Influence of rail and wheel roughness on rolling noise: Measurements and analysis
Roughness of the rail and wheel running surfaces produce rolling noise – the most significant form of noise due to wheel-rail contact. Rolling noise from conventional metro trains, tramways, streetcars, electrical or diesel multiple units and even high-speed trains is a key consideration during the design, homologation and testing phases; and rail and wheel roughness forms an intrinsic part of the examination. CETEST has extensive experience in rail and wheel roughness measurement and analysis, which has been gleaned during the course of several projects around the world. For Global Railway Review, Jesús Otero Yugat, Field Test Engineer at CETEST, explains further.
Wheel and rail roughness are characterised by the undulations of the surfaces. When the wheels turn the undulations produce vibrations of a particular wavelength – and therefore noise. In terms of rolling noise, important wavelengths of roughness are focused in the range of 5mm to 500mm, with amplitudes from tens of microns at long wavelengths to less than a micron at short wavelengths1. Evidently, this kind of roughness is not visible to the human eye and would appear as a smooth surface. Longer wavelength roughness excites lower frequencies and are not significant for rolling noise; instead they are relevant to ride comfort and ground vibration.