TLS, that is because you are comparing a download to a CD, not a 320 mp3 to a CD. I don't know where to find it on the internet but some people have posted audio that contains nothing but the bits removed during digital compression. At 320 kbps, it sounds like a barely audible hiss when you crank up the volume very high. That hiss is about 50db below the average signal. At 320 kbps, compression doesn't remove anything audible. Go do some bias controlled listening tests for yourself and then come back and tell me you could tell them apart.
Music downloaded from the internet is compressed a whole bunch more than 320 kbps and is compressed enough to be audible. That's not what I do. I do 320 kbps.
Doing a bias controlled test is simple. Just take a track and rip it both as a wav and as a 320 mp3. Then have someone substitute them back and forth in a manner that prevents you from knowing which is which. Tell the scorer which track you are hearing and have the scorer put right or wrong. Do about 20 random iterations and look at the score. The 320 mp3, by the way will be about 1/4 the size of the wav so that shows you how much inaudible data really exists in a CD track.
If you want to save the trouble just take it from me that not only have I, but all kinds of other people have tested this and 320 kbps compression isn't audible to anyone. Go do the test and see for yourself.
Comparing lossy to lossless as a generalization is fairly pointless. You need to understand how lossy the lossy is. Generalities aren't meaningful.
I have to disagree. Like a lot of technologies, these lossy codecs are pop industry geared.
In wave lab I can experiment with almost all the codec at varying bit rates.
I have a selection of torture samples, that make it easy to catch them out.
I have analyzed them carefully with my youngest son, a highly skilled and professional engineer. we even went to the trouble of recording various instruments played by professional players. We recorded them digitally, and on a Revox A700 at 15 ips wih fresh tape. The microphone was a Neumman SM 69 FET auditorium sound field microphone. This is excellent for preserving the ambiance.
The problem with these lossy codec, is that they do change the ambient envelope. The more ambient the recording, the more noticeable it is. We came to the conclusion, that all these lossy codecs are fundamentally flawed.
So the advice of the professionals stands. If you are serious about archiving, do not use a lossy codec to do it.
In fact we found out that the CD standard is the bare minimum, which the developers knew at the time. Anything below that standard and you a significantly short changed.
It is very very obvious on opera CDs, where you can compare the AC3 track and the loss less PCM track. I have tried this on a number of music lovers and all have a preference for the PCM, even not knowing which one is selected.
If this were not so, there would not be this huge push for Dolby True HD. Apparently many members have noted improved sound, as I would expect.
I will certainly get interested in this format when more opera is released on Blue Ray.