Sudden strange humming noise

Patient: My daughter has suddenly started making a strange humming noise that she can not control, she does not even realize she is doing it. I was wodering if this is associated with any disorder, or could be an indication of any disorder. She does have very large tonsils and gets very sick every year with some kind of throat thing (bacterial). She is not a child. She is 21 years old. This started about 6 months ago, and seems to be getting worse. Any information would be helpful. Thank you.