When I bring my MBP from sleep by opening it, it makes the disk eject sound. Is there anyway to turn this off so it isn't making that same noise when I'm in class or something?
Sure. Open the computer up and disconnect the power.
That's the initializing/power-up sound. All drives do that, but usually they have trays to seal up the sound. Not to mention they're usually thicker than 3/4"