silencing a home AC unit?

My grandmother has dementia, when it started, she swore she was hearing the mice in the walls running(we had an exterminator and they found zero trail of mice anywhere ) dementia is a shitty disease and nothing to be done to stop it.

I really had to listen to hear it, but then again, ive worked in manufacturing all my life. add to that my love for guns, and it wouldn't surprise me if im partially deaf, especially in those lower frequencies

its sure is tricky living with someone with dementia
shes in the early stages and right now, its more annoying then anything else
one of the things she does, is the dishes
which means that every time I need a plate or a bowl, I have to find out where they are today

we'll see it through as long as we can, and hopefully we can care for her till the end