So, there's absolutely an audio issue on Apple Vision Pro. It's not actually anything new. There's been an audio issue for years where the audio glitches when a notification comes in. It's pretty clear that it has to do with playing both sounds at the same time.
This wasn't too bad on iOS/iPadOS, but is a bit worse on visionOS because you can ACTUALLY do more than one thing at once (finally.)
We're aware and will be looking into it.