[Hiro_Antagonist]

Hey there,

I'm glad to hear you're liking the game!

That sound means that a status effect on a unit has expired gone away. If you hear it at the end of your turn, it means one the effects on your unit expired, and if you hear it at the end of your opponent's turn, it means one of their effects expired.

I hope that helps.

-Hiro_Antagonist