Hi
here whats in JRiver wiki:
Question: what is the fixed amount in an album?
___________________________
Volume Leveling
Have you ever put on an album and noticed that it was drastically louder than the last album you were listening to? Everyone has a few albums that every time you put them on you race for the volume control to turn them down. Similarly, I'm sure you've heard albums that were "too quiet" and you had to turn them up quite a bit to hear them at all (only to go racing for the volume control again when you followed them up with a loud one). This is the result of the fact that (unlike film) there's no loudness standard in audio engineering. Because louder audio is often perceived as sounding better, there has been a "loudness war" in mastering music to try and make the loudest sounding music possible, often through compression (reducing the Dynamic Range to make more of the song "loud"). One unfortunate side effect of the loudness wars is that albums have drastically varying average volume levels.
Volume Leveling is a solution to this problem. It does it by analyzing the "loudness" and dynamic range of the music (using the international standard R128 analysis method), and then adjusting the volume level of the music to a reference level. The result is that most music will sound close to the same average volume with volume leveling on. Volume leveling does not compress the music or affect dynamic range; it just changes playback volume. Volume Leveling also does not alter the audio content of files; all volume adjustment is done using DSP at runtime.
By default, when you play an album, the whole album gets adjusted by a fixed amount so that intertrack dynamics aren't affected (i.e. a "quiet" song on an album will still sound quiet compared to the rest of the album). When you play a mixed playlist, each track is adjusted individually so each track sounds about the same volume (like on the radio).
Because most music is mastered so that its peak level is close to (or sometimes even above) digital full scale, in order for volume leveling to work correctly (without clipping) most music must receive some amount of attenuation (rather than boost). This means that when you first turn it on you'll need to turn up the volume a little; but after that you'll be able to leave the volume control more or less alone.