Fan vibration, fan grilles, the whoosh and possible bearing/motor noise all add up. Pulling air over the hdd-cage? In most setups you really should have the front fan pushing air into the case, not pulling it out.
Try listening to the fan outside the sase holding it in your hand and put it on the table to check if it vibrates. Fan grilles are most likely also causing some noise, cut them out if you dont have kids or pets that like to stick fingers inside your computer
with the sonata, the fan is mounted after the hard drive cage, to pull air over the hard drives...that's what i meant..it's not blowing air out, it's technically sucking air in, but in a crappy way..