ISO9613-2 as a guideline for noise mapping of wind turbines, modelling vs measurements. CNOSSOS-EU vs ISO9613-2 for noise mapping of wind turbines

Standard ISO9613 is commonly used for noise mapping of wind turbines. This guideline is not a perfect solution as any wind turbine is not a typical industrial source and ISO9613 was not written to take into consideration such high sources (>90m) where the main noise comes from blade tips cutting air. Following ISO9613 standard a wind turbine can be characterized by a point source located at a nacelle height (>90m). To assess possible maximum impact of a wind farm, maximum sound power level (>100dB) which is reached at wind speed >8m/s should be taken into calculations. In contradiction to a maximum power level used when modelling is methodology for regular measurement of noise at dwelling areas - wind speed at 4m must not exceed 5m/s what is reasonable as wind stronger than 4 m/s has a real influence on measurements. The Assessment of noise impact by wind farms is complicated as modelling and measurements have conflicting requirements. The new guideline CNOSSOS-EU does not help to solve this situation and wind turbines are not treaded separately from any other industrial sources. Results are quite similar however wind turbines seem to be quieter under new regulation.