I purchased two of these fans for my Fractal design Define R3 case. I can run these fans at half the voltage I was running the stock fans at, and get better temps at the same time. Needless to say, my PC is quieter than having my fans running at full speed. Under normal noise conditions, I can barely hear the fans. They are however, audible when I have silent conditions in my room. Nothing annoyingly loud however, but audible just the same. I doubt you can shift this amount of air without having some kind of noise, so I see this as a trade off. I have mine on at around 6-7 volts, so I can shift plenty of air, and have them relatively quiet. A fair trade off in my opinion. I could have them more silent by lowering the voltage, using my fan controller, but am enjoying the lower temps far too much. Yes, they are a little on the pricey side, but I still recommend them.