. Why do some MP3 music files sound better than others?
A. Two factors probably have the most effect on the sound quality of digital audio MP3 files.
One factor is the sound quality of the source from which the MP3 was created. Although digitizing a tune on your computer can be quite straightforward — copying and encoding the MP3 file from a compact disc in your PC's CD-ROM drive — skilled audio hobbyists can create an MP3 file from cassette tapes, vinyl record albums and other analog or digital sources.
Although there are things that can be done to help improve the sound quality of digital music, an MP3 made from an old vinyl record is probably going to sound less crisp and clear than one made from a song taken from a compact disc.
Perhaps a more common factor in the sound quality of MP3 or other digital music files is the kilobits-per-second rate at which the file was recorded. The software that copies a song from a compact disc (a process called ripping) and then encodes it as an MP3 file — programs like MusicMatch Jukebox or SoundJam MP — usually let you adjust the bit rate. The higher the bit rate, the better the sound quality of the file, and the larger the MP3 file.
The rate of 128 kilobits per second is generally considered to be "CD quality" in terms of sound, and music recorded at lower rates, like 64 kilobits per second, may sound tinny and weak in comparison. Lower bit rates are usually fine for low-fidelity sources like spoken-word recordings.