Rolling Noise


TrainTrack_Rolling Noise

As a railway wheel rolls over a railway rail, rolling noise is generated, the faster the wheel runs, the more noise is produced. The general trend is that train speeds increase, at the same time as the number of trains trafficking railway lines increase, so, railway noise also increases if nothing is done to control it.

Rolling Noise

Strict noise regulations limit the possibility to build new dwellings near railway lines, at the same time existing dwellings limit the possibility to increase railway traffic, and to shift transports to rail, a high-priority goal in the EU.

Consequently, rolling stock and track builders need to build quieter trains and tracks. By selecting components with particular parameters (e.g. stiffness, mass, and damping a track can be low-noise optimized.

Our rolling noise prediction model is an invaluable tool in performing a low-noise optimization of a railway track. Calculations are performed in the time domain, and are thus more realistic than calculations with frequency-domain models, because non-stationary and non-linear rail-wheel–contact interaction effects are adequately accounted for, which becomes more important as train speeds increase. The model is well documented (see References below).

The picture below shows calculation results of rail vibrations for a railway wheel rolling over a railway rail at 300 km/h for two different cases: for a rail supported by stiff pads; and for a rail supported by soft pads. The pad is a piece of rubber isolating the rail from the sleeper. The stiffly supported rail vibrates more than the softly supported one above 1000 Hz; below 1000 Hz it is the other way around. This result applies for a specific choice of parameters such as train speed, rail roughness level, etc. Other parameters and rail/wheel combinations may give other results.

Rolling Noise Graph

The example above demonstrates the importance in performing a low-noise optimization as part of the design of a new railway track, which Sound View Instruments can help clients in the railway industry with.

 

References

  1. Anders Nordborg. Vertical Rail Vibrations: Noise and Structure-Borne Sound Generation. PhD thesis, Kungl Tekniska Högskolan, Stockholm, Sweden, 1995.
  2. Anders Nordborg. Vertical Rail Vibrations: Point force Excitation. ACUSTICA • acta acustica 84(2): 280‒288, 1998
  3. Anders Nordborg. Vertical Rail Vibrations: Parametric Excitation. ACUSTICA • acta acustica 84(2): 289‒300, 1998.
  4. Anders Nordborg. Wheel/rail noise generation due to nonlinear effects and parametric excitation. Journal of the Acoustical Society of America: 111(4):1772‒1781, 2002.
  5. Nordborg, O. Lundberg. Contributions of contact nonlinearities to wheel/rail noise generation. Forum Acusticum 2014 Krakow.
  6. Anders Nordborg, Torsten Kohrs. Ein Zeitbereichsmodell zur Beschreibung der Rollgeräuschentstehung. DAGA 2015 Nürnberg.