I've heard about people having this problem with certain combinations of motherboards and other hardware. The thing I would try is, put the sound card into another slot.
If the random sounds vanish, chances are that the slot on the motherboard is busted somehow, and you need to contact the manufacturer for a RMA or warranty service.
If the sounds do not vanish, then it probably is a motherboard/driver/soundcard problem. See if the manufacturers website has a new sound driver, that might fix the problem if they have a new one, since they are ALWAYS finding problems with some combinations of hardware, software and drivers.
That's the only thing I don't like about all this choice in components, sometimes they don't like each other and have problems when put into systems together in weird, non-one manufacturer combinations.