About the Authors xix
Preface xxi
Preface to the Unfinished Manuscript of the Book xxiii
Introduction 1
1 How to Study and Develop Communication Acoustics 7
1.1 Domains of Knowledge 7
1.2 Methodology of Research and Development 8
1.3 Systems Approach to Modelling 10
1.4 About the Rest of this Book 12
1.5 Focus of the Book 12
1.6 Intended Audience 13
References 14
2 Physics of Sound 15
2.1 Vibration and Wave Behaviour of Sound 15
2.1.1 From Vibration to Waves 16
2.1.2 A Simple Vibrating System 16
2.1.3 Resonance 18
2.1.4 Complex MassSpring Systems 19
2.1.5 Modal Behaviour 20
2.1.6 Waves 21
2.2 Acoustic Measures and Quantities 23
2.2.1 Sound and Voice as Signals 23
2.2.2 Sound Pressure 24
2.2.3 Sound Pressure Level 24
2.2.4 Sound Power 25
2.2.5 Sound Intensity 25
2.2.6 Computation with Amplitude and Level Quantities 25
2.3 Wave Phenomena 26
2.3.1 Spherical Waves 26
2.3.2 Plane Waves and the Wave Field in a Tube 27
2.3.3 Wave Propagation in Solid Materials 29
2.3.4 Reflection, Absorption, and Refraction 31
2.3.5 Scattering and Diffraction 32
2.3.6 Doppler Effect 33
2.4 Sound in Closed Spaces: Acoustics of Rooms and Halls 34
2.4.1 Sound Field in a Room 34
2.4.2 Reverberation 36
2.4.3 Sound Pressure Level in a Room 37
2.4.4 Modal Behaviour of Sound in a Room 38
2.4.5 Computational Modelling of Closed Space Acoustics 39
Summary 41
Further Reading 41
References 41
3 Signal Processing and Signals 43
3.1 Signals 43
3.1.1 Sounds as Signals 43
3.1.2 Typical Signals 45
3.2 Fundamental Concepts of Signal Processing 46
3.2.1 Linear and Time-Invariant Systems 46
3.2.2 Convolution 47
3.2.3 Signal Transforms 48
3.2.4 Fourier Analysis and Synthesis 49
3.2.5 Spectrum Analysis 50
3.2.6 TimeFrequency Representations 53
3.2.7 Filter Banks 54
3.2.8 Auto- and Cross-Correlation 55
3.2.9 Cepstrum 56
3.3 Digital Signal Processing (DSP) 56
3.3.1 Sampling and Signal Conversion 56
3.3.2 Z Transform 57
3.3.3 Filters as LTI Systems 58
3.3.4 Digital Filtering 58
3.3.5 Linear Prediction 59
3.3.6 Adaptive Filtering 62
3.4 Hidden Markov Models 62
3.5 Concepts of Intelligent and Learning Systems 63
Summary 64
Further Reading 64
References 64
4 Electroacoustics and Responses of Audio Systems 67
4.1 Electroacoustics 67
4.1.1 Loudspeakers 67
4.1.2 Microphones 70
4.2 Audio System Responses 71
4.2.1 Measurement of System Response 71
4.2.2 Ideal Reproduction of Sound 72
4.2.3 Impulse Response and Magnitude Response 72
4.2.4 Phase Response 74
4.2.5 Non-Linear Distortion 75
4.2.6 Signal-to-Noise Ratio 76
4.3 Response Equalization 76
Summary 77
Further Reading 78
References 78
5 Human Voice 79
5.1 Speech Production 79
5.1.1 Speech Production Mechanism 80
5.1.2 Vocal Folds and Phonation 80
5.1.3 Vocal and Nasal Tract and Articulation 82
5.1.4 Lip Radiation Measurements 84
5.2 Units and Notation of Speech used in Phonetics 84
5.2.1 Vowels 86
5.2.2 Consonants 86
5.2.3 Prosody and Suprasegmental Features 88
5.3 Modelling of Speech Production 90
5.3.1 Glottal Modelling 92
5.3.2 Vocal Tract Modelling 92
5.3.3 Articulatory Synthesis 94
5.3.4 Formant Synthesis 95
5.4 Singing Voice 96
Summary 96
