I started to notice with one character in particular but others as well that sometimes the voices start to change frequency while speaking.
Like a badly tuned piano that starts to get a bit too low then too high then too low again and so on, it modulates and doesnt stay constant in tone.
The one that really made me notice it was simenon, the ancient fellow sitting on a pillar in the Fjords. While he spoke it was rather strange, difficult to explain but really annoying.
I noticed also the narrator sometimes has that problem.
I use a X-fi Fatality soundcard from Creative. Havent had this problem in windows nor in other games, so i believe Divinity 2 itself is the culprit.
I own the "Dragon Knight Saga" with the latest hotfix.
This is my system :
I7 920 @ 3,2 Ghz
6GB Ram
X-Fi Fatality soundcard
Asus P6T motherboard