We are spending more time indoors than ever. But the levels of noise we’re exposed to at home, at work and at school have been shown to increase the risk of high blood pressure, mental illness and hearing impairment – and may even have an effect detrimental to the cognitive development of children. Now, a unique new study from Chalmers University of Technology, Sweden, has identified and eliminated the harmful noise that occurs in ventilation system fans – something that could dramatically improve our physical and mental health.
Today, we spend up to 87% of our lives indoors, according to an American study. The quality of indoor environments has therefore become an increasingly important factor for health and well-being. Temperature, carbon dioxide levels and humidity are just a few of the factors known to influence our indoor environments, but lately studies have also shown how indoor noise can have a significant negative impact.
Fans used in ventilation systems in homes, workplaces, and schools are a contributing factor to constant noise in indoor environments. The crux of the matter – and what irritates the human ear – occurs when fan blades spin, generating sound with a constant, predictable frequency known as “tonal” noise. Identifying exactly how this sound occurs and how to suppress it has been a long-standing quest that researchers and ventilator makers have been unable to find an answer to.
The source of the tonal sound has never been identified before on this type of fan. When you can lower that tone, the fans become extremely quiet and, in that regard, unique. This is the first time that anyone has succeeded in both identifying and eliminating the source of the noise.”
Martin Ottersten, industrial doctoral student in fluid dynamics at Chalmers University of Technology and research and innovation engineer at Swegon, and lead author of the study
Increased risks of physical and mental illness
According to a WHO report, tonal noise of the type that occurs in ventilation systems can have negative effects on human health. The study shows that long-term exposure to this type of sound increases the risk of high blood pressure, cardiac arrest, tinnitus, hearing problems, sleep disorders and stress. Children’s cognitive development can also be negatively affected by noise levels from ventilation systems.
Finding the source of what causes the tonal sound has therefore been of great interest to researchers and ventilator manufacturers for many years.
“I am sound sensitive and sometimes have difficulty concentrating and sleeping with disturbing sounds. And I know that tonal sound can mess with our brains. When I read the WHO reports on how the its tonal can also lead to diseases such as high blood pressure and even cardiac arrest, the work has taken on a whole new dimension”, explains Martin Ottersten, who has been working on the project for four years.
Reduced power consumption is another advantage
Using advanced computer calculations, which sometimes take weeks at a time, Martin Ottersten was able to study how air flows through the fan during rotation and where turbulence occurs. The calculations also provided audio data for the fan, which was used to locate the source of the tones.
After several variations, he succeeded in designing a fan in such a way that the tonal sound decreased considerably, an improvement that could allow for much quieter and healthier indoor environments.
“By trying out different fan modifications and measuring sound levels using very complex calculations on hundreds of computers, over several weeks, we were able to determine exactly where the tonal sound was coming from in the fan’s construction and how to eliminate it. And what’s more, we have also observed that the efficiency of the fan increases as the tonal sound decreases”, explains Martin Ottersten.
He believes that this research now has great potential to be put into practice and that extremely quiet fans that produce no tonal noise may soon be commercially available.
“We are currently pursuing a patent for this technology and implementing it in our fans. After that, we want to bring them to market, so that we can help create healthier indoor environments – as well as reduce energy consumption. energy and carbon dioxide emissions.
Chalmers University of Technology
Ottersten, M. et al. (2022) Tonal noise of scrollless centrifugal fan generated by turbulence from upstream inlet space. Fluid Physics. doi.org/10.1063/5.0055242.