nknown Sound from new iMac

Hello,

I've bought new iMac a few days ago and I'm pretty newbie on MAC OS. Recently, I've noticed that it makes unknown sound like "Funk" from time to time. It is not Skype, neither is email...and it's totally unpredictable.

Please help.

So far I've only skype and autocad installed.
Yes, funk is selected as sound effect in system preferences.
I've red somewhere that sound may cause wireless router?