It could be a good idea to prevent the sound from playing again specifically if it's tied to a timed shift. I have to be careful that I don't break any existing levels though. Having designers opt in would guarantee that no existing levels would be broken, but I feel like it would be too obscure of an instruction for most people to understand its purpose. It would never be used like slow-fade ambiance.
Well, it could be auto-added to World.ini of new levels.
I'm assuming you're bringing these things up because you're just now digging into Deep Freeze, so I'll stick this detail behind a spoiler if that's the case and you haven't finished the level yet:
No, I've finished it, and wrote a response in the thread
The difficulty with this one is that the the game still needs to be able to activate triggers so to play sounds from other shifts, since Deep Freeze starts incorporating the use of multiple, concurrent timed shifts. Unless you could call the ID of the specific instance of that specific sound played from that specific trigger, I'm not really sure how possible this would be.
I don't mean whether or not the sound is playing (it's actually impossible to find out because for that all sound emitting code in KS would have to be changed and in MMF2 it has to be done manually), but the timeout of shift itself (e.g. ShiftTime(A)), which isn't a problem.
You know, that does sound vaguely familiar. If it was possible to kill trigger sounds on death for both death effects, that would be great, as well - the countdown sounds playing after death was a minor complaint I got from playtesters who weren't familiar with KS's limitations. That said, I believe this was a functionality we spoke about way back when, and I think it was decided that there wasn't much that could be done about it.
Nothing can be done to stop shift sounds specifically, but a call to "Stop all sounds" function could be good enough.