Previous studies  have shown that the noise has more low-frequency content, when wind turbines get larger, and with todays’ megawatt turbines the low-frequency noise may cause annoyance for the neighbours. Therefore, low-frequency noise has been included in the noise regulations on wind turbines in Denmark. In this study, the data material has been increased to include more data on noise from modern production turbines up to 3.6 MW. In addition, the new Danish regulations are assessed. The previous result that the relative amount of low-frequency noise is higher for large turbines (> 2 MW) than for small turbines (≤ 2 MW) is confirmed. Due to the air absorption, the higher low-frequency content becomes even more pronounced, when sound pressure levels in relevant neighbour distances are considered. Even when A-weighted levels are considered, a substantial part of the noise is at low frequencies, and for several of the investigated large turbines, the one-third-octave band with the highest level is at or below 250 Hz. It is thus beyond any doubt that the low-frequency part of the spectrum plays an important role in the noise at the neighbours. The new Danish regulations are based on calculations of the indoor noise at the neighbours, but unfortunately, the calculation underestimates the level that would be measured, thus the regulation does not adequately prevent potential annoyance and sleep disturbance effects from future wind turbines in Denmark.
15th International Meeting on Low Frequency Noise and Vibration and Its Control, Stratford upon Avon, UK, 22nd–24th May 2012
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