Why is noise pollution harmful?
You may have read that the World Health Organization (WHO) hasdeemed noise pollution the second largest environmental cause of ill-health,with air pollution in first place. Is noise pollution really as harmful as theheadlines make it seem? The evidence is difficult to interpret, but in thisarticle, we will try to untangle it and present a balanced view of what we knowso far.
What is noise pollution and where does it come from?
Let’s start by defining what we mean by ‘noise’. Ask anacoustic consultant, a music teacher or anybody else who regularly gets askedthis question, and they will normally tell you, “Noise is unwanted sound.”
While we think this might give us a good intuitiveunderstanding of what noise is, it’s imperative that we go a bit further in ourdefinition of noise. The difference between a wanted sound and an unwantedsound is highly subjective. Your neighbour may not want to hear you listeningto Beethoven’s Fifth on full blast at midnight, but that doesn’t necessarily makeit noise in their eyes. For the purposes of this article, we could expand ourdefinition of noise to say that it is also “unorganised sound.”
Whereas music is organised according to rules of theory,tradition and culture, the sound an aeroplane makes while flying over anotherwise quiet suburb obeys no such conventions.
What do we mean by environmental noise? The body of researchlooking at the effects of noise on physical and mental health and cognition hastypically focussed on the effects of transport noise; that is to say, noisefrom aeroplanes, trains and road vehicles. More recently, and of growinginterest, there have been some studies on the effects of wind-turbine noise onhealth and well-being.
How big a problem really is noise pollution?
In 2011, The World Health Organization (WHO) published areport titled “Burden of disease from environmental noise” (1)which attempted to quantify the problem of environmental noise in direct,measureable impacts. The authors estimated that in Western European countries,at least one million healthy life-years are lost every year because ofenvironmental noise (from a population of about 340 milllion).
It’s worth diverging for a moment to explain that thisdoesn’t mean that one million people die each year, but instead it uses ametric which combines the concepts of (a) potential years of life lost due topremature death and (b) equivalent years of “healthy” life lost by virtue ofbeing in a state of poor health or disability. This metric is called adisability-adjusted life year (or DALY). (1)
The same report estimated that, at the time, children inSweden experienced 965 years lost due to disability, or to look at it anotherway, just over 1% of Swedish children aged 7 – 19 experienced temporary noise-inducedcognitive impairment.
Even though the health effects of noise pollution aredifficult to quantify and predict with certainty, we can see from the availableevidence that we have a real public health burden on our hands which does havea measurable impact on health and therefore on societies and economies.
It’s important to provide some perspective, and rememberthat noise is subjective, and relative. A 3 dB change is noise level is usuallythought of as ‘only just noticeable’. So if a new railway is proposed to runclose to a community that is already affected by rail noise, and the new trackwill only increase daily noise levels by 1 dB, then it is unlikely to have anytangible effect on the overall well-being of the nearby residents.
Can noise harm us physically?
It’s reasonable to ask whether noise and the related stressor annoyance it can cause have a direct association with health effects. It’simportant to remember that our emotional, mental and physical well-being areall interlinked, so when one suffers, very often so do the other two. Asalways, let’s see what the science says.
A number of studies have shown that increased exposure tonoise can result in annoyance, stress and lower quality sleep (2), all of whichare accepted, broadly speaking, to be bad for your health. See (MayoClinic).
When researchers analysed the results of several studiestogether (known as a meta-analysis), they found associations between chronicexposure to aircraft noise and high blood pressure (hypertension) in adults. (3) (4)A similar association was found for road traffic noise and high blood pressure.(5)
The available evidence shows a strong link between noise andhigh blood pressure. Other studies have attempted to examine a link betweennoise and birth outcomes, cardiovascular disease and mortality, but theevidence isn’t clear-cut at the moment. What this tells us is that we needmore, well-designed research before we can come to any firm conclusions onthese associations.
Why is noise harmful to health?
So how is it, that specific noises and their sound waves(which are really just tiny fluctuations in air pressure), are having a negativeeffect on our health?
Well, that’s a study area needing more research. Whileepidemiological studies have categorically shown that biological risk factorsare elevated in subjects exposed to high levels of noise, smaller-scale studieshave tried to clarify the physiological chain between noise and cardiovasculardisease, with varying rates of success. A number of studies have looked for alink between aircraft noise and measurable cardiovascular risk factors (such asinflammatory markers, cortisol and adrenaline) (6), but the research ison-going.
The best assumption we can make at the moment is that thenegative associations of air, road and rail noise and the resulting emotionalresponse cause a physiological and hormonal reaction, in the same way thatstress has been shown to. After all, if it was about a physical impact of soundwaves on us, then we would see similar effects on people attending loudconcerts, nightclubs, or social gatherings, and I would bet my bottom dollarthose people are broadly benefitting from the social and emotional interactions around them(risk of hearing damage aside).
Can environmental noise damage my hearing?
It’s generally believed that hearing damage mostly occursthrough prolonged exposure to high noise levels or very loud, single noiseevents. For instance, if you work in a noise environment, like manufacturing,the guideline limit for daily exposure is usually around 75 – 85 dB(A) over thecourse of the working day. (2)Alternatively, if you are exposed to significant one-off noise events, like gunblasts or machinery impulses, these could also damage your hearing if they are loudenough.
