A parametric method to synthesize wind turbine sounds

Paper in proceeding, 2019

The annoyance to wind turbine sound is today well known. There is no doubt that increased sound pressure level causes in general an increased annoyance. However, when it comes to additional descriptors of the wind turbine sound, such as e g equivalent frequency spectrum or amplitude modulation, there is no consensus on what parameters that are most important. In the research project Wind Turbine Noise Effects on Sleep (WiTNES) there was a need for 8 hour long sound signals from wind turbines that were completely free of extraneous sounds. Recordings from reality are difficult to maintain free from disturbances. Instead a parametric synthesis method was developed that is capable of creating wind turbine sounds of arbitrary length. The sounds can be designed in terms of equivalent frequency spectrum, what frequency bands that have amplitude modulation as well as frequency dependent amplitude modulation strength and variation. Recordings of wind turbine sounds at immission distances from different wind turbine types were used to find relevant values for the parameters. This paper describes the synthesis method and some examples of input parameters.