Tag: low-frequency noise

The results of wind turbines (WTs) noise calculations, calibrated with the outcomes of multi point continuous noise monitoring around the wind farm (WF) are presented in the paper. The Nord2000 noise calculation method was used to obtain contours of LAeq, taking into account instantaneous WTs parameters, its horizontal directivity and meteorological conditions . Noise contours of LAeq around a single WT are not symmetrical due to wind direction and directivity of WT. This is why sound levels in the noise protected (residential) areas around WF are not always the same. Usually, LAeq may be reduced by a few decibels by switching WT into noise reduced mode. Using an on-line -real time calibrated – calculation model this can be applied only to a selected WT influencing sound levels at a given area where current conditions might cause noise complaints (while the other WTs can operate in a normal mode). There are factors that increase the probability of noise complaints, such as amplitude modulation, as well as decrease this probability, such as masking effect of wind induced noise or high ambient noise which should also be taken into account while setting the current operation mode of individual WTs.

The industrial noise calculation method, which includes wind farm noise, is defined in Polish regulations and Directive 2002/49/EC. According to these documents, the method described in the ISO 9613-2 covering the frequency range from 63 Hz to 8 kHz should be used. However, wind turbines are also a source of the low-frequency noise in the band from a few Hz and thus well below the lower frequency of the existing models calculation range. These sounds are described as rumbling or pulsing, which is a source of annoyance to people living near wind turbines. Therefore, propagation of the low-frequency component should be modelled at the predicting acoustic impact stage of wind turbines on the environment. The paper reviews modelling methods in the low-frequency range and verifies the suitability of ISO 9613-2, CNOSSOS-EU and NORD2000 algorithms for modelling low-frequency noise including frequencies below 63 Hz. The results of the calculations were compared with the results of measurements carried out around the wind farm.

This research has been founded by the National Centre for Research and Development – project No. NOR/POLNOR/Hetman/0073/2019 and by the Polish Ministry of Science and Higher Education – project No. 16.16.130.942.