This paper develops and validates the first principle based numerical method for predicting the noise radiated from the rotating Horizontal-Axis Wind Turbine (HAWT) blades. The noise radiated to the far-field was predicted by the code based on Ffowcs Williams-Hawkings (FW-H) equation, using both original non-permeable formulation and permeable formulation. A commercially available CFD solver, ANSYS CFX 11.0, was used to calculate the flow parameters on and around the blade surface that are required for FW-H codes. A capability of the solver for modelling the flow field around the wind turbine blades was validated by comparing with the experimental results of NREL phase VI wind turbine blades. The FW-H codes were validated using acoustic results of UH-1H helicopter rotor in hover and Hartzell aircraft propeller in forward motion, which were measured in anechoic wind tunnel facility. Then the developed FW-H acoustic codes were applied to calculate the noise radiated from NREL Phase VI wind turbine blades. (C) 2010 Elsevier Ltd. All rights reserved.