Installation & Testing:
I'll start with some head to head comparison testing, putting the Effizio against a few other silent fan models from other manufacturers. My ears will the measurement tool, classifying where amongst the competition the Effizio falls in terms of quietness. I'll also be observing the airflow coming out of the fans to see if the Effizio does seem to be moving as much air as they claim.
The models being compared will be the SilenX Effizio, Nexus 120mm Real Silent Case Fan and the Noctua NF-S12. Noise levels are rated from the manufacturers at 15dBA, 18dBA and 17dBA respectively.
In my tests, audible noise levels place the Nexus fan as the quietest, running at only a whisper of noise, the Noctua fan as second quietest, it could be heard but was still relatively soft, and the Effizio as being the loudest. The Effizio was only marginally louder than the Noctua fan, but the difference was still distinguishable by the human ear. Being someone who is experienced with noise level ratings (I do part time audio engineer work on the side), I am going to say that the 15dBA noise rating on the Effizio is not accurate - or - SilenX is placing their measurement mic much further away from the fan than would be considered standard.
However, the Effizio does exhibit strong airflow and it did seem to move the most air out of all three fans that were tested. Even though it is on the louder range of being a "silent" fan, it would still make a great fan if airflow is your first priority and noise levels were second.