Turning the volume down in Europe's cities
Millions of European city dwellers endure urban noise pollution every day. Apart from its nuisance value, noise in Europe has health risks with stress and cardiovascular issues being particular concerns, according to the World Health Organisation (WHO). The social costs of traffic noise in Europe have been estimated to 0.4% of total economic output, mainly from road transport.
This phenomenon has now been recognised by the European Union (EU) as an environmental issue. The European Commission unveiled plans in December 2011 to cut vehicle noise in the coming years. And the 2002 EU Environmental Noise Directive already placed heavy obligations on city authorities to sort the problem out. To support them, the Commission has invested millions of Euros in research projects to find new ways of reducing urban noise.
Until recently, research into noise reduction focused mainly on insulating buildings against urban noise. Little attention has been given to quietening the urban environment itself, but this is now changing.
“Urban noise can be tackled in two ways. If we can do something with the source of the noise first, we will. After that, we look at the way sound is propagated and perceived,” says Jens Forssén of Chalmers University of Technology, Gothenburg, and the project coordinator of HOSANNA, an EU-funded project tasked with looking at urban noise.
HOSANNA provided a toolbox to reduce road and rail noise pollution that goes beyond traditional solutions such as sound barriers and speed limits. “We looked at a range of solutions that can help with urban noise reduction. For example, sound barriers that exploit soft materials, vegetation or possibly recycled materials could achieve significant reduction in noise compared to the straight-sided sound barriers commonly used now,” Forssén says. “The perception of the sound scope overall is very important, which is why we applied a range of assessments, including questionnaires and even physiological measurements of stress, to assess the effectiveness of the measures we will finally recommend.”
The 13 project partners involved in HOSANNA, which ran for three years until November 2012, are supported by a €3.9 million EU grant. The project’s wide-ranging proposals have already attracted interest from architects, city planners, acoustic consultants, noise control engineers, and various other decision makers.
One success story supported by HOSANNA was in Lyon, where researchers showed that a natural plant sound shield could deliver significant noise reduction. The project involved setting up a barrier just 15m long, 1m high and 40cm thick in front of the Church of St George on Lyon’s busy Quai Fulchiron.
The wall was made of recycled materials - including coconut fibres and lava stones - and some 1,200 different plants. “Although it is low in height, it is able to muffle sounds,” says Bruno Vincent, who is a director of Acoucité, a Lyon-based urban noise observatory that worked with HOSANNA on the project. The acoustic performance of the barrier was measured before and after the barrier was erected, with pedestrians asked to assess the sound environment. “The prototype was able to stop sound waves and create a quiet acoustic zone: the noise reduction behind the wall was estimated at between four and eight decibels,” Vincent says.
Vincent, who has worked on noise issues for 25 years and has a PhD in environmental psychoacoustics, says the barrier was also successful in raising interest with politicians and city engineers. “It showed how vegetation could be used to deal with noise,” he says. A key to the success is that it reduced noise and also raised the attractiveness of the location. “It addressed a real problem with a solution that is both practical and visually pleasing: it could be both acoustically efficient and aesthetically attractive,” says Vincent. “So it is good for us, and it is good for our quality of life.”
Reducing noise at source is an obvious place to start when tackling noise pollution. While tyres are widely acknowledged as the biggest source of noise in the urban environment, noise from cooling systems in vehicles such as cars and trains can come close.
ECOQUEST, a research project backed by a €2.4 million EU grant addressed the issue by looking into vehicle cooling systems. The three-and-a-half year project, which runs until mid-2013, has developed innovations that could lead to cooling units with reduced noise profiles and decreased carbon dioxide emissions.
ECOQUEST’s focus was on cooling systems in trains and cars, designing new compact layouts, innovative heat management strategies and low energy/noise components. “We developed methodology for tools to make predictions about more efficient and quieter systems. And we have been applying these tools to fans,” says Manuel Henner, one of ECOQUEST’s research leaders.
Henner, who is also an expert on fan systems and airflow management at French car parts maker Valeo, says ECOQUEST has already written some patents from its research on how to use the fan system to counter downswings, and adapt to the real conditions of the engine. “This will reduce costs, weight and electrical consumption. So this improves fan system efficiency, and therefore the performance of the engine,” Henner says. A prototype of the system was due by the end of 2012 to test the research and show the various efficiency gains. “It is about reducing 1 or 2% of engine consumption. That might not seem much, but it matters when you talk about the entire European car market,” he says.
Henner says that the project, which began at the end of 2009, arrived at the right time, just as the economic downturn was hitting. “Without this project, we probably would not have been able to learn what we did,” he says. “Sometimes, you are shooting in the dark, and so you need a framework of a project, with a budget and partners. ECOQUEST gave us the consistency to carry on. This project was an opportunity to invest, continue and learn.”