This fan is silent if he turns slowly. Corsair 645D installed, connected to the minimum position Rhéobus integrated into the housing, it was still too much noise. Had to add a black Noctua resistive cable (included with the ventilator) to arrive to a satisfactory level of silence.
Cooling is very satisfactory in these terms (28 ° C at rest, non-OC system), despite the fact I have replaced the original two 200mm Noctua 140mm.