|I'm sure you could find some ultra-cheap $10 product and connect 10+ metres of unshielded USB cable from 1998 wrapped around a motherboard and power supply, and detect some noise that may be attributed to USB.
1. Maximum cable lenght for USB is 5m. After that, you need a repeater. So you can buy a 5m cable, and add a 5m extension cable with built-in repeater. 5 repeaters are allowed, stretching the limit to 30m while fully maintaining integrity.
2. Any decent USB cable is shielded. And no, not foil but braid (or even both).
In any case, USB offers 16bit CRC error detection and correction for it's data payload. For the simple isochronous transfers most audio devices use this means most bit errors will be detected AND corrected. Even better: around 99.998% of all errors can be detected, but not all can be corrected: with a isochronous transfer you're guaranteed bandwith and lowest possible latency, but at the cost of not being able to re-send the data.
For a more advanced USB bulk transfer it means bit error correction, multi-bit detection AND a re-send of data. But since you don't get access to the available bandwidth all the time, you need to buffer things cause you're bound to miss the "bus" every now and then.
No matter what method you choose, USB is one of the best (and cheapest) ways to transfer data from a PC to another device.