The issue I have with Yoda's voice is that his speech problem, if you can call it that lol, seems more natural in TESB and ROTJ. In the PT he is simply talking backwards, and to an exaggerated degree which is annoying.
I seem to remember his speech being largely okay in TPM, but not in the others. Imagine OT Yoda delivering this line: "around the survivors a perimeter create". Haha, Lucas really took the backwards talk a bit too far there me thinks.