Talk to the teacher and ask him if you can join his class as a listener, unless you are a reknown ahole, or have severe hygiene issues, he'll most likely say yes. You get no voice, so if you have doubts or whatnot, Google, Books, and your own reasoning will be your only ways out. You also get no qualifications of any kind, but you don't study for the piece of paper you get at the end of the course, do you? Take it easy, anon.