Overview
- Using total internal reflection and cameras up to one million frames per second, researchers visualized wrinkle-like detachment pulses sweeping along rubber soles at speeds approaching 300 km/h.
- The emitted sound’s pitch equals the repetition rate of these opening slip pulses, which is set by the sole’s stiffness and thickness.
- Tread geometry organizes and confines the pulses: patterned soles produce clear, pitched squeaks, whereas flat rubber yields irregular pulses and broadband swishing noise.
- By tailoring block height, the team tuned squeak frequency and demonstrated control by playing the Star Wars “Imperial March” on a glass plate.
- Experiments occasionally captured triboelectric discharges associated with pulses, and the results point to tunable frictional materials and a lab platform relevant to earthquake rupture physics, though tests used glass as a court proxy.