At what bitrate should you encode your MP3 files? Listening tests show that at 256kbps, you can’t tell the difference. But that’s with 2 amplifiers and big speakers. What about headphones?
I tried an experiment with my cousin, who has the best ear for music that I know. We ripped a good audio CD of his at 128 kbps. He put on a pair of headphones (the kind that fit into your ear) connected to my laptop. I played the first half a minute of the original and the ripped version 10 times, in a random order, asking him to guess which was which. Result: 5 correct and 5 wrong. He couldn’t tell the difference.
We tried again, ripping at 64kbps this time. Same experiment, and surprisingly, same result — 5 correct and 5 wrong.
Conclusion: With a pair of headphones, even a good ear can’t tell the difference between a 64kbps MP3 and an original CD. So, if you want to cram in more songs into your iPod, just re-encode them at 64kbps. You’ll easily shrink the size in half, as most of them are at least 128kbps.