 Ms Walker recorded noise around Boston |
Driven to distraction by
her noisy apartment building, US environmental health student Erica Walker
thought it worthy of further investigation. While she could block out the sound
of running footsteps in the apartment overhead, she could still feel the thumps
of each step in her body.
It was this sound
component that interested Walker and so the environmental health PHD student, at
Harvard T.H. Chan School of Public Health, decided to look into infra noise and low
frequency noise.
She said: ‘It’s like
supernoise. If there’s something that’s high pitched and you want to get away
from it you can put your fingers in your ears and you can severely abate it.
But this low frequency noise is outside of the auditory system and you can’t
escape it. It is being sensed by other organs. It’s really unwanted because
there’s nothing you can do about it.’
An example of low
frequency sound is a bus (which is very low but can still be heard) but there
is also an infra sound component, as the rumbling of the bus is also felt by
the body.
Examples in nature of
infra sound, or vibrational sound, are earthquakes and volcanoes. So there is a
question around how the body has evolved to react to these sounds considering
that in nature they relate to dangerous natural events.
To answer some of
these questions Ms Walker has been cycling all over Boston with recording
equipment to map the different levels of sounds of the city. She will share her
findings at the conference NoiseCon 2016 in June in Providence city, Rhode
Island.
Ms Walker is also
contributing to a study examining the cardiovascular effects of low frequency
noise. The paper will be published in Environmental Research and does indicate
that low frequency noise has a negative impact on heart rate variability.
Ms Walker said: ‘Low
frequency noise has an impact on - above and beyond – high frequency noise on
short term cardiovascular activity. Over a period of time how this is
manifested over ten or 20 years we don’t have any answers but that’s where we
need to gear our future research.’
Infra sound sits in
the category 0-20 hertz, while low frequency sound sits in the category of
between 20-150/200 hertz. The WHO has set guidelines on high frequency noise at
55 decibels during the day and 45 decibels at night. Ms Walker’s research is
showing that these guidelines are often being exceeded by 15-20 decibels
routinely. However, there are currently no guidelines on low frequency noise.
She said: ‘The WHO
organisation has identified it as an issue that needs to be addressed for the
future. This part is able to seep in after we’ve done something to keep the
noise out. It’s something that needs legislation.’