Noise pollution causes violence

An aircraft lands at an international airport. 

WRRAAAAOOOOOOAAAAUUUUUUMMMM! 

Just seconds later, another aircraft lands. 

WRRAAAAOOOOOOAAAAUUUUUUMMMM! 

And so it continues, for hours on end. Day in and day out. Week after week. Month after month. 

In Europe alone, 4.2 million people live near an airport, and given the noise levels, it is quite understandable that it gets on their nerves. And it really does! In fact, some people are so severely affected by the noise that they lose their temper and become violent. 

Timo Hener, associate professor at the Department of Economics and Business Economics at Aarhus BSS, has examined the impact of noise pollution on crime, and the results, which have been published in the scientific journal Journal of Public Economics, are literally striking. 

“It’s reasonable to assume that if noise can lead to the levels of aggression found in our study, then it can probably also influence other economic behaviour.

^{Timo Hener, associate professor at the Department of Economics and Business Economics, Aarhus BSS, Aarhus University}  

Men, during daytime, in the summer 

According to the study, if an area experiences an increase in background noise of 4.1 decibels, the rate of violent crime in the same area will increase by 6.6 per cent. Men in particular are the victims of the violence derived from noise according to the study, and it is therefore reasonable to assume that the perpetrators are men as well, and that noise triggers aggressive behaviour in men in particular.   

The additional violence occurs mostly between 06:00 and 18:00, which leaves out nightlife as a possible setting of the crimes. And it occurs more often during summer, when people spend more time outdoors and are therefore more exposed to outdoor noise. 

"There is a strong focus on air pollution and the health impacts of air pollution but not much research to explain how noise pollution affects us. We know that noise can also affect health, but all the other effects of noise on humans have only been studied to a limited extent," says Hener about the background for his study. 

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Frankfurt Airport 

More than 1,300 aircraft land in Frankfurt Airport every day and approx. 70 million passengers move through the airport annually. It is the fourth busiest airport in Europe. 

Background noise in and around airports is consistently monitored, and Timo Hener examined the noise levels in 12 municipalities up to 30 km to the east or west of Frankfurt Airport. 

Frankfurt Airport was the obvious site for Timo Hener's experiment, because the wind and weather conditions at the airport determine whether the aircraft land on the east-facing or west-facing runway. This circumstance makes the relationship between noise pollution and the increase in violent crime causal. 

Landings make more noise

Timo Hener only examined aircraft landings. There were three reasons for this.

• Firstly, more than half of all departures from Frankfurt are in a southward flow via a dedicated take-off runway, which operates independently of landings.
• Unlike landing aircraft, departing aircraft do not have to fly in a straight line for a longer period of time, and they therefore have more flexibility with regard to avoiding densely populated areas.
• Departing aircraft ascend quicker than landing aircraft descend, and departing aircraft therefore affect fewer areas for shorter periods of time.

For example, if you live west of Frankfurt Airport, you may be exposed to noise from 700 landings one day and then zero landings the next day. The same applies if you live in one of the municipalities to the east. And this variation in noise exposure is directly reflected in the violent crime rates.

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It is reasonable to assume that house prices are lower in areas adjacent to an airport, thus attracting economically disadvantaged population groups, which could negatively affect crime rates in the area. However, this is not the case for Frankfurt Airport. There are no special characteristics about the population in the affected areas around Frankfurt Airport, according to Timo Hener’s study. 

"The 30 km long descent paths used in the empirical analysis affect municipalities with large populations and average socio-economic characteristics," he writes in his article. 

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More violence 

The 12 municipalities have an average population of 61,000. Over a period of around three years, the study analysed a total of almost 14,000 observations, distributed more or less equally between the east-facing and west-facing landing runways. 

When considering all variables and alternative options, Timo Hener's analyses show that for each decibel increase in the noise, the rate of violent crime increases by 1.6 per cent. This may not sound like much, but the study also shows that, with approx. 700 aircraft landing at the airport during a day, the background noise increases by an average of 4.1 decibels. This corresponds to an experienced noise increase of 33 per cent, which leads to an actual increase of 6.6 per cent in the rate of violent crime. 

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Massive cost 

In human terms, this amounts to 246 more people becoming victims of violence every year in the areas of Frankfurt covered by the study. All because of noise from the airport. For the 4.2 million people who live near an airport in Europe, this corresponds to a total of 1,033 additional incidents of violent crime each year due to noise pollution from air traffic. 

Estimates of the cost for society of just one violent crime incident vary between DKK 189,000 and DKK 749,000 annually, which means that the increased violence caused by air traffic in Europe leads to increased costs of between DKK 189 and 777 million. 

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Road-traffic noise 

If we transfer the results to estimates of noise from road traffic, assuming that the effect may fluctuate from ‘the same level’ to ‘one-third of the same level’, then a 2-decibel reduction in road traffic noise could cut violent crime incidents by 4,000-13,000 each year in Europe and 4,800-14,400 in the USA, totalling a socio-economic cost of DKK 1.7 and 21 billion. 

According to Timo Hener, the study reveals three things in particular. 

"First of all, the study shows that noise has a causal effect on crime. Noise can trigger aggressive behaviour in people. Secondly, it affects everyone, and the impact is instantaneous. On the other hand, how people react varies. Thirdly, it is reasonable to assume that if noise can lead to aggression to the extent shown, then it can probably also influence other economic behaviour, which could even have long-term implications. For example, productivity or financial decisions. But more research is needed to verify this," says Timo Hener.