Thanks for all your inputs! I am now convinced that with the release of the new third party 3d sound system, bugs were implemented that somehow affect some players specifically (either because we have older audio devices, or just an unlucky combination of pieces we share in common).
I believe we will, or rather hope to, see a hot fix of audio issues in the next days to come.

In the meanwhile, the ONLY thing I've managed to do to get SOME remedy is to close literally every single other application that could consume GPU/CPU cycles. Close everything, play only the game. This has solved MOST of the ambient stuttering and voice stuttering in the overworld and in cutscenes, but you even THINK about doing anything combat related and the popping will begin again.