How to make the volume of an audio stream equal

I have loads of audio streams of conversations and lectures and there is a distinct difference between two people speaking in that one is way too quiet and the other way too loud. I need to make them both even by putting them somewhere in the middle, normalize doesn’t really work and amplify does but the problem is that it takes ages to alter the right parts and I can only select a segment to the closest second which means there would be a really loud or quiet bit between edits. I want to change the whole stream in one go, can I do this with audacity and any of it’s addons or is there some other software to use?

Compression only makes the loud bits quiter, doesn’t reduce the volume of the quiet bits.
Audacity 1.3 does come with a compressor but other free ones are available which can be used in Audacity,
e.g. “Chris’s compressor”, “Blockfish” (the latter requires “VST enabler” to be installed in Audacity).

Chris’s Compressor is highly recommended. It has the same affect as a radio station’s compressors – it goes both ways, bringing up the low bits and squashing the high ones. I change the Compression number to .77 from .5 and otherwise leave it alone.