ZDoom

I played around with adding ambient audio and other graphical effects to maps semi-procedurally in the past, but it's a real mess under the hood. I've thought of ways to do it slightly more gracefully, and I might even play around with that in the future.

Heretic and Hexen didn't have reverb (they had environmental sounds, but not reverb). I'm not aware of any mods that add reverb to the original games' levels (unless you count the PSX TC, though it has just a global per-map preset that's disabled in certain sectors), but I'd be interested in checking something out like this too. Adding environmental sounds to the original Doom maps would be nice as well.

Heretic, not Hexen. Hexen did all its sounds with ACS.

That was a feature introduced in HEXEN and eventually added to ZDOOM and now GZDOOM.
So, no, that won't work in vanilla.

sweet dude - do you know if anyone has done this for any of the vanilla maps (dont want to recreate the wheel here if i dont have to)

If you are looking for an example on how to do this
then check out eax.wad

https://zdoom.org/wiki/Reverbedit

Are there any sound packs or mods of original levels that anyone has done which adds reverbs and such to certain areas of maps to enhance the audio? Thanks guys