Environmental noise levels are unlikely to be as high as75dB(A) where you live or work, especially indoors. Some outdoor urbanenvironments can begin to approach that level close to very busy roads. So,environmental noise is unlikely to damage your hearing, and noise pollution ismore an insidious threat to health, affecting us over a long time without usnecessarily realising.
Hearing damage is known as an ‘auditory health effect’,while the links shown between noise pollution and cardiovascular health areknown as non-auditory health effects. (2)
Can noise harm our mental health?
A 2018 review of the evidence for links between noisepollution and mental health found that there was not much evidence for aneffect, and that the evidence there was, was of a very low quality. (7)
That’s not to say there is no link between noise and mentalhealth, it just means that we need more good-quality evidence and research intothe subject.
Is noise harmful to Children?
Most of the research on the effect of noise on children has lookedat how it affects their cognition and learning outcomes.
It’s also worth noting that most of these studies havelooked at aviation noise, that is, the sound of aeroplanes flying overhead,while fewer studies have considered noise from cars or trains. (7)
There is a clear link between exposure to environmentalnoise at school and cognitive impairments (usually measured in terms of readingage). The good news is that it looks like these effects can be reversed, if thesource of the noise is removed, the noise levels are reduced, or the child isplaced in a different environment. Below, I’ve summarised two well-knownstudies which looked at the impact of environmental noise on children’scognition and learning.
Munich Study
‘The Munich Study’ (8) is one of the fewlarge-scale prospective, longitudinal[1]studies we have available, which demonstrates a strong causal link betweenaircraft noise and children’s learning.
In the mid 1990s, Munich airport was relocated from Riem tothe Erdinger Moos area. Researchers found that, before the relocation, highnoise exposure was associated with poorer long-term memory and readingcomprehension in 10-year-old children. After the airport was closed, theseeffects were no longer present, which suggests that the effects of aircraftnoise on learning and cognition can be reversed if the noise stops.
To further strengthen the hypothesised link between aircraftnoise and children’s school performance, the children living near the newairport developed the same cognitive impairments that the children near the oldairport had recovered from.
RANCH Study
The Road traffic and Aircraft Noise and children’s Cognition& Health (RANCH) study (9) looked at 2844children living around major airports in the UK, Netherlands and Madrid. Thestudy found an association between aircraft noise and poorer readingcomprehension and poorer recognition memory, even once socio-economic statusand road traffic noise had been taken into account.
In the UK, the researchers found a linear effect of a2-month delay in reading age for each 5 dB increase in aircraft noise exposure.This was found to be 1-month in the Netherlands.
Why is noise bad for children’s learning?
There have been some attempts to explain these associationsbetween noise and reading comprehension or memory. From the research (9), it seems like themost likely causes are:
· Communication difficulties (i.e. children andteachers not hearing each other due to lots of noise).
· Learned helplessness (i.e. if there’s nothingthat can be done to improve the noise levels, what’s the point in trying?)
· Teacher and pupil frustration.
· Reduced morale.
· Impaired attention.
· Increased arousal (e.g. hyperactivity or energylevels)
· Sleep disturbance
· Annoyance and the resulting physiological andpsychological stress responses.
It’s understandably difficult to know how each of thesefactors weighs up against one another, or what other factors may contribute,but the above points all seem plausible contributors to the link between noisepollution and comprehension.
Is noise bad for my sleep?
Intuitively, the answer is a resounding, “Yes.” If you thinkback to a time when you were woken up by a fox calling, or kept awake byneighbours playing dance music until the early hours; if you have lived at all,you will know that noise wakes us up, noise keeps us up and noise diminishesthe quality of our sleep.
The evidence is clear on this. It has been shown that humansperceive, evaluate and react to environmental sounds when asleep. Repeatednoise-induced sleep disturbance has been shown to negatively impact sleepquality through changes in sleep structure, including increasing the length oftime it takes us to fall asleep, waking up earlier, and less deep and REMsleep. Deep and REM sleep have been shown to be important for memoryconsolidation and recuperation. Some recent evidence also indicates thatnight-time noise exposure may be more relevant for long-term health effectsthan daytime noise. (6)
It is worth noting, that while there is a clear link betweennoise and sleep disturbance, the evidence also suggests this disturbance is ofsmaller consequence than clinical sleep disorders like obstructivesleep apnea, and that aircraft noise tends to be less likely to affectsleep than road or rail noise. (6)
Emerging technologies
Noise from electric cars
Will electric cars reduce road traffic noise levels?
While the adoption of electric cars is a significant step inaddressing climate change, it’s worth asking about their noise impact. At lowspeeds (below about 30 miles per hour), car noise tends to be dominated by theengine. Given that electric vehicle engines make no sound, this will have atangible effect on streets with slow-moving traffic. However, as speeds pickup, and on roads where traffic is free-flowing, the noise emissions becomedominated by the interaction of the tyres with the road surface. So,unfortunately, electric cars will not have any benefit for noise pollution onthose busy, faster roads where we need it most.