Further Reading 97
References 97
6 Musical Instruments and Sound Synthesis 99
6.1 Acoustic Instruments 99
6.1.1 Types of Musical Instruments 99
6.1.2 Resonators in Instruments 100
6.1.3 Sources of Excitation 102
6.1.4 Controlling the Frequency of Vibration 103
6.1.5 Combining the Excitation and Resonant Structures 104
6.2 Sound Synthesis in Music 104
6.2.1 Envelope of Sounds 105
6.2.2 Synthesis Methods 106
6.2.3 Synthesis of Plucked String Instruments with a One-Dimensional Physical Model 107
Summary 108
Further Reading 108
References 108
7 Physiology and Anatomy of Hearing 111
7.1 Global Structure of the Ear 111
7.2 External Ear 112
7.3 Middle Ear 113
7.4 Inner Ear 115
7.4.1 Structure of the Cochlea 115
7.4.2 Passive Cochlear Processing 117
7.4.3 Active Function of the Cochlea 119
7.4.4 The Inner Hair Cells 122
7.4.5 Cochlear Non-Linearities 122
7.5 Otoacoustic Emissions 123
7.6 Auditory Nerve 123
7.6.1 Information Transmission using the Firing Rate 124
7.6.2 Phase Locking 126
7.7 Auditory Nervous System 127
7.7.1 Structure of the Auditory Pathway 127
7.7.2 Studying Brain Function 129
7.8 Motivation for Building Computational Models of Hearing 130
Summary 131
Further Reading 131
References 131
8 The Approach and Methodology of Psychoacoustics 133
8.1 Sound Events versus Auditory Events 133
8.2 Psychophysical Functions 135
8.3 Generation of Sound Events 135
8.3.1 Synthesis of Sound Signals 136
8.3.2 Listening Set-up and Conditions 137
8.3.3 Steering Attention to Certain Details of An Auditory Event 137
8.4 Selection of Subjects for Listening Tests 138
8.5 What are We Measuring? 138
8.5.1 Thresholds 138
8.5.2 Scales and Categorization of Percepts 140
8.5.3 Numbering Scales in Listening Tests 141
8.6 Tasks for Subjects 141
8.7 Basic Psychoacoustic Test Methods 142
8.7.1 Method of Constant Stimuli 143
8.7.2 Method of Limits 143
8.7.3 Method of Adjustment 143
8.7.4 Method of Tracking 144
8.7.5 Direct Scaling Methods 144
8.7.6 Adaptive Staircase Methods 144
8.8 Descriptive Sensory Analysis 145
8.8.1 Verbal Elicitation 147
8.8.2 Non-Verbal Elicitation 148
8.8.3 Indirect Elicitation 148
8.9 Psychoacoustic Tests from the Point of View of Statistics 149
Summary 149
Further Reading 150
References 150
9 Basic Function of Hearing 153
9.1 Effective Hearing Area 153
9.1.1 Equal Loudness Curves 155
9.1.2 Sound Level and its Measurement 156
9.2 Spectral Masking 156
9.2.1 Masking by Noise 157
9.2.2 Masking by Pure Tones 159
9.2.3 Masking by Complex Tones 159
9.2.4 Other Masking Phenomena 161
9.3 Temporal Masking 161
9.4 Frequency Selectivity of Hearing 163
9.4.1 Psychoacoustic Tuning Curves 164
9.4.2 ERB Bandwidths 166
9.4.3 Bark, ERB, and Greenwood Scales 167
Summary 169
Further Reading 169
References 169
10 Basic Psychoacoustic Quantities 171
10.1 Pitch 171
10.1.1 Pitch Strength and Frequency Range 171
10.1.2 JND of Pitch 172
10.1.3 Pitch Perception versus Duration of Sound 173
10.1.4 Mel Scale 174
10.1.5 Logarithmic Pitch Scale and Musical Scale 175
10.1.6 Detection Threshold of Pitch Change and Frequency Modulation 176
10.1.7 Pitch of Coloured Noise 176
