Board Thread:Lore Discussion/@comment-14027812-20131027182513/@comment-1403309-20131108171049

It is said that Arngeir has the strongest voice out of all the Greybeards. However, he is the one that speaks. And nothing trembles when he does.

That is also the case with dragons. They can speak normally and nothing trembles, but when they use the Thu'um, it's far more powerful than it should be when a human does.

My theory is that the Thu'um is a power like any other. But it's a power that is used through the human voice. People with a powerful Thu'um will most likely be able to crush the earth with their voices, but they will be unable to stop doing so. They lack control.

Arngeir and the dragons, on the other hand, can speak normally because they have control over their voices, so they don't Thu'um the hell out of everything whenever they moan while having sex (lol).

In short, the Thu'um isn't all about power. It's about power and control. It doesn't depend on what you say, but on your control over your voice. Most of the Greybeards have probably trained the Thu'um so hard and spoken so little in their lives that they just don't know how to speak without crushing the earth.