Handbrake Audio

If your voices are too low, it's possible the center channel isn't properly being downmixed. What audio settings are you using? What inputs (from the disc) and what output settings?

doesn't your TV have a setting for this? dynamic compression? so that there's not such a difference between voices and loud audio?

the hacker's way would be to pull out the audio track, run it through a sound editor like SoundForge, normalize the audio, and then reinsert the audio track back into the video file. this way, you're not having to re-encode the video (which would reduce quality and take forever, depending on how long the video is).