Sneaker squeaks become a design variable

A team of researchers has turned one of indoor sport’s most familiar irritations into a controllable design variable: the high-pitched squeak of sneakers.

According to Ars Technica, experiments described in a Nature paper show that the pitch of squeaking is not a random byproduct of “stick-slip” friction, but is largely set by the geometry of the sole’s tread. The researchers—working with a setup reminiscent of Leonardo da Vinci’s early friction studies—slid a commercial basketball shoe across a smooth glass plate while recording sound and imaging the contact surface. They observed travelling “opening pulses” at the interface: brief local separations between the rubber and glass that repeat at a regular rate. The squeak’s frequency follows that repetition rate.

The group then built simplified test pieces: silicone rubber blocks, one with a flat underside and one with parallel ridges meant to mimic tread. Both produced interface pulses once sliding exceeded a threshold speed of roughly 0.3 metres per second. But the ridged block behaved like an instrument rather than a hiss: it generated a more stable, narrow-band pitch and reduced the large fluctuations in slip that made the flat block sound like broadband noise.

That is a small result with large implications. Shoe companies already compete on grip, weight, durability and cushioning, but sound is an underpriced attribute: it matters in school gyms, indoor courts, office corridors, and any space where dozens of people share hard floors. A sole that keeps traction while staying quiet can be a competitive feature the moment consumers start noticing it—and a liability once competitors do.

The paper’s more interesting twist is that the usual toy model for stick-slip predicts frequency should rise with sliding speed. Here, the researchers found the fundamental tone stayed essentially fixed as speed increased, pointing away from a generic friction explanation and toward a geometric one. If tread can “lock in” a frequency, it can also be tuned—by altering ridge spacing, block height, or pattern—to move the squeak out of the most annoying band, or to suppress it.

In the lab, the team pushed the point to its dry conclusion: they designed rubber blocks tuned to specific frequencies and slid them across glass to play the “Imperial March” from Star Wars. It is a party trick, but it also demonstrates repeatable control over a phenomenon that normally arrives as noise.

There is also a second audience for the work: geophysicists. The same slip pulses and intermittent separations resemble dynamics seen in tectonic faults, offering a tabletop model for processes that are otherwise inferred from sparse sensors and post-event reconstruction.

For most people, the takeaway is simpler. A squeak that once sounded like an unavoidable feature of rubber on polished floors is, in part, a design choice—etched into the pattern under your foot.