Are we talking mp3 or other codecs here? mp3 has a a couple of encoding ”tells” that a trained listener can pick up on (although it gets increasingly hard to do so beyond 128kbit IIRC). Other codecs don’t even have those & at higher bitrates people can’t pick them out in blind listening tests.
Also many encoders have things like a lowpass filter even on their higher presets - some people (often younger) may be able to hear those frequencies.
It may be that two different people have different results of being able to tell the difference due to physical differences, no matter the "effort" the put into listening, or training.
But most of the time that's intentional, as high frequencies you "can't hear" just waste bits that could be used on something more useful, or even cause noise from aliasing and harmonics, as no actual playback equipment is perfect. And extending the frequency range makes it much harder to design the circuitry. All for something you can't hear :P
It's another reason why high frequency (96khz) playback is kinda useless, or even make things worse, as the extra frequency range that gives cannot be heard by humans anyway, and just gives more opportunity for those higher frequency patterns to cause distortion. It may even be that people can "tell the difference" precisely because of those distortions. But that doesn't mean it's "better", indented, or even get the same result on different playback equipment.
Even 128kit from a modern encoder is harder to pick out than it was 25 years ago. Most of the self-appointed experts proclaiming how woefully inadequate MP3 is are basing their assessment on outdated experience from the distant past.
You can literally point to artifacts in a spectrogram which exist within the range of human hearing with many lossy codecs. It doesn't even have to be subjective.
Sure - these codecs lose information. The clue is in the name!
The question is can you hear those differences, to which the answer is basically no, for a modern codec at high enough bitrate. "enough" is 128kbit or more in blind listening tests.
The answer is not "basically no", and the qualifier of the initial argument was specifically 320kbps mp3.
No one here is arguing that modern, high-bitrate codecs aren't much better at producing imperceptible artifacts. But 128kbps is absolutely not enough in blind listening tests, 128kpbs typically produces a ton of perceptible artifacts. You're just making that up.
