This is a fun little video to show what is taken out in MP3 encoding:
Note that you cannot conclude what he is concluding. That is, the difference sounds like a lot. But much of that is "masked" by the music itself. The learning here is how how MP3 works. What is taken out tends to be transients and some high frequencies -- both of which are difficult to encode. So if you want to learn to hear lossy compression artifacts, that is where you want to focus on. By performing such tests, you will be training your ears on what to listen for. As I noted though, the test is not valid with respect to what fidelity is lost.
Note that you cannot conclude what he is concluding. That is, the difference sounds like a lot. But much of that is "masked" by the music itself. The learning here is how how MP3 works. What is taken out tends to be transients and some high frequencies -- both of which are difficult to encode. So if you want to learn to hear lossy compression artifacts, that is where you want to focus on. By performing such tests, you will be training your ears on what to listen for. As I noted though, the test is not valid with respect to what fidelity is lost.