It was all because of mumble. I figured it after I turned on music alongisde with the game. All the sounds were gone, even windows ones, except for mumble. I thought that sound is disappearing when I switch teams, because everytime I joined the game I was getting placed in other team than 3dAC guys, so I was immediately changing teams, and it took about the same amount of time as mumble to run

. And after I was sure that's swtiching teams casuses it, even though it made no sense to me, I kept changing teams when trying out

The reason why it worked before, is that I joined a server without mumble. And the reason for sound to disappears is that, no idea why, I had "exclusiveness" (or smth like that I don't know how is it translated) checked in output settings.
Cheers
Boberczus
PS. If mod could change the title to "Losing sound after map loads" I'd be grateful.
Yea... right...