Look up tardive dyskinesia, a side effect of medications. Especially for lip-smacking, but maybe humming may be a side effect of meds. Meds that can be changed. Apparently, the patient can be suffering more than we know. We can ignore it, tolerate it, or distract them from it after thoroughly checking this out.
My MIL had this habit. My husband and I lived with her and she would go out to the patio to water her flowers humming away at 11 or 12 PM.. Only problem, our bedroom window opened out onto the patio and if we were "cuddling" , on came the lights and the humming. It always cracked us up.
Since you did not specify as to the type of humming your mother does it does not help to narrow it down. My mother hums constantly, like a low growl, and claims, most of the time she does not know she is doing it. If pressed to stop she does give an explanation. She has had a problem with her throat tickling for years. Sucking on peppermint candy used to help, but no longer. Now she claims she hums to stop the tickling. The vibration in her larynx causes movement which may temporarily stop the tickling or at least take her mind off of it. Tickling in the throat can be caused by sinus or by some daily medications or even acid reflux. Her Dr. has no clue, at this point and gives no recommendations. Welcome to the frantic world of elderly quirks. Oh, and she shuffles her feet, on all floor surfaces, wearing down the rug fibers, while sitting, repeatedly, rolls food around in her mouth, sometimes for hours and spits in the kitchen sink, to mention a few, all unknown to her. Good luck.
Mrsprim, you are not alone. There is no doubt that it is we, the caretakers who get upset. I really believe these sounds are something that makes our loved ones feel better in some way. My mom used to make a sound after eating that would drive me nuts. So that I wouldn't go crazy, I would ask her to brush her teeth. Sometimes it helped, sometimes it didn't. My trigger was when my Mom would start to tap her fingers. I would go from 0 to 100 and feel like I wanted to jump out the window, and run. It got so bad, that I did end up on anti-anxiety meds. Sometimes it helped, sometimes it didn't
I was so surprised to see this thread. My MIL has been sort of humming for over a year now. It started as something that sounded more like whimpering. We thought perhaps she was in some sort of pain upon moving, but she said, 'no.' Over the months it has morphed into something not quite musical, but much more like humming than whimpering. It makes me nuts, and I really try to just tune it out because I'm pretty sure she doesn't realize she's doing it.
My Dad whistles softly and has done that as long as I can remember. It wasn't until my high school grandson commented on how he knew I was happy because I was whistling softly that , indeed, I do and have done the same as my Dad.
We thought perhaps she was in some sort of pain upon moving, but she said, 'no.' Over the months it has morphed into something not quite musical, but much more like humming than whimpering. It makes me nuts, and I really try to just tune it out because I'm pretty sure she doesn't realize she's doing it.