1 Introduction.- 1.1 Current Situation of Wind Energy and Perspectives.- 1.2 Advantages of Wind Energy.- 1.3 Current Problems of Wind Energy.- 1.4 Road Map of the Book.- 2 Noise and its Effects.- 2.1 Sound and Noise.- 2.2 Definitions.- 2.3 Noise Regulations.- 3 Introduction to Aeroacoustics.- 3.1 Introduction.- 3.2 Definitions.- 3.3 The Linear Wave Equation.- 3.4 Elementary Solutions of the Wave Equation.- 3.5 Lighthill's Acoustic Analogy.- 3.6 The Influence of Boundaries.- 3.7 Application of Aeroacoustic Theory.- 3.8 Conclusions.- 4 Noise Mechanisms of Wind Turbines.- 4.1 Classification of Noise Mechanisms.- 4.2 Low-Frequency Noise.- 4.3 Inflow-Turbulence Noise.- 4.4 Airfoil Self-Noise.- 4.5 Summary.- 5 Noise Prediction.- 5.1 Introduction.- 5.2 Low-Frequency Noise.- 5.3 High-Frequency Noise.- 5.4 Summary.- 6 Noise Propagation.- 6.1 Introduction.- 6.2 Mechanisms.- 6.3 Prediction.- 6.4 Results.- 6.5 Summary.- 7 Measurement of Noise and Flow Field.- 7.1 Acoustic Measurement in the Wind Tunnel.- 7.2 Acoustic Measurements on Operating Turbines.- 7.3 Flow Visualization on Operating Turbines.- 8 Noise Reduction.- 8.1 Introduction.- 8.2 Reduction of Tip Speed and Angle of Attack.- 8.3 Reduction of Trailing-Edge Noise.- 8.4 Reduction of Tip Noise.- 8.5 Reduction of Inflow-Turbulence Noise.- 8.6 Reduction of Blunt-Trailing-Edge Noise.- 8.7 Conclusions.- 9 Future Work.- 10 References.- 10.1 Recommended References.- 10.2 List of References.- Annex: Description of Tip Planform Shapes.