10.1.8 Repetition Pitch 177
10.1.9 Virtual Pitch 178
10.1.10 Pitch of Non-Harmonic Complex Sounds 178
10.1.11 Pitch Theories 178
10.1.12 Absolute Pitch 179
10.2 Loudness 179
10.2.1 Loudness Determination Experiments 179
10.2.2 Loudness Level 180
10.2.3 Loudness of a Pure Tone 180
10.2.4 Loudness of Broadband Signals 182
10.2.5 Excitation Pattern, Specific Loudness, and Loudness 183
10.2.6 Difference Threshold of Loudness 185
10.2.7 Loudness versus Duration of Sound 187
10.3 Timbre 188
10.3.1 Timbre of Steady-State Sounds 189
10.3.2 Timbre of Sound Including Modulations 189
10.4 Subjective Duration of Sound 189
Summary 191
Further Reading 191
References 191
11 Further Analysis in Hearing 193
11.1 Sharpness 193
11.2 Detection of Modulation and Sound Onset 195
11.2.1 Fluctuation Strength 195
11.2.2 Impulsiveness 197
11.3 Roughness 198
11.4 Tonality 200
11.5 Discrimination of Changes in Signal Magnitude and Phase Spectra 201
11.5.1 Adaptation to the Magnitude Spectrum 201
11.5.2 Perception of Phase and Time Differences 202
11.6 Psychoacoustic Concepts and Music 206
11.6.1 Sensory Consonance and Dissonance 206
11.6.2 Intervals, Scales, and Tuning in Music 208
11.6.3 Rhythm, Tempo, Bar, and Measure 211
11.7 Perceptual Organization of Sound 212
11.7.1 Segregation of Sound Sources 213
11.7.2 Sound Streaming and Auditory Scene Analysis 214
Summary 216
Further Reading 217
References 217
12 Spatial Hearing 219
12.1 Concepts and Definitions for Spatial Hearing 219
12.1.1 Basic Concepts 219
12.1.2 Coordinate Systems for Spatial Hearing 221
12.2 Head-Related Acoustics 222
12.3 Localization Cues 226
12.3.1 Interaural Time Difference 227
12.3.2 Interaural Level Difference 228
12.3.3 Interaural Coherence 231
12.3.4 Cues to Resolve the Direction on the Cone of Confusion 232
12.3.5 Interaction Between Spatial Hearing and Vision 234
12.4 Localization Accuracy 235
12.4.1 Localization in the Horizontal Plane 235
12.4.2 Localization in the Median Plane 236
12.4.3 3D Localization 237
12.4.4 Perception of the Distribution of a Spatially Extended Source 238
12.5 Directional Hearing in Enclosed Spaces 239
12.5.1 Precedence Effect 239
12.5.2 Adaptation to the Room Effect in Localization 240
12.6 Binaural Advantages in Timbre Perception 241
12.6.1 Binaural Detection and Unmasking 241
12.6.2 Binaural Decolouration 243
12.7 Perception of Source Distance 243
12.7.1 Cues for Distance Perception 244
12.7.2 Accuracy of Distance Perception 245
Summary 246
Further Reading 246
References 246
13 Auditory Modelling 249
13.1 Simple Psychoacoustic Modelling with DFT 250
13.1.1 Computation of the Auditory Spectrum through DFT 250
13.2 Filter Bank Models 255
13.2.1 Modelling the Outer and Middle Ear 255
13.2.2 Gammatone Filter Bank and Auditory Nerve Responses 256
13.2.3 Level-Dependent Filter Banks 256
13.2.4 Envelope Detection and Temporal Dynamics 258
13.3 Cochlear Models 260
13.3.1 Basilar Membrane Models 260
13.3.2 Hair-Cell Models 261
13.4 Modelling of Higher-Level Systemic Properties 263
13.4.1 Analysis of Pitch and Periodicity 263
13.4.2 Modelling of Loudness Perception 265
13.5 Models of Spatial Hearing 265
