[dankoss]

The information present here isn't really "lost" as much as it can't be heard in the context of the other sounds in the original recording. These forms of audio compression take advantage of auditory masking[1] which means those sounds likely wouldn't be heard in the original.

[1] http://en.wikipedia.org/wiki/Auditory_masking

[sejje]

The information is lost in the sense that it's in the original, and not in the lossy version.

Whether or not you can hear it, the information is gone.

[mdisraeli]

If you can't hear it, was it ever information?

[daeken]

We can't see in infrared, but there's clearly information there. Same with infra/ultrasound and other sounds that are buried in our hearing.

It may not be pertinent information in the case of music, but it's definitely information.

[sejje]

If you cover your eyes and can't see me, do I still exist?

[TheOtherHobbes]

MP3 is audibly lossy, especially at lower sample rates.

So yes - you can hear it's gone.

And if you look at a spectrograph, you can see it's gone, too.