New research at a UK university, says people are being bombarded with ultrasound without their knowledge and it may be causing tinnitus. The research has been conducted by the University of Southampton and it suggests that people are being exposed, without their knowledge, to airborne ultrasound from a number of sources including loudspeakers, door sensors and public address systems in railway stations, museums, libraries, schools and sports stadiums.
Continuing exposure led to complaints of nausea, dizziness, migraine, fatigue and tinnitus – the same symptoms reported over the years by workers who have been regularly exposed to occupational ultrasound through industrial devices for cleaning and drilling.
While there has not yet been sufficient research to confirm or deny a link, the study by Professor Tim Leighton from the University’s Institute of Sound and Vibration Research, says that current guidelines and research knowledge for occupational safe levels are inadequate to cope with the current mass exposure of large numbers of people. Commenting on the University’s website Professor Leighton says: “most guidelines refer to occupational exposure, where workers are aware of the exposure, can be monitored and can wear protection. Furthermore, the guidelines are based on the average response of small group, often of adult males.
“The guidelines are also based on an insufficient evidence base, most of which was collected over 40 years ago by researchers who considered it insufficient to finalise guidelines, but which produced preliminary guidelines. This warning of inadequacy was lost as regulatory bodies and organisations issued ‘new’ guidelines based on these early guidelines, and through such repetition generated a false impression of consensus.”
He says 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. 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. The lack of research means that it is not possible to prove or disprove the public health risk or discomfort. However, it is important that sufferers are able to identify the true cause of their symptoms, whether they result from VHF/US exposure or not.