13.5.1 Delay-Network-Based Models of Binaural Hearing 265
13.5.2 Equalization Cancellation and ILD Models 268
13.5.3 Count-Comparison Models 268
13.5.4 Models of Localization in the Median Plane 270
13.6 Matlab Examples 270
13.6.1 Filter-Bank Model with Autocorrelation-Based Pitch Analysis 270
13.6.2 Binaural Filter-Bank Model with Cross-Correlation-Based ITD
Analysis 272
Summary 274
Further Reading 274
References 274
14 Sound Reproduction 277
14.1 Need for Sound Reproduction 277
14.2 Audio Content Production 279
14.3 Listening Set-ups 280
14.3.1 Loudspeaker Set-ups 280
14.3.2 Listening Room Acoustics 282
14.3.3 Audiovisual Systems 283
14.3.4 Auditory-Tactile Systems 284
14.4 Recording Techniques 284
14.4.1 Monophonic Techniques 285
14.4.2 Spot Microphone Technique 285
14.4.3 Coincident Microphone Techniques for Two-Channel Stereophony 286
14.4.4 Spaced Microphone Techniques for Two-Channel Stereophony 286
14.4.5 Spaced Microphone Techniques for Multi-Channel Loudspeaker Systems 287
14.4.6 Coincident Recording for Multi-Channel Set-up with Ambisonics 287
14.4.7 Non-Linear TimeFrequency-domain Reproduction of Spatial Sound 290
14.5 Virtual Source Positioning 293
14.5.1 Amplitude Panning 293
14.5.2 Amplitude Panning in a Stereophonic Set-up 294
14.5.3 Amplitude Panning in Horizontal Multi-Channel Loudspeaker Set-ups 295
14.5.4 3D Amplitude Panning 295
14.5.5 Virtual Source Positioning using Ambisonics 296
14.5.6 Wave Field Synthesis 296
14.5.7 Time Delay Panning 297
14.5.8 Synthesizing the Width of Virtual Sources 298
14.6 Binaural Techniques 298
14.6.1 Listening to Binaural Recordings with Headphones 299
14.6.2 HRTF Processing for Headphone Listening 299
14.6.3 Virtual Listening of Loudspeakers with Headphones 300
14.6.4 Headphone Listening to Two-Channel Stereophonic Content 301
14.6.5 Binaural Techniques with Cross-Talk-Cancelled Loudspeakers 301
14.7 Digital Audio Effects 302
14.8 Reverberators 303
14.8.1 Using Room Impulse Responses in Reverberators 304
14.8.2 DSP Structures for Reverberators 305
Summary 306
Further Reading and Available Toolboxes 306
References 307
15 TimeFrequency-domain Processing and Coding of Audio 311
15.1 Basic Techniques and Concepts for TimeFrequency Processing 311
15.1.1 Frame-Based Processing 311
15.1.2 Downsampled Filter-Bank Processing 313
15.1.3 Modulation with Tone Sequences 315
15.1.4 Aliasing 316
15.2 TimeFrequency Transforms 317
15.2.1 Short-Time Fourier Transform (STFT) 318
15.2.2 Alias-Free STFT 320
15.2.3 Modified Discrete Cosine Transform (MDCT) 321
15.2.4 Pseudo-Quadrature Mirror Filter (PQMF) Bank 323
15.2.5 Complex QMF 323
15.2.6 Sub-Sub-Band Filtering of the Complex QMF Bands 325
15.2.7 Stochastic Measures of TimeFrequency Signals 325
15.2.8 Decorrelation 327
15.3 TimeFrequency-Domain Audio-Processing Techniques 328
15.3.1 Masking-Based Audio Coding 328
15.3.2 Audio Coding with Spectral Band Replication 328
15.3.3 Parametric Stereo, MPEG Surround, and Spatial Audio Object Coding 329
15.3.4 Stereo Upmixing and Enhancement for Loudspeakers and Headphones 330
Summary 332
Further Reading 332
