Berlin - That noise poses negative health risks is undisputed, says André Fiebig, visiting professor at the Institute of Fluid Mechanics and Technical Acoustics at TU Berlin. But to what extent does the risk of damage increase when noise levels rise by five, 1o or 15 decibels? A conversation about Berlin's worst noise sources, why people stop noticing the impact of a speed limit, and how trashed parks diminish people's relaxation.

Berliner Zeitung: Mr Fiebig, what is noise?

André Fiebig: Noise is everything that comprises the negative side of sound pollution. An unwanted sound, in other words, that can lead to damage and impairment. This can be based on a subjective impression, for example if one feels annoyed by traffic. But even sounds that are not consciously perceived as annoying should be considered noise if the sound pollution has a medium- to long-term effect on health.

Why do some people find traffic more disturbing than others?

Many factors influence an individual's perception of an unwanted noise or noise source. Certainly, individual background plays a role, be it the question of where one grew up or the general state of one's health. Some people are particularly sensitive to noise by nature. On average, however, people react similarly to many sources of noise. Hardly anyone loves loud honking cars. A certain volume of traffic noise leads to a certain degree of annoyance.

Does the layout of an apartment or its location influence noise pollution?

There are factors that can reduce the negative effects of noise. In flats that have rooms facing a quiet courtyard or a quieter side of the façade, residents feel less annoyed by traffic noise. The same is true for people who have access to a quiet area near their home. While a quiet room or the park around the corner does not change the extent to which people in their flats are affected by traffic noise, they can then cope better with the noise and feel less annoyed on average.

What are the most critical noise sources in Berlin?

The dominant source is road traffic, because most people are exposed to it. Rail and air traffic, but also noise generated by industry and businesses are other issues that are as relevant in Berlin as in other cities. In recent years, new sources of noise have been added: drones or the pedestrian warning sounds emitted from electric vehicles, which are now required by law. There is still no data on how we should assess these sources. In a large city as dense as Berlin, neighbourhood noise is also a major issue. Studies show that more and more people feel disturbed by it. Such critical attitudes are becoming more prevalent.

André Fiebig

André Fiebig obtained his doctorate in acoustics/psychoacoustics from the Technische University (TU) Berlin. Since January 2019, he has been a visiting professor at the Institute for Fluid Mechanics and Technical Acoustics (ISTA) at TU Berlin, where he leads the field of psychoacoustics.

He is also chairman of the Noise: Effects and Protection committee at the German Acoustics Society. He sits on the editorial board of Akustik Journal. 

Don't you eventually tune out noise sources like the neighbour's crying baby or the construction site outside your door?

We humans tend to come to terms with stress and say: We can't change the noise, we have to learn to deal with it. From a psychological point of view, we try to adapt, develop coping strategies, convince ourselves that the noise isn't so bad. Health impacts can still occur, even if subjectively one has more or less come to terms with the situation. Of course, the exact opposite can also happen: the noise stresses you more and more and you accept it less and less.

A psychological burden, then.

There are noise impact studies that show that people who are exposed to traffic noise in their homes over a long period of time can develop mental illnesses such as depression. Because they can't escape the noise, they feel powerless and eventually resign themselves to it. These are only probabilities, though, and by no means mono-causal links. Every person has different health conditions and can cope better or worse with stress. Not everyone automatically gets sick from noise. Noise is considered a risk factor for health along with many other factors such as diet, lack of exercise, tobacco and alcohol consumption.

Is this the big challenge in noise impact studies?

It's difficult to grasp a life situation in all its complexity. That noises like the sound of traffic are associated with an increased risk of heart attack is no longer questioned among experts. Noise causes negative health risks, that is undisputed. But to what extent does the risk of disease increase if the noise is five decibels louder, or 10 or 15? Determining this is a challenging task.

What else?

Socially disadvantaged groups are significantly more likely to live in noisy areas than people who are financially secure. Those who have money may be able to afford a house or a large flat in a quieter part of town. Those who don't have money live in an area where a lot of people live in a confined space. There are many other factors that determine whether people can live in quieter environments or have to live in noisier ones. We need to include such factors as part of the puzzle in noise impact studies.

Can any harmful effects of noise be directly identified?

Aural noise effects, i.e. damage to the hearing, can be easily proven. Acute stress reactions triggered by sounds are also easy to prove. If I subject a person to loud noise in an experiment, I will be able to measure changes in their heart rate, an increase in skin conductance or a decrease in finger pulse amplitude. If such acute stress reactions are triggered without recovery phases over a long period of time, chronic disease can be the result.

What is the function of hearing in evolutionary terms?

That we can detect danger at any time, even at night. Unlike our eyes, we cannot simply close our ears without aids. So they play a special function, a warning function. Permanent evaluation of noise takes place in order to recognise whether acoustic information is being conveyed in the environment that could be dangerous or relevant for oneself.

Can you give an example?

If you were talking to someone at a party, focusing only on your conversation partner, and someone were to call your name in that noisy room, you would probably register it immediately. This shows that we are constantly evaluating the aural environment, even if we're concentrating on one source of sound. We cannot escape these automatic processes. Psychologically speaking, getting used to sounds to some extent is possible. It is easier for us to tune out the sound of water than spoken language. Even if we do not understand the language, we constantly scan it for relevant information, as studies on office noise show. It is not possible to completely block out sounds, because the ear is always ready to receive sound.

