THEORETICAL OPTIMIZATION OF TRACK COMPONENTS TO REDUCE ROLLING NOISE

The control of railway rolling noise requires a reduction in wheel and track noise emission. In this paper, a parametric study of the possib le minimization of the track sound power is presented. In an initial g lobal approach, a number of potential variations in track parameters a re assessed in terms of their likely effect on rolling noise. From thi s, two main themes are selected for deeper study by use of TWINS model . The first parameter considered is the stiffness and damping of the r ail-pad. By reducing the pad stiffness, the noise radiation from the s leeper is reduced but that from the rail is increased, and vice versa. An optimum is found when the rail and sleeper components are equal, f or which the track radiation is a minimum. Starting from one existing track design, this optimum pad stiffness has been derived for an examp le wheel. The second area investigated is the increase of the attenuat ion rate of rail vibrations by the addition of damping measures. The i mplementation of dynamic absorbers with a mass of 5 kg every sleeper b ay (0.6 m) leads to predicted reductions of track radiation of 2 dB(A) if the rail-pad stiffness is already optimal. For softer pads a large r reduction has been found, but the total effect is less than the comb ined effect of first changing to the optimum pad stiffness and then ad ding absorbers. Globally, for ballasted track with bibloc concrete sle epers, a 2-6dB(A) reduction in track sound power can be expected throu gh a rail-pad optimization and/or the implementation of dynamic absorb ers on the rail. (C) 1996 Academic Press Limited