General MP3 Problem

Just thought I would see if anyone has any thoughts on this rather odd probelm I am having with quite a few MP3 files.


Started playing a few film soundtracks and classical music pieces that I ripped a few years ago (at the maximum bitrate), but as I am going through certain ones, some have developed what I can only describe as a distortion.


I noticed it at first on tracks where a piano is the lead instrument, these tracks used to play fine, but now sound like they are being played full blast out of tinny speakers, regardless of how they are played (iPod, speaker system, macbook speakers).


I've re-ripped one of the cds and the problem is no longer an issue for those tracks, but I am more concerned with what has actually caused this in the first place (obviously don't want to end up re-ripping 9000 cd singles and albums ).


Can digital files degrade over time?