Wind turbines - a study on the correlation between rotor size and noise characteristics

Wind power is a massively increasing energy source in the European Union, due to the 2020 goals that 20% of EU:s energy flow has to originate from renewable sources. Big wind turbines produce low frequency noise, which is a growing problem as the rapid technical development leads to larger and larger turbine. This master thesis aims to examine the frequency distribution of the noise emitted from wind turbines of different sizes with the ultimate goal to establish trends. Using sound recordings from Vestas V27, V42 and V90 turbines, the noise is divided into octave bands using MATLAB to study the amount of low frequency noise. Due to a lack of accessibility to turbine sites, some site observed in the study suffer from a large amount of nearby noise pollution. However, a change in sound level in the region of the 63 to 250 Hz one-third octave bands is shown when comparing the V90 turbine data to the smaller sizes, correlating well with previous research in the field, but more research and measurements are needed to explain the occurrence on a more detailed level