If you are in a situation where you have a serious pile of interference, you can always use foil sheild cable. I think Matt is correct, in most situations the source of the interference is really pretttyobvious and you can just move your cable a little.
Here is my real world worse case scenario. I have a 50 watt ham radio transmitter. Let's just say that it has the ability to create some serious interference. If I use it upstairs around the normal computer (cheapo computer speakers, crummy cables, etc) every time I transmit the computer freaks out, speakers hum like crazy, etc. Down in my studio.. nothing
Here is my real world worse case scenario. I have a 50 watt ham radio transmitter. Let's just say that it has the ability to create some serious interference. If I use it upstairs around the normal computer (cheapo computer speakers, crummy cables, etc) every time I transmit the computer freaks out, speakers hum like crazy, etc. Down in my studio.. nothing