Again, Outlast fails to do anything scary with its audio. I think sound is really underrated when it comes to horror - that's what distinguishes Silent Hill and the older Resident Evils from the overly-orchestrated, raucous swells and booms of modern "scary" music. (See: Dead Space series, Resident Evil 5-6, FEAR 3.)
A Machine For Pigs does have its share of bombastic moments, but that's balanced out by plenty of unnerving and memorable sounds.