Visiting Dog COMPLETELY Freaks Out at Unfamiliar Sounds

My mom’s dog – a rescue of suspected Schnauzer descent – comes TOTALLY unglued at unfamiliar sounds. We’re talking jumps, shakes (violently enough to shake the entire chair), pants, tries to climb on my head. I have small birds. When they chirp (sweetly not squawking) the dog freaks out. When my little mutt squeaks her fav toy – freak out! It takes her awhile to calm down. I have tried Rescue Remedy but I’d have to give it to her in a constant IV to anticipate the things that freak her out.
Does anyone have any pointers?