Hahahaha stock fans are fairly quiet... yeah until you put a load on the cpu then they sound like a vacume cleaner.
So that pretty normal but you can try adding another case fan or two to get better airflow though your case, this will help to keep the fan from hitting full speed.
The best thing to do is replace the stock heatsink/fan with aftermarket one
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PhenomII 1100T// Asus Sabertooth R2.0 // 2X HD5850 CF //8Gb of 1866Mhz ram, H50 cooling, HX850W psu all stuffed into a NZXT Phantom case.
Was a member of AMD Processer forum since 2008. Last post count 1818.