Acoustics and Psychoacoustics

Cover Page......Page 1
Copyright......Page 2
Preface......Page 3
Introduction to Sound......Page 5
Pressure waves and sound transmission......Page 6
The velocity of sound waves......Page 7
The velocity of sound in air......Page 9
The velocity of transverse waves......Page 13
Quasi-longitudinal waves......Page 14
Transverse shear waves......Page 15
Bending (flexural) waves......Page 16
The wavelength and frequency of sound waves......Page 18
The wavenumber of sound waves......Page 21
The relationship between pressure, velocity and impedance in sound waves......Page 22
Sound intensity level......Page 25
Sound pressure level......Page 27
Adding sounds together......Page 30
The level when correlated sounds add......Page 32
The level when uncorrelated sounds add......Page 34
Adding decibels together......Page 38
The inverse square law......Page 40
The effect of boundaries......Page 43
Sound interactions......Page 44
Superposition......Page 45
Sound refraction......Page 46
Sound reflection from hard boundaries......Page 48
Sound reflection from bounded to unbounded boundaries......Page 50
Sound interference......Page 51
Standing waves at hard boundaries (modes)......Page 53
Standing waves at other boundaries......Page 57
Sound diffraction......Page 59
Sound scattering......Page 62
What is Fourier theory?......Page 63
The spectrum of periodic sound waves......Page 64
The effect of phase......Page 66
The spectrum of non-periodic sound waves......Page 67
Filters and filter types......Page 68
Filter time responses......Page 69
Time and frequency representations of sounds......Page 73
Bibliography......Page 76
Introduction to Hearing......Page 77
The anatomy of the hearing system......Page 78
Outer ear function......Page 79
Middle ear function......Page 80
Inner ear function......Page 83
Critical bands......Page 87
Frequency and pressure sensitivity ranges......Page 93
Loudness perception......Page 95
Measuring loudness......Page 99
Loudness of simple sounds......Page 100
Loudness of complex sounds......Page 103
Noise-induced hearing loss......Page 105
Integrated noise dose......Page 108
Protecting your hearing......Page 110
Interaural time difference (ITD)......Page 111
Interaural intensity difference (IID)......Page 115
Pinnae and head movement effects......Page 117
ITD and IID trading......Page 118
The Haas effect......Page 119
Stereophonic listening......Page 120
Notes and Harmony......Page 124
Musical notes and their fundamental frequency......Page 125
Musical notes and their harmonics......Page 127
Musical intervals between harmonics......Page 130
Hearing pitch......Page 134
Place theory of pitch perception......Page 136
Problems with the place theory......Page 140
Temporal theory of pitch perception......Page 145
Contemporary theory of pitch perception......Page 149
Secondary aspects of pitch perception......Page 151
Harmonics and the development of Western harmony......Page 153
Consonance and dissonance......Page 154
Hearing musical intervals......Page 156
Pythagorean tuning......Page 161
Just tuning......Page 164
Equal tempered tuning......Page 166
References......Page 168
Acoustic Model for Musical Instruments......Page 169
A “black box” model of musical instruments......Page 170
Stringed instruments......Page 172
Sound source from a plucked string......Page 174
Sound source from a struck string......Page 175
Sound source from a bowed string......Page 178
Sound modifiers in stringed instruments......Page 180
Wind instruments......Page 183
Sound source in organ flue pipes......Page 184
Sound modifiers in organ flue pipes......Page 187
Woodwind flue instruments......Page 194
Sound source in organ reed pipes......Page 196
Sound modifiers in organ reed pipes......Page 198
Woodwind reed instruments......Page 199
Brass instruments......Page 205
Sound source in percussion instruments......Page 210
Sound modifiers in percussion instruments......Page 211
The speaking and singing voice......Page 218
Sound source in singing......Page 219
Sound modifiers in singing......Page 221
Tuning in a capella (unaccompanied) singing......Page 227
References......Page 231
What is timbre?......Page 233
Acoustics of timbre......Page 235
Note envelope......Page 236
Note onset......Page 239
Critical bands and timbre......Page 244
Acoustic cues and timbre perception......Page 246
The pipe organ as a timbral synthesizer......Page 255
Perception of pure tones......Page 260
Masking of one sound by another......Page 262
Note grouping illusions......Page 266
Pitch illusions......Page 272
Hearing Music in Different Environments......Page 278
The direct sound......Page 280
Early reflections......Page 282
The effect of absorption on early reflections......Page 286
The reverberant sound......Page 287
