Power Supply Fundamentals & Recommendations
 

Often one of the biggest noise maker in a PC, the Power Supply Unit delivers regulated DC voltages to various components. Computer PSUs are switching mode types, which provide relatively high efficiency at low cost. They utilize forced air cooling, usually an 80mm fan, and sometimes incorporate a second fan. The fan is the primary source of noise in a PSU. Coils in a PSU can buzz and hum, especially when pushed under high loads, but usually fan noise masks coil noise. Typically, the fan is rated for higher than the maximum airflow needed to keep the PSU cool. It's cheap engineering insurance for the manufacturer and also fulfills the case cooling role of the PSU fan.

http://www.silentpcreview.com/article28-page1.html

Seasonic S-12 500W

http://www.madshrimps.be/?action=get...&articID=3 28

39.8 dBA reading from my meter at about one centimeter.:)

yes their dBA readings have always been a bit off :)

Well, my ambient noise level is high ~37 dBA ;)

Seasonic is very well made; high to moderately priced.