Please keep all related discussions to one thread instead of separate ones. It helps keep things organized.
Anyway, like I said, he got the mask in Part 3. It was one of the victim's, Shelly's, masks that he used to scare people. Jason stole it and put it on. In part 2 he wore the sack over his head, but it wasn't as memorable and ripped off The Town That Dreaded Sundown. They used the hockey mask because they wanted to craft Jason into an image that people will remember, similar to Michael Myers's mask in Halloween.
As for him not talking, it was an artistic decision that the filmmakers made because he is scarier without a voice. Jason, like Myers, is supposed to be a symbol for pure, unstoppable and relentless evil. Having him not talk dehumanizes him and turns him into a monster. Again, this was an artistic decision (opposed to the decision to humanize such monsters as Hannibal Lecter by making them very intelligent and articulate, which also works in that situation). But on a side note, Jason in 2-4 DID make noises, especially when he got hurt. This was the pre-zombie Jason.