A new experiment has uncovered the mechanism responsible for the screeching sound made by peeling sticky tape. Using a combination of ultrafast imaging and synchronized acoustic recordings, Sigurdur Thoroddsen and colleagues at King Abdullah University of Science and Technology have shown that the noise is produced by a rapid train of tiny shockwaves, released through a specialized form of stick–slip motion. The research is published in Physical Review E.

If you’ve ever used sticky tape, you’ll probably be all too familiar with the harsh sound it makes as it peels away from a surface. Yet despite decades of experimental scrutiny, physicists have yet to fully explain the origins of this intriguing acoustic effect.

Previous studies established that peeling proceeds via a “stick–slip” mechanism—a jerky motion characterized by brief, rapid accelerations interrupted by sudden stops. Similar dynamics underpin phenomena ranging from earthquakes to the squeak of basketball shoes on a polished wooden court. However, the fine details of how this process unfolds in peeling tape turned out to be more complex than they first appeared.

Basketball shoes on a gym floor, bicycle brakes in need of a tune-up, or the squeal of tires are everyday examples of squeaking sounds. Such sounds have long been attributed to stick-slip friction, or a cycle of intermittent sticking and sliding between surfaces. While this framework explains many rigid-on-rigid systems such as door hinges, it does not fully capture the physics of soft-on-rigid interfaces, like shoes on a floor.

To shed light on this little-understood physical process, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), in collaboration with the University of Nottingham and the French National Center for Scientific Research, have used high-speed imaging to investigate the dynamics of soft solids sliding rapidly on rigid substrates.

In a study published in Nature, the team led by first author Adel Djellouli, a postdoctoral fellow in the lab of Katia Bertoldi, the William and Ami Kuan Danoff Professor of Applied Mechanics at SEAS, reports that squeaking emerges from a previously unseen mechanism.