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What You Can’t Hear Won’t Hurt You? Maybe Not


Wind Turbines
Wind turbines make infrasound noise
that bothers some people.

Wind turbines, giant propellered contraptions that turn wind power into electricity, are rapidly becoming popular as green energy sources in Europe and the United States. This is good for the environment, but the rotors and blades of wind turbines generate noise in the infrasound range that some people claim makes them feel dizzy or unable to sleep, among other symptoms. Infrasound is defined broadly as any sound lower than 20 Hertz (Hz), which is the lowest pitch that most people can hear. Many scientists assume that frequencies too low to be heard can’t have any effect on the function of the ear. But NIDCD-funded researcher Alec Salt, Ph.D., at Washington University in St. Louis, has observed otherwise. For years, he and his colleagues have used infrasound as a way to slowly displace the structures of the inner ear for study in the lab, and they noticed inner ear function being disturbed by frequencies as low as 5 Hz. Salt believes that outer hair cells, which normally help amplify sound vibrations in the inner ear, actively work to keep the inner hair cells, which turn sound waves into electrical signals destined for the brain, from being stimulated by lower frequencies. While the brain may not hear the sound, the responses of the outer hair cells could cause unfamiliar sensations in some people. Read more on the NIDCD website. The study is published in Hearing Research.

Last Updated Date: 
October 26, 2010