Unraveling the Mystery of Sneaker Squeaks: A Boston Celtics Game-Inspired Study
Uncover the science behind the squeaky shoes you hear during a Boston Celtics game.
Have you ever watched a Boston Celtics game and wondered why the players' shoes squeak so loudly when they slide on the floor? Adel Djellouli, a materials scientist at Harvard University, was captivated by this very sound. As he watched the game from the stands of TD Garden, he noticed that the squeaking sound was omnipresent, always there in the background.
Squeaky shoes are an integral part of the symphony of a basketball game. The rubber soles rasp against the hardwood floors as players jab, step, cut, pivot, and defenders move their feet to stay in front of their assignment. But how is that sound produced?
Djellouli and his colleagues decided to find out. They slid a sneaker against a smooth glass plate over and over, recording the squeaks with a microphone and filming the whole thing with a high-speed camera. In a study published in the journal Nature, they described what they found.
As the shoe works hard to keep its grip, tiny sections of the sole change shape as they momentarily lose then regain contact with the floor thousands of times per second. This frequency matches the pitch of the loud squeak we hear. The grip patterns on the soles may also play a role. When researchers slid blocks of flat, featureless rubber against the glass, they didn't hear squeaks.
The ridge-like designs on the bottom of your shoes may organize the bursts to produce a clear, high-pitched sound. This study examines friction happening at much faster speeds and links the speedy pulses with the squeaking sound they produce.
These insights don't just serve to satisfy the curiosity of a basketball fan. They could also help answer important practical questions. Understanding friction better could help scientists better understand how the Earth's tectonic plates slide and grind during earthquakes, for example, or to save energy by reducing friction and wear.
It could also help eliminate moments off the court when squeaky shoes can be a little awkward or embarrassing, such as in a quiet office hallway. While this research doesn't offer a fix, some of the insights from the study could help design squeak-free shoes in the future. For example, one additional experiment found that changing the thickness of the rubber could make the squeak sound lower or higher in pitch.
Could we fine-tune our shoes to squeak in a pitch so high we can't even hear it? The possibilities are exciting. As Bart Weber, a physicist, noted, we can now start designing for it. We can start making interfaces that either do it if we want to hear this sound or don't do it if we don't want to hear it.
