What are Ferrite Cores and How do I use one?

This video just hits a generic use at a high level. If you want to dive deep, there's a good, simple website called audiosystemsgroup.com, and I found their PDF to be a handy way of explaining various other ways you could use Ferrite Cores (also called "beads" or "chokes") to try to solve an interference problem. http://audiosystemsgroup.com/SAC0305F...
FAQs:
Can I try 2 or more cores? Yes, 2 or more cores can make a difference. Manufacturers that install a core most often do so at the end of the cord where the device is and not the end that goes into the computer. Putting one at each end could help if you believe RF may be a pretty intense problem. You can also try a different USB cable and even buy a more shielded cable.