Findings: End of the line for train noise

April 4, 2003

Living near a railway line could soon become less stressful thanks to research from the University of Southampton, writes Martin Ince.

The Institute of Sound and Vibration Research at Southampton has been developing a method of silencing rail noise that would make railway lines a more acceptable neighbour, especially in inner cities where noise is one of the main objections to new railway routes.

A European patent has just been granted for the invention and it is being commercialised by Corus, the UK-Netherlands steel producer.

Chris Jones, a former British Rail researcher now at Southampton, said: "We started this work in 1997 with funding from the European Commission's Framework programme for research, under an initiative called Silent Track.

We have developed a damper that fits inside the rail along its whole length and massively reduces the sound produced when a train passes along and makes the rail vibrate, which is the main source of noise in middle frequencies."

The material is a rubber elastomer chosen by Southampton from 47 samples supplied by companies across Europe. It reduces the vibration of the rail that causes the noise. Each piece is tuned to the particular stretch of track where it is used, either in the factory or when it is retrofitted to an existing line.

Dr Jones said: "The material is fitted along the track on both sides of the rail. It has to be narrow enough not to interfere with the clips that hold the rail in place, and shallow enough to allow the machinery that lifts rails to grip them."

The institute's role was to find materials that could fit into the corner of the rail but had enough stiffness to dampen the rail's vibration.

Dr Jones said: "Using this material typically produces a 6 decibel reduction in the noise you hear. Imagine standing in a room with ten vacuum cleaners running. That reduction is equivalent to turning seven or eight of them off. You can get a higher reduction, about 10 decibels, by building a noise barrier all along the track, but they are intrusive and cost more."

Some European countries, including the Netherlands and Switzerland, impose a maximum "noise dose" along railway lines. A damping system would allow tracks with such limits to carry four times as many trains as they can today. The material has been tested on railways in France and the Netherlands along two 900m test tracks. Eventually, Corus could sell thousands of kilometres of it. The main uses would be in cities and on railways used for very heavy freight trains, which can be a substantial noise nuisance at night.

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