Sound power levels in decibel

In this study wind turbine sound power levels were calculated. The measurement is valid when all wind turbines in the vicinity of a respondent's residence are turning on a high, but not maximum speed.

For the measurement, wind velocity is set at 8 m/s at a height of 10 meter. The atmospheric conditions are neutral, which means inbetween stable and instable. Neutral atmospheric conditions occur in case of strong winds and/or thick clouds.

Sound power levels are measured in decibel (dB). This is a logarithmic unit. This means that when the amount of sound doubles, for instance when a second wind turbine is situated next to the first one, the amount of decibel increases by 3. An example is given below to illustrate this matter:

A wind turbine produces 40 dB of sound at a surrounding residence. When a second wind turbine is placed at an equal distance from this residence the amount of decibel increases to 43. To obtain 46 dB the sound power level has to double again, which means 4 wind turbines are required. And for 49 dB 8 turbines are required.

The program used in the WINDFARMperception project to calculate sound levels and visual size of wind turbines will be available for all interested. It has now been completed for external users and can be downloaded for free from this site.