Auralex's RC-8 Resilient Channel is a specially-formed, sturdy metal device that, when used to hang drywall (instead of just attaching the drywall to the studs or joists), GREATLY improves the sound transmission characteristics of the wall or ceiling system.
RC-8 should be installed horizontally at the bottom and top of your wall, then every 2' or less in between. Up to (2) layers of 5/8" drywall and a layer of SheetBlok may be hung on RC-8, even on a ceiling.
RC-8 is available in handy 8' lengths that are ground shippable. There are (24) 8' pieces per box. It's unbeatable!