MP3Gain
MP3Gain is a really helpful ‘tiny tool’ that is able to analyze and adjust MP3 files, so that they have the same volume.
The app does not just undertake a peak normalization exercise, as many normalizers do. Instead, it performes a statistical analysis to determine how loud the file actually sounds to the human ear.
The changes MP3Gain makes are completely lossless. There is no quality lost in the change because the program adjusts the mp3 file directly, without decoding and re-encoding the file.
By modifying the appropriate metadata of each file, music software and portable players can determine what the volume should be.
Overall, MP3Gain is not a bad utility for freeware, and it does what is says on the tin, namely equalizes MP3 volume levels. The interface is very simple though, and power users may be put off by this.
Support languages include: Arabic, Spanish, French, Brazilian Portuguese, Danish, Indonesian, Latvian, Lithuanian, Macedonian, Norwegian, Slovak, Slovenian, Swedish, Tagalog, Thai, and Ukrainian.