http://www.mp3-box.org/mp3-normalize/
How to normalize the gain of mp3 files of different sources?
I wish to create an album with some mp3 music files. Most of them are converted from audio cassettes, which are of different volume. Some are from audio CDs. I use “mp3gain ” (http://mp3gain.sourceforge.net/download.php) to normalize the gain at a equal level. Physically or literately it is doing so. But when playing the music files, I noticed all of the files are not of equal volume. How to correct the problem.
heres a web site for all you answer just copy paste and read
Audacity Tutorial: Amplification, Compression, Normalizing and Exporting Your Podcast