35 dB Lamax is easily achievable with modern technology.
Crossrail is working towards this 35dB maximum (Lamax) for residential properties (see clauses 2.13 & 2.14 of their D10 document on groundborne vibration by clicking here). This is going to be applied to large parts of central London.
These clauses force the contractor to analyse any residential property where noise of the trains will be above 35dB and to use extra measures to reduce the sound levels. These extra measures are a combination of resilient track support and floating slab track. This combination is being used for large areas of the Crossrail tunnels following complaints by local residents (property week article). An email from Crossrail confirmed that they are using such technology on a third of the tunnels.
At the meeting of 25 May 2011, the Northern Line team said that they were looking into extra mitigation measures that will be applied in the more affected areas - but they are not - yet - committing to doing it.
Property week article:
Rubber “noise dimming” rail tracks will have to be installed on parts of the £16bn Crossrail scheme after businesses and residents on the route complained about noise.
Floating slab track, which is the most expensive type of rail track and costs £467 per metre more than standard track, will have to be installed across 4.17km of the route. This will add about £2m to the cost of the rail.
Residents and local businesses affected by the project complained about noise and vibration levels during the Crossrail Bill’s petition period in parliament. As a result, Crossrail has agreed to use the noise-dimming tracks in specific areas.
The slab track will be laid underneath Soho, the Barbican Hall and Bow in east London. A Crossrail spokesperson said other areas were still under discussion, but a decision depended on the final design details.
The project team said the extra cost was included in the Crossrail budget. “We are not prepared to say how much the tracks will cost at this point, but it is nothing compared with £16bn,” a Crossrail source said.
An industry specialist said: “Slab track reduces the noise by about 30-35dB. It was last used in the UK in 1996 on the tube.”
