I found some actual, confirmed, useful information on the World of Warcraft forums: Ventrilo Normalization.
Thrux of the Darkspear realm wrote:
Vent Normalization makes every bodies voice the exact same volume. In essence, you won’t blow your ear’s 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. (I use 15)
– Attack = 0.01
– Release = Around 500
– Threshold = Around -30
– Ratio = 100
– Pre delay = 4.0
I tried this last week and can report that for me, with my guild’s Ventrilo, it worked like a charm. We have this one Canadian guildmember who is prone to deepthroating his microphone so that we’ll have to rip off our headsets and shout “GODDAMMIT” in real life — plus, we have a couple of low-talkers who, for all we know, are trying to cyber us on Vent.
After making the above adjustments to my Vent setup, both extremes were comfortably audible. And no, it wasn’t cyber.