Measures Against Mechanical Noise from Large Wind Turbines: A Design Guide

摘要

The noise generated by the machinery of the two Swedish prototypes contains puretones which are very important with respect to the environmental impact. A discussion of the results of noise measurements carried out at these turbines, that are meant to be used as a guide as to how to predict and control the noise around a large wind turbine during the design stage, is presented. The design targets are discussed, stressing the importance of the audibility of pure tones and not only the annoyance; a simple criterion is cited. The main noise source is the gearbox and a simple empirical expression for the sound power level is shown to give good agreement with the measurement results. The influence of the noise of the gearbox design is discussed in some detail. Formulas for the prediction of the airborne sound transmission to the ground outside the nacelle are presented, together with a number of empirical data on the sound reduction indices for single and double constructions. The structure-borne noise transmission is discussed.