Scientists Crack the Case of 'Screeching' Scotch Tape

Source: Slashdot

Background

The screeching sound that Scotch tape makes when it is ripped off a surface—a fingernails‑on‑a‑chalkboard noise most people try not to think about—is produced by shock waves from micro‑cracks that travel across the peeling tape at supersonic speeds, according to a new paper published in Physical Review E.

Researchers led by Sigurdur Thoroddsen of King Abdullah University in Saudi Arabia previously identified a sequence of transverse cracks racing across the width of the adhesive during peeling (2010) and later established a direct correspondence between those cracks and the screeching sound (2024). However, those studies did not pinpoint the underlying mechanism.

Methodology

The team used simultaneous high‑speed imaging and synchronized microphones to capture both the propagating fractures and the sound waves they generate in the surrounding air. This approach allowed them to observe the dynamics of each crack as it formed and moved.

Findings

The new findings reveal that a partial vacuum forms between the tape and the surface each time a crack opens. Because the crack moves faster than air can rush in to fill the void, the vacuum travels along the tape until it reaches the edge, where it collapses into the stationary air outside. This collapse produces a discrete sound pulse, which manifests as the familiar screeching noise.

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