Can only go by what I recall reading here & there when the Dark Sky DVD was first released: that a couple of screams present in the original mono track are missing in the 5.1 mix.

I watched the DS disc and didn't notice anything missing... Of course, I've only seen the film about four or five times, whereas some folks, it seems, have screened it a gajillion times and know every scream by heart!

"Damn it, it's jammed!"