There is no effective shield material against 60 Hz interference which can be built into a standard cable. However, there are four solutions to 60 Hz interference:
- Move the cables farther apart. Twice the distance is 1/4 the effect (called "inverse square law")
- Put the cable in corrugated steel armor. This increases 60 Hz isolation by approximately 18 dB, but it is expensive.
- Put the cables in separate steel conduit. Conduit can increase isolation up to 25dB depending on the thickness of the conduit and the workmanship of the joints.
- Filter out the 60 Hz signal from the signal you want. These filters are sometimes called "humbuckers" and are torroids tuned to 60 Hz. They can be very effective buy are very expensive ($200+ per channel).