I am using the latest version of TTW; version 2.2.
When I started up the Broken Steel section after turning on the purifier, I meet with Lyons and everything involving him at the time works properly. Strangely, I did see Sarah standing while unconscious, but that's a sidenote. I went to Rothechild and his map exposition and lines went properly. I decided to put off the Death from Above quest and attack Fort Bannister. I found some BoS in the area and talked to them. They had no sound. After I killed some of the Talon Company in the base, I met Private Jensen and he had no voice either. I then followed the mute BoS into the bunker and dealt with the Talons. I went back to the Citadel to make sure my sound didn't break itself and the BoS there sounded as they should.
I finished a few more quests, and I went back to Rivert City to stock up on more ammo. I went down the ramp outside and met up with Lepelletier's men. They were completely unvoiced, including the caravaners. I then went to Lepelletier herself and found her to be unvoiced as well. Fearing a trend, I went to Project Purity to see if they were voiced. I noitced that, at the very least, the Scribes, Alex Dargon, and Daniel are unvoiced. Bigsley, strangely, *was* voiced.
As a side note, Jack Smith was partially voiced. His greeting was fine, but when I asked him about the state and voting for governor, he was mute.
All of the mutes had no lipsynch, and no sound. Everything else associated with them still seems to function. (Such as scripts) All of this investigation happened before I spoke with Paladin Tristan in Death From Above.