Hey, are you a linguist in need of a dissertation topic? I have one, maybe: “The September 2001 Accent: Generational/Temporal Accents in the 9/11 Tapes.”
The voices in that audio (in the FAA/Norad/AA tapes released by the NY Times in 2011 and also the 911 calls used in Zero Dark Thirty) are a mix of generational accents (from the ’50s-’80s, I think?) with a 2001 temporal spin, and, already, just eleven years later, sound absolutely nothing like the way people talk now. (Note: it’s probably not a good idea to try to listen to them casually, they’re very hard to listen to, obviously, and I’m not suggesting that they be treated lightly.)
But because these tapes are of real people speaking off the cuff (not even just off the cuff - in a highly stressful situation), on one particular day (as opposed to the showbiz/political speech audio we have so much access to), they accidentally provide a unique audio cross-section, a (somewhat) representative snapshot of the American accent as it was in 2001.
There’s probably no way to do it without suggesting (or at least entertaining) the idea that the chaos and fear of September 11th, 2001 and its aftershocks caused us all to start treating declarative and imperative sentences as if they were interrogative, though, whether that’s true or not.
Anyway, that would be interesting (to me.)