The interaction of harmonics and how it affects sound perception is a highly debated subject, but it’s same for every sense. Both eyes and ears have practical limits on what it hears, but even with that limits, brain can distinguish details so small, we have no ways to describe them.
Some people will describe higher bitrate, higher sampling rate sound to be smoother, even if they can’t tell what is the difference. Similarly, some people will describe same higher bandwidth signal to be more airy or open. Hearing tests do not quantify these details.
A solid example is Foo Fighters’ album, Wasting Light. Recorded and mastered on analog equipment, the album has sound qualities hard to describe. Yet it feels full, satisfying to listen, and doesn’t fatigue the ears. Maybe you can point a difference with a spectrogram, but the difference can be highlighted by your ears and brain in much more detailed manner.
Another example is how people listen to higher bandwidth music. People are more engaged with higher quality, higher bandwidth sound. They concentrate for longer periods and listen more intently. Again, the brain can notice something or hearing tests can’t quantify.
Lastly, people find images taken by cameras with Foveon sensors more appealing from color perspective, because the color resolution is much higher. While Bayer sensors’ color reproduction is both true and high resolution, brain can detect higher color resolution with ease.
All senses are trained on real world over the decades, and know how to distinguish between real and fake. So, it’s no surprise that brain can detect things which we can’t put our finger on squarely.
My rooms are not acoustically special. They are pretty standard, if not mundane. The equipment I use is high end, vintage stuff; but they are not exotics. Cabling is done per manuals of components.
The only power conditioning I have is a surge protector which claims to have line noise filtering, but this is not why I got it.
However, all the qualities I discussed here is audible on that set. The interesting part is, I’m using the same set for 30 years, and I know its sound character like my name. I can hear the same details and get the same atmosphere when I listen to the same albums (mostly CDs), so brain can reconstruct something we can’t describe from how sound interacts with both air and our ears.
Lastly, I can still easily hear switch mode power supply noise, without even trying.