We have changed our method of measuring noise levels. Ambient noise in the room is around 28 dBa. We measure from a distance of around 1 meter from the chassis and 4 foot from the ground with our Extech digital sound level meter to mirror a real world situation.
Our system was left in an overclocked state, running at 4.8ghz.
KitGuru noise guide
10dBA – Normal Breathing/Rustling Leaves
20-25dBA – Whisper
30dBA – High Quality Computer fan
40dBA – A Bubbling Brook, or a Refridgerator
50dBA – Normal Conversation
60dBA – Laughter
70dBA – Vacuum Cleaner or Hairdryer
80dBA – City Traffic or a Garbage Disposal
90dBA – Motorcycle or Lawnmower
100dBA – MP3 player at maximum output
110dBA – Orchestra
120dBA – Front row rock concert/Jet Engine
130dBA – Threshold of Pain
140dBA – Military Jet takeoff/Gunshot (close range)
160dBA – Instant Perforation of eardrum
These noise results are excellent, especially considering we are pumping almost 1.5 volts through the 990x at 4.8ghz. Unless you will be running a similar system, you can be assured that the noise levels will be lower. For those interested, the noise levels at idle drop to just over 31 dBa which is barely audible.