spaces
Echoes
Spaciousness

354

355
355
357
357
357
357
358
358
359
359
359
360

Comb-Filter Effects

363

What Is a Comb Filter?

363

Superposition of Sound

364

Tonal Signals and Comb Filters
Combing of music and speech signals
Combing of direct and reflected sound
Comb Filters and Critical Bands

365
367
368
371

Comb Filters in Stereo Listening

374

Coloration and Spaciousness

374

Combing in Stereo Microphone Pickups

375

Audibility of Comb-Filter Effects
Comb filters in practice
Estimating comb-filter response

Chapter 18

350

Law of the First Wavefront

Chapter 17

348

Mode Summary

Chapter 16

348

375
376
380

Quiet Air for the Studio

385

Selection of Noise Criterion

386

Fan Noise

388

xv


xvi

CONTENTS
ASHRAE

Machinery Noise

390

Effect of Terminal Fittings

391

“Natural” Attenuation

391

Duct Lining

392

Plenum Silencers

393

Packaged Attenuators

394

Reactive Silencers

394

Resonator Silencer

395

Duct Location

395

Some Practical Suggestions

395

Acoustics of the Listening Room

399

The Acoustical Link

399

Peculiarities of Small-Room Acoustics
Room size
Room proportions
Reverberation time
The Listening Room: Low Frequencies
Control of modal resonances
Bass traps for the listening room
Modal colorations
The Listening Room: The Mid-High Frequencies
Identification and treatment of
reflection points
Lateral reflections: Control of spaciousness

Chapter 20

390

Air Velocity

Chapter 19

389

400
401
401
403
403
406
406
408
409

Acoustics of the Small Recording Studio

415

Acoustical Characteristics of a Studio

416

Reverberation

418

Studio Design

419

Studio Volume

419

Room Proportions

421

Reverberation Time

422

411
413


CONTENTS
Diffusion
Noise

424

Some Studio Features

424

Elements Common to all Studios

427

Acoustics of the Control Room

429

The Initial Time-Delay Gap

429

The Live End

431

Specular Reflections vs. Diffusion

432

Low-Frequency Resonances in the Control Room

434

Initial Time-Delay Gaps in Practice

436

Managing Reflections

438

The Reflection-Free-Zone Control Room

439

Control-Room Frequency Range

441

Outer Shell of the Control Room

442

Inner Shell of the Control Room

442

Representative Control Rooms

442

Some European Designs

444

Consultants

Chapter 22

424

Studio Design Procedure

Chapter 21

423

450

Acoustics for Multitrack Recording

453

Flexibility

545

Advantages of Multitrack

455

Disadvantages of Multitrack

456

Achieving Track Separation

457

Studio Acoustics
Distance between artists
Microphone management
Barriers for separation
Electronic separation
Electronic instruments and separation
The Future of Multichannel

458
458
458
459
459
459
460

Automation

460

xvii


xviii

CONTENTS

Chapter 23

468
468
468
469

Adjustable Acoustics

473

Draperies
Adjustable Panels: Absorption
Adjustable Panels: The Abffusor™
Hinged Panels
Louvered Panels
Variable Resonant Devices
Rotating Elements
Portable Units: The Tube Trap™
Portable Units: The Korner Killer™

473
474
476
478
479
480
483
484
485

Acoustical Distortion

489

Acoustic Distortion and the Perception of Sound

489

Sources of Acoustic Distortion
Coupling of room modes
Speaker-boundary interference response
Comb filtering
Poor diffusion
Conclusion

Chapter 26

462
462
462
463
463
464
465
465

The Voice-Over Booth
Dead-End Live-End Voice Studio
Voice-Over Booths

The Quick Sound Field™

Chapter 25

461

Selection of Space: External Factors
Selection of Space: Internal Factors
Work Space Treatment
Audio/Video Work Place Example
Appraisal of Room Resonances
Control of room resonances
Treatment of work place
Calculations

Chapter 24

Audio/Video Tech Room and Voice-Over
Recording

490
490
491
493
498
500

Room Acoustics Measurement Software

501

The Evolution of Measurement Technologies

502


CONTENTS
Building a Better Analyzer
Time-delay spectrometry (TDS) measurement
techniques
Maximum-length sequence (MLS) techniques
AcoustiSoft’s ETF Program
Frequency-response measurements
Resonance measurements
Fractional-octave measurements
Energy-time curve measurements
Reverberation time
Conclusion

Room Optimizer

529
529

Modal Response

530

Speaker-Boundary Interference Response

531

Optimization

533

Theory
Prediction of room response
Optimizing procedure
Cost parameter
Optimization Procedure

536
536
541
543
545

Results
Stereo pair
Stereo pair with two woofers per loudspeaker
THX home theater
Multichannel music
Subwoofer
Conclusion

Chapter 28

504
508

509
513
517
520
521
524
526

Introduction

Chapter 27

504

549
549
550
551
554
556
558

Desktop Auralization

565

Introduction

565

The Auralization Process

569

Summary

581

Appendix

585

Glossary

589

Index

599

xix


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EPIGRAPH

Directly or indirectly, all questions connected with this subject must
come for decision to the ear, as the organ of hearing; and from it there

can be no appeal. But we are not therefore to infer that all acoustical
investigations are conducted with the unassisted ear. When once we
have discovered the physical phenomena which constitute the foundation of sound, our explorations are in great measure transferred to
another field lying within the dominion of the principles of Mechanics.
Important laws are in this way arrived at, to which the sensations of
the ear cannot but conform.
Lord Raleigh in The Theory of Sound,
First Edition 1877.
(Also in first American edition, 1945,
courtesy of Dover Publications Inc.)

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INTRODUCTION

Excerpts from the introduction to the third edition.
In 1981, the copyright year of the first edition of this book, Manfred
Schroeder was publishing his early ideas on applying number theory
to the diffusion of sound. In the third edition a new chapter has been
added to cover numerous applications of diffraction-grating diffusors
to auditoriums, control rooms, studios and home listening rooms.

Introduction to the fourth edition.
The science of acoustics made great strides in the 20th century, during
which the first three editions of this book appeared. This fourth edition, however, points the reader to new horizons of the 21st century. A
newly appreciated concept of distortion of sound in the medium itself

(Chap. 25), a program for acoustic measurements (Chap. 26), and the
optimization of placement of loudspeakers and listener (Chap. 27), all
based on the home computer, point forward to amazing developments
in acoustics yet to come.
As in the previous three editions, this fourth edition balances treatment of the fundamentals of acoustics with the general application of
fundamentals to practical problems.
F. Alton Everest
Santa Barbara

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