The PSU doen´t have 12db(A)! If you know a bit about measuring the noise-level you´ll know it. Normally a really quiet room for measuring noise has a base-level of 14-16db(A) - so the 12db(A) can´t be measured there.
They just took the manufacturers value which is determined by calculation when the fan is free blowing which means it is not mounted into a PSU or case. If you put it into a OCU the minimum value will be 22 to 25db(A) as a realistic value.
Just take a look at the Verax PSU sold by PCSilent - this power-supply has a real value of 20 to 22db(A) because of the verax fan inside. But be careful in germany there´re some version sold which only have 230V!! The original version from verax has a wide rage input 110-264V. You´ll find the pcsilent pages here: http://www.pcsilent.de/en/index.asp