Air Conditioners Slinger Ring
All room air conditioners have a "slinger ring" around the rear fan blade. The ring is designed to pick water up off the bottom of the pan and throw it against the condenser coils. This design feature helps improve the efficiency of the unit by reducing heat on the coils, and helps remove moisture from the pan.
It is normal to hear a pinging or sloshing sound as the fan blade moves through the water.