Board Thread:General Discussion/@comment-24991718-20140726213036/@comment-17114085-20140920161707

Actually his mastery of the voice is much greater than the other Greybears, which is why he can talk normally in the first place. The other Greybeards don't have full mastery yet so whenever they try to speak they accidentally use the thu'um, which is why they only whisper. Arngeir doesn't do that because he has full control of his voice.