It's not weird at all, but you have to ask your lecturer. I recorded most of my lectures in my first year, although in this last year, I haven't recorded any, as they have generally moved to a lecture-seminar format. If you need to, just email your professors, explaining the situation, but best to do it up front if you can. I'd also reccommend to get tested by your university. it could make the difference in exams, if you have them...