Reduction of Freight Train Noise: Wheel Absorbers are Entering the Real Operation Phase

Freight train noise is still the main annoying kind of railway noise. The launch of composite brake blocks has shifted the need for further measures by about ten years into the present days. However, freight train operation is determined by very different constraints compared with passenger traffic. The main feature is that no freight would pay a higher price for travelling with a silent train. Therefore, the implementation of any measure must be triggered and supported by an external support, usually a public authority. At first, the general absorbing principles together with technology constraints are shown, followed by an assessment of the operational usability. The operational conditions are leading to highly increased requirements on the mechanical strength of the wheels. Also, the resistance to chemical impacts became important when the related loads are carried. A very special condition is a high temperature load up to 500 °C at the wheel tire. Schrey & Veit has started the setup of freight wheel absorbers in about 2000, keeping the principle of the wheel specific tuned mass-spring systems. GHH-Radsatz has set up a related wheel design. During a research & development project, funded by the Swiss Federal Office for Environment, an important step towards the real operation phase was taken. This includes design improvements as well as field measurements for the standardized benefit quantification. A benefit of 4 dB was proved. The paper gives an overview on the current end user's view together with political/co-funding options, on the technical/acoustical requirements, on the development methodology and presents an example of a ready-to-market product. Additionally, today barriers for a widespread usage are summarized, leading to ideas on next steps.