It should NEVER touch anyway. 101 cables routing. When the cables are routed correctly you will have ZERO noise. Off the ground off each other cross at 90 degrees. I use as little shielding as possible. It KILLS the dynamics of a system if your not careful.. Routing is a LOT better alternative.
There is a place for shielding.. The right kind is more important than just having shielding. Cable construction (weaves) are quiet because of construction, not shielding..