Annoyance to wind turbine noise - influence of different acoustical characteristics

Due to the growing production of wind energy worldwide, increasing portions of the population are exposed to wind turbine noise. Results of field and laboratory studies suggest that wind turbine noise is more annoying than other noise sources at comparable sound pressure levels. This effect might be caused by various properties of wind turbines, such as their visibility or their acoustic characteristics (e.g., amplitude modulation). However, knowledge on the annoyance effects of wind turbine noise alone, i.e., without confounders such as visibility, is still scarce. In the present study, the short-term annoyance to different sound scenarios was investigated in laboratory listening tests under fully controlled conditions, which allowed for exclusion of potential confounders like visual effects present in field surveys. The sound scenarios comprised different situations of wind turbine and similar noise sources, covering different acoustic characteristics. In particular, the impact of three factors on annoyance ratings were tested, namely, spectral shape, depth of periodic amplitude modulation, and occurrence of random amplitude modulation due to turbulence. The specific sound scenarios were generated by sound synthesis, taking care that the set of (synthetic) scenarios sounded realistic. Subjects were exposed to the different sound scenarios reproduced via loudspeakers at a sound pressure level LAeq of 40 dB, and their ratings on subjectively perceived annoyance were collected. The factorial design of the experiment allows for separation of the individual contributions of the above three factors to the annoyance ratings. Further, semantic differentials and questionnaires are used to interpret and discuss the findings. Here we present the setup of the listening tests, the most important results including a preliminary comparison with the psychoacoustic parameter loudness, and possible implications for future research and applications.