A free app for Android, by Video Music Smart New.

Volume Booster Music Equalizer – Tubily Music is a free audio player for Android phones. It allows you to enhance the sound of your device by increasing the volume of your audio files and also allows you to set the sound to a specific profile.

How does it work?

It is very simple, just install this application, open it and then select the profile that you want to activate. After that, just turn on the boost and your audio files will be boosted. You can now select how much louder you want the sound to be.