"Cape Fear" movie. Robert DeNiro accent.

Hi everybody,
Have you seen the movie Cape Fear?.
I was wondering where Robert DeNiro's accent comes from.
I like to watch movies in english (I am Spanish) to educate my hearing (or ear, please correct me). The thing is I have come across this very strange accent
I hardly understand what he says.
Maybe is some sort of Southern accent but I am not sure.

Thanks.

The Robert Deniro accent in that movie was supposed to be some kind of coastal Southern accent. Trust me when I say it sounded just as weird to this native English speaker than it probably did to you.

«to educate my hearing (or ear, please correct me).»
Maybe 'perception'?

or:

To train my hearing?

Thanks for all of your answers folks.

«To improve my speech perception» - final version.