In another topic people were squabbling about which bitrate provides "true"
CD quality. I myself opted for 192Kb/sec but after some non-scientific
research, I've come to the conclusion that 256Kb/sec is the data rate at
which MP3 sound quality becomes indistiguishable from CD.

How did I come to this conclusion? I encoded some music works with MP3 using
a VBR (variable bit rate) MP3 encoder. Such encoders acutually vary the bit
rate to match the sonic information which has to be packed into the MP3
file. After encoding several tracks and playing them back I noticed that
very few (none actually) showed bitrates higher than 256Kb/sec at any time.
On the other hand: average bitrates of 192Kb/sec showed up on almost all
tracks, leading to the conclusion that 128Kb/sec encoding (the dominant
encoding so far for 'shared musc') is insufficient to encode the sound
without degradation in sound quality.

Actually VBR MP3 encoding would be even better for the music shared on the
Internet but very few people seem to do this at the moment, I don't know
why, since most MP3 encoders support it.