Do you care how fast your fan goes?

Good cooling fans are designed to push air into or out of a chassis with the most efficient RPMs for the lowest audio levels. There are many figures available to inform consumers if a fan is good or not. RPM, dBA, CFM and other technical jargons sound impressive when it comes to fan technology, but is it really important? CoolIT is here to set the record straight on what really matters when choosing a fan for your cooling system.

There are two factors that are important when deciding on fans to use inside of your chassis – noise levels and airflow. You want the most airflow for the least amount of noise. So how do you go about determining which fans run quietly with high air flow? Most fan manufacturers will list noise levels and RPMs on their packaging or product specifications, but the data is often irrelevant to actual noise levels. Fan manufacturers typically measure sound pressure levels of a fan in a sound proof room at varying distances from the fan, and report them to the consumer in dBAs (decibel levels). While these tests are valid measurements, they tend to be highly subjective unless you test all fans on the same test rig.

Even then, sound pressure doesn’t necessarily translate into noise because it doesn’t gauge frequency levels. Higher frequencies tend to be more annoying to the human ear than low frequencies.  With this in mind, the focus should be on the ratio of airflow to sound pressure levels.

For a fan to be considered of good quality it should maximize airflow (measured in CFMs) while maintaining low decibel readings during testing.

XBit Labs conducted an extensive study on fan noise comparing 57 different fans from 29 manufacturers to come up with a list of fans with the best (and worst) dBA to air pressure ratings. According to the article one of the best fans available was the Noiseblocker NB-Multiframe MF12-S3HS, which ran at higher CFM when tested against competitors at similar decibel readings (xbitlabs.com, 2010). This fan was able to run at 1080RPM when set to 33 dBA while others ran quite a bit slower at the same noise level (xbitlabs.com, 2010). This meant that the Noiseblocker managed to keep CPU temperatures lower than other fans it tested against because it was able to run at a faster speed at the same noise level.

So what makes a good fan? To put it simply, its ability to run at high RPM and CFM with low dBA. A fan that runs at high RPM isn’t necessarily a good thing, if it means it will sound like it’s screaming at you. Similarly, low dBA isn’t necessarily a good thing either, if it doesn’t get any airflow pressure in the process of being quiet.  You want to find a fan with the best airflow to dBA ratio.