This mod was a must have for Oblivion.

Its primary feature was to provide an 8 second long silence ( I increased it to 24 seconds for myself ) with a lip sync for any dialogue that did not have a voice file attached to it. This allowed 8 seconds to read the subtitles for other mods.

I loved it for its secondary feature. You could turn off all subtitles. Then whenever it encountered dialogue that had no voice file it would use the silent voice file and temporarily show dialogue subtitles for that instance.

If there is one for FO3 then please point my snot filled nose in its direction. If not, it's not the end of the world. I'll just have to play with subtitles on and have less immersion.