(1.) Scientifically proven means we have a predictive theory that proves
it's IMPOSSIBLE for USB cables to make a difference
for all ears, for all equipment, for all environments.
(2.) Because we're talking about the transmission medium of an encoded signal, we'd need to show that the signal BEFORE encoding is ALWAYS reproduced 100% by the receiver AFTER decoding - why?
(3.) This means we need to understand how the decoder works and deals with signal variance during transmission: can this results in errors, and if so how does the decoder deal with that, and if so can we hear it?
(4.) The
USB audio spec doesn't provide for error correction, i.e., unlike a USB file transfer which can check for errors and re-ask for data, UAC doesn't re-ask, plus UAC also must account for timing (go back and read any of my posts with charts, graphs, tables, copies of the USB spec where all of this is explained)
(5.) If USB bulk transfers do check for errors and re-ask for the data .... are those errors 100% originating from the sender-only for all equipment in all environments, or might some of those errors happen during transmission? And if some of those errors happen during transmission, that means the cables, and if UAC can't correct for errors, then cables might make a difference through shielding or other factors.
[5b]. We'd need to understand all of that before we could begin to know what to measure.