As covered in an earlier slide, the three main fan form factors have different sound characteristics. Apart from this, they also move air in different ways. Axial fans are the most straightforward in that they move air in one direction. Both centrifugal fans and blowers impart a 90° turn on the exhaust air, with the difference being that blowers exhaust the air in a focused outlet. Knowing which type of fan best suits the chassis to efficiently pull in and exhaust air is a key consideration that will affect the sound.