One trick is to use small zip ties around the cable so the long end/tail will stick out, put a few of those like every 4-6" or so along the cable. Then feed it into the tube. You can put a few close to one another also, like on opposite sides so the cable is either suspended/lodged between the tube walls while inside of it, or just one side and hope there is enough force to keep it against the tube so it won't make noise.
I basically did that, haven't had any noises/rattling.
There are also specific designed ones you can buy. But the small ones are good too from your local hardware store.http://www.evanscycles.com/products/shi ... 0-ec037141