What are professional indoor tournament courts made from?
I've heard of the term "carpet" and that it's 2nd only to grass in terms of ball speed.
What exactly is it?

Also, is the rebound ace material on the courts at the Aussie Open different from actual hardcourt? How about the US open courts?

Indoor tournament courts could vary between each tournament. You probably already know that there are several different types of surfaces. From what I've seen indoors, carpet, a synthetic bounce-able plastic, or just hard court. Also clay is popular indoors.

I hear that US open is faster than Aussie, but the court material is supposed to be the same (hard court).