I get voles and mice in my hanger during the winter, the colder it gets, the more activity. those little buggers manage to learn from the "last" guy and are able to figure out a lot of traps I set up it seems. I end up rotating them.
At the cabin, I use a 5 gal bucket trap, with peanut butter about 2 inchs down from the lip and a couple inches of RV antifreeze at the bottom. keeps them from stinking, even after all winter. I would do this in my hanger, but the dog and toddler would find their way into it for sure.
I have had no luck with ultrasonic.