Summary: Super quite although not amazingly effective. You certainly will have trouble hearing this fan. Also! Make sure you buy fan screws or have some that come with your case as this package comes "screw-less" including this silicon mounting "screws". They're nice, but don't fit all cases or work in all situations.
Summary: They're definitely quiet. Don't move a lot of air, but those are kind of directly related. I installed 2 in my HTPC case since the CPU fan kept revving up while I was watching shows. Now that fan doesn't ever come on so my computer is nice and quiet. I'm happy with them.
Summary: Pros: It really is silent. Cons: It is hard to fit in a case... if it were not for this, then I would have given this fan 5 stars. So, I got this to go in my Cooler Master N200 case. I was wanting to put it in the back of the case to push air out, while moving the fan that was there to the front to have dual fans pulling air into the case from the front.
Summary: This fan was was to install, I have never used the rubber "tool-less mounting" systems before, and It worked just fine. I have this fan mounted on the GPU side of my Antec GX700 case, a product I am also quite pleased with.
Summary: Barely noticeable sound unless you put your face up to it and pushes a decent amount (35 CF/M) of air. The only problem is that you may have to use case fan or mounting screws, because the rubber ones didn't want to work for me.
Summary: Fan gets the job done but runs slower than any case fan I have ever used. According to my pc control and monitoring utility program fan only runs at 732 rpm, I don't know how accurate that is but it looks like its moving slow
Summary: Quietest fan I have had the liberty to listen to. Even on highest setting this fan cannot be heard over 2 antec tri-cools on low. The alternate attachment method using rubber grommets is nice extra, but prevented me from using this fan in the top exhaust spot of my Antec P183. It uses two screws and two slots that slide over the outer lip of a standard 120mm box fan.