Modelling the acoustic performance of slab tracks
Licentiate thesis, 2020
Transport is a major contributor to anthropogenic greenhouse gas emissions. Railway transport has a small footprint compared to other means of transport. This is one reason for the construction of new high-speed railway lines world-wide. These lines are often constructed using slab track technology, in which the traditional track configuration of concrete sleepers and ballast is replaced by concrete slabs. In earlier work, it has been found that traffic on slab tracks has higher noise emissions than on ballasted tracks. Rolling noise, radiated from wheels and track, is an important contributor to these noise emissions. To predict the acoustic performance of slab tracks, first, a model for the high-frequency vibration in these tracks is necessary, for which there is currently no standard solution. Further, the effect of the reflective slab track surface on the wheel radiation has not been researched.
In this work, a model for the high-frequency vibrations and acoustic radiation of slab tracks has been developed and implemented. The validity of the dynamic model has been tested on a full-scale test rig. The developed model was then used for researching the influence of track parameters on noise emission. In this investigation, the rail pad stiffness was identified to have a major influence. Besides, a model for the sound radiation of railway wheels over hard reflective surfaces was developed, implemented, and validated. The effect of the slab track surface on the radiation efficiency of the vibrating wheel was evaluated and found negligible. The developed models are steps towards predicting the rolling noise generated by rail vehicles on slab tracks, which is significant both for the planning of new lines and the investigation of potential abatement measures.