Our bodies are constantly surrounded by a variety of potentially harmful waves – we all carry mobile phones, use Wi-Fi, live near big radio transmitters and so on. However, some of the waves are harder to detect and damage may be harder to imagine. Scientists from the University of Southampton say that we are exposed to airborne ultrasound too, especially in such places as railway stations, museums, libraries, schools and sports stadiums. And we never even think about it.
It is difficult to tell, if the airborne ultrasound is harmful to us, but visitors of these places have been complaining about nausea, dizziness, migraine, fatigue and tinnitus. Sources of this ultrasound are many – loudspeakers, door sensors and public address systems. Although usually visitors do not stay for long in these establishments, some people have to spend a big portion of their time there, because of their work or studies and there have been complaints that could be the result of exposure to ultrasound.
Scientists stress that better guidelines should be developed to help people avoid such negative effects. Professor Tim Leighton, author of the study, said: “Existing guidelines are insufficient for such large public exposures as the vast majority 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.”
Current guidelines are based on evidence collected as much as 40 years ago. And although they have been renewed, they still relied on old researches. Now scientists used simple equipment – smart phones and tablets equipped with an app that produced a spectrogram of the microphone reading – to research very high frequency/ultrasonic fields in many public buildings.
Researchers found that public is being exposed to over 20 kHz of these waves – the level which is the threshold of the current guidelines. It is because nowadays there are more sources of harmful ultrasound. Furthermore, it affects people of different age differently, which means that further investigation is needed. And, of course, new guidelines have to be developed.
This research shows that we still do not know about invisible forces damaging our health in public places. Although museum, gym and other public buildings visitors should be fine, further research is needed and guidelines should be develop to help those spending majority of their day in these environments.