Apart from the obvious one of running it outside 🙂 which I don't really fancy.
seems to be quite noisy at the top of the headstock area, I've used a couple of plans up to now which seems better.. but doesn't really please me fully.
I was hoping for something a bit more scientific than "electrical tape".
I put a cable tie right next to the entry on the outer and then pulled it tight through the frame and out another one at the exit point on the outer, solved the issue on my last bike
Crazy foam 🙂
Get some of those little clear plastic doughnuts from your LBS and slide them along the cable inside the frame. You will need something like a length of plastic tube or some cunifer brake pipe to do this.
Note sure if this works but MBR seem to have a good idea http://www.mbr.co.uk/how-to-2/silence-bike-four-easy-steps/