ACOUSTIC OPTIMIZATION OF RAILWAY SLEEPERS

A mathematical model of vertical wheelset/track interaction is developed and adopted for minimization of sound power generated by railway sleepers (mono-bloc or bi-bloc). The influence of sleeper material properties, sleeper shape and properties of ballast and rail pads on sleeper sound power can be investigated. The wheelset/track interaction is simulated in the frequency domain by using a so-called moving irregularity model with a given displacement amplitude spectrum. Boundary element models of the acoustic medium (air) are developed for mono-bloc and bi-bloc sleepers. Radiation efficiencies are calculated and compared for the different sleeper designs. From the results obtained in a parametric study, it is concluded that the sound power generated by the sleepers is strongly influenced by ballast stiffness and damping and by rail pad stiffness. Further, it is concluded that a bi-bloc sleeper with appropriate dimensions of the connecting bar can lead to a 2–3 dB(A) reduction of sound power compared to a reference mono-bloc sleeper.