Why then can children sleep through the night in noisy environments?

Toddlers often cry when they are alone in a room. Presumably, this has something to do with the fact that they fear that there is no one around to keep an eye on them and to recognise and ward off possible dangers. If you think about it, you can imagine that at the beginning of a child's development it doesn't seem so important to be able to recognise sounds in one's own environment, i.e. potential dangers. After all, someone else is paying attention. That seems to change over the years. The auditory system is always working and that will also be the case with toddlers. But what the brain makes of it - that is obviously different in toddlers than in adults.

Can sounds trigger different reactions?

Recent studies show that we don't just evaluate our acoustic environment by the degree of annoyance. There are environments that are not actually quiet at all - chirping birds, rustling leaves, splashing water - and yet people find such places relaxing. A day on the well-frequented Tempelhofer Feld or at a public festival in summer is not perceived by most people as annoying, but as exciting in a positive sense. This also applies to the sound situations experienced there. Acoustic environments can of course also trigger negative emotions - loud hectic situations, for example. But silence can also be oppressive and frightening. In noise impact research, we have tried for many decades to establish connections between risk of disease and noise exposure, but we know hardly anything about whether there are acoustic environments that can be beneficial to health. It's changing now. Which sounds trigger which affects is now being researched in a more detailed way.

How would a 30kph speed limit in Berlin affect people's well-being?

We can assume that it would become quieter by a few decibels. To estimate the effect qualitatively: A 30kph speed limit is roughly equivalent to halving the amount of traffic. The actual noise reduction, however, would again be influenced by the actual composition of traffic, i.e. how many trucks, motorbikes and cars are on the road or also the question of the road surface - cobblestones or asphalt. Moreover, it won't be possible to remember the reduced volume with our long-term memory. No one will be able to remember a year after the introduction of the new speed limit how much louder it was before.

So no positive effects at all?

Yes, there are. Even if no one will hear a clear difference, statistically there will be many people who feel significantly less disturbed with a lower speed limit. This is because, in addition to the reduction in the average noise level, the character of noise would change. There would be fewer loud individual vehicles passing by and fewer fluctuations attracting our attention. The flow of traffic would be more constant. Drivers would brake or accelerate less. Road traffic noise will still exist at 30kph, but it would be less noticeable from a psychoacoustic standpoint. With regards to noise impact, it is a sensible and, above all, simple measure. Basically, all you need to do is put up new signs. Of course, there is no guarantee that everyone will adhere to the speed limit.

Would car-free city centres make even more sense?

From the noise impact point of view, it would of course be great because residents there would no longer be bothered by traffic noise. But the reality could be different. If certain urban areas were car-free, this would probably create more traffic in other urban areas. This complicates the overall picture. People living along car-free streets would benefit from the measure. Others would probably be more burdened than before. Would it be fair and ethical that certain people might be exposed to higher health risks than others? Here one has to weigh the effects for everyone. What's more, the mobility needs of a society cannot be completely forgotten. Overall, you don't just need bans, you also have to think about the alternatives.

How can individuals escape urban noise?

If you're alert to the fact that the noises in your environment can affect your health, you have already taken an important step. Then you will more consciously grant yourself rest periods for your hearing and, for example, refrain from permanent media consumption in the form of continuous sound. If we realise that sounds play a major role in our quality of life, we might also be more considerate of others. Society as such would benefit from this. Active Noise Control headphones are also a way of decoupling oneself acoustically from the environment to a certain extent. However, I could imagine that wearing them all the time can also lead to subliminal insecurity, because you no longer recognise possible dangers through your hearing. Another acoustic alternative: white noise.

White noise...

When a person is trying to concentrate, it is extremely counterproductive that they inevitably and permanently scan their noise environment with their hearing. This is familiar from open-plan offices. When two colleagues are talking to each other, you can't help but listen. Short-term memory suffers from this background noise. To reduce this effect, some people listen to white noise. It serves as a measure to mask speech or other attention-grabbing noise sources.

What can the city of Berlin do to reduce noise?

Berlin is already involving the public and listening to where there are particular noise problems in the reality of people's lives and where the city needs to take action. The city can also continue to work on protecting inner-city recreational areas and quiet areas from noise. And make sure that the city does not become even more densely populated. The more people living in a confined space, the more noise problems can arise. Electrification of vehicles like delivery trucks, garbage trucks and public transport, is another important element in reducing noise.

Protecting restful places from noise - why is that so important?

Studies show that quiet areas can have a compensatory effect. They can mitigate certain potential health risks or perhaps even be beneficial to health. Of course, it takes a lot of effort to maintain such small recreational oases or even to create new ones and to keep them permanently clean and maintain them. Because studies also show that a completely littered city park without seating or with broken benches can have a negative impact on the quality of people's stay there, meaning the quieter environment loses its relaxing quality. In this respect, these measures must also be considered when creating green spaces.

This interview was translated from the German original by Maurice Frank.

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