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E-grāmata: Acoustic Absorbers and Diffusers: Theory, Design and Application

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(University of Salford, UK),
  • Formāts: 575 pages
  • Izdošanas datums: 18-Nov-2016
  • Izdevniecība: CRC Press Inc
  • Valoda: eng
  • ISBN-13: 9781315352220
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Acoustic Absorbers and Diffusers: Theory, Design and ApplicationPalielināt
  • Formāts: 575 pages
  • Izdošanas datums: 18-Nov-2016
  • Izdevniecība: CRC Press Inc
  • Valoda: eng
  • ISBN-13: 9781315352220
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This definitive guide covers the design and application of absorbers and diffusers in acoustics. Surface diffusion is a relatively young subject area, and diffuser design, application and characterisation are often not well understood. Although there is greater knowledge of absorption, it is also informed by new research. As two of the main design tools for altering the acoustic conditions of rooms, the correct use of absorbers and diffusers is important to the creation of quality acoustics. This text details the evolution and the current state of the art in diffuser and absorber research and application. It covers a range of practical and theoretical aspects, with extensive examples of installations and case studies to cater to practitioners working in the measurement, modelling and design of rooms, semi-enclosed spaces as well as in noise control. It is also invaluable for students and researchers wanting a grounding in acoustic treatment, as well as understanding the latest developments.

All chapters have been revised and brought up to date in this new edition, with new applications, absorbers and diffusers featured. Sustainability, portable vocal booths, and fast time domain models for diffusers are just a few of the new sections. Improved techniques for measurement and prediction are included, as well as bringing old methods up-to-date with the latest refinements from standards and research. Most of the prediction methods in the book are now linked to open source implementations and downloadable MATLAB scripts, enabling readers to exploit the knowledge in this book more readily in design and research.

Recenzijas

"This revised edition consolidates the research and theory of acoustic materials known to date and will be a valuable resource for acoustic researchers, consultants and acoustic product manufacturers. I would also expect acoustic standards committee members to find useful information If you have an earlier edition, as I do, there is sufficient new material in this edition to recommend purchasing this reference volume." Noise Control Engr. J.

"This book is a vibrant update of previous editions which incorporates the latest 21st century thinking on absorbers and diffusers and as such it should be in every acousticians possession." Raf Orlowski, Ramboll Environ

"A valuable treatise in filling a great need to provide the essential basis for anyone who is or may be involved in architectural acoustics research, study, education and design practice." Ning Xiang, Rensselaer Polytechnic Institute

"The current edition is a must-have in any acousticians library. Even if you own an earlier edition, the updates and cosmetic reworking of the third edition breathes new life into this now-classic text."

-- Brandon Cudequest, Journal Audio Engineering

"Cox and DAntonio can still claim authorship to the most comprehensive text on sound-absorptive and diffusive materials."

