Traffic, trains, nightlife – in cities everywhere, there is a near constant background hum that most people simply get used to.

But research shows that this background noise can affect your sleep, stress levels and even increase your risk of heart disease and high blood pressure.

Indeed, noise is now considered the second biggest environmental health risk in Europe after air pollution. Around one in five people living in European cities are exposed to harmful levels of environmental noise.

I study how sound shapes cities, including how environmental noise affects health and everyday life. This makes Denmark and England an interesting comparison because, despite facing similar challenges, each country has made different choices about how much noise is accepted as part of urban life.

Health Gap / Sundhedskløften is a collaborative series from The Conversation UK and Denmark’s Videnskab.dk exploring what the two countries can learn from each other when it comes to health and wellbeing.

From cycling and alcohol to inequality, healthcare and everyday habits, the series looks beyond hospitals and medical treatment to explore how culture, politics and society shape the way people live – and how healthy they are.

Take both capital cities, for example. At roughly 13 times the size of Copenhagen, London is a much busier and louder city, so you might expect it to have a much bigger noise problem. But the reality is more nuanced.

As the largest cities in their respective countries, both London and Copenhagen experience substantial noise from busy roads, railways and airports.

But while from the outside, Copenhagen can look like a quieter city characterised by cycling and low-rise neighbourhoods, it would be wrong to romanticise it as quiet.

Indeed, across Denmark, the Danish Environmental Protection Agency has found that almost one in three homes are exposed to road traffic noise above the national guideline of 58 decibels (dB).

A noise level of 58dB is roughly comparable to a normal conversation or the background noise in a quiet office. While it’s not loud enough to damage hearing, long-term exposure, especially in the home, can disturb sleep and increase the risk of certain health problems, which is why it’s used as a planning guideline.

Overall, around 16% of the population in Denmark – roughly 918,000 people – are exposed to transport noise above recommended levels, most of it from road traffic.

England uses a different threshold, making direct comparisons difficult. Even so, around 40% of adults in England are exposed to long-term road traffic noise of above 50 decibels.

Managing noise

The biggest difference between Denmark and England, however, is not simply how noisy cities are, but how it’s decided what level of noise is acceptable.

Denmark treats noise as both a planning issue and a public health concern, with responsibility shared across government and society. Noise limits are used to decide where homes can be built.

In England, there is no equivalent national threshold that acts as a cut-off for further development. Instead, planning decisions are made on a case-by-case basis, balancing noise against housing need and economic growth.

This approach gives local authorities more flexibility, but can also mean people end up living in areas that would be considered too noisy under Danish guidelines.

And it means that whether people can sleep with their windows open, whether children have quiet places to play, or whether green spaces actually feel restorative, can vary a lot area to area.

Can cities ever be quiet?

Both Denmark and England map traffic noise and identify the worst-affected neighbourhoods.

Denmark’s approach, however, places greater emphasis on reducing exposure through measures such as lower speed limits, noise barriers and better insulation. While England gives local planners more flexibility to balance noise against competing priorities like housing and economic growth.

But should noise really be treated just as an unavoidable consequence of modern cities, or more as a public health risk that can be designed around?

Indeed, as the comparison between England and Denmark shows, urban noise is not simply an unavoidable feature of modern life. City planners can choose how they design streets, buildings and neighbourhoods around sound.

As populations grow and cities become denser, such choice will become increasingly important. The question then is not whether cities will be noisy – they will – but how much noise people should be expected to have to live with.

This series was commissioned as part of a partnership between Videnskab.dk and The Conversation, where articles are published in English and Danish.