Exposure to ultrasound may pose health risk

Telegraph : Humans are increasingly being exposed to noise in the ultrasonic range without even knowing it. A host of devices emit noise with frequencies of greater than 20 kHz, which is at or above the audible limit of human hearing. That means that most adults can’t hear the noise emitted by fluorescent lights, loudspeakers, automatic door sensors, spotlights, and other sources. In a study published in the Proceedings of the Royal Society A, Timothy Leighton of the University of Southampton says there have been reports of people complaining of nausea, dizziness, tinnitus, fatigue, and headaches after spending time in certain public places where noise at the ultrasonic level has been measured, such as train stations, museums, libraries, schools, shopping malls, and sports stadiums. He also points out the similarity between symptoms reported for ultrasound exposure and those for motion sickness. Leighton says the subject has not been adequately studied and further research is needed to determine whether better guidelines for ultrasound exposure need to be put in place.