1- Download MP3Gain.[mp3gain.sourceforge.net]

2 - Install the software and launch it.

3 - Click on "Add Folder" on the upper left corner.

4 - Add the music folder of the game

5 - Now set the "Target 'Normal' Volume" between 95 to 100 dB (Higher is louder).

6 - Select all of the files and click "Track Gain".

7 - Let the software do it's job and launch the game.

8 - Re-scan the files and you all good.