Image: GE Reports, used with permission.
GE Reports, a blog created by GE, has a nice infographic that shows how loud a wind turbine is on average depending on how far away you are. While GE makes wind turbines and has a horse in this race, they are using data from the NIDCD (part of the National Institute of Health), a pretty credible source.
At 500 meters (0.3 miles) away, that sound pressure level drops to 38 decibels. In most places, according to Keith Longtin of GE Global Research, background noise ranges from 40 to 45 decibels, meaning that a turbine's noise would be lost amongst it. For the stillest, most rural areas, Longtin says the background noise is 30 decibels. At that level, a turbine located about a mile away wouldn't be heard. (source)
You'll rarely find wind turbines that are at the minimum distance of 300 meters from residential areas, but at that distance, a turbine produces around 43 decibels. The average air conditioner can reach 50 decibels of noise, and most refrigerators run at around 40 decibels.
You can see a large version of the infographic here.
Via GE Reports
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