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Smooth Commutation Drive

Next to aerodynamic noise and bearing related noises, the so called "commutation noise" or "switching noise" can play a major role in the noise emission of axial fans with brushless DC motors. At each transition from one stator coil to another, the rotor receives a sudden torque pulse when the next coil switches on. Each of these torque pulses causes a minute deformation of the whole fan structure. Depending on rpm, torque and the material of the fan, this can result in noticeable noises.

Noctua's Smooth Commutation Drive system provides more continuous switching in order to achieve a smoother transition between the stator coils and thereby significantly contributes to the fan's overall quietness. The second generation of this technology (SCD2) further improves running smoothness and reduces minute noises in close proximity to the motor.

26.03.2015 - NH-L9x65
Test verdict: "65 mm yükseklikle sınırlı kalan bu işlemci soğutucusu son derece sessiz ve HTPC sistemler için ideal." (Gorkem Yildirim,

26.03.2015 - NH-U9S
Test verdict: "Den er meget stĝjsvag ved standardfrekvensen, og selv ved et OC pċ 4,2 Ghz larmer den ikke vildt meget." (Kim Monberg,

25.03.2015 - NH-U9S
Test verdict: "If you are in the market for a cooler that will not suck up volume inside your case, look no further because the NH-U9S will blow your mind with the cooling capabilities at this size." (Chris McCart,

25.03.2015 - NH-L9x65
Test verdict: "Auf einem kleineren System kann der Kühler eine sehr gute Leistung bringen, welche fast an die Leistung eines Top-Blow-Kühlers mit einem 120-mm-Lüfter herankommt." (Patrick Seus,