I still hear game sound when i minimize client

There's this annoying problem that I think shouldn't happen when you minimize LoL client. For a few seconds the sound will be muted and then out of nowhere I start hearing it again. Except when the sound starts up it's sort of a softer version of the client music, and when you open it again it will come on regularly. It doesn't seem like a problem you an fix manually but riot should know about it. Is anyone else having this problem?