I'm lifting this verbatim from my Warhammer guild's forum:
Vent Normalization makes everyone's voice the exact same volume. In essence, you won't blow your ears out or have difficulty hearing people.
Go to Setup
Enable Direct Sound
Select the SFX Button
Select Compressor and click Add.
Under Compressor Properties use the following settings
Gain = Adjust for how loud you want people to be. (Try 15)
Attack = 0.01
Release = Around 500
Threshold = Around -30
Ratio = 100
Pre delay = 4.0
What the settings do:
Gain: How much volume you feed into the compressor. Not really relevant unless everyone is too quiet, then you can turn this up a little; turning it up too much will sound EXTREMELY bad.
Attack: How fast volume change will happen. Example: setting this to 500 means that anything coming in will only be dropped in volume after a half a second. For vent this should be set as low as possible.
Release: How fast the compressor stops changing things. Not really that relevant with vent, setting it around 500 is good for voice material.
Threshold: This sets the point where we actually start changing what’s coming in. Whereas 0 is the absolute loudest you can have for an input, -60 is super quiet. Average users will probably come in somewhere around -25 to -15, with the occasional few being really quiet, which is why I have this set so low.
Ratio: How much any sound below the set threshold gets compressed and/or modified in the volume department. If you still want to hear SOME volume variation then set this lower (2-4). The higher you set it the closer in volume everyone will be.
Pre delay: Mostly just deals with processing; with computer and digital processors they can look ahead a few milliseconds to see what needs to be dropped in volume or changed before it actually comes through the speakers. Highest is ideal.
So far this has made a world of difference for me.