@andy2 wrote about Insertion Loss. I was curious, so I spent some time reading about it. He’s right: There are two objective measurements, Insertion Loss and Return Loss, that measure signal attenuation in metal and fiber cables. These are evidently well-understood phenomena that are commonly measured.
He’s also right that Insertion Loss and Return Loss show different results depending upon which end of the cable the measurements are taken from. These two measurable parameters clearly show a difference in measurement depending upon the direction of the cable.
If you do some reading, you’ll quickly find many engineering shops that offer this measurement service. You’ll also find that it’s common to measure from both sides of the cable, then average the different results from each side to get a single basic reference value for Insertion and Return loss.
There’s no argument about this - it’s real, measurable, and there’s a whole industry built around it.
But - can a person hear these directional differences in a 3 foot interconnect? I have no idea and I’m not asserting an opinion about that. Some people claim to be able to hear it; some people say they don’t hear it. That’s fine with me because this is basically the normal state of everything in the world.
All I’m asserting is that cable directionality is in fact measurable as @andy2 wrote, via the Insertion and Return Loss parameters. And if there’s a measurable difference, however small, then it seems reasonable to believe that some people may be able to hear that difference.
