Silence is golden.
I bought 3 of these models to replace the fans in my PC11ART tower bought on LDLC.
The original fans made the noise of an aeroplane engine as it took off, but these noctua fans ensure almost perfect silence, with a slight murmur audible when it's completely quiet.
As for the cooling, no worries, they do the job perfectly.
What's more, I was able to fit them in without any problem, despite the anti-vibration lugs.