You can decompress to raw PCM float data (from WAV/OGG/MP3), i.e. in the range 0.0 .. 1.0, and then potentially do something interesting with the data.
A more practical application is to use a Fast Fourier Transform to split the frequencies of the sound data, i.e. to create a visualizer that reacts to bass hits. Or you can use onset detection: https://code.google.com/p/audio-analysis/
If you just want to play
the audio files in your game, you should use a solution like TinySound:https://github.com/finnkuusisto/TinySound
Or if you are using LibGDX, it should be fairly simple to include audio in your game.