Study on the Mechanism of Train Noise and its Countermeasures : Part11, The Effect of Velocity and Load, and the Characteristics of Sound Radiation

Abstract

In a previous paper (Part I), the mechanism of wheel vibration was investigated theoretically and experimentally. In this paper, the effect of the rate of rotation and the load on the vibration, and the characteristics of sound radiation are discussed. The vibration and the noise levels increase with the rate of rotation. The load, however, has no significant effect on them. The frequency distributions of both are affected by the rate of rotation and the load; i.e. under a high rotation with a low load, the frequency distribution approaches that of a free disk. Coefficient of sound radiation (the sound power divided by the mechanical power) is introduced to investigate the characteristics of sound radiation. The coefficient has a large value at low order natural frequencies and a peak at a frequency which is higher than the coincidence frequency. As the diameter of a wheel increases, the peak frequency approaches the coincidence frequency and the peak value increases.