First and foremost, make sure that the volume on the computer and the player you’re using is turned all the way up.

If you’ve done that and the audio on your computer is still not loud enough, below are some options:
1. Try using another player that has an amplification option.  There are several available online.  The best one that I found, and by best, I mean FREE is VLC Player.  This player can amplify your audio by 200%.
Of course, the problem with using third-party software is that it may not play the type of audio file you’re working with, therefore; the second option is better (in my opinion).

2. You can purchase an amplifier for your headset.  Below are the names of the top manufacturers of headset amplifiers.
* HeadRoom
* Grado Labs, Inc.
* Grace Designs Professional Audio
* Beyerdynamic

I hope this helps.

Verification Source: In-house testing