It's worse than that, even.

One of the side effects of MP3 compression is "compression artifacts". If you've ever listened to a low-bandwidth audio/video stream, you know what compression artifacts sound like already. A description of it might be that it sounds like bits of "garbage" in the air around the sounds. They are usually gurgly, watery kinds of sounds which "surround" the other sounds. Hard to describe in words, I suppose.

Even high-bandwidth MP3s have them, they're just so faint that you don't notice them except in really rare situations.

If you re-compress an MP3 that was already compressed once, you will be piling compression artifacts on top of more compression artifacts. They will become significantly worse.

It's funny. Just the other night I turned on TechTV and they had a program on called "AudioFile", which is their regular program about MP3s and internet audio. On this program, someone wrote in and asked how to make all their MP3s sound like they're playing at the same volume.

I was just aghast at their answer. Did they suggest a real-time dynamic compressor plug-in for WinAmp? No. Did they even talk about why MP3s sound like they're at different volumes? no. The first word out of their mouth was "normalization". "NO!" I screamed. But okay, when I realized that they were dolts who didn't know that most albums are already normalized, I calmed down to see what they suggested for normalizing the MP3s. Did they suggest re-ripping them with Normalization turned on? No. Did they suggest using MP3Trim, which will normalize a file without decompressing it? No. They suggested de-compressing the files, normalizing them, and recompressing them. NO!!!!!!!

I turned off the television at that point. Their advice was wrong on so many levels... I will no longer trust a single thing they say on that program...

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Tony Fabris