User blog comment:Kagimizu/Attributes?/@comment-1492918-20111009031558/@comment-1617565-20111009043256

Ah, that.

Sound is expressed and explained as pressure-waves traveling through matter, and all sound waves are created through the motion of matter. Aura is thought to be the energy of living things, and as described in the Pokemon series, are sensed as "waves" by Lucario and Riolu.