Here are a few questions.
- Do you know any actors who speak "perfect GenAm" without any trace of a local accent?
- For instance, do the following actors have a noticeable local accent? Anne Hathaway, Scarlett Johansson*, Natalie Portman, Brad Pitt, Edward Norton, Leonardo DiCaprio, Robert John Downey Jr... (not counting films in which they fake a specific accent, e.g. Pitt's Southern accent in Inglourious Basterds)
- It seems to me that the center of gravity has moved westwards. When I see movies from the 1970's, I think I hear more of a "Midwestern" thing, while present-day actors sound more "West Coast" to my ears (even those not from the West Coast). Not only because of the low-back merger, but the overall tone and voice quality. Am I just talking out of my ass here?
By the way, what about the Joker's accent in The Dark Knight? It seems like a mix between New York and Chicago. (Now that I think about it, this description could apply to Gotham City...)