I answered this in another thread, I thought it might be useful to have it in here as well.
Originally Posted by SamsungGalaxySVibrant
thanks, mind walking me through the steps to set the volume higher please.
also, besides blowing out my speaker, what other damage could this cause?
WARNING: 100 IS VERY LOUD!
 SRC Speech RX Volume
5_lvl : 88
Menu -> Key Input
Change to any number greater than 88 (Max:100)
Press back to save.