People are probably being exposed to large amounts of airborne ultrasound without their knowledge, according to researchers at the University of Southampton in the U.K.
The recent study claims such exposure is likely happening in train stations, museums, libraries, stadiums and schools due to the prevalence of public address systems and door sensors, amongst other sources.
According to a write-up of the findings, areas with an increased likelihood of ultrasound exposure are fertile grounds for increased instances of "...nausea, dizziness, migraine, fatigue and tinnitus."
Such symptoms are similar to the effects of prolonged ultrasound exposure long known to impact those who regularly encounter it in occupational settings through the use of industrial cleaning and drilling devices.
Study author, Professor Tim Leighton, said: "The guidelines are ... based on an insufficient evidence base, most of which was collected over 40 years ago by researchers who considered it insufficient to finalize guidelines, but which produced preliminary guidelines. This warning of inadequacy was lost as regulatory bodies and organizations issued 'new' guidelines based on these early guidelines, and through such repetition generated a false impression of consensus."