So this is interesting. I'm pushing 60 and have been recording/mixing/producing for about 40 years.
I zoomed through the basic/bronze and the first part of silver until I got to the mp3 part.
For some reason I can't tell the difference in the mp3s.
It's just a guess, but at my age maybe I don't really hear well enough but have trained my ears to hear the things I do in mixing/producing. When it comes to subtle eq, stereo, FX on tracks, etc. etc. I can blast through those with ease. Everything up to the mp3 part took me minutes as I hear about 5 seconds and know which one to pick. It will come up if you only listen to 2 and tell you to listen to all 3 before selecting, but that's not generally necessary for me.
However, in a mixing/production situation I'm NEVER trying to hear mp3 artifacts. I rarely listen to mp3s, sure I make them for people who want them but in a production environment I have no need to do anything with mp3s. All my work is done in things like cakewalk or final mastering of wavs for a CD or something. After I'm done if someone wants an mp3 I run it through lame and provide it.
hahaha, It's all in good fun. Now it's got me interested in training my ear to hear this as it's all part of getting better. Assuming I CAN train these old ears to hear stuff they haven't been used to hearing!
gabo