Vibration damping to control railroad wheel squeal Free

The squeal noise radiated by rapid transit wheels on sharp turns is an important instance of friction generated noise. It is caused by the lateral slip‐stick frictional force between the wheel and railhead. Noise control methods such as rail lubrication, hard faced rails, tuned wheel dampers, and resilient wheels have not been entirely satisfactory from the standpoint of either cost effectiveness or of safety. This paper will focus on several lightweight vibration damping treatments which have been economical and effective means of reducing squeal noise. Several ring and constrained layer damping treatments which make use of efficient viscoelastic damping materials have resulted from extensive development and laboratory testing programs. Treatments ranged from 1% to 2% of the total weight of wheels weighing 450–800 lb. Wayside noise reductions of 34 dB have been measured in recent field tests on rapid transit systems. These measurements have shown excellent correlation with vibration spectra measured in the laboratory and confirm the effectiveness of vibration damping in controlling friction generated noise of this type.