Friction-Induced Sound and Vibration
The phenomenon of sound and vibration generation by rubbing action has been known since ancient times. Friction-induced sound phenomena have been used to advantage in developing musical instruments where rubbing strings causes them to vibrate at their natural frequency and generate sound with predictable tones. This chapter describes a brief introduction to the mechanism of sound generation. The relation between the sound pressure level and surface roughness under various contact loads was established. The measurement of the coefficient of friction as a function of sliding velocity has been the subject of many studies to determine the influence of controlling factors as materials, surface roughness, temperature, and lubrication condition. The irregularities of the disk surface during rotation can also produce variations of the measured coefficient of friction. The friction-induced vibration, which has been studied by several investigators, may be classified into three types: stock-slip, vibration induced by random surface irregularities, and quasiharmonic oscillation.