Olaf Axe sound bug

Olaf has a bug that when you thrown an axe through an enemy ( minion, champion or jungle monster) it produces no sound. You hear when he goes to throw it but when it slices through enemies it has no sound effect. When the axe stops theres another sound to indicate that the axe has stopped. The bug occures when the axe is flying THROUGH enemies. This happens everytime you use Undertow In every Skin he has.