But are the trains getting any quieter?

To reduce railway noise effectively a good knowledge of the source mechanisms is first required. Wheel/rail interaction in particular results in a multiple source environment where wheels, rails and sleepers all play a role. This is a classic noise control problem where treatments will not be successful unless they take account of the relative importance of each source and apply appropriate measures for all the significant sources. Starting from theoretical research into source modelling, a number of practical techniques have been developed for reducing railway noise in the last 10-20 years, which will be discussed. While focussing on rolling noise, the related problems of curve squeal, bridge noise, aerodynamic noise and vehicle interior noise will also be mentioned. Finally it is recognised that the railway industry faces many pressures that make it reluctant to change, so the difficulties of practical implementation will be discussed