I want to soundproof a wood stud wall on my house that faces a busy road and want to use RC to do so. Since the wall is already built, can I apply the RC directly over the existing interior drywall? Will doing it this way negate the ability of the RC to absorb sound via vibration? Or is it best to remove the existing drywall and apply it to the studwall then re-drywall the interior. Please advise. Thank you for you help.