References 332
16 Speech Technologies 335
16.1 Speech Coding 336
16.2 Text-to-Speech Synthesis 338
16.2.1 Early Knowledge-Based Text-to-Speech (TTS) Synthesis 339
16.2.2 Unit-Selection Synthesis 340
16.2.3 Statistical Parametric Synthesis 342
16.3 Speech Recognition 345
Summary 346
Further Reading 347
References 347
17 Sound Quality 349
17.1 Historical Background of Sound Quality 350
17.2 The Many Facets of Sound Quality 351
17.3 Systemic Framework for Sound Quality 352
17.4 Subjective Sound Quality Measurement 353
17.4.1 Mean Opinion Score 353
17.4.2 MUSHRA 354
17.5 Audio Quality 356
17.5.1 Monaural Quality 356
17.5.2 Perceptual Measures and Models for Monaural Audio Quality 356
17.5.3 Spatial Audio Quality 359
17.6 Quality of Speech Communication 360
17.6.1 Subjective Methods and Measures 361
17.6.2 Objective Methods and Measures 362
17.7 Measuring Speech Understandability with the Modulation Transfer Function 363
17.7.1 Modulation Transfer Function 363
17.7.2 Speech Transmission Index STI 367
17.7.3 STI and Speech Intelligibility 368
17.7.4 Practical Measurement of STI 369
17.8 Objective Speech Quality Measurement for Telecommunication 370
17.8.1 General Speech Quality Measurement Techniques 371
17.8.2 Measurement of the Perceptual Effect of Background Noise 372
17.8.3 Measurement of the Perceptual Effect of Echoes 373
17.9 Sound Quality in Auditoria and Concert Halls 374
17.9.1 Subjective Measures 374
17.9.2 Objective Measures 375
17.9.3 Percentage of Consonant Loss 377
17.10 Noise Quality 377
17.11 Product Sound Quality 378
Summary 380
Further Reading 380
References 380
18 Other Audio Applications 383
18.1 Virtual Reality and Game Audio Engines 383
18.2 Sonic Interaction Design 386
18.3 Computational Auditory Scene Analysis, CASA 387
18.4 Music Information Retrieval 387
18.5 Miscellaneous Applications 389
Summary 390
Further Reading 390
References 390
19 Technical Audiology 393
19.1 Hearing Impairments and Disabilities 393
19.1.1 Key Terminology 394
19.1.2 Classification of Hearing Impairments 395
19.1.3 Causes for Hearing Impairments 396
19.2 Symptoms and Consequences of Hearing Impairments 396
19.2.1 Hearing Threshold Shift 397
19.2.2 Distortion and Decrease in Discrimination 398
19.2.3 Speech Communication Problems 400
19.2.4 Tinnitus 400
19.3 The Effect of Noise on Hearing 401
19.3.1 Noise 401
19.3.2 Formation of Noise-Induced Hearing Loss 402
19.3.3 Temporary Threshold Shift 402
19.3.4 Hearing Protection 404
19.4 Audiometry 405
19.4.1 Pure-Tone Audiometry 405
19.4.2 Bone-Conduction Audiometry 406
19.4.3 Speech Audiometry 406
19.4.4 Sound-Field Audiometry 407
19.4.5 Tympanometry 407
19.4.6 Otoacoustic Emissions 408
19.4.7 Neural Responses 409
19.5 Hearing Aids 409
19.5.1 Types of Hearing Aids 409
19.5.2 Signal Processing in Hearing Aids 410
19.5.3 Transmission Systems and Assistive Listening Devices 414
19.6 Implantable Hearing Solutions 414
19.6.1 Cochlear Implants 414
19.6.2 Electric-Acoustic Stimulation 416
19.6.3 Bone-Anchored Hearing Aids 416
19.6.4 Middle-Ear Implants 416
Summary 416
Further Reading 417
References 417
Index 419
