ZDoom

To use reverb, you need to place a [url=https://zdoom.org/wiki/Classes:SoundEnvironment]SoundEnvironment[/url] thing in the map, with the area it effects enclosed with linedefs marked as zone boundaries. Then either select [url=https://zdoom.org/wiki/REVERBS#List_of_reverb_IDs]a preset[/url] for the sound environment thing (I'd probably recommend trying Padded Cell, or some other really dull/quiet reverb, if not Off to remove it completely), or define [url=https://zdoom.org/wiki/REVERBS#Defining_a_reverb_environment]a custom one[/url] to suit your taste.

As for the direct response, a hacky way might be to reduce the volume of individual sound instances manually as they move away from the player. I'm not quite sure how you'd do that, though. Otherwise, it will need a new feature request to change the individual sound instances' min/max distance (or min distance and rolloff, depending on type) during playback.

Ok so what would I have to do to achieve the intended effect then? Also I couldn't get a reverb room response anyways using custom reverb environments too, so I actually just flat out couldn't test around with one at all.

Reverb environments only affect the reverberation (room response). What you describe is wanting to alter the direct response (as well as having basically no reverb). AFAIK, there's currently no way to adjust the rolloff or reference distance of a sound's direct response during play, it'll use whatever's set for the game or the particular SNDINFO entry.

So i'm trying to make a custom reverb environment to try and mimic what the sound experience would be most like if you were stuck in a vacuum in space, in other words, extreme volume falloff from sounds that aren't coming from inside your suit, etc.

But I sort of can't figure out how to do custom reverb environment setups, even after making multiple attempts to digest the wiki page regarding REVERBS. I could use a bit of help figuring this one out.