Shout out for peace and quiet

PV sound barrier
Green solutions to noise reduction could improve our mental and physical wellbeing.


We all suffer stress and anxiety to some degree and reported stress levels are generally increasing.  The Mental Health Foundation recently found that three quarters of people in the UK had felt so stressed in the past year that they were overwhelmed or unable to cope.

It would be in everyone’s interest to tackle the various causes of stress.  Many are related to work situations, many to personal and financial circumstances, but a proportion is attributable to environmental noise. Noise can be defined as unwanted sound. The descriptor “unwanted” immediately suggests that there will be an emotional or psychological response to the intrusion of noise into our lives.

Recent research is beginning to suggest that we need to take noise more seriously.  

Noise impact 

In 2015 a German study reported that there was a 25 percent higher rate of depression in areas with high traffic noise compared to quieter neighbourhoods, allowing for other socioeconomic factors.  The complexity of noise impact is evident in the finding that the highest rates of depression were found in areas where intermediate noise was being experienced for 24 hours each day – not in the areas with the highest noise levels.  It was postulated that in the particularly noisy areas, people take measures to block out the noise

The mechanisms for noise impact on human health and wellbeing remain uncertain.  Noise will cause both psychological and physiological distress, disturbing homeostasis and increasing allostatic load.  That means the internal balance within the human body, controlled by the nervous system and by hormones, is thrown out, resulting in elevated or fluctuating endocrine and nervous responses.

There can be constriction of blood vessels, tightening of muscles, increased heart rate and raised blood pressure.  In turn these can have very evident effects, causing annoyance, anxiety, hypertension, sleep disturbance and cardiovascular disease. 

Persistent hypertension, or high blood pressure, can increase the risks of heart attack, stroke and kidney disease. There is some evidence of reduced cognitive performance in children. Many people can tune out noise, to varying degrees, but that doesn’t mean to say that the purely physiological responses are eliminated.

The World Health Organisation (WHO) has recently issued a set of guidelines and thresholds for environmental noise.  For example, it is recommended that human exposure to road noise should be limited to no more than 53 dB as an average.  Above that level then there will be negative health impacts. At night, the level should not exceed 45 dB in order to maintain relatively healthy sleep patterns.  For rail noise there are marginally different thresholds, 54dB and 44 dB respectively.  Of course, industrial noise is already regulated by existing legal controls so should not be creating additional problems to any significant extent.

Ambient noise 

The dB, or decibel, is not a measure most of us are very familiar with. It attempts to reflect the loudness of a noise as we hear it but, in technical terms, is a logarithmic scale because the human ear is capable of responding to an enormous range of powers of sound waves.  

Zero, of course, is set at the threshold for healthy hearing to first detect any sound at all. So, just as examples, I’m sitting writing this article at my desk, beside a window which overlooks a fairly quiet road at the bottom of a 20m garden - perhaps 10 cars or trucks passing each minute at the moment.  In this room I have secondary glazing which is very effective at reducing sound.  In the room itself there are a couple of PCs, screens, and a central heating radiator that probably makes some noise.  Today there is no wind at all. Otherwise, just the background sounds of any house. 

The noise sensor right beside me nearly always shows about 35 or 36 dB.  If I put the radio on fairly low, so that I can listen in to the news, but not be so disturbed that I can’t block it out and write, then the noise level increases to 55 dB roughly.  If I put the vacuum cleaner on, then the noise level is 66 dB and I can’t really think very rationally and, after more than a few minutes, it becomes quite annoying. An increase of 10 dB is likened to a doubling in the loudness of a sound to the human ear. 

The European Union adopted a Directive on environmental noise in 2002. It stipulates that measurements must be taken of ambient noise, the results must be made publicly available, and action plans for noise reduction must be agreed.  As yet there are no fixed target noise levels.

Major problem 

The measurements provided under the Directive make interesting reading. In Scotland, within the four main cities of Glasgow, Edinburgh, Aberdeen and Dundee, there are over 1 million people exposed to 24-hour noise levels in excess of 55 dB (so slightly higher than the WHO recommended maximum exposure level of 53 dB) while there are almost 800,000 exposed to night-time noise levels in excess of 50 dB (well above the WHO recommendation of 45 dB).  

In England, across 65 urban areas, it was reported in early 2014 that there were 7.4 million people living in areas with road noise levels in excess of 55 dB as an average, while there were almost 5 million living with night-time road noise above 50 dB. Adding in exposure to rail noise as well, the figures increase to 8.4 million and 5.6 million respectively.  

It has been suggested that 10 percent of people in England & Wales live with day-time noise in excess of 65 dB, and 16 percent with night-time noise in excess of 55 dB.  These exposures seem to be fairly stable, with little change either for better or worse over time.  However, complaints about noise have certainly been increasing over the past 20 years.  As you would expect, there is also an inherent equalities issue since more deprived communities are more likely to be exposed to a combination of both greater noise and air pollution. 

You would think there would be good reason to be very concerned. Opinion surveys across Europe in 2016-17 revealed that one third of citizens said they experienced problems with noise, and in cities this proportion rose to half.  Another poll indicated that 15 percent of people place noise pollution in the top 5 environmental issues that worry them.  

