Those things don't make any noise.
3 seconds sound clip from the Night of the Living Dead (1968) movie soundboard.
You can hear this line at 00:41:28 in the Blu-ray version of the movie.
Quote context
[...]
- That's the cellar. It's the safest place.
- You mean you didn't hear the racket we were making up here?
- How were we supposed to know what was going on?
- Could've been those things, for all we knew.
- That girl was screaming. Surely you must know what a girl screaming sounds like.
- Those things don't make any noise.
- Anybody would know somebody's in need of help.
- Look, it's kind of hard to hear what's going on from down there.
- And you wouldn't come up and help?
[...]