4 min learnNew DelhiUp to date: Feb 26, 2026 08:47 PM IST
Anybody who has watched a basketball sport is aware of the sound. The sharp squeak of rubber sneakers sliding throughout a refined courtroom is nearly as fixed because the bounce of the ball. That very same high-pitched noise can be heard in screeching automotive tyres, previous bicycle brakes, and even windscreen wipers. Now, scientists say they lastly perceive what causes it, and the reply may have implications far past sports activities arenas.
In a brand new research printed in Nature on February 25, researchers describe a beforehand unseen behaviour in friction that explains why sneakers squeak. The group, led by supplies scientist Adel Djellouli at Harvard College of Engineering and Utilized Sciences, set out with a easy query: why do basketball footwear make that particular noise?
Scientists have lengthy recognized that squeaking comes from what is known as “stick-slip” friction. This occurs when two surfaces briefly stick collectively after which out of the blue slip aside, time and again. These speedy cycles create vibrations within the air, which we hear as sound.
However Djellouli’s group discovered that this clarification was solely a part of the story.
Utilizing high-speed cameras able to recording as much as a million frames per second, the researchers intently noticed how rubber sneaker soles moved throughout a glass floor. In addition they used imaging instruments to trace the precise factors the place the rubber touched the glass. Delicate devices measured every tiny sound produced throughout the sliding movement.
What they found stunned them.
As an alternative of random stick-slip actions, the squeaks had been pushed by repeating slip pulses shifting by the fabric. The pitch of the sound trusted how shortly these pulses repeated. That repetition charge was influenced by the rubber’s stiffness and thickness.
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In brief, the design of the shoe performs a direct function within the noise it makes.
Form issues greater than anticipated
To check their findings additional, the group experimented with easy rubber blocks pressed towards glass. When the blocks had flat edges, the sounds modified. The noises turned extra irregular and produced softer, swishing tones reasonably than sharp squeaks.
This proved that geometry, the precise form and floor options of the rubber, strongly impacts how friction behaves.
Research co-author Gabriele Albertini from the College of Nottingham mentioned the outcomes problem older fashions that handled friction as a easy, one-dimensional course of. Even tiny floor particulars can reorganise the movement in sudden methods.
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From sneakers to earthquakes
The analysis even took a playful flip. After studying management the slip pulses, the scientists organized rubber blocks of various heights and manually recreated a tune, together with the well-known theme related to Darth Vader from Star Wars.
However past novelty, the findings may have critical functions. Engineers have lengthy wished to design supplies with adjustable friction surfaces that may swap between excessive grip and easy glide when wanted.
The research may additionally assist scientists higher perceive earthquakes. Related slip pulses happen when tectonic plates shift alongside fault traces. Physicist Shmuel Rubinstein famous that the physics behind a squeaking shoe can resemble the speedy ruptures seen in seismic occasions.
In different phrases, the identical forces at work on a basketball courtroom might echo deep beneath the Earth’s floor.
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Whereas the squeak of sneakers might by no means disappear completely, scientists now have a clearer understanding of why it occurs and management it.
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