-- Brandon Cudequest, Journal Audio Engineering

List of figures xv
List of symbols xxxix
List of acronyms xliii
Preface to the first edition xlv
Preface to the second edition xlix
Preface to the third edition li
Acknowledgements liii
Authors lv
1 Introduction 1(10)
1.1 Absorption versus diffuse reflections
4(1)
1.2 Sustainable absorbers and diffusers
5(5)
References
10(1)
2 Absorbers: applications and basic principles 11(30)
2.1 Types of absorber
11(1)
2.2 Reverberation control
12(8)
2.2.1 A statistical model of reverberation
17(3)
2.3 Noise control in factories and large rooms with diffuse fields
20(2)
2.4 Modal control in critical listening spaces
22(1)
2.5 Echo control in auditoria and lecture theatres—basic sound propagation models
23(6)
2.5.1 Sound propagation—a wave approach
24(1)
2.5.2 Surface impedance, admittance, reflection coefficient, and absorption coefficient
25(4)
2.6 Absorption in sound insulation—transfer matrix modelling
29(2)
2.6.1 Transfer matrix modelling
29(2)
2.7 Pipes, ducts, and silencers—porous absorber characteristics
31(2)
2.7.1 Characterizing porous absorbers
32(1)
2.8 Enclosures, barriers, and roads
33(1)
2.9 Natural noise control
34(1)
2.10 Hearing protection devices
35(1)
2.11 Loudspeaker cabinets
36(1)
2.12 Automotive absorbents and vehicle refinement
36(1)
2.13 Portable vocal booths
37(2)
2.14 Summary
39(1)
References
40(1)
3 Diffusers: applications and basic principles 41(50)
3.1 Echo control in auditoria
41(9)
3.1.1 Example applications
41(3)
3.1.2 Aesthetics
44(1)
3.1.3 Wavefronts and diffuse reflections
44(5)
3.1.4 Some terminology
49(1)
3.2 Reducing coloration in small reproduction rooms
50(9)
3.2.1 Reflection free zone
51(6)
3.2.2 Surround sound
57(1)
3.2.3 Ambechoic
58(1)
3.3 Reducing coloration in small live rooms
59(5)
3.4 Promoting diffuse fields in reverberation chambers
64(2)
3.5 Improving speech intelligibility
66(1)
3.6 Promoting spaciousness in auditoria
66(1)
3.7 Reducing the effects of early arriving reflections in large spaces
67(1)
3.8 Stage enclosures
68(10)
3.8.1 Overhead canopies
69(3)
3.8.2 Rear and side of stage enclosures
72(5)
3.8.3 Orchestra pits
77(1)
3.8.4 Outdoor stage shells
77(1)
3.9 Blurring the focusing from concave surfaces
78(1)
3.10 In audience areas
79(5)
3.10.1 Coverage
79(2)
3.10.2 Diffuse fields
81(3)
3.11 Diffusing and absorbing lighting
84(2)
3.12 Barriers and streets
86(1)
3.13 Conclusions
86(1)
References
87(4)
4 Measurement of absorber properties 91(40)
4.1 Impedance tube measurement for absorption coefficient and surface impedance
91(9)
4.1.1 Transfer function method
94(3)
4.1.2 Least mean square method
97(1)
4.1.3 Transmission measurements
97(3)
4.2 Two-microphone free field measurement
100(3)
4.2.1 Multimicrophone techniques for nonisotropic, nonplanar surfaces
101(1)
4.2.2 Multimicrophone free field measurement for periodic surfaces
102(1)
4.3 Reverberation chamber method
103(7)
4.3.1 Measurement of seating absorption
108(2)
4.4 In situ measurement of absorptive properties
110(4)
4.5 Measurement of internal properties of porous absorbents
114(12)
4.5.1 Measurement of flow resistivity
115(3)
4.5.2 Measurement of flow impedance
118(1)
4.5.3 Measurement of wavenumber and characteristic impedance
119(2)
4.5.4 Measurement of porosity
121(2)
4.5.5 Measurement of tortuosity
123(2)
