Why does some mp3's make loud noises during the song.

Because they are MP3's.

I have never had any problems with any of my several thousand mp3's
downloaded from newsgroups.


Loud noises like milliseconds of pure static or pops are caused by someone
with a computer that had a noisy CD-ROM, slow hardware (CPU's buffer
overrun) or poorly-written MP3-encoding software (early versions years ago
or freewares)...I've heard such byproducts from all three scenarios...but
such noises absolutely are not inherent of MP3s in of themselves...that's
sort of an ignorant remark.

MP3 is a lossy compression - it will *lose* data of the original PCM Wave
source, but there is no reason to believe it will *add* this sort of
extraneous data.