When you tear packing tape, you’re creating supersonic sonic booms.
Today we’re talking about a tiny thing everyone has experienced — opening packages, or more precisely, the moment you rip clear packing tape open.
It’s just cheap clear tape sold in stationery stores, and most people think there’s nothing worth exploring about it. Yet behind this simple movement lies a physical puzzle that has baffled physicists for decades. A newly published paper finally solves the mystery, and the conclusion is so surprising you won’t believe it at first glance.
Many of us accidentally spotted clues when we were kids. If you paid close attention to the texture back then, you’d notice horizontal cracks appear as you tear the tape, and these cracks are closely linked to that sharp, distinctive noise tape makes. There’s even a trick you can use: pull the tape gently and steadily, and it will separate smoothly with far fewer horizontal cracks and much less harsh sound. As children, we only observed the phenomenon without understanding the science, never knowing supersonic mechanics were at play.
Tearing tape produces a shrill, shuddering, teeth-grating sound; the faster you pull, the sharper the noise, audible even across two desks.
Most people assume the loud noise arises from friction: the sticky tape’s two layers rub and vibrate against each other, agitating the air to create sound, just like a violin bow sliding across strings.
This logic sounds reasonable at first glance, yet it has a critical flaw. The noise changes drastically depending on pulling speed, angle, and tape brand. Simple frictional vibration cannot account for such wide variations.
Physicists have studied this puzzle for decades and uncovered a vital clue: tape does not separate smoothly. The bonding interface alternates between sticking tight and slipping abruptly, moving in jerky fits like a stuck zipper. This alternating cycle of adhesion and sliding is known as stick-slip motion.
Stick-slip motion is a common frictional phenomenon that exists everywhere in daily life and nature:
Earthquakes: Rock layers on fault lines lock together. Stress builds up until a critical threshold is reached, triggering sudden sliding.
Basketball quick stops: The squeaky noise produced when sneaker soles rub against wooden courts.
Aged wooden doors: Hinge friction creates harsh creaks when you push the door open.
Writing on blackboards: Chalk slides jerkily and emits an uncomfortable shrill sound.
Stick-slip itself is nothing rare. However, the stick-slip movement during tape peeling happens far faster than scientists once assumed. Older observation equipment lacked sufficient precision and frame rate to record the full process, leaving research stalled for decades.
In 2025, a research team adopted brand-new observation technology and innovative experimental ideas, and for the first time fully visualized the real mechanism behind the harsh noise produced when tearing tape.
The experiment setup was straightforward: researchers stuck regular clear packing tape to a glass plate. While peeling the tape, multiple devices simultaneously recorded the whole separation process:
A high-speed camera mounted under the glass captured the peeling shape of adhesive layers and the propagation speed of cracks in real time through the plate;
Schlieren imaging system: Air is invisible to the naked eye, yet light bends slightly when passing through air of different densities. This optical device magnifies and records such light deflection, making the compression waves and shockwaves formed in air visible;
High-precision microphones recorded audio synchronously, precisely matching every sound pulse to the corresponding material fracture captured on camera.
The experiment shot footage at an ultra-high frame rate of 2 million frames per second. For comparison, standard movies run at only 24 fps, and common slow-motion videos top out at 240 fps. Two million frames means every tiny movement within one second is split into two million individual frames.
By accurately aligning audio signals with visual footage, the researchers finally identified the genuine source of tape’s shrill noise.
When you pull the tape upward, a horizontal crack forms right behind the boundary between peeled and unpeeled sections. Perpendicular to the tape’s length, the crack races across the tape from one edge to the other.
The crack spreads faster than the speed of sound in air, qualifying as supersonic fracture; The moment the supersonic crack reaches the tape edge, massive energy discharges into the air and forms an outward-spreading arc-shaped shockwave. It shares the exact shape of blast shockwaves, only on a minuscule scale;
This shockwave is essentially a tiny sonic boom, following the identical physical principle as the sonic boom created when fighter jets break the sound barrier;
The cycle repeats continuously: after one horizontal crack and sonic boom, a new supersonic transverse crack forms further up, releasing shockwaves nonstop until you stop tearing the tape.
The continuous shrill “rip” sound we hear is not a single vibration noise. Instead, countless tiny shockwaves strike the eardrum one after another. The shockwaves occur at such a high frequency that human ears cannot distinguish individual pulses, blending together into a persistent piercing noise.
The general public holds a traditional view that friction on tape generates vibrations which agitate the air and create noise. Yet the actual physical mechanism tells a different story: tearing tape triggers supersonic fracture of the material. Massive energy is instantly released at the crack edges, compressing the surrounding air and producing that harsh shrill noise via shockwaves. Though the two explanations differ by merely one verb, their underlying physical logic is worlds apart.
The most captivating part of this research is more than its counterintuitive experimental findings — it reveals a profound truth: countless trivial routines in daily life conceal physical mysteries that have yet to be fully unraveled. A plain roll of stationery tape costing just one US dollar, the casual act of ripping it, the visible horizontal cracks and fluctuating piercing noise all tie into an intricate system of shock physics, including supersonic fracture and miniature sonic booms. Within the most ordinary moments of everyday life lies the purest romance of science.
Post time: 2026-06-22 14:58:15