In the UK, 4 percent of respondents have a major problem with noise, and 22 percent a moderate problem.  There is evidence that the trend is towards increasing public concern.

Premature deaths

Admittedly, there are many ways to combat noise – sound insulation in homes, double-glazing, sleeping in the quietest part of the house.  So individuals will personally experience a noisy environment in very different ways.

However, overall, the European Environment Agency stated in 2014 that there were 10,000 premature deaths caused by noise pollution in Europe, 43,000 hospitalisations and 900,000 cases of hypertension.

It is also reckoned that 1 million DALY are caused every year in Europe (a DALY is a disability adjusted life year) from traffic noise.  This suggests that there is a very considerable burden placed on people across Europe, principally through annoyance and sleep disturbance.  

Each DALY can be costed.  In Netherlands a cost of Euros 77k has been calculated, while in the UK it has been valued at £20k to £30k, and in the USA between $50k and $100k.  Taking a middle figure of £50k, then the total cost of noise-related disability in Europe could be about £50 billion per year.  A fairly recent estimate put the annual cost of obesity in Europe at £70 billion.

Green solutions

So what is being done?  Well, the European 7th Environmental Action Programme commits to noise pollution being significantly reduced by 2020 and moving closer to the WHO levels. Additionally, the European Union has set standards for engine noise in cars and heavy vehicles.  

Obviously, the routine annual MoT test requires silencers and exhaust systems to be maintained. It has also set improving standards, since 2005, for noise created by vehicle tyres.  Opportunities can be taken to improve road surfaces by laying low-noise coatings.  Many indoor and outdoor appliances now have noise standards applied.  Certainly, there are ongoing business innovations in devising better sound insulation building materials and products.  

At the more local level, noise impact assessments are required of new road infrastructure, while controls can be exercised in construction of new housing, and in baffling from noise by built or green infrastructure.  It’s been shown that a planted stand of trees and shrubs 30m wide can reduce noise levels by 10 dB, effectively a halving of the perceived noise level, and this provides a significant benefit when a typical noise level beside a motorway might be around 70 dB.  A tree or shrub barrier can also reduce air pollution by half.

There are clearly multiple benefits to be derived from green solutions to climate change, poor air quality and excessive noise – in terms of tree planting, green roofs, green walls, and increased walking and cycling, as well as use of public transport, in place of private vehicles.  Overall, however, there is very poor centralised collection of information or data in the UK  on how much effort is going into any of these local remedial actions.

Harming biodiversity 

The impacts of noise pollution on biodiversity are, perhaps, even less well established.  There have been many laboratory tests which indicate significant physiological responses for various species but impacts in the natural environment are poorly understood.

A study was undertaken across all the protected areas in the USA, amounting to 14 percent of the total land area, which found that intrusive man-made noise reduced the area in which only natural sounds could be heard by between 50 percent and 90 percent, depending on location.  This means that natural sounds that could normally be heard at a distance of 50m could only be heard at 25m.  Overall 63 percent of the land area experienced twice as much sound as it should.

Clearly unnatural noise will impact on many species.  Animals rely on sound for communication, navigation, finding food and avoiding danger. For example, it’s been shown that foraging efficiency of owls is adversely impacted by traffic noise.  There is much less bat activity in noisy places.  There is evidence of impact on breeding bird communities through a change in composition of the community and a reduction in nesting species richness.  

However, some species clearly get an advantage in noisy places through reduced competition and predation.  There have been studies of wild populations of species as distinct as rats and deer showing avoidance behaviour of noisy places, causing behavioural and social changes which can result in disturbed and reduced feeding.  

There have been many studies of the effect of aircraft noise on wild species.  This distinct type of noise can be very loud and very sudden, possibly even causing panic and injury and abandonment of young.   

On the other hand, studies have also shown that roadside verges can be refuges for many insects, butterflies, moths and bees – so it would appear the relative lack of physical disturbance is a benefit compared to the possibility of some relatively minor disbenefits from noise.  However, it is recognised that good inter-comparison studies between similar noisy and quiet locations are needed. 

The future 

Accepting that we will have to continue living with noise, despite ongoing efforts to tackle the problem at source and make various technologies quieter, then we should be working hard to disrupt the pathways for noise transmission.

What does the future hold?  The existing European directive on environmental noise has the feel of a preliminary exercise to gather evidence and to prepare member states for more prescriptive action later.  This is confirmed by the commitment in the 7th environmental action programme.  

It’s clear there are potentially great benefits to be gained by properly aligning green interventions to enhance climate change mitigation, climate change adaptation, infrastructure resilience, air pollution reduction, biodiversity enhancement, local amenity, and noise reduction.  

Perhaps the best approach would be to build on the existing 2013 EU green infrastructure strategy and to agree an EU framework directive on green infrastructure, designed to deliver all those well-established multiple benefits that would improve our own lives and physical and mental wellbeing.

This Author 

Professor James Curran retired recently as Chief Executive of the Scottish Environment Protection Agency.  He researches, writes and talks on climate change, sustainability, air pollution and biodiversity.

Image: A PV sound barrier near Munich airport with solar panels incorporated, Wikimedia

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