Wind Farm Noise

Professor Colin Hansen has been consulting, researching and teaching in the field of noise and vibration for 40 years. He has authored or co-authored eleven books, edited two books, and contributed seven chapters to various other books. His current research is focused on the generation, assessment and control of wind farm noise, on which he has been working since 2010 and for which he has been funded by the Australian Research Council. He is an Honorary Fellow and past-president of the International Institute of Acoustics and Vibration, a Fellow of the Australian Acoustical Society and a Fellow of Engineers Australia. He was awarded the 2009 Rayleigh Medal by the British institute of Acoustics for outstanding contributions to acoustics, the 2013 A.G.M. Michell medal by Engineers Australia for outstanding service to the discipline of Mechanical Engineering and the 2014 Rossing Prize in Acoustics Education by the Acoustical Society of America. AssociateProfessor Doolan has an Honours Degree in Mechanical Engineering and a PhD in Aerospace Engineering from the University of Queensland.  He has over 20 years experience in research and development, teaching and consulting, with over 150 technical publications.  His research interests focus upon compressible flow, which includes the area of aeroacoustics - the science of how fluid flow creates sound - with the aim to control noise from modern technologies such as aircraft, wind turbines and submarines.  Associate Professor Doolan has been involved for many years in the understanding and control of wind turbine noise, with funding from the Australian Research Council to perform aeroacoustic testing of scaled turbines in wind tunnels. Dr Kristy Hansen completed an Honours Degree in Mechanical Engineering and a PhD in Aerodynamics/Fluid Mechanics at the University of Adelaide. She spent 3 years working on an Australian Research Council funded grant investigating the impact of wind farm noise on rural communities. This work involved collection of an extensive data set which resulted from simultaneous measurements of noise, vibration and meteorological data at rural locations near different wind farms. Results from the analysis of these data have been presented in a number of peer-reviewed journals and conference papers. She is continuing her research on wind farm noise as part of her current employment at Flinders University.

