Stick-slip friction generates sound vibration in chalk, violins, and scribes

Evidence

What causes the high-pitched screech and the associated digging of closely spaced pits? The answer is stick-slip vibration, a type of resonance phenomenon that most famously powers a bowed violin and most obnoxiously results in screeching chalk on a blackboard. As a steel scribe is forced point first across a plate, the frictional force of the tip on metal can be momentarily greater than the pushing force, causing the tip to stick to the plate. As the pushing continues, it overcomes the sticking force and the scribe springs free, only to land again further along, more relaxed, after relieving the tension. It then slows down and sticks again, repeating the process. The vibration of the scribe and/or of the metal plate play a role in the frequency of the chattering that generates the sound. — Eric J. Heller, Why You Hear What You Hear- An…, 456

Categorization

• DEFINE: Defines stick-slip vibration with a concrete mechanical mechanism, tying it to the familiar cases of violin bowing and chalk screech.
• XREF: Connects to the reader’s broader interest in why we hear what we hear — stick-slip is a foundational excitation mechanism — and recalls Milgrom’s work on institutional mechanisms as a parallel of explaining phenomena via underlying mechanism. — connects to: Bowed strings alternate between stick and slip motion — David Howard, Jamie Angus, coustics and Psychoacoustics, 1129
• SHARE: A violin teacher or luthier friend would enjoy the insight that bowing a violin and screeching chalk share the exact same stick-slip mechanism.