(Fresno, CA, USA)
My mother hums constantly, from the moment she wakes until she goes to bed. She's 87. It's not all humming either, it's grunting and hissing sounds.
I've heard the same tunes and grunts and hisses for years. It's driven me bonkers. She hums while eating, while in the doctor's office, the car, anywhere. I can even hear the hums through the walls if I sit outside to get away from it.
It's so annoying and distracting. If I ever do mention it to her, she'll go ballistic and take it very personal. Don't know how much longer I can contain myself. Never heard of anyone doing this. Must be some type of disorder.