For the Sonata IV Mid-Tower Case from Antec, it's all about silent performance. In order to achieve a quieter build, the enclosure must be designed to maximize air circulation and component cooling. The cooler the components are, the less need there is for the fan to run on high. Antec includes a rear-mounted 120mm TriCool fan with a 3-speed control switch, so you can to control how fast and how loud you want the fan to run.
The bulk of the blame for noise is usually placed on the cooling fan, but hard drives are just as guilty. You can just imagine the mind-numbing hum that would be emitted from eight hard drives. The Sonata IV solves this problem by using silicone grommets to reduce the vibrations caused by the hard drives while they operate.
It's not enough to rely on a fan to cool the internal components of your build. Vents and air filters are required to increase air intake as well as dissipate heat. The Sonata IV does both with a perforated section of the front bezel as well as washable side air filters.