Sound quality

I´m using a music for background on a projector, but it´s quality is very poor comparing with the original.

How can I make it better?

In your library, double click the sound file and an option box should come up. There should be a compression dropdown box, and if you choose MP3, you can choose its quality setting. From there you can preview the sound without permanently changing it. This overrides whatever your publish options are set at for your audio. Hope that helps.