The behavior of the reverberant sound field......Page 289
The balance of reverberant to direct sound......Page 290
The level of the reverberant sound in the steady state......Page 291
Calculating the critical distance......Page 296
The effect of source directivity on the reverberant sound......Page 298
Reverberation time......Page 300
Calculating and predicting reverberation time......Page 301
The effect of room size on reverberation time......Page 303
A simpler reverberation time equation......Page 305
Reverberation faults......Page 306
Reverberation time variation with frequency......Page 309
Reverberation time calculation with mixed surfaces......Page 311
Reverberation time design......Page 313
Ideal reverberation time characteristics......Page 316
Early decay time......Page 317
Lateral reflections......Page 318
Early reflections and performer support......Page 319
The effect of air absorption......Page 322
Axial modes......Page 323
Tangential modes......Page 325
Oblique modes......Page 326
A universal modal frequency equation......Page 327
The Bonello criteria......Page 328
The decay time of axial modes......Page 330
The decay time of other mode types......Page 331
Critical frequency......Page 335
Calculating the critical frequency......Page 337
Porous absorbers......Page 340
Resonant absorbers......Page 342
Summary......Page 344
Diffusion materials......Page 346
How diffusers work......Page 347
Discussion......Page 348
Amplitude reflection gratings......Page 349
Sound isolation......Page 352
Ways of achieving sound isolation......Page 353
Independent partitions......Page 354
Flanking paths......Page 355
The effect of room boundaries on loudspeaker output......Page 357
Reduction of enclosure diffraction effects......Page 359
References......Page 363
Applications: Acoustics and Psychoacoustics Combined......Page 365
Loudspeaker arrangements for critical listening......Page 367
IEC listening rooms......Page 368
Energy–time considerations......Page 369
Reflection-controlled rooms......Page 370
The absorption position for reflection-free zones......Page 373
Non-environment rooms......Page 375
The diffuse reflection room......Page 376
Pure-tone and speech audiometry......Page 381
Psychoacoustic testing......Page 388
Psychoacoustic experimental design issues......Page 389
Psychoacoustic rating scales......Page 390
Speech intelligibility: Articulation loss......Page 392
Filtering and equalization......Page 394
Equalization and tone controls......Page 397
Correcting frequency response faults due to the recording process......Page 398
Timbre modification of sound sources......Page 399
Altering the balance of sounds in mixes......Page 400
Reverberation......Page 402
The effect of reverberation on intelligibility......Page 403
The effect of more than one loudspeaker on intelligibility......Page 404
The effect of noise on intelligibility......Page 405
Requirements for good speech intelligibility......Page 407
Achieving speaker directivity......Page 408
A design example: How to get it right......Page 409
More than one loudspeaker and delays......Page 413
Noise-reducing headphones......Page 415
“Mosquito” units and “teen buzz” ring tones......Page 417
Audio coding systems......Page 418
The archetypical audio coder......Page 419
What exactly is information?......Page 420
The signal redundancy removal stage......Page 421
How do we measure information?......Page 424
How do we measure the total information?......Page 425
Entropy coding......Page 427
The psychoacoustic quantization stage......Page 428
Quantization and adaptive quantization......Page 429
Psychoacoustic quantization......Page 432
References......Page 434
Fourier’s theorem......Page 437
Fourier analysis......Page 439
The complex Fourier series......Page 440
Frequency analysis of non-periodic signals: the Fourier transform......Page 441
The convolution theorem......Page 442
A Fourier transform example: The single pulse......Page 443
The discrete Fourier transform......Page 445
Solving the ERB Equation......Page 447
Converting between Frequency Ratios and Cents......Page 448
Deriving the Reverberation Time Equation......Page 450
Deriving the Reverberation Time Equation for Different Frequencies and Surfaces......Page 454
An array of point sources......Page 457
Application to diffuser design......Page 462
Application to array loudspeakers......Page 463
Application to constant directivity horns......Page 465
The effect of mouth, or array, size on beamwidth......Page 466
References......Page 468
Track Listing for the Audio Compact Disc......Page 470
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H......Page 479
M......Page 480
N......Page 481
P......Page 482
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Y......Page 485