The equalizer and sound improvement options are both on. What I did try doing, though is cutting the bass on the master track of the garageband song. It made most of the buzzing go away, but it is still there. The strange part about it is that the bass wasn't any quieter in iTunes, even though it was in Garageband. And changing the equalizer in iTunes didn't help, and no other songs I have in iTunes have that problem, just the ones recently imported from Garageband.