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Could overexposure to ultrasonic noise pollution be causing health problems?

Is ultrasound in the air around making you sick? New research by the University of Southampton in England says that it just might be.

Most will associate ultrasound with those cute pictures of babies inside the womb, but that actually not what we’re talking about here (although it works on the same concept). Ultrasound is actually defined by any noise higher than the limit of human hearing, which generally falls around 20 kilohertz. Most people’s ears simply aren’t designed to pick up sounds above this frequency, but just because we can’t hear these noises doesn’t necessarily mean that prolonged exposure to them is okay.

Too much ultrasound may make you sick, some argue, and those that believe it does claims it will bring on a variety of symptoms, including nausea, dizziness, migraine, fatigue, and tinnitus. Ultrasound is emitted from a variety of sources including loudspeakers, door sensors, and cleaning and drilling devices used in industry. For years, both workers and people exposed to these types of devices have complained of malaise. Until now, there was no link.

Related: Elliptic Labs wants to replace the proximity sensor on your smartphone with ultrasound

University of Southampton researchers now think they have one, or at least the beginnings of finding a true link. They found the current standards for safe levels of exposure were inadequate, and based on nearly four-decade old study results. At the time, researchers feared that the data was too preliminary to base guidelines on. Standards organizations did anyway, but once they were published, the guidelines were never updated based on new understanding of very high frequency and ultrasound exposure.

“[More] recent data suggests that one in 20 people aged 40-49 years have hearing thresholds that are at least 20 decibels (dB) more sensitive at 20 kHZ than that of the average 30-39 year old,” study author Tim Leighton says. “Moreover, five per cent of the 5 to 19 year age group is reported to have a 20 kHz threshold that is 60 dB more sensitive than the median for the 30-39 year age group.”

Leighton and his team’s suggestion is to rethink the guidelines for exposure based on more recent data. He did admit that it is still too early to prove a link between sufferers’ symptoms and exposure, but he blames it on a lack of research on the topic overall.