I am sure when you played HL1 you heard these weird sounds twice in OaR near the electrified water and a room with a bullsquid and dead HECU grunts , and also in Interloper in the Xenian Grunt factory supply room, and right before nihilanth next to the portal it looks like a nightmarish version of the anti-mass spectrometer you can also hear the scientist and security guard lines like “Someone get him out of there” “Rescued at Last thank god you’re hear”. I think these sounds are the ghosts of the scientists and guards killed by the Xenians, HECU and BlackOps soldiers.
What do you think these sounds are? and I wish they could be included in Xen too also add some voices of the marines.
They’re the infected horde amassing for a panic event.
(Not joking, Valve used the same samples for that in the L4D games)
I know I hear in Left 4 Dead during zombie hordes.
The souls of the scientists who got lost in the maze of rails and are now cursed to haunt these tracks for eternity.
They are “the_horror1/2/3/4” sounds, if you wish to download them, see here: https://www.mediafire.com/download/rqf7nwnahkqnbcb/horror.zip
When played on their own, they are even more eerie. Most people should recall them from L4D hordes or CS’s zombie mode.
At least two of them play during On a Rail: one near the beginning of the chapter when riding the first rail zone, and the second one under the rocket, where a really large amount of blood and HECU corpses are found. The third one plays when standing near the final Nihilanth’s portal, mixed with scientist sounds saying something like “shut the equipment and someone get him out!”. What could it mean? The On a Rail probably represent Gordon’s fear overwhelming him, the next chapter being titled Apprehension supports this even further. Having faced two bosses in a quick succession (tentacles and gargantua) he’s probably fearing a next very powerful creature. The one near Nihilanth’s portal: well, the portal itself loosely resembles the Anti-Mass Spectrometer. One theory I like very much is that the alien invasion never happened; Gordon just received radioactive dose and is imagining all of this in a coma, he’s actually lying in the test chamber and scientists are trying to get him out of there. Both OF/BS expansion packs and HL2 came later, and Valve didn’t even know back then if they would ever be done, so it seems all HL games except HL1 are huge retcons… but that’s just a theory.
I’ll never forget that creepy screamy sound in On A Rail after you find that optional area with water. It scares the shit out of me every time I go there.
You enter an empty room, only to find on the right and left bullsquids, headcrabs, and lots of blood on the floor, and then, the sound plays. Spine-shaking every single time.
The nightmarish scene on Xen on the other side is actually very cool, far from scary imo.
As about ,what could the sounds be, well, especially in ONR, well… There’s no logical explanation for where they could come from. I think Valve simply wanted to add a horror element to the chapter, since in HL1 the whole level already looks abandoned/desolate and has a hostile atmosphere toward anything that moves (or that’s how I see it).
It could also be that maybe Gordon has a shock after he sees the area. After all, the incident was surely a traumatizing one. No one expected this to happen. He could be overwhelmed by fear.
As about Xen, I have no idea what that could be. Maybe Nihilanth is just playing with Freeman’s mind, who knows? Trying to break his nerves and sanity because, after everything he’s been through, that wouldn’t be such a difficult task to do. Reminding him of what he’s been through, and of course, the place where it started.
The first time I heard them in-game, I mistook them for the sound of wind blowing through the tunnels or steam in some sort of pipe system, so that’s still my explanation.
I’ve always been creeped out by this room in particular, I believe ‘the_horror3’ and ‘the_horror4’ play in this room on a loop.
This area Gordon explores in Xen resembles some sort of manufacturing plant, so whatever purpose this room served is beyond my imagination. 
I’ve always thought when replaying Xen that this room held the spirits of all the dead survey team members, maybe powering the facility in its own grisly way. Ambiguous interactive storytelling. Fun times. :retard:
Souls? That’s not Doom or Metro 2033, that’s Half-Life. I doubt that they believe in souls there.
I’m pretty sure that’s the room where they stored the bodies of surveyors they had found- their version of the Questionable Ethics lab. I initially thought that the horror_# sounds might be coming from live survey team members held elsewhere in the complex, but now that I’ve heard them in isolation they don’t actually sound particularly human, so wind currents are still my number one bet (it’s a big, round room with a bunch of thin platforms in the middle, if for some reason air blows through it you could probably get a good resonance).
In that area are ,built, Alien Grunts by the Vortigaunts as far as I’m aware, and they’re staying inside the barrels, which, of course, the player can kill.
If I was going to take a deeper than necessary analysis at that room, I’d say that compared to the rest of ‘c4a1e’, the manufacturing facility, had rooms with actual machines such as conveyer belts and elevators, this room just seems to be there, hidden behind alien ventilation shafts, occupied only by a few Vortigaunts, Grunts, and later Controllers.
Despite being in an alien world, one could surmise the purpose of what everything in Xen is, but this room is left so ambiguous, it receives a somewhat sinister vibe… and the fact ‘the_horror’ hasn’t been heard since OaR is unsettling.
…or maybe Valve just wanted to make a storage room for those barrels, throw some bodies around higglety pigglety, and nothing more.
Just some harmless theorycrafting.