Division Vehicle, track and superstructure transfer function
United Kingdom
Three speed-independent transfer functions, LH,TR,i LH,VEH,i and LH,VEH,SUP,i , are defined: the first for each j-th track section and the second two for each t-th vehicle type. They relate the total effective roughness level with the sound power of the track, the wheels and the superstructure respectively.
The superstructure contribution is considered only for freight wagons, therefore only for vehicle type ‘a’.
For rolling noise, therefore, the contributions from the track and from the vehicle are fully described by these transfer functions and by the total effective roughness level. When a train is idling, rolling noise shall be excluded.
For sound power per vehicle the rolling noise is calculated at axle height, and has as an input the total effective roughness level LR,TOT,i as a function of the vehicle speed v, the track, vehicle and superstructure transfer functions LH,TR,i , LH,VEH,i and LH,VEH,SUP,i , and the total number of axles Na :
for h = 1:
| LW,0,TR,i = LR,TOT,i + LH,TR,i + 10 × lg(Na ) | dB | (2.3.8) |
| LW,0,VEH,i = LR,TOT,i + LH,VEH,i + 10 × lg(Na ) | dB | (2.3.9) |
| LW,0,VEHSUP,i = LR,TOT,i + LH,VEHSUP,i + 10 × lg(Na ) | dB | (2.3.10) |
where Na is the number of axles per vehicle for the t-th vehicle type.
Figure [2.3.c]
Scheme of the use of the different roughness and transfer function definitions
A minimum speed of 50 km/h (30 km/h only for trams and light metro) shall be used to determine the total effective roughness and therefore the sound power of the vehicles (this speed does not affect the vehicle flow calculation) to compensate for the potential error introduced by the simplification of rolling noise definition, braking noise definition and impact noise from crossings and switches definition.