p4radox said:Rated noise levels mean nothing. To put it bluntly, companies lie.
No 2 fan manufacturers test their fans to the same criteria, so figures can vary wildly.
These may well be very good fans, but will almost certainly be louder than 11dB. The only opinion I'd trust is from someone who has compared them to known performers like Yate Loon, Scythe and Noctua.