If there's an opening in the bottom of the case (as your case has: http://www.techpowerup.com/reviews/C...rearbottom.jpg
) where you mount the PSU the side with the fan should go towards the opening.
The fan on the PSU takes in cold air and blows it out of the back.
If you put the fan side of the PSU towards the inside of the case it will take in the warm air generated by the components in your case.
Normally a PSU would not generate a buzzing noise, but if youre shure it's your PSU you could put some dampening material between the case and the PSU (not obstructing the fan intake)
You could use some dampenig foam with an adhesive side to it or something like this: Kustom PCs AcoustiPack BLOCKS Acoustic Foam Blocks
Cut it to size and use double sided tape.
Or you could put some dampening feet on the bottom side of your case: Kustom PCs Nexus Dampers Black / White (Pack of 4)
or: Kustom PCs AcoustiFeet™ ACF3007-25 Clear
I suspect it might be your harddrives that make the buzzing noise (more common), so be sure you know were the buzzing comes from.
Also for HDD's there are different sound dampening options: Kustom PCs Scythe Anti-Vibration HDD Stabilizer 2 for 3.5" HDD
or: Kustom PCs Nexus DiskTwin Black