User blog comment:FairyRaven/Fairy Tail Chapter 328: Zodiac, Review and Commentary/@comment-5871436-20130420180412/@comment-7418318-20130421151708

And then in the starry key of heaven arc Cobra erased that weakness completely by gaining the ability to manipulate sound.

Now if someone shouts at him, he can amplify it and send it back as a shockwave.