Dell Inspiron 7348 - Sound goes lower and then back to noraml

Hello,

I bought a new Dell Inspiron 7348 just a week ago. I noticed that sometimes while watchin something or listening to music, the sound suddenly goes lower (about half the volume it was) by itself and goes back to the original volume after a few seconds. The computer does not show any visual change of the volume.

Furthermore, it does not only happen with a specific program - it happens in youtube, BSplayer, my univercity player and more (so it's not related to a specific program).

Anyone experienced something like that? Knows how to solve it? Or do I need to go to a repair lab?

Thanks,

Or.