Noise from wind turbines
Why do wind turbines make noise?
The noise from wind turbines occurs as a result of theblades’ interaction with air, creating turbulence in an effect called vortexshedding. This is the same reason fans, aeroplane propellors and helicopterblades make noise.
Wind turbine noise and health
There have been a number of health effects attributed windturbine noise, ranging from sleep disturbance, headaches, tinnitus and vertigo.A systematic review conducted in 2014 did find an increased risk of annoyanceand self-reported sleep disturbance. (10)The authors noted, “There is no statistically-significant evidenceindicating any association between wind turbine noise exposure and tinnitus,hearing loss, vertigo or headache … Future studies should focus oninvestigations aimed at objectively demonstrating whether or not measureablehealth-related outcomes can be proven to fluctuate depending on exposure towind turbines.”
In other words, there is currently no evidence for directhealth effects of wind turbine noise, but we need more research into thesubject to be sure.
Noise from drones
Drones make noise for a similar reason to wind turbines;where there is turbulence, there is noise. However, the smaller blades andfaster rotation speeds used by drones give the sound a distinct humming orbuzzing sound, and this can be a very real source of annoyance.
At the time of writing, there is very little research on theeffect of drone noise on human health. A 2021 review found that the availablestudies “provide a fairly consistent picture on annoyance effects of dronenoise on humans,” and that “available literature suggests that dronenoise is substantially more annoying than road traffic or aircraft noise at thesame level.” (11)
While it hasn’t been shown categorically, it wouldn’t take agreat leap of imagination to hypothesise that the annoyance could feed intostress and the related emotional and physiological reactions we have seen withother noise sources.
What can we do about environmental noise pollution?
Tackling noise from cars, planes and trains is an importanttask if we are to reduce the health, social and economic impacts of noise on alargely-unsuspecting public.
Broadly speaking, there are three ways to reduce the impactof noise on a person (or receiver). Firstly, we can reduce the noise level atsource. Secondly, we can install mitigation measures which attenuate (reduce)the sound levels as the sound travels from the source to the receiver. Thirdly,we can relocate the receiver.
The first two of the three measures outlined above requiregood design; good design of the vehicles, the roads and any noise barriers orpositioning that might benefit the noise impacts. The third measure isunfortunately out of reach for many households, as their location is often amatter of necessity, rather than choice.
Conclusions
It’s clear that high levels of transport noise are already having a detrimental impact on our health and well-being, but it’s importantthat we continue to undertake research to better understand the range andseverity of impacts, if we are to work towards mitigating them. There is also aclear need for more research into the effects of noise from wind turbines anddrones on human health and well-being.
In order to reduce the effects of noise pollution from air,rail and road traffic, we need them to be designed with the health consequencesin mind. This requires not just forward-thinking architects, civil engineersand acoustic designers, but also the political and economic will and means.Without the forethought of those who are ordering and paying for theinfrastructure that is vital to our socio-economic well-being, the designerswon’t be empowered to make those changes that are necessary to save lives andreduce the burden on national health systems and economies.
References
1. World Health Organization. Burden of disease from environmental noise. Copenhagen : WHO Regional Office for Europe, 2011.
2. Auditory and non-auditory effects of noise on health. Basner et al. April 12, 2014, The Lancet, Vol. 383, pp. 1325 - 1332.
3. Exposure-response relationship of the association between aircraft noise and the risk of hypertension. Babisch W, Kamp I. 161-8, s.l. : Noise Health, 2009, Vol. 11.
4. Is there an association between aircraft noise exposure and the incidence of hypertension? A meta-analysis of 16784 participants. Huang D et al. 93-7, s.l. : Noise Health, 2015, Vol. 17.
5. The quantitative relationship between road traffic noise and hypertension: A meta-analysis. van Kempen E, Babisch W. 1075-86, s.l. : Journal of Hypertension, 2012, Vol. 30.
6. Aviation noise impacts: State of the science. Basner et al. 41-50, s.l. : Noise Health, 2017, Vols. Mar-Apr 19(87).
7. WHO Environmental Noise Guidelines for the European Region: A systematic Review on Environmental Noise and Quality of Life, Wellbeing and Mental Health. Clark, Charlotte and Paunovic, Katarina. London : International Journal of Environmental Research and Public Health, 2018.
8. A prospective study of some effects of aircraft noise on cognitive performance in schoolchildren. Staffan Hygge, Gary W Evans, Monika Bullinger. s.l. : Psychological Science, 2002, Vol. September.
9. Aircraft and road traffic noise and children's cognition and health: a cross-national study. Stansfeld et al. s.l. : The Lancet, 2005, Vol. 364.
10. Schmidt, Jasper Hvass and Klokker, Mads. Health effects related to wind turbine noise exposure: A systematic review. s.l. : Plos One, 2014.
11. Schaeffer, Beat et al. Drone noise emission characteristics and noise effects on humans - a systematic review. Berlin : International Journal of Environmental Research and Public Health, 2021.
[1] Aprospective study is a type of longitudinal study where researchers followgroups of populations over the course of time. See https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4669300/for more information.
