When you are washing up a wineglass, your fingers slide over the surface of the glass because a thin film of grease acts as a lubricant. This grease comes from your food, but also from the oil naturally occurring in our fingers. As you wash the glass, the detergent removes this grease and your fingers don’t slide so easily any more. At a microscopic level, tiny ridges on your skin catch and release against surface roughness on the wineglass. This makes the vessel vibrate at high frequency and it’s this that creates a squeaking sound which tells you the glass is now clean.
Answered by Luis Villazon.