The case fan in my very elderly Lian-Li PC7 have given up the ghost after 6 years, it had something new here. These fans were tests recommended to me in div. And I can only confirm these tests, the rubber coating and isolation works, and at heruntergeregeltem fan is virtually not hear him. Nevertheless, enough air is moved through the housing.
If this fan is to be mounted on a CPU cooler, you have to pay attention where the clamps grip the fan, due to the coupling can be "outside" taken only by the bolt holes.