Advanced noise-dampening technology has been retrofitted to UK rail tracks for the first time as part of the Thameslink Programme.
SilentTrack was developed by researchers at Southampton University and engineers at Tata Steel, and is already installed at more than 90 miles (140km) of localised ‘noise hot-spots’ in 13 countries around the world.
Due for completion in 2018, Thameslink will provide more frequent and longer new-build trains to three central London stations.
This will mean significantly increased traffic through Blackfriars station with associated noise concerns, as David Benton explained to The Engineer.
‘You don’t just go out and measure one train and say: “ah yes, that train is noisier”. In fact, the train may be even quieter. But if there are more trains the overall noise impact during a particular day or period will be increased… it’s called a time-weighted average.’
In all, 0.8 miles (1.3km) of SilentTrack will be required to bring the stations within noise regulations based on the technology delivering up to a 50 per cent reduction in noise.
The system comprises two or three resonant masses of Scunthopre-made steel embedded in elastomer with a high damping factor. The dampers are attached to either side of the rail with spring clips.
The original development stage at Southampton’s Institute of Sound and Vibration Research focused on acoustic phenomenon at the wheel-rail interface.
As a result, the dampeners can be tuned to the characteristics of a particular stretch of track. According to Tata, this includes any type of rail profile (UIC54, 60E1, 56E1 and so on), fastening type (Vossloh, Pandrol, Nabla and so on), or sleeper (concrete mono-block or bi-block, concrete slab, steel, timber and so on).
‘The main track parameter that affects acoustic behaviour is something called decay rate, which is the rate at which vibration in the rail dies away for each particular frequency. It is a physical property of the track that can be readily measured,’ said Benton.
‘After doing this you can then understand for a particular track what are the main frequencies that you’ve got to try and target, because the frequencies where the decay rate is the worst will be the frequencies producing the noise.’
SilentTrack has undergone extensive technical and safety testing to check it does not interfere with the operation or maintenance of railways, according to Tata.