I've found one better, which is someone with the calibre of gear capable of measuring digital equipment down to femtoseconds. However, regardless, if we take those measurements Oyaide did of their USB cable, we don't know how the DAC it is used with will be affected or not without knowing enough about and measuring the DAC's performance. It's not something, I think, that can be generalised as being all nonsense or all genuine as different electrical circuits don't behave the same way. Some useful data, per DAC, is much needed though. Other than that, I'm not a big fan of the idea of expensive USB cables unless one already has spent a considerable amount of money on (genuinely high quality) digital gear relative to their cost. However it shouldn't matter by then anyway.
As for what is audible, if our eardrums can detect movement of as little as 5 angstroms (equivalent IIRC to someone dropping a pin on tarmac a few miles away) then I'm not going to write off everything below any supposed cut-off as inaudible. On one of the online sites where you can test your hearing, you listen to sine waves at different frequencies which are different from about 1dB down to about 1/16th dB. However the site also has the same tests using square waves, which are far easier to determine the differences between, depending on the frequency being tested. Considering that everyone's hearing ability is different at different frequencies, dependant on the waveform, the type of music, the noise floor of the gear used and how that gear is affected by its digital input electrically and any jitter and how that tonally distorts the sound if at all (see what Dan Lavry wrote in another thread about the effects of jitter), the most one might say is that something is unlikely to be audible. This goes for any equipment, not just cables.
Arguing about whether or not, in this case, expensive USB cables are nonsense or not is actually doing people a disservice. Finding some useful answers that will help people determine if purchases are good value or not, eg: if their DAC will benefit from, say, a higher quality USB to S/PDIF converter (I'm not going to suggest USB cables to someone personally, at least not without their having a worthy cost/performance improvement that is undoubted) and at what point the price/performance ratio suggests they should just spend the money on better gear I think is considerably more valuable.
