If you listen to MP3 files on your computer, iPod, or MP3/media player then there's a good chance that you've had to adjust the volume between tracks because of varying loudness. If a track is too loud then 'clipping' can occur (due to overload) which distorts the sound. If a track is too quiet, you'll normally need to increase the volume; audio detail can also be lost. By using audio normalization you can adjust all your MP3 files so that they all play at the same volume.
The following tutorial will show you how to use a freeware program for the PC, called MP3Gain, to normalize your MP3 files without losing audio quality. This lossless technique (called Replay Gain) uses the ID3 metadata tag to adjust the 'loudness' of the track during playback rather than resampling each file which some programs do; resampling typically decreases sound quality.
Before we begin, download MP3Gain and install it now.
For Mac users, there's a similar utility called, MacMP3Gain, which you can use - read this excellent MACMP3Gain tutorial from the Tech Talk Point website for more information.