Alright, first I gotta say congratulations on the release of black mesa source and hope you give yourselves all a pat on the back, you deserve it. Now the question I have for you today is what sound editing program and the settings used in said program did you use when dealing with the HECU grunt voices such as the radio sound effect you added to the marines in particular. I just figured it sounded pretty badass and wanted to try it out for a couple of projects of my own, so if you guys are willing to disclose such information then it would be greatly appreciated. Once again, thanks in advance for any response you give me because that in itself would be good enough and I wish you luck on the development of the final Xen chapters.
I’ve actually been a little curious about where some of the sounds have come from myself. Really curious what programs you guys did for the alarms and things like that and how you made them in said programs. Also, I’m really interested on how you made a lot of the “Half-Life-ish” sounds like the Houndeyes and really interested how you made the Antimass Spectrometer’s sounds. It has the same pattern to the hum but the hum itself is different. I would think that those sounds are custom right? I really want to know!
And to your question about the soldier’s voices, I’m not that much of an audio expert so take my advice with caution: Try adding an “echo”, (assuming you’re using audacity, if not, then find the equivalent of an echo) NOT REVERB to your audio clip. Make the delay “0.005” and the decay factor “0.5”. Then add a low pass filter of some kind. Play with the echo and the low pass filter until you get your desired effect. What you basically hear in the game is a really small echo (that’s the sort of echo-ish thing you hear) combined with a muffling effect caused by the low pass filter.
EDIT: I should also add: You can also use reverb if you wish, It just gets more complicated than echo as echo only has two boxes (the ones I mentioned). Just give it a little reverb, not a whole lot. Try searching around the interwebs for scuba, gas masks, or any of those kinds of effects. Oddly enough, the HECU grunts actually sound a lot like Darth Vader when it comes to their helmets, so search some stuff on making his voice too. 
You could maybe try googling “spaceman v2 vst” and crank up the volume when using it, it works for a radio sound.
I also want to know how the majority of the sound effects were made, especially the houndeye, snark and weapons. That and the music.
I can sort of answer that. The music was obviously made by Joel Nielsen, the main sound designer/composer for Black Mesa. He’s really good at what he does because he’s been doing it since his childhood. He’s got a really nice studio from what I’ve read. He’s said in an interview the majority of the songs for the game came from him messing around on his keyboard. If you’re looking for the actual sound fonts, that might be kind of tough unless Joel or someone else refers you to them. He more than likely has a large library of various sound fonts he’s built up over the years.
Here’s an interview with him (it’s three parts):https://www.youtube.com/watch?v=Kd9OC1lQHZs
And here’s his mega list of audio equipment (I don’t know how up to date this one is though): https://www.joelnielsen.com/studio/