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.
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