I dunno, I kind of like it.
Sound Type
Strong Against: Fighting, Psychic, Bug*, Steel (Fighting and Psychic are both human-related elements, and sound could interrupt the focus of Fighting and Psychic types. Sound on Steel causes reverberation--enough sound can cause it to shift.)
Weak Against: Electric, Ground, Rock (The sound of thunder would drown out any sound, so Electric. As for Ground and Rock, sound doesn't go through those substances very well, and usually just bounces off of them.)
No effectiveness against: Ghost, Bug*
Thing is, I don't know where Bug would go. Some studies are saying there are sound repellents for bugs, but otherwise, I don't think it'd be effective.
So, depending on how you looked at it, the Bug type would end up either being weak to Sound or not affected by Sound.
But yeah, it could work. Really now, people, all you had to do is think about it for a second.