Low frequency sound and infrasound from wind turbines

Low frequency noise (LFN) has a range between 12.5 Hz and 200 Hz. Infrasound is any noise below 20 Hz. Permitting processes often question the acceptability of LFN and infrasound from wind turbines, and there are currently no nation-wide regulations on LFN in Canada or the United States. This PowerPoint presentation discussed the results of a study conducted to determine the effects of LFN and infrasound on the environment surrounding a wind power facility. Objective criteria for the study included the threshold of hearing; annoyance; perceptible vibration and rattle; disturbance; and acceptability. The study was conducted at a large wind farm with different types of turbines sited on a generally flat terrain with minimal vegetation. Multiple participating residences were located at close proximity to the turbines. Data were collected at different heights over a period of 5 days in a variety of wind conditions. Sound levels at 4 houses located near the turbines were also measured. Data were compared with ambient noise measurements and assessed in relation to the determined criteria. Results of the study showed that the wind turbines at the site did not pose LFN or infrasound problems at a distance of 305 meters or more. Recent developments in acoustic standards were reviewed. tabs., figs.