It’s almost impossible to find complete peace and quiet. Even if you live deep in the countryside away from aircraft routes, traffic and building work, your home is probably filled with the buzz of computers and other modern appliances. In some locations, there are even claims of mysterious low-pitched noises with no known origin. For example, residents of Bristol in the west of England recently complained of a “hum”, which followed reports of a similar sound in the city in the 1970s.
Such sounds aren’t just annoying. There is increasing evidence that long-term environmental noise above a certain level can have a negative influence on your health. These effects can be physical, mental and possibly even disrupt children’s learning.
Recent research shows that road traffic and aircraft noise increase the risk of high blood pressure, especially noise exposure at night. A study of aircraft noise around London’s Heathrow airport found that high levels of aircraft noise was associated with increased risks of hospital admission and death for stroke, coronary heart disease, and cardiovascular disease in the nearby area.
Another large study that looked at aircraft noise exposure over a much longer time period of 15 years found that deaths from heart attacks increased when the noise was louder and endured over a longer period of time. The latest estimates suggest a ten decibel average increase in aircraft noise exposure was related to an increase in high blood pressure, heart attacks and strokes of between 7% and 17%.
Your emotional response to noise pollution can also be significant, so much so that it has a specific name: noise annoyance. This describes the negative feelings noise can create such as disturbance, irritation, dissatisfaction and nuisance, as well as a feeling of having one’s privacy invaded. Annoyance can vary widely between different people, however.
As well as the type and volume of the sound, other factors include how much it interferes with your activities, the fear you feel associated with the source of the noise, your coping mechanisms and even your belief about whether the noise is preventable. For example, you’re likely to feel more annoyance to aircraft flying overhead if you feel the airport is taking no measures to regulate the noise. However, the impact of annoyance on long-term health isn’t clear and the evidence actually suggests mental ill-health may increase the risk of annoyance rather than the other way round.
The health effects of quieter, background noises and “hums” such as the one heard in Bristol are also less clear, although they can certainly cause discomfort and annoyance. Similarly, a recent review of very-high frequency ultrasound (which cannot be consciously heard) concluded that the general population is much more exposed to ultrasound than in the past. It recommended that reports of symptoms such as nausea, headaches and dizziness that some people have linked to ultrasound should be further investigated.
Another important area of noise research is the effects on children’s learning. About 20 studies have found effects of either aircraft or road traffic noise on children’s reading abilities and long-term memory. One found that aircraft noise was associated with poorer reading comprehension and memory, after taking both the children’s social position and the road traffic noise into account. In the UK, reading age was delayed by up to two months for a five decibel average increase in aircraft noise exposure.
Now that we know noise can be harmful, the difficult question is why? Aircraft and traffic noise is inevitably tied to the production of air pollution but researchers usually take this into account when studying the problem. And there are probably separate reasons why noise and air pollution can impact our health. The effects of particles from air pollution are largely to do with inflammation, whereas noise exposure increases stress levels leading to physiological arousal, such as raised heart rate and blood pressure.
This can lead to increases in established cardiovascular disease risk factors such as blood pressure, blood glucose concentrations, blood fats and even central obesity. And in turn, this can produce sustained elevation of blood pressure and atherosclerosis (narrowing of arteries due to fat deposits) and eventually in some people to serious events such as heart attacks and strokes.
Because people’s bodies still respond to noise during sleep (and it wakes you up), one suggested pathway to ill-health is through repeated sleep disturbance. Being exposed to sound while you’re asleep can particularly affect breathing, body movements, heart rate, and when you wake up. And you’re more likely to be affected if you’re elderly or a child, or you work shifts or have poor health. Research has also found that self-reported sleep disturbance is worse when it comes from aircraft noise than road traffic.
The impact of noise on children’s learning is less well understood. It may be as simple as aircraft noise interfering with teachers communicating with pupils, or it may be that pupils focus their attention so narrowly in noisy conditions that they exclude useful speech as well as unwanted noise. But we do know that it’s not just due to the fact that people living around airports are sometimes poorer because when researchers have taken this into account they’ve found their results still apply.
What is clear is that noise pollution does affect a large number of people and is a significant risk to their health. Because of this, we need to think about interventions to reduce noise at source by masking or screening it using barriers or sound insulation, or even better by designing our society to be less noisy in the first place.