It’s not just shoes that squeak when they slide over a hard surface. Bike brakes, rubber tyres, even some biomedical implants such as artificial hips have been known to squeal as soft and hard surfaces come into contact with each other.
Read the paper: Squeaking at soft–rigid frictional interfaces
So to better understand exactly what is causing these noises, a team of researchers have used high speed photography to capture a rubber block sliding across a hard acrylic sheet.
They found that driving the squeaks were pulses more commonly associated with the dynamics of earthquakes, and they observed tiny bolts of lightning initiating those pulses.
This understanding could lead to advances in engineering, metamaterials or earthquake research – or even new musical instruments.
