>My trig professor was the same way. It was very frustrating to sit in his classes. He would stand at the front of the room facing the chalkboard and mumble all through the class. We could never hear what he was saying and couldn't see the chalkboard either. When he filled the chalkboard up, he would erase it entirely without even turning around. In fact, I don't remember him every facing the class or once acknowleding whether anyone was there! Most of the students dropped the class the first week and took it later from a different teacher.

Well this was not such a case - this guy was just doing his regular lecture in a firm voice, he even beat the bad accoustic of the classroom. What he mumbled were additional comments, pretty much like footnotes in small print and not-so-official language. And these didn't make much sense immediately. But later they did.

I was teaching five years. If they can't hear you, you've done nothing.