User blog comment:Luffayking12/A Fourth haki ?????/@comment-4477846-20120105105054

gold roger could hear the voice of all things not just people so that might be a form of haki (evolved form of the color of observation) and it might be exclussively for swordmen since zorro "heard" the breating of his suroundings ( http://www.mangareader.net/103-2302-17/one-piece/chapter-195.html ) or i might be wrong just a guess