When the traffic on the West Metro line begins, the metro will be a fairly silent affair, as revealed by the measurements of Akukon Oy, the company responsible for the noise abatement designs of the metro. Akukon has measured in the buildings near the metro line the so-called structure-borne noise, i.e. the noise of the metro train transmitted through the bedrock. Without noise abatement, the sound of the metro train passing underground could be heard as a booming sound in nearby buildings.
Control measurements performed late last year and early this year show that the noise insulation designed by Akukon are functioning everywhere the way they should – up to the point where the metro noise actually remains significantly below recommended values. In practice, the noise made by the metro cannot be heard in the buildings above the metro line, and even in silent spaces, they cannot be distinguished from other background noise.
The check-ups involved four different locations, representing all materials used in the insulation of the structure-borne noise of the metro. The measurement locations were purposefully selected among those with the potentially highest noise levels: houses directly above the rail on the crest of the rock or from rocky areas. Measurements were always performed at the lowest floor of each building.
“We have succeeded with the design, material choices and building of the West Metro in that the noise of the metro will not disturb people living or working in the area,” says Timo Peltonen, Technical Director at Akukon Oy.
Noise abatement was designed combining empirical professional knowledge gathered over decades and computer-assisted 3D modelling. This made it possible to predict which houses and areas could be the most exposed to structure-borne noise and to choose suitable materials for noise abatement.
Steel rails are now resting on a bed of macadam and noise insulation. A mat under the macadam helps to absorb the vibration travelling from the tracks to the bedrock. The noise insulation has been installed throughout the West Metro line excluding sections that pass under the sea or the Länsiväylä motorway, as it is not needed there.
Further information: Timo Peltonen, Technical Director, Akukon Oy: tel. +358 50 584 9814