We measure from a distance of around 1 meter from the closed chassis and 4 foot from the ground to mirror a real world situation. Ambient noise in the room measures close to the limits of our sound meter at 30dBa.
We manually adjust the voltages from 5V to 12V.
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
Running at 5V the fans did not produce enough noise to register on the lower limits of our noise meter.
Increasing the voltage to 12V resulted in an average noise level of 37.0 dBa. Whilst not loud, it does make the system very noticeable.