Artefacts in hi-res audio?

[Boye]

I'm thinking that if you up-sample the low resolution file you should get an apples-to-apples comparison in the FFT/spectrum.

Sure, but then again the software I use might have different algorithms, making comparisons less fair.

When there is an obvious difference, the first thing I suspect is different mastering. Or it could be a different mix or a completely different recording. The high-resolution version might be better, or if it's newer it might be a victim of The Loudness War and sound worse! (Or you might prefer the more dynamically compressed loudness war version.)

Just choose the version that sounds best to you!

Absolutely, but some people still claim that one is 'objectively better' than the other, despite that they just prefer a version that is 6 dB hotter, without listening level matched.

Noise is the "rumor". Maybe distortion too. I'm not sure, but if it's ultrasonic, by definition it's NOT "sound".

Yeah, I bundled noise and distortion together. I also used the expanded meaning of sound, even ultrasonic. My aim was to find out whether hi-res files contained actual sonic information like true overtones or bat sound or cricket sounds (or waves of variations in air compression like when a tree falls in the forest and so on). The audibility is another discussion, which is largely over and done
But it appears that any additional information contained in hi-res files at best is just a waste of data like I previously stated.

 

[danadam]

When I fiddle with the 'size' setting in the Plot Spectrum the artifacts seem to disappear, so perhaps I am drawing conclusion on the wrong basis.

Increasing FFT size decreases the apparent level of noise-like signals. In your case it made the level fall below the configured range of the plot. You can change the range in preferences:

Interface Preferences - Audacity Manual

manual.audacityteam.org

Fox example, here's 96 dB range and the noise disappears:

After changing the range to 145 dB it appears again: