Wear hearing protection. Ear plugs are okay, the big ugly earmuffs have a better attenuation than plugs. Wear both if you need to.
If you don't you will ruin your hearing and it will never come back. Hearing aids are expensive...
If you ever find your ears ringing after doing something (working in the data center, hanging out at a bar friday night, riding your motorcycle, etc) that is your body's way of saying "your harming your hearing. If you don't stop you will lose it forever, and it may already be too late." Eventually the noise (data center, bar, motorcycle) won't bother you but you'll also hear a ringing / single pitched noise in your ears when it is quiet and when you try to talk to people with background noise, you won't understand a damned thing they say. All this happens because you've lost some of your ability to hear in certain frequency ranges...
I modify all my personal computers to make them quieter, but such things aren't really possible or appropriate for a data center. You certainly can't run a program that makes the computer quiet -- it is all those damned fans in the 1u racks that spin at 7000 rpm and they just make a lot of noise.