Wind turbine noise measurement: an efficient and reliable method for extracting the wind turbine noise out of the background noise

摘要

Wind turbines are mostly implanted in the countryside where the background noise is usually low and at typical distances of 350 to 500 meters from the nearest neighboring dwellings. As a result, their specific noise is about the level of the background noise (typically 35 to 50 dBA) and as such difficult to extract from it. However one can take advantage of the typical wind turbine sound modulation. The method consists first in measuring and storing the time history of the short LAeq(1s) every second in continuous over the period of investigation (typically not less than 1 month if a statistical figure is to be obtained). Then the diagram of occurrences (step 0.5 dB) of these LAeq(1s) is to be plotted for each consecutive period of 10 minutes. On each graph the specific contribution of the wind turbine noise appears out of the background noise, as a group of five consecutive bands that correspond to the typical 2 to 3 dB wind turbine sound modulation. The wind turbine noise over the 10 minutes period is then the value of the fourth band. This method has been applied and validated on 5 different sites during more than 500 measuring days in continuous.