In a bid to reduce the impact of aircraft noise on local communities, Stockholm Bromma airport is on the verge of erecting a transparent perimeter wall that will minimise the sound of its operations, while enabling onlookers to view them.
However, in keeping with the thorny nature of noise pollution issues, the desirability and effectiveness of this type of solution is open to debate.
The SkyWall concept was designed by French architecture firm Red-architectes as an entry to a competition run by Swedish airports operator Swedavia. The competition called for solutions to reduce ground noise for local residents living near Stockholm Bromma, and drew almost 100 entries.
SkyWall is a glass barrier designed for construction along one side of the airport’s single runway, with the dual aim of reflecting aircraft noise back into the airport, while also preserving the view for residents in the neighbouring Bromma Kyrka district. At its maximum height, the wall can reduce aircraft ground noise for local residents by “between 10 and 12 decibels [dB]”, says Albin Rousseau of Red-architectes. The greatest noise reduction is achieved closest to the wall.
“One of the difficulties was to determine the maximum height of the wall, because of regulations. We had to find a good height to meet the regulations and reduce noise,” says Rousseau. This meant the design of the wall is “not totally flat”, with its height varying from 3m (9.8ft) to 10m along its length.
Swedavia is in the “very early stages” of technical investigations to determine whether to go ahead with installing SkyWall, but is hoping to have it built by the end of next year, according to Stockholm Bromma environmental advisor Linnéa Franzén.
Part of the reason why SkyWall was selected as the winning entry, says Franzén, was that “we can adapt the solution to the landscape to make the airport part of the city”. She adds that local residents have stressed the importance of keeping “as much of a view of the airport as possible”.
However, this is where other airports differ in their views on transparent solutions such as SkyWall. London Gatwick, for example, is of the firm belief that its local residents do not wish to see or hear its operations.
“Communities around Gatwick would rather not see it or hear it. Visual intrusion is seen as being the same as noise intrusion,” says the airport’s head of corporate responsibility, Tom Denton.
Gatwick currently has a large earth bund to the northwest of the airport, which serves to “reduce noise for communities and visibly shield them from seeing aircraft”, Denton says.
The SkyWall was chosen as residents indicated they want to retain a view of the airport
Red-architectes
If the airport succeeds in its bid to add a second runway it will construct “a mix of noise walls and bunds”, says Denton – but it is “not looking at any see-through solutions.
Denton acknowledges both solutions can only reduce aircraft noise for residents by “a few decibels”, but points out that anything resulting in noise reduction in excess of 3dB is “more than worth doing”.
Acoustic bunds and walls are among a number of other noise reduction measures under consideration at Gatwick, as it fights to win the right to build an additional runway. The airport has set aside £45 million ($75 million) for a council tax reduction initiative that would entitle households newly affected by the noise from a second runway to shave £1,000 off their council tax bills annually.
Denton says the proposal has “gone down reasonably well” with local residents, although he adds: “£1,000 is never going to take the noise away. We could have offered £10,000 and [residents] would have said it’s not enough.”
Under its domestic noise insulation scheme, Gatwick offers residents living 15km (9.3mi) to the east and west of the airport up to £3,000 towards installing double-glazing and loft insulation in their homes. If a second runway is approved, the size of this zone of entitlement would double, Denton adds.
Back at Stockholm Bromma, the airport has recently insulated 900 buildings from an inventory of 1,300 nearby homes and schools it will analyse on an annual basis to see if more measures need to be taken. Swedavia says it will use an established international noise calculation model in conjunction with local Swedish standards “to ensure that buildings don’t have a yearly average noise level indoors, caused by air traffic, of higher than 30dB”.
However, noise level measuring techniques – and the way in which the effects of noise can be monetised – are controversial issues. A recent study by noise specialists at Berry Environment and Anderson Acoustics said: “Monetising noise effects appears as a critical issue for noise policymakers and private airport operators to facilitate decision-making.
“However, the uncertainties and lack of agreement on threshold levels over relationships, as well as the implications of confounding factors, are major limitations for monetisation purposes.”
Aircraft noise management, the report says, is a “context-dependent process” for which there is “no silver bullet”.
The UK Airports Commission, as part of the process for deciding where to build additional airport capacity in the southeast of the country, is considering “incorporating the monetary values from the impacts of aircraft noise on annoyance, sleep disturbance and cardiovascular diseases”, the report adds.
Different methodologies will be used for the annoyance versus health factors, but the report concludes that “the results are indicative and should only be used to understand trends, rather than being used to absolutely qualify the effects”.
The Aviation Environment Federation (AEF) agrees there is no silver bullet, and is calling for alternative approaches to be considered. “For example, it would be possible to set a target to limit aviation noise to a given decibel level, and then to calculate the cost of bringing noise down to this level – whether by limiting aircraft activity or by using quieter aircraft,” the AEF says. “Such an approach, which focuses on the cost of reducing the issue rather than the cost of the damage caused by the issue, is now widely used in relation to applying a monetary value to carbon dioxide emissions.”
Noise is a particularly prevalent issue in the ongoing debate over where to build additional runway capacity in the UK. London Heathrow, which is hoping to be given the green light to build a third runway, recently opened a public consultation on new noise compensation proposals.
In addition, the airport has released data from the UK Civil Aviation Authority which shows that if a different noise calculation method to the one favoured by UK regulators were to be used, significantly fewer people would be affected by noise from a third runway by 2040 than are affected today.
Using the 55dB Lden measure, Heathrow says 28-45% fewer people would be affected by 2040. However, using the UK Government’s preferred 57dB LAeq measure, this percentage would drop to 15-21%.
However, Gatwick’s Denton says while there is “nothing to stop us as an airport from using Lden, we can’t use it from a regulatory point of view for noise action plans” because the CAA has “no plans” to adopt this approach.
Source: Flight International
