Hello Cidershed,
Ethernet has been around for decades and was probably a theory at start, but is now a very mature technology used in pretty much every network. Cabling has been and can be tried and tested using scientific tools like software or professional cable testers. Problems with interference can occur, that's why you need to conform to specific standards when deploying cabling in large buildings etc.There are people who do certified cabling in buildings in order to avoid transmission problems.
Now for 1 or 2 metre cables and in a home environment, in my experience it would be very hard to introduce that much interference to cripple down a 100Mbps ethernet connection to less than say 2-3Mbps bandwidth required to transfer a digital audio file. You would notice dropouts and not loss in quality in my opinion too. Even UTP (unshielded twisted pair) standard cables have some sort of sealing, but you could also try some STP (shielded twisted pair). I doubt it very much though that you have that much interference and this is why most people don't mention that to you.
Please bear in mind that I could be providing some theory here but it is based on quite a few years of personal experience.
Regards,
Harris