Q: What dB value does mp3gain normalize to? How does this compare with normalize-audio? A: mp3gain and normalize-audio use different methods to determine the perceived volume of a file, so the numbers are not comparable. As I understand it, normalize-audio applies a smoothing filter and then sets the maximum to -12dBFS. mp3gain sorts the volume and then uses the value at 95% (i.e. 5% of the file are louder, 95% are quieter). This value is set to -20dBFS. I have tried a few files and found the difference in the recomended values to vary between 3dB and 6dB. The method mp3gain uses to determine the perceived volume is described at http://www.replaygain.org/. Q: Why are the files not exactly at the same volume? A: Since mp3gain changes the global gain value in every mp3 frame, it can only use 1.5dB steps for adjusting the volume. It will however write replaygain values to tags with finer accuracy than these 1.5dB steps.