The cheapest scream in cinema is the sudden surprise.
It's a common device for lazy or bad writers incapable of scaring people. The scene on screen is quiet, everything seems okay - then a zombie jumps out from behind a bus or something, accompanied by loud-ass music in A-minor.
That's not scary. It's just startling. They're two different emotions. The people responsible need to try harder - like, put an evil clown in a sewer and have it devour a curious child. That's what the pros do!
