At your disposal you have yourself, your cat, another person, and two modern smartphones. You’ve tried wandering around, and you just can’t figure it out off the top of your head.
What technical/non-technical method would you use to locate the source of the sound?
put the other person and the cat in the rear bedroom and lock the door.
cotton balls.
if you don't have them, you can cut up your socks.
you put them in your ears.
if the sound keeps on, then the source of the sounds is just that you're crazy and delusional.
if not, it's just the furnace
it doesn't matter which, because the other human will have called emergency services and you'll be going to a nice place