Some people think high-voltage power lines cause cancer while others are convinced that wi-fi is a threat to human health. Others worry about cell phones. And don't even think mention non-stick skillets.
But wind farms? Oh sure, the giant blades may slice through a buzzard now and then but how would a wind farm be harmful to humans?
Well, a new German study suggests that the very-low-frequency sounds generated by the windmill's rotor blades and windflow may be detected by the human brain, contradicting the assumption that the sounds are below the threshold of human hearing.
Researchers at the European Meteorology Research Program (EMRP) found that humans can hear sounds lower than previously thought. Also, the mechanisms of sound perception are much more complex than expected, the researchers said.
People living in the vicinity of wind farms have reported experiencing sleep disturbances, a decline in performance, and other negative effects, apparently from the "infrasound" generated by the turbines. Infrasound refers to very low sounds, around 16 hertz, generally thought to be below the limit of hearing.
Earlier studies have come to similar conclusions. In 2014, researchers at Washington University in St. Louis found that the low-frequency sounds could cause panic, sleep disturbances, stress and elevated blood pressure.
The wind power industry dismisses such complaints, saying that the sounds generated by the wind farms are too low and too faint to be detected by humans. But Christian Koch, the lead researcher in a study conducted by the Max Planck Institute for Human Development in Berlin, says it's not that clear-cut.
"Neither scaremongering nor refuting everything is of any help in this situation. Instead, we must try to find out more about how sounds in the limit range of hearing are perceived," Koch said.
Koch and his team used brain imaging to tell when test subjects were aware of very low sounds and found that humans hear sounds as low as 8 hertz -- a full octave lower than previously thought. The test subjects confirmed that they heard something and MRI-type devices showed a reaction in parts of the brain that play a role in emotion.
"This means that a human being has a rather diffuse perception, saying that something is there and that this might involve danger," Koch said. "But we're actually at the very beginning of our investigations. Further research is urgently needed."