As a person who suffers from tinnitus, this story is just too relatable. It's enough to drive a person mad. I've adapted to it, I use a white noise machine to sleep, and avoid quiet rooms, keeping either a bit of low music or a podcast on most of the time. But it's still always there, thinly veiled behind it all. That ever persistent, high-pitched private purgatory.

I believe she hears something, tho. I've heard sounds in movies and machinery that are definitely the same tone as my tinnitus. But I can always tell the difference between an external sound and my squealing ear.

I'd be curious if you dig what you might find. Perhaps before destroying the basement wall, you could try digging in the ground just outside the basement wall to start with. If she says it's coming from just beyond the basement wall it seems like a good place to start, and it's definitely less pricey than repairing a foundation in case you need to get rid of the place.