The sound is similar whether I rub clean hair together or my finger over a scrubbed pot.
In: Other
It’s caused by the combination of stiction and elasticity, similar to screeching tires or a violin bow.
Basically, while touching something you can move your finger a little bit without sliding across the surface, when you move your finger too far, it breaks free from the surface, quickly moves in the direction you’re moving your finger because dynamic friction is less than static friction, then it sticks again until it breaks free once more. This repeated sticking and releasing causes a vibration, which is what sound is.
When a surface is dirty, there is often some kind of grease, oil or other stuff that lubricates the surface, allowing your finger to glide smoothly. When that surface is squeaky clean the oil or grease has been removed, causing your finger to stick to the surface. As you drag your finger across the surface, it sticks and breaks free over and over, which causes the squeak.
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