Tear drainage air. This issue is usually related to an abnormality allowing air to enter the tear drainage system which is released and causes the noise with rubbing. It is nothing to worry about. If it persists, see an eye doctor for further evaluation.
Air trapping. Sometime air trapping within the moist surfaces can make a tiny noise as you rub your eyes. If you are having vision changes, crusting in your eyes or any symptoms, you should see an optometrist or get referred to an opthalmologist. If you persistantly rub your eye, it can stimulate an inflammatory response and can give your eyes a red appearance.