I know there's a DSP tool to compress audio in fb2K but I was wondering if is there a tool that can do the opposite, I know that's easy to compress (losing dynamics that you have) while it's nearly impossible to get a good result in rebuilding dynamics that you don't have, however it would be interesting to know if there's a program that can rebuild them by using an efficient alg. ...
Thanks for answers

Sadly there are no good ways of increasing the dynamics of a compressed audio signal that i know of. Expanders are a way of achieving this but will only have limited success. An expander decreases the level as the level gets lower, so the quiet bits get even quieter. The probelm with this approach is that you need some dynamics in the original signal to make it effective.

-Iain

Well, besweet should do it. Try choosing 'inverse' in 'dynamic compression'. Never used it myself though.

The problem is that dynamic range compression is a lossy process - that is, some of the dynamics are lost in the compression process. So while an expander will make the quiet quieter and the loud louder, the dynamics of the original signal are lost forever. I would imagine sounds with a higher bit resolution would lose less of the dynamics information during range compression, so you might have more luck with 24 bit audio.