A video compares the audio in the original IMAX preview with the finished film.
First things first: I believe this video embodies the whole purpose of fair use.
Next: A while ago Collider ran a story about Warner Bros remixing Bane's voice after people complained that he was unintelligible in the IMAX preview. Warner Bros denied it, Collider retracted the story.
They were right.
We all know it, and we all knew it as we watched the film. Bane's voice played like Godzilla movie ADR. What's really interesting, though, is that this comparison indicates that this wasn't just a remix, but that Tom Hardy completely rerecorded his lines for the finished film. Some of these line reads are quite different from the original preview.
Fixing the audio was a good idea, but I do wonder if Christopher Nolan went a bit too far the other way, making Bane so crisp and clear that he never sounds like he's in the scene.