4.5.6 Measurement of characteristic lengths
125(1)
4.5.7 Inverse methods for multiple material parameters
126(1)
4.6 Summary
126(1)
References
127(4)
5 Measurement of reflections: scattering and diffusion 131(44)
5.1 Diffusion coefficients vs scattering coefficients
131(3)
5.2 The diffusion coefficient
134(20)
5.2.1 Measuring polar responses
135(15)
5.2.1.1 Near and far fields
145(4)
5.2.1.2 Sample considerations
149(1)
5.2.2 Calculating the diffusion coefficient
150(3)
5.2.3 Obtaining polar responses
153(1)
5.2.4 Discussion
153(1)
5.2.5 Diffusion coefficient table
153(1)
5.3 The scattering coefficient
154(12)
5.3.1 Principle
155(1)
5.3.2 Rationale and procedure
156(2)
5.3.3 Sample considerations
158(1)
5.3.4 In situ measurement
159(1)
5.3.5 Predicting the scattering coefficient
160(2)
5.3.6 The correlation scattering coefficient (from polar responses)
162(3)
5.3.7 Scattering coefficient table
165(1)
5.4 Other methods for characterizing diffuse reflections
166(5)
5.4.1 Measuring scattering coefficients by solving the inverse problem
166(1)
5.4.2 Temporal evaluation
167(4)
5.5 Summary
171(1)
References
171(4)
6 Porous sound absorption 175(50)
6.1 Absorption mechanisms and characteristics
175(3)
6.2 Some material types
178(10)
6.2.1 Mineral wool
178(2)
6.2.2 Foam
180(1)
6.2.3 Sustainable materials
180(3)
6.2.4 Curtains (drapes)
183(1)
6.2.5 Carpets
184(1)
6.2.6 Acoustic plaster
185(1)
6.2.7 Aerogels
186(1)
6.2.8 Activated carbon
186(2)
6.2.9 Ground
188(1)
6.3 Covers
188(3)
6.4 Basic material properties
191(6)
6.4.1 Flow resistivity
191(3)
6.4.2 Open porosity
194(3)
6.5 Modelling propagation within porous materials
197(13)
6.5.1 Macroscopic empirical models such as Delany and Baxley
197(5)
6.5.2 Further material properties
202(2)
6.5.2.1 Viscous and thermal characteristic lengths
202(1)
6.5.2.2 Tortuosity
203(1)
6.5.3 Semi-phenomenological models
204(5)
6.5.4 Relaxation model
209(1)
6.6 Predicting the surface impedance and absorption coefficient
210(6)
6.6.1 Single layer of a porous absorber with a rigid backing
211(1)
6.6.2 Modelling covers
212(1)
6.6.3 Ground
213(2)
6.6.4 Multilayer porous absorbers
215(1)
6.7 Local and extended reaction
216(1)
6.8 Oblique incidence
216(2)
6.9 Biot theory for elastic framed material
218(1)
6.10 Time domain models
219(1)
6.11 Summary
219(1)
References
219(6)
7 Resonant absorbers 225(40)
7.1 Mechanisms
225(2)
7.2 Example constructions
227(12)
7.2.1 Low-frequency membrane absorber
227(2)
7.2.2 Absorbing wood
229(2)
7.2.3 Absorption and diffusion
231(4)
7.2.4 Micro perforation
235(1)
7.2.5 Clear absorbers
236(3)
7.2.6 Masonry devices
239(1)
7.2.7 Plate resonators
239(1)
7.3 Design equations: resonant frequency
239(14)
7.3.1 Helmholtz resonator
241(5)
7.3.2 Membrane absorber
246(1)
7.3.3 Losses
247(6)
7.3.3.1 Porous layer right behind perforations
249(1)
7.3.3.2 Porous layer in the middle of cavity with a perforated covering
249(1)
7.3.3.3 More complete solution using transfer matrixes
250(2)
7.3.3.4 Oblique incidence
252(1)
7.4 Example calculations
253(2)
7.4.1 Slotted Helmholtz absorber
253(1)
7.4.2 Porous absorbent filling the cavity
254(1)
7.4.3 Bass Helmholtz absorber
255(1)
7.5 Other constructions and innovations
255(7)
7.5.1 Shaped holes and slots
255(1)
7.5.2 Double resonators
256(1)
7.5.3 Micro perforation
256(4)
7.5.4 Lateral orifices
260(1)
