Cox T.J. Acoustic absorbers and diffusers: theory, design and application (London; New York, 2009). - ОГЛАВЛЕНИЕ / CONTENTS
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ОбложкаCox T.J. Acoustic absorbers and diffusers: theory, design and application / T.J.Cox, P. D'Antonio. - 2nd ed. - London; New York: Taylor & Francis, 2009. - xvii, 476 p.: ill. - Incl. bibl. ref. - Ind.: p.463-476. - ISBN 978-0-415-47174-9
 

Оглавление / Contents
 
   Preface to the first edition ................................ ix
   Preface to the second edition ............................. xiii
   Acknowledgements ........................................... xiv
   Glossary of frequently used symbols ......................... xv

Introduction .................................................... 1
   Absorption versus diffuse reflections ........................ 4

1  Applications and basic principles of absorbers ............... 7
   1.1  Reverberation control ................................... 7
   1.2  Noise control in factories and large rooms with
        diffuse fields ......................................... 13
   1.3  Modal control in critical listening spaces ............. 14
   1.4  Echo control in auditoria and lecture theatres - 
        basic sound propagation models ......................... 16
   1.5  Absorption in sound insulation - transfer matrix
        modelling .............................................. 22
   1.6  Pipes, ducts and silencers - porous absorber
        characteristics ........................................ 24
   1.7  Enclosures, barriers and roads ......................... 26
   1.8  Natural noise control .................................. 28
   1.9  Hearing protection devices ............................. 28
   1.10 Loudspeaker cabinets ................................... 28
   1.11 Summary ................................................ 29
   1.12 References ............................................. 29
2  Applications and basic principles of diffusers .............. 31
   2.1  Echo control in auditoria .............................. 31
   2.2  Reducing coloration in small sound reproduction
        rooms .................................................. 40
   2.3  Music practice rooms ................................... 49
   2.4  Promoting diffuse fields in reverberation chambers ..... 52
   2.5  Improving speech intelligibility in underground or
        subway stations ........................................ 53
   2.6  Promoting spaciousness in auditoria .................... 54
   2.7  Reducing effects of early arriving reflections in
        large spaces ........................................... 55
   2.8  Stage enclosures ....................................... 56
   2.9  Blurring the focussing from concave surfaces ........... 63
   2.10 In audience areas - diffuse fields ..................... 64
   2.11 Barriers and streets ................................... 66
   2.12 Conclusions ............................................ 67
   2.13 References ............................................. 67
3  Measurement of absorber properties .......................... 70
   3.1  Impedance or standing wave tube measurement ............ 70
   3.2  Two-microphone free field measurement .................. 80
   3.3  Multi-microphone techniques for non-isotropic,
        non-planar surfaces .................................... 82
   3.4  Reverberation chamber method ........................... 84
   3.5  In situ measurement of absorptive properties ........... 90
   3.6  Measurement of internal properties of porous
        absorbents ............................................. 95
   3.7  Summary ............................................... 107
   3.8  References ............................................ 107
4  Measurement and characterization of diffuse reflections
   or scattering .............................................. 110
   4.1  Measurement of scattered polar responses .............. 111
   4.2  Diffusion and scattering coefficients - a general
        discussion ............................................ 127
   4.3  The need for coefficients ............................. 128
   4.4  The diffusion coefficient ............................. 130
   4.5  The scattering coefficient ............................ 135
   4.6  The correlation scattering coefficient - from polar
        responses to scattering coefficients .................. 143
   4.7  Contrasting diffusion and scattering coefficients -
        a summary ............................................. 147
   4.8  Other methods for characterizing diffuse
        reflections ........................................... 147
   4.9  Summary ............................................... 153
   4.10 References ............................................ 153
5  Porous absorption .......................................... 156
   5.1  Absorption mechanisms and characteristics ............. 156
   5.2  Some material types ................................... 160
   5.3  Basic material properties ............................. 169
   5.4  Modelling propagation within porous absorbents ........ 172
   5.5  Predicting the surface impedance and absorption
        coefficient of porous absorbers ....................... 184
   5.6  Local and extended reaction ........................... 189
   5.7  Oblique incidence ..................................... 189
   5.8  Biot theory for elastic framed material ............... 191
   5.9  Summary ............................................... 192
   5.10 References ............................................ 193
