Weird noises in house?

Don't know where else to post, delete if not applicable.

I keep hearing noises in the house like someone is rustling papers. It doesn't sound like mice or rats running around (and we also haven't noticed any signs like food containers being open or droppings) or any scurrying or chittering, it really sounds like someone loudly going through a stack of letters. I called out because I thought it was my partner coming home from work for some reason and then it stopped suddenly, then started up again later.

I don't think it's a burglar since it's not possible to open the door or any of the windows quietly without being seen, and I didn't see or hear anything else. And there aren't any papers lying around for someone to rifle through.

Does anyone have any ideas (aside from ghosts)?