Wind Farm Noise Measurement, Assessment, and Control

A comprehensive guide to wind farm noise prediction, measurement, assessment, control and effects on people

Wind Farm Noise covers all aspects associated with the generation, measurement, propagation, regulation and adverse health effects of noise produced by large horizontal-axis wind turbines of the type used in wind farms.

The book begins with a brief history of wind turbine development and the regulation of their noise at sensitive receivers. Also included is an introductory chapter on the fundamentals of acoustics relevant to wind turbine noise so that readers are well prepared for understanding later chapters on noise measurements, noise generation mechanisms, noise propagation modelling and the assessment of the noise at surrounding residences.

Key features:

• Potential adverse health effects of wind farm noise are discussed in an objective way.
• Means for calculating the noise at residences due to a wind farm prior to construction are covered in detail along with uncertainty estimates.
• The effects of meteorological conditions and other influences, such as obstacles, ground cover and atmospheric absorption, on noise levels at residences are explained.
• Quantities that should be measured as well as how to best measure them in order to properly characterise wind farm noise are discussed in detail.
• Noise generation mechanisms and possible means for their control are discussed as well as aspects of wind farm noise that still require further research to be properly understood.

The book provides comprehensive coverage of the topic, containing both introductory and advanced level material.

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.

Preface xiii

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 30

1.6 Regulations 33

1.7 Enquiries/Government Investigations 44

1.8 Current Consensus on Wind Farm Noise 53

References 55

2 Fundamentals of Acoustics 59

2.1 Introduction 59

2.2 Basic Acoustics Concepts 59

2.3 Basic Frequency Analysis 82

2.4 Advanced Frequency Analysis 89

2.5 Summary 121

References 122

3 Noise Generation 123

3.1 Introduction 123

3.2 Aeroacoustics 125

3.3 Aerodynamic noise generation on wind turbines 131

3.4 Aeroelasticity and Noise 152

3.5 Other Noise Sources 153

3.6 Summary and Outlook 155

References 157

4 Wind Turbine Sound Power Estimation 161

4.1 Introduction 161

4.2 Aerodynamic noise prediction 161

4.3 Simple models 162

4.4 Semi-empirical methods (Class II models) 163

4.5 Computational methods (Class III models) 173

4.6 Estimations of Sound Power From Measurements 174

4.7 Summary 182

References 183

5 Noise propagation 185

5.1 Introduction 185

5.2 Principles Underpinning Noise Propagation Modelling 186

5.3 Simplest Noise Propagation Models 217

5.4 Danish Low-Frequency Propagation Model 219

5.5 CONCAWE (1981) 220

5.6 ISO9613-2 (1996) Noise Propagation Model 229

5.7 NMPB-2008 Noise Propagation Model 238

5.8 Nord2000 Noise Propagation Model 250

5.9 Harmonoise (2002) Noise Propagation Engineering Model 269

5.10 Required Input Data for the Various Propagation Models 277

5.11 Off-Shore Wind Farm Propagation Models 281

5.12 Propagation Model Prediction Uncertainty 281

5.13 Outside vs Inside Noise at Residences 286

5.14 Vibration Propagation 289

5.15 Summary 294

References 295

6 Measurement 299

6.1 Introduction 299

6.2 Measurement of Environmental Noise Near Wind Farms 300

6.3 Vibration 406

6.4 Wind, Wind Shear and Turbulence 408

6.5 Reporting on Noise, Vibration and Meteorological Conditions 417

6.6 Wind Tunnel Testing 423

6.7 Conclusions 439

References 440

7 Effects of wind farm noise and vibration on people 447

7.1 Introduction 447

7.2 Annoyance and Adverse Health Effects 452

7.3 Hearing Mechanism 466

7.4 Reproduction of Wind Farm Noise for Adverse Effects Studies 476

7.5 Vibration Effects 478

7.6 Nocebo Effect 479

7.7 Summary and Conclusion 480

References 482

8 Wind Farm Noise Control 487

8.1 Introduction 487

8.2 Noise Control by Turbine Design Modification 488

8.3 Optimisation of turbine layout 498

8.4 Options for Noise Control at the Residences 499

8.5 Administrative Controls 503

8.6 Summary 504

References 505

9 Where to from here 507

9.1 Introduction 507

9.2 Further Investigation of the Effects of Wind Farm Noise on People 508

9.3 Improvements to Regulations and Guidelines 510

9.4 Propagation Model Improvements 515

9.5 Identification and Amelioration of the Problem Noise Sources on Wind Turbines 516

9.6 Reducing Low-Frequency Noise Levels in Residences 517

References 518

A Basic mathematics 519

A.1 Introduction 519

A.2 Logarithms 519

A.3 Complex Numbers 520

A.4 Exponential Function 520

B The BPM model 521

B.1 Boundary layer parameters 521

B.2 Turbulent trailing edge noise model 523

B.3 Blunt trailing edge noise model 525

References 527

C Ground Reflection Coefficient Calculations 529

C.1 Introduction 529

C.2 Flow Resistivity 530

C.3 Characteristic Impedance 530

C.4 Plane Wave Reflection Coefficient 533

C.5 Spherical Wave Reflection Coefficient 533

C.6 Incoherent Reflection Coefficient 537

References 539

D Calculation of Ray Path Distances and Propagation Times for the Nord2000 Model 541

D.1 Introduction 541

D.2 Equivalent Linear Atmospheric Vertical Sound Speed Profile 542

D.3 Calculation of Ray Path Lengths and Propagation Times 544

D.3.1 Direct ray 544

D.3.2 Reflected ray 546

References 549

E Calculation of Terrain Parameters for the Nord2000 Sound Propagation Model 551

E.1 Introduction 551

E.2 Terrain Effects 551

E.3 Approximating Terrain profiles by Straight Line Segments 556

E.4 Calculation of the Excess Attenuation Due to the Ground Effect for Relatively Flat Terrain with no Diffraction Edges 558

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 559

E.6 Calculation of the Excess Attenuation Due to the Ground Effect for Valley-Shaped Terrain 561

E.7 Identification of the Two Most Efficient Diffraction Edges 561

E.8 Calculation of the Sound Pressure at the Receiver for Each Diffracted Path in Hilly Terrain 564

E.9 Calculation of the Combined Ground and Barrier Excess Attenuation Effects 575

References 583

F Calculation of Fresnel Zone Sizes and Weights 585

F.1 Introduction 585

F.2 Fresnel Zone for Reflection From Flat Ground 585

F.3 Fresnel Weights for Reflection From a Concave or Transition Ground Segment589

F.4 Fresnel Weights for Reflection from a Convex Ground Segment 591

References 592

G Calculation of Diffraction and Ground Effects for the Harmonoise Model 593

G.1 Introduction 593

G.2 Diffraction Effect, _LD 596

G.3 Ground Effect 598

G.3.1 Concave model 600

G.3.2 Transition model 604

G.4 Fresnel Zone for Reflection from a Ground Segment 606

References 610

H Active Noise Control System Algorithms 611

H.1 Introduction 611

References 616

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