There is a header/tag in MP3 files telling you the bitrate, but it doesn’t necessarily contain the actual bitrate used. The fact that MP3 files can be variable bitrate complicates the issue.
EncSpot can show you the actual bitrate(s) used in MP3 files. EncSpot is no longer maintained as far as I can tell and the original homepage is gone, but you can download it here.
[quote=StarryKnight;2191519]128kbps tracks have cutoff at ~16000Hz (thats why they suck ).[/quote] Actually the MP3 encoder cuts off frequencies above a certain point in order for the encoded file to suck less than it otherwise would have, if it had to encode the highest frequencies at a low bitrate.
Cutting off frequencies above 16000 Hz (which few adults can hear anyway) makes it easier for the MP3 encoder to produce something that sounds good or OK at 128kbps.