Acoustic measurements in the area of wind turbines are challenging on different levels. Even before the actual measurement begins, a suitable measurement location with low extraneous noise (e.g. from traffic or agriculture) has to be found. In addition, agreements have to be made with operators and landowners, whose help is needed for successful measurements over long distances and over a long period of time. From a technical point of view, the acoustical investigation of a complex source in the open field, under undefined measurement conditions, and partly under strong wind conditions is difficult. High wind speeds are necessary in order to achieve a high sound power level of the wind turbine. At the same time, however, this leads to additional sources such as wind-induced noises at the microphone or wind-induced noise from vegetation. The greatest challenge for acoustic measurements in the surrounding area of wind turbines is therefore a sufficiently high signal-to-noise ratio between wind turbine and background noise. A significant improvement of the signal-to-noise ratio can be achieved by reducing the wind-induced noise at the microphone.

In this contribution, the various challenges of acoustic measurements on wind turbines are presented and suitable solutions are discussed. The focus of this work is on the reduction of wind-induced noise at the microphone by using secondary windscreens. On the basis of measurements, various secondary windscreens are compared with regard to their acoustic properties and their reduction of excess noise. A recommendation for an optimal secondary windscreen is given. The efficiency of such a windscreen is demonstrated with field tests.