The effect of temperature on railway rolling noise

The stiffness and damping of railpads in a railway track are affected by changes in the temperature of the surrounding environment. This results in the rolling noise radiated by trains increasing as the temperature increases. This paper quantifies this effect for a ballasted track equipped with natural rubber railpads and also studies the behaviour of a cork-reinforced rubber railpad. By means of measurements in a temperature-controlled environment, it is shown that the shear modulus of the natural rubber increases by a factor of six when the temperature is reduced from 40 ℃ to −20 ℃. The loss factor increases from 0.15 at 40 ℃ to 0.65 at −20 ℃. The shear modulus of the cork-reinforced rubber increases by a factor of 10, and the loss factor shows the typical trend of transition between rubbery and glassy regions. The railpad stiffness estimated from decay rate measurements at different temperatures is shown to follow the same trend. Field measurements of the noise from passing trains are performed for temperatures between 0 ℃ and 35 ℃; they show an increase of about 3–4 dB. Similar results are obtained from predictions of noise using the measured dependence of pad stiffness.