It depends upon where they take the measurement from, and I dont think there is a standard on this... my fan is rated at 43dba, but its a 60mm fan, and its f***ing loud. But I installed a homemade baybus, so I can switch between 7 and 12 volts, which makes it slightly more bearable for sleeping and stuff. As Shooters said, however it may be a more pleasant 43dba than a 60mm.