Summary: Very quiet, my graphics card fan sounds like a vacuum cleaner compared to these fans; at idle my hard drive is louder than these. The rubber mounts included reduce vibrations against the case, however they slipped through the slots in my case so was unable to use them for one location.
Pros: -Extremely quiet
-Great airflow for such a low RPM fan
-Rubber vibration dampeners supplied require holes to mount (not slots)
Summary: This is the quietest fan I could find anywhere. The quietest Noctua makes and still moves air really good. This is a great way to cut down on computer noise....I bought one and a few weeks later bought another.