My daughter did that for about a year maybe when she was around two. Then she just grew out of it, thank goodness too because it was a bit annoying at times.
My son hums when he eats and drinks!!!!
Prior to my 8-year old aspie daughter's diagnosis, she frequently got in trouble at school for "disrupting the classroom." Finally, I asked her 1st grade teacher what she was doing that was so disruptive and she said she was humming while the rest of the class was trying to work or when she was in front of the class teaching.
Yep we have all sorts of noises here. They rotate every few months. He also does finger movements. We started ABA last week and tomorrow she will see him for the first time while doing his school work. (We homeschool) and she is going to help us work on ways to get him to do it less.
Stimming is very common, and my son does it a lot when he is either nervous or concentrating on something. We generally let him do it and work his way through, but if it gets bad we just redirect him, or talk to him about something, and he stops doing it. It is just their special way to calm themselves.