Those techniques were around before a3d and are used today by acoustics engineers in software like Odeon and CATT. So if someone wanted to make their own engine, there would be nothing stopping them legally.
Ray and cone tracing are standard terminology, but perhaps you are referring to something else?
There are more explanations in the article and in the video.
Interesting, thanks for the link. I'll have to give it a read when I have some time.
From what I am getting from the article, it only processes the players gunfire with early reflections, may only use 1 ray per surface, and it seems the ray disappears when it hits it's first material (It's not real clear on that though). So it sounds like it's a very limited implementation, but it's still an improvement over having none at all, so I can't knock em I suppose. Ideally, you'd want each sound source casting ray spheres that would bounce around the environment while being filtered by each surface's material properties they encountered, and they wouldn't disappear until the surfaces absorptive properties along with it's natural decay silenced the sounds rays. I guess a single calculation per material is an alright workaround at this stage, but having it limited to only the players gun fire is an unfortunate compromise.
Ray became the standard term, couldn't tell you why. I agree though, would likely be better renamed since it would differentiate it from the visual technique.
A3D sound cards did it in the late 90's with multiple sources. I can't say it sounded all that great, but if they are still struggling to make it work now, I see that as a problem. Killzones implementation doesn't sound particularly intensive though, Instead of a sound source shooting out potentially hundreds of rays, it seems like it targets a single ray at each unique material within range of the source, then kills the ray immediately after collecting the material data.
