Ooooh, neat idea!!!! Now that I think about it, I can't believe that, with all the fic out here, that this hadn't been done, because there *are* people who prefer audio stuff. I'm not one of them myself, so probably won't listen to any. But the idea is awesome, and I know people who listen to books on tape and stuff, so . . . just have to find some FoLCs who do that.
For speech, bitrate is usually lower than music, because speech can get away with lower sound quality. What bitrate do you have the file at?