place on one side of the rail 10 first and second resonant members 102 and 104 are embedded in a deformable material 106 a third resonant member 108 lies over the deformable material a 06 and has one or more clamps 110 which extend beneath the rail foot 12 these clamps resiliently urge the third resonant member 108 towards the rail foot 12 and thus trap the first and second resonant members 102 104 to hold the damper 100 in place on the rail a small clearance is provided between one end of the third resonant member 108 and the rail 10 to allow the former to vibrate this could of course be replaced by a layer of deformable material but a manufacture step is avoided by using a clearance instead vibrations will still be transmitted to the third resonator 108 via the deformable material 106 in which the first and second resonators 102 104 are embedded the three resonators 102 104 108 are all of a different cross sectional profile and all thus generate a system with multiple resonant frequencies in practice some resonators could be matched if desired or if only a single or double frequency damper was required in fig4 a standard single mass damper 112 is provided on the second side of the rail the frequency damped by this.