I thought the same thing, why does he also have to put on his "Batman" voice when changing into his suit? I thought Heath Ledger did a really good job. Was it good because it was Heath Ledger? Or was it more to do with the vision of the director/producers had for the actor? I dare say that Jack Nickelsons version of the joker STRONGLY inspired the version Heath Ledger played (ie voice).
The movie was really good, much better than "Batman Begins." Stronger story, better acting, better supporting cast.
btw.. the Tim Burton versions didn't have different actors playing batman... Micheal Keaton played only in the 2 that he directed.. the other Batmen were by different directors.