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Contents

Chapter 1 - Basic Techniques 1

A Little Mathematics 1

The Fourier Transform and Fourier Series 2

Orthogonal Functions 4

Orthogonal Coordinate Systems 5

Electronic Basics 7

Passive Circuits 8

Active Circuits 11

Newton's Equations 15

The Simple Harmonic Oscillator 16

Coupled Systems 17

Basic T-Matrices 19

Series and Parallel Elements in a T-matrix 20

Correlation and Spectral Analysis 21

Modeling Transfer Functions 23

Summary 25

Chapter 2 - Transducer Mechanisms 26

Moving Coil Motor Structure 26

Variable Reluctance Motor Structure 27

Magnetic Circuits 30

The Electrostatic Motor 34

The Piezoelectric Motor Structure, 36

A Simply Supported Piston 38

A Simple Driven Piston Example 39

Summary 41

Chapter 3 - Acoustics 42

The Wave Equation 42

The Helmholtz Equation in Rectangular Coordinates 43

Cylindrical Coordinates 46

Spherical Coordinates 49

A Spherical Example 51

A Cylindrical Example 58

The Cylindrical Near Field 65

Summary 70

Chapter 4 - Simple Radiation 71

Circular Disk 71

Examples of Circular Aperture Radiation 75

The Rectangular Aperture As a Transform Pair 78

Generalized Rectangular Radiation 80

Transform Relationships for Circular Apertures 83

Non-planar Sources in a Flat baffle 85

Summary 87

Chapter 5 - Enclosures 89

The Simple Closed Box 89

An Enclosure in T-matrix Format 95

T-matrix and Lumped Parameter 96

A Ported Enclosure Using T-Matrices. 100

The Mechanical Acoustical Interface 103

Front and Rear Port Radiation 105

General Enclosure Types, 108

Summary 125

Chapter 6 - Waveguides 126

Historical Notes 126

Waveguide Theory 130

Waveguide Geometries 136

The Oblate Spheroidal Waveguide 137

Approximate Numerical Calculations, 147

Treatment of Mouth Diffraction 152

Diffraction Horns 161

Summary 163

Chapter 7 - Crossovers 164

Background 164

Two-Way Crossovers 166

Examples 169

Passive Electrical Effects 173

Acoustic Filters As Crossover Components 178

Summary 179

Chapter 8 - Room Acoustics 181

The Rectangular Room 181

A Wall With an Impedance 189

Fundamental Concepts in Small Room Acoustics 192

Source Placement 196

Summary 202

Chapter 9 - Transducer Arrays 203

Simple Point Source Arrays 203

Spherical Arrays 205

Displaced Spherical Arrays 208

Line Arrays in Cylindrical Coordinates 210

The Effect of Wavefront Curvature on Line Arrays 214

Cardiod Enclosures 216

Passive Low Frequency Directivity 219

Summary 221

Chapter 10 - Distortion 223

Nonlinear Systems Theory 223

Loudspeaker Component Nonlinearity 226

Simulated Results of a Nonlinear Transducer 233

Background On Distortion Perception 236

The Psychoacoustics of Distortion Perception 237

Thermal Nonlinearity 240

Summary 245

Chapter 11 - Microphones 246

Background 246

Microphone Noise 247

A Microphone Example 249

Microphone Enclosures 252

Microphone Pattern Control 254

Microphone Arrays 255

Summary 258

Chapter 12 - Measurements 259

Philosophy of Measurement 259

Measuring the First Mode Parameters 260

Polar Response Measurement 266

Measuring Component Nonlinearity 273

Measuring the Thermal Parameters 277

Summary 278

Chapter 13 - Psychoacoustics 279

Anatomy and Physiology 279

Theories of Hearing 280

Psychoacoustic Measurement Protocols 284

Masking 286

Loudness 289

Binaural Hearing 294

Summary 295

Last modified May 20, 2008  by Earl Geddes                                                   

Copyright 2000, GedLee Associates