Wiley Series in Acoustics, Noise and Vibration xv

Preface xvii

1 Wind Energy and Noise 1

1.1 Introduction 1

1.2 Development of the Wind Energy Industry 2

1.3 History of Wind Turbine Noise Studies 13

1.4 Current Wind Farm Noise Guidelines and Assessment Procedures 18

1.5 Wind Farm Noise Standards 29

1.6 Regulations 32

1.7 Inquiries and Government Investigations 43

1.8 Current Consensus on Wind Farm Noise 52

References 52

2 Fundamentals of Acoustics and Frequency Analysis 57

2.1 Introduction 57

2.2 Basic Acoustics Concepts 57

2.3 Basic Frequency Analysis 79

2.4 Advanced Frequency Analysis 88

2.5 Summary 117

References 117

3 Noise Generation 119

3.1 Introduction 119

3.2 Aeroacoustics 122

3.3 Aerodynamic Noise Generation on Wind Turbines 128

3.4 Aero-elasticity and Noise 148

3.5 Other Noise Sources 149

3.6 Summary and Outlook 151

References 152

4 Wind Turbine Sound Power Estimation 157

4.1 Introduction 157

4.2 Aerodynamic Noise Prediction 157

4.3 Simple Models 158

4.4 Semi-empirical Methods (Class II Models) 159

4.5 Computational Methods (Class III Models) 168

4.6 Estimations of Sound Power From Measurements 169

4.7 Summary 177

References 177

5 Propagation of Noise and Vibration 180

5.1 Introduction 180

5.2 Principles Underpinning Noise Propagation Modelling 182

5.3 Simplest Noise Propagation Models 212

5.4 Danish Low-frequency Propagation Model 213

5.5 Concawe (1981) 214

5.6 ISO9613-2 (1996) Noise Propagation Model 223

5.7 NMPB-2008 Noise Propagation Model 231

5.8 Nord2000 Noise Propagation Model 242

5.9 Harmonoise (2002) Noise Propagation Engineering Model 260

5.10 Required Input Data for the Various Propagation Models 269/

5.11 Offshore Wind Farm Propagation Models 272

5.12 Propagation Model Prediction Uncertainty 272

5.13 Outside versus Inside Noise at Residences 276

5.14 Vibration Propagation 280

5.15 Summary 283

References 285

6 Measurement 289

6.1 Introduction 289

6.2 Measurement of Environmental Noise Near Wind Farms 290

6.3 Vibration 393

6.4 Wind, Wind Shear and Turbulence 395

6.5 Reporting on Noise, Vibration and Meteorological Conditions 405

6.6 Wind Tunnel Testing 408

6.7 Conclusions 425

References 425

7 Effects of Wind Farm Noise and Vibration on People 436

7.1 Introduction 436

7.2 Annoyance and Adverse Health Effects 441

7.3 Hearing Mechanism 455

7.4 Reproduction of Wind Farm Noise for Adverse Effects Studies 465

7.5 Vibration Effects 467

7.6 Nocebo Effect 467

7.7 Summary and Conclusion 468

References 470

8 Wind Farm Noise Control 476

8.1 Introduction 476

8.2 Noise Control by Turbine Design Modification 477

8.3 Optimisation of Turbine Layout 487

8.4 Options for Noise Control at the Residences 488

8.5 Administrative Controls 492

8.6 Summary 493

References 493

9 Recommendations for Future Research 496

9.1 Introduction 496

9.2 Further Investigation of the Effects of Wind Farm Noise on People 497

9.3 Improvements to Regulations and Guidelines 499

9.4 Propagation Model Improvements 504

9.5 Identification and Amelioration of the Problem Noise Sources on Wind Turbines 504

9.6 Reducing Low-frequency Noise Levels in Residences 506

References 506

A Basic Mathematics 507

A.1 Introduction 507

A.2 Logarithms 507

A.3 Complex Numbers 508

A.4 Exponential Function 508

B The BPM model 509

B.1 Boundary-layer Parameters 509

B.2 Turbulent Trailing-edge Noise Model 511

B.3 Blunt Trailing-edge Noise Model 513

Reference 515

C Ground Reflection coefficient calculations 516

C.1 Introduction 516

C.2 Flow Resistivity 517

C.3 Characteristic Impedance 518

C.4 Plane-wave Reflection Coefficient 520

C.5 Spherical-wave Reflection Coefficient 521

C.6 Incoherent Reflection Coefficient 524

References 525

D Calculation of Ray Path Distances and Propagation Times for the Nord2000 Model 526

D.1 Introduction 526

D.2 Equivalent Linear Atmospheric Vertical Sound-speed Profile 527

D.3 Calculation of Ray Path Lengths and Propagation Times 529

References 532

E Calculation of Terrain Parameters for the Nord2000 Sound Propagation Model 534

E.1 Introduction 534

E.2 Terrain Effects 534

E.3 Approximating Terrain Profiles by Straight-line Segments 539

E.4 Calculation of the Excess Attenuation due to the Ground Effect for Relatively Flat Terrain with no Diffraction Edges 540

E.5 Calculation of the Excess Attenuation due to the Ground Effect for Relatively Flat Terrain with a Variable Impedance Surface and no Diffraction Edges 541

E.6 Calculation of the Excess Attenuation due to the Ground Effect for Valley-shaped Terrain 543

E.7 Identification of the Two Most Efficient Diffraction Edges 544

E.8 Calculation of the Sound Pressure at the Receiver for each Diffracted Path in Hilly Terrain 547

E.9 Calculation of the Combined Ground and Barrier Excess-attenuation Effects 556

References 563

F Calculation of Fresnel Zone Sizes and Weights 564

F.1 Introduction 564

F.2 Fresnel Zone for Reflection from Flat Ground 564

F.3 Fresnel Weights for Reflection from a Concave or Transition Ground Segment 567

F.4 Fresnel Weights for Reflection from a Convex Ground Segment 570

Reference 571

G Calculation of Diffraction and Ground Effects for the Harmonoise Model 572

G.1 Introduction 572

G.2 diffraction Effect, ΔL d 574

G.3 Ground Effect 577

G.4 Fresnel Zone for Reflection from a Ground Segment 584

References 587

H Active Noise-control System Algorithms 588

H.1 Introduction 588

H.2 Single-input, Single-output (SISO) Weight Update Algorithm 588

H.3 Multiple-input, Multiple-output Weight Update Algorithm 590

References 592

Index 593