TL;DR
The railgun makes a fun sci-fi zappy noise, but in atmosphere, railguns should have a loud crack and a roar.What?
The railgun sound should be updated to have a crack and a roar instead of a sci-fi gun zappy sound. Possibly preceded by a electric arc noise. For extra points, having it just be the electric arc noise and some rumbling (projectile passing through the barrel) in space would be excellent.Examples:
* https://www.youtube.com/shorts/dXb3p5HEam0
* https://www.youtube.com/watch?v=O2QqOvFMG_A
I don't think directly using these example sounds would be effective in gameplay. I think the sound form the first video should be amped up a bit, and the crack much more heavily emphasized. That gun as asking a whole lot of air to move out of the way NOW when the projectile leaves the barrel. It should sound like a lightning strike.
The second video is mostly an example of the loud electric buzzing as all the very large capacitors discharge nearly instantly.
Why?
Mostly for reasons of realism. And also, a desire for the railgun to sound like it has the massive punch that it does (and should) have.And, in space, of course, all the effects the projectile would have on the air (the loud crack and thunderous roar) would be absent.
Gun turrets in space are a bit more justified in their noises because the vibrations would be transmitted through the turret into the deck of the space platform. And explosives will work without oxygen. But for a railgun, the crack and roar effect is a direct result of air being pushed out of the way of the projectile.