Sources for railway community noise modeling

For rail traffic, the wheel-rail interaction is one of the most important sources of noise, and is included in different ways in the noise calculation methods being used in Sweden today. However, if the rolling stock exhibit other noise sources it is not clear how they are handled by the different calculation methods. Recent measurements in Sweden of the newly refurbished 'X2' passenger trains indicate that cooling fan exhausts mounted high up on the driving unit radiate noise at levels corresponding to the wheel-rail noise at speeds of 200 km/h. The NMT96 calculation method currently used in Sweden represents the whole train as one line source per octave band, each placed at different heights. The newer Nord 2000 method, applies three sources at low heights for rolling noise and allows additional sources but without defining how to accommodate them. The Cnossos-EU method puts all potential exhaust and fan noise at the higher of two sources, at 4 m above the rail. None of the models define how to apply a source to just the locomotive as sound power is given per meter train or per rolling axis. The impact on noise exposure and mitigation is discussed in this paper.