7.5.5 Passive electroacoustic absorption
260(1)
7.5.6 Activated carbon
261(1)
7.6 Summary
262(1)
References
262(3)
8 Other absorbers and diffusers 265(26)
8.1 Audience and seating
265(3)
8.2 Absorbers from Schroeder diffusers
268(11)
8.2.1 Energy flow mechanism
269(1)
8.2.2 Boundary layer absorption
270(1)
8.2.3 Absorption or diffusion
271(1)
8.2.4 Depth sequence
272(1)
8.2.5 Use of mass elements
273(1)
8.2.6 Number of wells
274(1)
8.2.7 Theoretical model
274(11)
8.2.7.1 Admittance of wells
274(2)
8.2.7.2 From well impedance to absorption: BEM
276(1)
8.2.7.3 From well impedance to absorption: wave decomposition
277(2)
8.3 Volumetric diffusers
279(2)
8.4 Metamaterials and absorbing sonic crystals
281(4)
8.5 Natural absorbers
285(3)
8.5.1 Tree belts, hedges, shrubs, and crops
285(1)
8.5.2 Green walls, roofs, and barriers
286(2)
8.6 Summary
288(1)
References
288(3)
9 Prediction of reflection including diffraction 291(40)
9.1 Boundary element methods
291(14)
9.1.1 The Helmholtz—Kirchhoff integral equation
292(2)
9.1.2 General solution method
294(4)
9.1.2.1 Determining surface pressures
294(2)
9.1.2.2 Determining external point pressures
296(1)
9.1.2.3 2D versus 3D
297(1)
9.1.3 Thin-panel solution
298(3)
9.1.3.1 Non-absorbing surface
298(2)
9.1.3.2 Planar, thin surface with non-zero admittance
300(1)
9.1.4 Acceleration schemes
301(1)
9.1.5 BEM accuracy: thin rigid reflectors
301(1)
9.1.6 BEM accuracy: Schroeder diffusers
302(2)
9.1.7 BEM accuracy: hybrid surfaces
304(1)
9.2 Kirchhoff
305(3)
9.3 Fresnel
308(2)
9.4 Fraunhofer or Fourier solution
310(3)
9.4.1 Near and far field
311(1)
9.4.2 Fraunhofer theory accuracy
312(1)
9.5 Finite difference time domain
313(9)
9.5.1 Stability: spatial and time steps
317(1)
9.5.2 Numerical dispersion and simulation bandwidth
318(1)
9.5.3 Boundary modelling and including objects in domain
318(2)
9.5.4 Excitation
320(2)
9.5.5 Near to far field transformation
322(1)
9.5.6 Realization
322(1)
9.6 Time-domain boundary integral methods
322(3)
9.6.1 Kirchhoff and Fraunhofer solutions
323(1)
9.6.2 BEM solution
324(1)
9.7 Other methods
325(2)
9.7.1 Finite element analysis
325(1)
9.7.2 Edge diffraction models
325(1)
9.7.3 Wave decomposition and mode matching approaches
326(1)
9.7.4 Random roughness
326(1)
9.7.5 Boss models
327(1)
9.8 Summary
327(1)
References
327(4)
10 Schroeder diffusers 331(42)
10.1 Basic principles and construction
331(2)
10.2 Design equations
333(1)
10.3 Some limitations and other considerations
334(3)
10.4 Sequences
337(8)
10.4.1 Maximum length sequence diffuser
337(3)
10.4.2 Quadratic residue sequence
340(1)
10.4.3 Primitive root sequence
340(3)
10.4.4 Index sequences
343(1)
10.4.5 Other sequences
343(2)
10.5 Periodicity and modulation
345(10)
10.5.1 Fractal
352(1)
10.5.2 Diffusing covers
352(3)
10.6 Improving the low-frequency response
355(3)
10.7 Multidimensional devices
358(4)
10.8 Absorption
362(1)
10.9 Do the simplest theories work?
363(2)
10.10 Optimization
365(5)
10.10.1 Process
365(3)
10.10.2 Results
368(2)
10.11 Summary
370(1)
References
370(3)
11 Geometric reflectors and diffusers 373(42)
11.1 Plane surfaces
373(9)
11.1.1 Single-panel response
373(6)
11.1.2 Panel array response: far field arc
379(1)
11.1.3 Panel array response: near field
380(2)
11.2 Triangles and pyramids
382(5)
11.2.1 Arrays of triangles
385(2)
11.3 Concave surfaces
