It could be that you have a shitty souncard, or a bad computer overall.
Or you could not be mixing your songs (as some call it mastering.) Just EQ everything correctly, use a lot of effects, and it should drown out the static. Some presets in Toxic III have been known to do that though, just mess around with the settings in Toxic III for each preset.
But could you be a little specific? Does it do it on each pattern? Or when you play them all together in song mode? When you extract an mp3 from song mode is that static still there?
Try what I said first, and if nothing woks be a bit more specific as I asked, and I'll try and help you find a solution.