The Results of the Measurements and Analyses of Impact of Wind Farms on Acoustic Climate

Noise emitted to environment is one of the basic factors connected with wind farm operation. That is the reason why each wind farm localization should be analysed to assess the impact on environment considering noise. At the stage of the project, the prognosis of localization results considering emitted noise may be only predicted theoretically, mostly by computer simulation. The existing farm can be assessed by performing local measurements. Conducting local measurements of wind farms, minding the specificity of their work, requires generally applied and suggested modifications of noise measuring methods. The basic problem while carrying out noise measurements is choosing the proper wind speed, which should not exceed 5 m/s at the height of measurement point (usually 4 m). In the article there are presented examples of own local measurements conducted at more than 5 big wind farms. It was proved that at the distance of more than 500 m from the farm, lots of results of measurements are comparable to measurements of existing acoustic background. For cases when noise measurement results, including background noise, were unrecognizable when compared with only acoustic background and the values were lower than permissible level in the measurement point, some interpretations of such situations were suggested. In the article, there has been made an attempt to assess measured levels of equivalent sound level regarding admissible levels of audible noise applicable in various countries in the world. Local measurements were carried out according to Polish measurement methodology. That is why, for comparison, there have been chosen only those countries in which admissible level of noise is defined by index A - which is an equivalent sound level. Indices dependent on wind speed - which are used in Denmark or Canada (Ontario) for example, were not considered. To get complex info about noise emission of analyzed windfarm it is suggested to conduct measurements in a year period for example in four following seasons. Then we can get results for different weather conditions. and especially for different directions and speeds of wind. Conducting such measurements four times a year give us greater probability of making measurements at wind speed equal or close to maximum levels of acoustic power of turbines. Applying this rule we can get wilder material for analysis which preparing complex assessment.