6  Resonant absorbers ......................................... 196
   6.1  Mechanisms ............................................ 197
   6.2  Example constructions ................................. 198
   6.3  Design equations: resonant frequency .................. 208
   6.4  Example calculations .................................. 221
   6.5  Other constructions ................................... 223
   6.6  Summary ............................................... 228
   6.7  References ............................................ 228
7  Some other absorbers ....................................... 230
   7.1  Seating and audience .................................. 230
   7.2  Absorbers from Schroeder diffusers .................... 232
   7.3  Absorbing sonic crystals .............................. 244
   7.4  Trees and vegetation .................................. 248
   7.5  Summary ............................................... 249
   7.6  References ............................................ 250
8  Prediction of scattering ................................... 252
   8.1  Boundary element methods .............................. 252
   8.2  Kirchhoff ............................................. 268
   8.3  Fresnel ............................................... 272
   8.4  Fraunhofer or Fourier solution ........................ 273
   8.5  Finite difference time domain (FDTD) .................. 277
   8.6  Other methods ......................................... 284
   8.7  Summary ............................................... 286
   8.8  References ............................................ 287
9  Schroeder diffusers ........................................ 289
   9.1  Basic principles ...................................... 289
   9.2  Design equations ...................................... 291
   9.3  Some limitations and other considerations ............. 292
   9.4  Sequences ............................................. 295
   9.5  The curse of periodicity and modulation ............... 303
   9.6  Improving the bass response ........................... 312
   9.7  Multi-dimensional devices ............................. 315
   9.8  Absorption ............................................ 319
   9.9  But ................................................... 322
   9.10 Optimization .......................................... 324
   9.11 Summary ............................................... 329
   9.12 References ............................................ 329
10 Geometric reflectors and diffusers ......................... 331
   10.1 Plane surfaces ........................................ 331
   10.2 Triangles and pyramids ................................ 339
   10.3 Concave arcs .......................................... 343
   10.4 Convex arcs ........................................... 344
   10.5 Optimized curved surfaces ............................. 352
   10.6 Fractals .............................................. 364
   10.7 Volumetric diffusers .................................. 368
   10.8 Materials ............................................. 369
   10.9 Summary ............................................... 371
   10.10 References ........................................... 371
11 Hybrid surfaces ............................................ 373
   11.1 Planar hybrid surface ................................. 373
   11.2 Curved hybrid surfaces ................................ 375
   11.3 Ternary and quadriphase surfaces ...................... 377
   11.4 Simplest theory ....................................... 377
   11.5 Number sequences ...................................... 378
   11.6 Absorption ............................................ 389
   11.7 Accuracy of the Fourier theory ........................ 390
   11.8 Diffuse reflections ................................... 393
   11.9 Summary ............................................... 398
   11.10 References ........................................... 398
12  Absorbers and diffusers in rooms and geometric models ..... 399
   12.1 Converting absorption coefficients .................... 399
   12.2 Absorption in geometric room acoustic models .......... 404
   12.3 Diffuse reflections in geometric room acoustic
        models ................................................ 407
   12.4 Summary ............................................... 417
   12.5 References ............................................ 417
13 Active absorbers and diffusers ............................. 419
   13.1 Some principles of active control ..................... 420
   13.2 An example active impedance system and a general
        overview .............................................. 422
   13.3 Active absorption in ducts ............................ 425
   13.4 Active absorption in three dimensions ................. 425
   13.5 Hybrid active-passive absorption ...................... 431
   13.6 Active diffusers ...................................... 434
   13.7 Summary ............................................... 438
   13.8 References ............................................ 438

Appendix A
   A.l Table of absorption coefficients ....................... 440
   A.2 References ............................................. 444

Appendix В
   MATLAB scripts ............................................. 446

Appendix С
   C.l Normalized diffusion coefficient table ................. 453
   C.2 Correlation scattering coefficient table ............... 458

   Index ...................................................... 463


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