Low-frequency background noise may damage ears

Science : Although prolonged exposure to loud noises has long been known to lead to hearing loss, a new study shows that low-frequency sounds may also cause damage. Neurobiologists at the Ludwig-Maximilians University in Munich exposed 21 volunteers to a deep, vibrating noise in the 30-Hz range—barely audible to the human ear. Such noise levels are regularly generated by wind turbines, roaring crowds, and jet engines. Then the researchers measured the spontaneous otoacoustic emissions (SOAEs) produced by the participants’ inner ears. Healthy ears regularly emit SOAEs; damaged ears do not. The researchers found that just 90 seconds of exposure to low-frequency sound caused participants’ SOAEs to start oscillating erratically. Although that is not proof that such sounds can cause permanent damage, the effect may leave the ear temporarily more prone to damage, they say.