Whether or not Hitler made buzzing sounds when he was shaved is, unfortunately, like a lot of questions we get here about Hitler: It's just not that interesting, and more importantly, it doesn't tell us anything important. You may be interested in this Monday Methods post from u/commiespaceinvader on Hitler, great man theory, and asking better historical questions: https://www.reddit.com/r/AskHistorians/comments/4cewq8/on_adolf_hitler_great_man_theory_and_asking/