Effects of Railway Ballast on the Sound Radiation From the Sleepers
Regular paper
Dynamics Group
Wednesday 3 june, 2015, 11:40 - 12:00
0.1 London (90)
Abstract:
Railway ballast is an important component in the railway system. It is a layer
of
stones located below and around the sleepers; it supports the track vertically
and provide lateral stability. The gaps between the stones make it behave
acoustically as a porous material, absorbing noise to some extent. In addition
ballast can itself vibrate and reradiate noise during train pass by. It is not
clear, however, to what extent ballast contributes to noise and how much its
mechanical and acoustical properties modify the radiation of the sleeper and the
rail. This paper focuses on quantifying the influence that ballast has on noise,
particularly the sleeper radiation. A one-fifth scale model of the track is
adopted to conduct acoustic and vibration measurements on ballast. Two different
scaling factors are adopted to reproduce the ballast properties: for the
acoustic
absorption the scaling factor for the stone dimensions is 1/sqrt(5), without
modifying the geometrical scale of the problem, while the mechanical behaviour
is
correctly reproduced by scaling the stones at 1/5. Analytical models will be
proposed to predict ballast vibration and absorption. Finally, the effects on
the
noise radiation from a scaled concrete sleeper are compared with the
experimental
results.