Yes, I have noticed this as well. The subtle buzz has been an issue that I have never completely figured out. In fact, it's present in other packs I have created as well (like the Metroid pack). I've tried adjusting volume, pitch, and have tried various other changes to the .ogg files. But, changes to the actual sound files seem to have only minor effects. The item room theme in the Metroid pack is another area where you may also notice it. I'm not sure if it's a performance issue, an emulator issue, or something else. But, if anyone figured out the root cause, I'd be very interested to know.