387(2)
11.4 Convex surfaces
389(7)
11.4.1 Geometric theory and cutoff frequencies
390(2)
11.4.2 Performance of simple curved reflectors
392(4)
11.4.2.1 Arrays of semicylinders
393(3)
11.5 Optimized curved surfaces
396(11)
11.5.1 Example application
396(1)
11.5.2 Design process
396(3)
11.5.3 Performance for unbaffled single optimized diffusers
399(1)
11.5.4 Periodicity and modulation
400(3)
11.5.5 Stage canopies
403(4)
11.6 Fractals
407(4)
11.6.1 Fourier synthesis
408(1)
11.6.2 Step function addition
409(2)
11.7 Materials
411(1)
11.8 Summary
412(1)
References
412(3)
12 Hybrid surfaces 415(26)
12.1 Example devices
415(4)
12.2 Concepts
419(1)
12.3 Number sequences
420(10)
12.3.1 One-dimensional MLS
420(2)
12.3.2 One-dimensional optical sequences
422(1)
12.3.3 One-dimensional ternary and quadriphase sequences
423(1)
12.3.4 Optimized sequences
424(2)
12.3.5 Two-dimensional sequences
426(4)
12.4 Absorption
430(1)
12.5 Accuracy of the Fourier theory
431(2)
12.6 Diffuse reflections
433(6)
12.6.1 Boundary element modelling
435(2)
12.6.2 Planar devices
437(2)
12.7 Summary
439(1)
References
439(2)
13 Absorbers and diffusers in rooms and geometric room acoustic models 441(18)
13.1 Converting absorption coefficients
441(4)
13.1.1 From impedance tube or free field to random incidence
441(4)
13.1.2 From the reverberation chamber to real rooms
445(1)
13.2 Absorption in GRAMs
445(2)
13.3 Diffuse reflections in GRAMs
447(8)
13.3.1 Ray redirection
448(1)
13.3.2 Transition order using particle tracing
449(1)
13.3.3 Diffuse energy decays with the reverberation time of the hall
449(1)
13.3.4 Radiosity and radiant exchange
450(1)
13.3.5 Early sound field wave model
450(1)
13.3.6 Edge scattering for small surfaces
450(1)
13.3.7 Distributing the diffuse energy
450(3)
13.3.8 Scattering coefficients
453(2)
13.4 Summary
455(1)
References
456(3)
14 Active absorbers 459(16)
14.1 Some principles of active control
459(2)
14.2 An example active impedance system and a general overview
461(3)
14.3 Active absorption in ducts
464(1)
14.4 Active absorption in three dimensions
465(4)
14.4.1 Low-frequency modal control—example results
466(1)
14.4.2 Low-frequency modal control—alternative control regime
467(2)
14.5 Hybrid active—passive absorption
469(4)
14.6 Summary
473(1)
References
473(2)
Appendix A: Table of absorption coefficients 475(6)
Appendix B: Normalized diffusion coefficient table 481(6)
Appendix C: Correlation scattering coefficient tables 487(10)
Appendix D: Random incidence scattering coefficient table 497(6)
Index 503
Trevor Cox is Professor of Acoustic Engineering at the University of Salford, and a past president of the UKs Institute of Acoustics (IOA). He was award the IOAs Tyndall Medal in 2004. Trevor has a long track record of communicating acoustic engineering to the public and is a regular popular lecturer and broadcaster.

Peter DAntonio is chairman of RPG Diffusor Systems, Inc, and has also worked at the Naval Research Lab in Washington, D.C. and as a musician and recording engineer. He has served as Chairman of the Working Group for the Characterization of Acoustical Materials of the AES Subcommittee on Acoustics and is a member of the ISO Working Group for the Measurement of the random-incidence scattering coefficient of surfaces.
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