The sounds of high winds

IV.8 Comparison of emission and immission sound levels 51
IV.9 Atmospheric stability and Pasquill class 52
IV.10 Additional measurements 53
IV.10.1 Measured and calculated immission sound levels 54
IV.10.2 Immission level increase due to inversion layer? 58
IV.11 Conclusion 59
V
VI
THE BEAT IS GETTING STRONGER:
low frequency modulated wind turbine sound 61
V.1 Effects of atmospheric stability 61
V.2 Measurement results 66
V.2.1 Locations 66
V.2.2 Frequency response of instruments 67
V.2.3 Measured emission and immission spectra 68
V.2.4 Beats caused by interaction of several wind turbines 74
V.2.5 Summary of results 78
V.3 Perception of wind turbine sound 80
V.4 Conclusion 84
STRONG WINDS BLOW UPON TALL TURBINES:
wind statistics below 200 m altitude 87
VI.1 Atmospheric stability in wind energy research 87
VI.2 The Cabauw site and available data 87
VI.3 Reference conditions 88
VI.4 Results: wind shear and stability 90
VI.4.1 Wind velocity shear 90
VI.4.2 Shear and ground heat flux 94
VI.4.3 Wind direction shear 95
VI.4.4 Prevalence of stability 96
VI.5. Results: effects on wind turbine performance 97
VI.5.1 Effect on power production 97
VI.5.2 Effect on sound production 99
VI.6 Other onshore results 102
VI.7 Conclusion 104
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