One of my students hums when she writes. I don't think it is conscious, and it is just quiet enough that it would feel strange to make a fuss about it...but not so quiet that it's not annoying. I am contemplating how to approach the issue because this student is autistic and has confided in me that certain things can really fluster her. What if she can't stop?
I am reminded of a very bubbly student I often worked with at my old post in the disability center. She was talkative and happy, but when she was alone with a test suddenly she would let out the most aggressive strings of curses, tell herself she was stupid, scream, pound on tables. We put her in a one-person study room for exams. The one-person study rooms were highly coveted. No door opening like in the ADD room. No scratching of others' pens. Lots of space to stretch. Students who had mild anxiety would often try to weasel their way into those rooms. "They are reserved," we would explain. We didn't allow anyone in even if they weren't going to be used all day so no one would get used to the treatment.
But I would show this girl to her room and she would say, "Oh, no thank you. I would like to be in the bigger room." I would explain she was placed in the private room. "No, I don't want it." We would explain she was a distraction to others and she just couldn't believe it. She fought us basically every time.