Impulse can read lips really well..... or so he says

From Young Justice issue 20

This is, from my understanding, the first time the audience gets a hint that Impulse can do what no other speedster can - read a book at superspeed and remember it for more than a couple of seconds.

 Of course, reading something and understanding it are two completely different things..
Last panel, I really love this. Especially Bart's "What kinda stupid name is Timmy Drake??"