I got a copy of Oblivion earlier today from the internet since I lost my original copy, and got a bunch of mods for it. Unfortunately, after starting the game, I soon discovered that whenever I would talk to an NPC, they didn't talk back. Their text showed up fine, but absolutely no sound. I could hear them just fine otherwise, out in the world, but face to face nothing. After reinstalling a couple times and clearing out what I thought was everything associated with it, I kept having the same problem, so I decided to svck it up and just drop the $20 for the GOTY edition off of steam. Turns out, I'm still having the exact same problem.
TL;DR the NPCs don't have sound when talking to them.