Jiang Yi had indeed realized something. He had found out something new related to his Divine Sound Heaven Skill: it wasn't the case of the louder the sound, the more terrifying the attack. A loud sound would only destroy one's eardrums. However, the Divine Sound Heaven Skill's real aim was to impact one's soul spirit without form or shape.
A sudden thunder from nothingness would bring about a greater amount of shock; that would then inflict greater damage to one's soul spirit!
As for how to be hurt by such, Jiang Yi had not figured that out yet. He had only managed to figure out this little nugget of truth, and he had only reached the Entry Stage of this nomological mystical ability. To fully understand and use this skill effectively depended on how he realized this from now on.
