Although there is a growing interest in the use of wind energy, noise from wind turbines represents a major obstacle to greater uptake. The main aim of the SIROCCO project was to reduce by three to six decibels the aerodynamic noise from the turbines' rotating blades. Researchers achieved considerable reduction in noise levels without any corresponding loss of power performance. Improvements were made by applying a new approach which combined aerodynamic and acoustic design techniques. The work undertaken was based on the earlier EU funded DATA project, which designed acoustic blades for a model turbine in a wind tunnel. The intention of the SIROCCO project was to extend this work to a full-size turbine. The turbine's performance was validated using a new measurement technique, which was capable of localising and quantifying noise sources from a rotating blade. The SIROCCO project aimed to lower the level of noise originating from wind turbines by improving the aerodynamic flow at the trailing edge of the blades. A significant reduction in noise levels would result in greater public acceptance of wind energy. Calculations of aerodynamics and for predicting noise were improved as a result of detailed experiments on boundary layers. This is the layer of air immediately next to the blade. These improvements greatly improved the ability of researchers to accurately predict the level of noise generated by the airfoils trailing edge. The airfoil is the shape of the blade in cross section and its aerodynamic and aeroacoustic properties were verified in a wind tunnel. The work carried out by the SIROCCO project has enabled silent, high performance airfoil sections to be developed for the wind turbine industry.