CityHush leads to less traffic noise in European cities . CityHush asks the question: how do we reduce the noise from traffic in our cities? Seven countries and several companies are engaged in the joint European project called CityHush. The project co-ordinator is acoustic specialist Martin Höjer of Tyréns in Stockholm.

“Noise is a major health problem, which creates stress, raises blood pressure and shortens lives. We are developing various measures to help city planners, traffic specialists and others to be able to reduce the problem,” Martin says.

The challenge of CityHush
More than a fifth of Europe's population lives with persistent disturbing traffic noise (over 60 decibels) that is a danger to health.

Even more live in the constant roar of traffic. Noise pollution is one of our worst environmental problems. It is no easy task that Tyréns's acoustic engineer and his colleagues are working with in the joint European project CityHush.

There are partners from 7 countries engaged in CityHush. From Sweden the construction company NCC is participating, along with the Stockholm Environment Department, the Traffic Authority in Gothenburg and KTH (Kungliga Tekniska Högskolan - .the Swedish Royal Institute of Technology). They are to assist in developing complete solutions to reduce noise in cities by up to 10 decibels.

At the same time it is desired to reduce the spread of particles, reduce carbon dioxide emissions and bear in mind that cities need functional traffic flows. They will also indicate the costs for various types of measures.

CityHush is a further development of an earlier EU project called Qcity, which mapped the noise problems in larger cities.

“Now it is a matter of producing an action plan and giving social planners tools in order to tackle the problem,” continues Martin.

Solutions with CityHush
CityHush looks at several concepts. One is to create quiet zones (Q zones) inside cities, such as for example by redirecting traffic, only permitting electric vehicles in certain areas and introducing parks.

“We will be able to show to what extent noise can be reduced and what this means in terms of costs and the traffic situation in general,” Martin says.

Completely eliminating noise in towns and cities is not realistic. On the other hand, one can build in quieter areas. Just to be able to get away from noise for a while is very important, for example in back yards, parks and vehicle-free areas.

The need is greatest in so-called hot spots, densely populated city areas with a lot of noise where the death and illness rates are higher than normal. In order to assist city planners, CityHush is developing methods for easily identifying hot spots. Noise mapping and hot spots are put on public display so that they can be seen by everyone.

Another concept for quieter towns and cities as to have quieter road surfacing and car tyres. In this case, among others, NCC's road surface specialists in NCC Roads are helping to develop low-noise road surfaces. Tyréns is studying, together with tyre company Goodyear, low-noise tyres, which among other things has led to a completely new type of tyre, which Tyréns has patented. It consists of two narrow tyres joined as a pair, instead of a broader tyre. This reduces the tyre noise that is caused by the rubber striking the ground during driving.

There is also a focus on studded tyres. These generate much more noise than non-studded winter tyres. In addition they tear up damaging particles and necessitate tougher and harder road surfacing that leads to all types of tyre making more noise.

Another concept under study to reduce tyre noise is to provide cars with reinforced wheel housings. Noise inside houses in locations with disturbing traffic not only comes from so-called airborne noise. Noise can also spread through structures in the form of vibrations. Low frequency vibrations can pass right through a house and radiate noise from walls, ceilings and floors of rooms.

“More knowledge about this problem will affect how we build houses in the future,” says Martin.

Results from CityHush
The quiet zones and calculation methods for finding hot spots are important facets of CityHush. The zones are set up in particularly exposed areas and create calming breathing spaces for the local residents.

“However it is not certain that quiet zones are always the best solution. In some conurbations they can be unreasonably expensive, and in others lead to severe traffic jams. However they could work in some cases,” says Martin.

The aim of CityHush is to examine the possibilities of various concepts, such as road surfacing, tyre technology and giving city planners calculation models to determine how suitable and efficient it would be to create quiet zones.