Harvard scientist finds basketball sneaker squeaks come from organized ripples in rubber soles on hardwood, with tread patterns creating high-pitched sounds.

A Harvard materials scientist, Adel Djellouli, discovered that basketball sneaker squeaks result from rapid, organized ripples—like fast-moving wrinkles—in the rubber sole as it slides on hardwood, with ridge-like tread patterns creating consistent, high-pitched sounds. Flat rubber without such patterns produced chaotic ripples and no noise. The study, using high-speed cameras and microphones, is the first to directly link these fast friction pulses to the squeak, advancing understanding of dynamic friction with potential applications in earthquake modeling, energy efficiency, and future shoe design that could eliminate or tune the sound.