Measurement of Dry Sliding Friction Rubbing Noise Using Nearfield Acoustic Holography

Improvements in tread-pattern design have reduced the noise generated by tyres to a point where some new patterned tyres are as quiet as smooth tyres. However, considering that smooth tyres also generate noise the generation mechanisms that are independent of tread pattern must also be studied in order to further reduce tyre/road noise. The rubbing noise generated by dry sliding friction within the contact patch of a rolling tyre is a mechanism that is independent of tread pattern and has the potential to be a critical generation mechanism in future efforts to further reduce tyre noise. In this paper the rubbing noise generated by dry sliding friction has been studied with a view to gaining an understanding of the fundamental mechanism. A controlled laboratory experiment was built to generate rubbing noise between a rotating steel disk and a small stationary specimen of Tancast10, a rigid polyurethane foam. Nearfield Acoustic Holography has been used to measure the rubbing noise produced. Using this technique the leading edge of contact has been identified as the source location of the rubbing noise being generated. Furthermore, it was found that for an increasing sliding velocity the amplitude of rubbing noise increased, however, the frequency content of the noise did not alter with changing velocities.