In the soundspace parameters for Battlefront, there are two Obstruction parameters (ObstructionHFGain & ObstructionLFRatio) and two Occlusion parameters (OcclusionHFGain & OcclusionLFRatio).

I know perfectly what obstruction is, but when I looked for a definition of occlusion, I found things like "close up or block off" and even "to obstruct".

So I'd like to know what is the difference between occlusion and obstruction in SWBF2 when it comes to soundspaces?

You know, I'm not quite sure. I've always sorta seen them as doing essentially the same thing. This is probably something that you should e-mail psych0fred about and report back here what he says. Also, try just playing around with the parameters and see if you can hear any differences.