Masking

There are suggestions to put wind turbines next to high ways to mask the wind turbine noise. Our study, however, shows that louder road noise does not effectively mask wind turbine sound.

The reason for this might be that road noise has other sound characteristics than wind turbine noise. One difference is that cars have two sound levels. The first is the engine sound. This sound is low pitched and is in the range of 60 Hz to 80 Hz. The high pitched tire noise has frequencies above 1000 Hz. With a frequency between 400 Hz and 1000 Hz wind turbine sound is right between these two car sounds.

A second difference is the ‘pulsating’ characteristic of wind turbine noise, contrary to traffic noise which is fairly constant at larger distances. Pulsating means that the noise of the wind turbines is not constant, but varies with the rotation speed of the blades. Three out of four respondents stated that the term swishing and lashing best described the wind turbine sound.

Finally, at night traffic levels decrease, while wind turbine noise levels remains constant or even increase.