Never noticed it until I decided to take the PSU out of my case, short out pin 13 and 14 and see how loud it actually was (7800GT's stock heatsink drowns out EVERYTHING), but there's something really funny with the fans.
Powerstream has two fans, the one near the power plug, and the other near the cables.
Other than the one near the power plug being lit by a blue LED, both fans look identical, down to the clear plastic used and the fan blade's shape.
However, while the LED fan has a rather smooth character and a slight buzzing noise, the non-lit one goes "whump-whump-whump-whump-whump...," and is also louder than the LED fan.
Not sure whether this is common to all Powerstream PSUs (mine's a 520W SLI version), but just a word of warning to those considering the Powerstream...
OCZ Powerstream = poop
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