If it's a little scratching noise, I'd say it's a mouse. A big noise might be a squirrel. I would call animal control or an exterminator.
My DH was the same way. I knew there was something up in our attic (it was a squirrel) and DH said oh that's just the wind or something outside. Um, no, it was a squirrel chewing its way into our attic and deciding to live there! The exterminator caught it with a trap.