Ogham is still processing the fact that the man spoke directly in his head. A magic spell, probably, although there is a difference from the magics occasionally used by his commanders during the War. To the warforged it confirms that the man is a soldier of sorts, and that makes sense to him.
”Yes sir,” Ogham answers aloud on instinct, as if answering to a superior. Then he looks at Liutbrand to confirm the order.