Experimental and Theoretical Studies on Impact Noise Generation due to Rail Joints

Abstract

When a train passes over discontinuities on a rail, e.g. rail joints, impact noise due to the discontinuities is generated impulsively. In this paper, an attempt is made to understand the impact noise generation mechanism experimentally and theoretically. By performing static and running tests, vibratory properties of the track and wheel are investigated first. Second, on the basis of the measurements in the tests, a theoretical model to predict impact noise is developed.

Through the static test for the track, it is found that two facing rails at a rail joint no longer move together above 1000 Hz. In the running tests, for both the wheel and rail vibrations, the measured A-weighted levels at three rail joints show an increase of about 9 dB for a doubling of train speed. Also, by using the measured results, the separate contribution of noise from wheel, rail and sleeper to the total impact noise at one rail joint is estimated quantitatively. The results show that the sleeper has the greater contribution below 630 Hz, whilst the wheel is predominant above 2000 Hz. By using the prediction model, the overall trends in noise are well predicted. Also, the model gives an estimate of the contributions of wheel, rail and sleeper to the total impact noise at the rail joint, and the predictions show good agreement with the results estimated by the measurements.