heading TECHNOLOGIES Focused Flow™ Frame AAO Frame Our AAO (Advanced Acoustic Optimisation) frames feature integrated anti-vibration pads as well as our proprietary Stepped Inlet Design and Inner Surface Microstructures, both of which further refine the fan’s performance/noise efficiency. Anti-Stall Knobs The NF-S12A’s Anti-Stall Knobs reduce flow separation phenomena in medium to high impedance situations and thereby increase the fan’s stall margin. This means that the NF-S12A is even more versatile than its renowned predecessor and can achieve better performance on heatsinks and radiators. Bevelled Blade Tips Reducing critical rotor stator interaction, the NF-S12B's and NF-B9's Bevelled Blade Tips permit to combine a higher blade surface area with quieter operation and thus form a cornerstone of the fans' outstanding efficiency. Custom-designed PWM IC with SCD Our custom-designed NE-FD1 PWM IC integrates our Smooth Commutation Drive (SCD) technology. By providing smoother torque impulses, SCD suppresses PWM switching noises and thus makes the fan quieter at low speeds. Flow Acceleration Channels By speeding up the airflow at the crucial outer blade regions, Flow Acceleration Channels reduce suction side flow separation and thus lead to better efficiency and lower vortex noise. Focused Flow™ Frame Designed for pressure demanding applications such as heatsinks and radiators, the Focused Flow™ frame features eleven stator guide vanes that straighten, channel and focus the airflow, which allows the NF-F12 to rival the performance of conventional fans running at much faster speeds. Inner Surface Microstructures With the tips of the fan blades ploughing through the boundary layer created by the Inner Surface Microstructures, flow separation from the suction side of the blades is significantly suppressed, which results in reduced blade passing noise and improved airflow and pressure efficiency. Metal bearing shell In order to guarantee the highest possible degree of manufacturing precision, minimum tolerance and excellent long-term stability, our newest 120 and 140mm fans sport a CNC milled bearing shell made entirely from brass. Smooth Commutation Drive The latest version of our advanced Smooth Commutation Drive system ensures superb running smoothness by eliminating torque variations and switching noises. This makes our fans remarkably quiet even at very close distances. SSO-Bearing Combining the proven concept of hydrodynamic bearing with an additional magnet that supports the self-stabilisation of the rotor axis, our time-tested SSO-Bearing technology has become synonymous with supremely quiet operation and exceptional long-term stability. SSO2 Bearing SSO2 is the further optimised second generation of our renowned, time-tested SSO bearing. With SSO2, the rear magnet is placed closer to the axis to provide even better stabilisation, precision and durability. Stepped Inlet Design Our Stepped Inlet Design adds turbulence to the influx in order to facilitate the transition from laminar flow to turbulent flow, which reduces tonal intake noise, improves flow attachment and increases suction capacity, especially in space restricted environments. Sterrox® liquid-crystal polymer (LCP) Noctua’s novel Sterrox® liquid-crystal polymer (LCP) compound features extreme tensile strength, an exceptionally low thermal expansion coefficient and dampening characteristics that are ideal for reducing resonance and vibration phenomena in advanced fan-blade designs. Vortex-Control Notches Vortex-Control Notches split up trailing edge vortices and thus spread the fan’s noise emission over a wider range of frequencies. This measure makes the fan sound more pleasant to the human ear. Designed for superior performance in pressure demanding applications such as heatsinks and radiators, the Focused Flow™ frame features eleven stator guide vanes that straighten, channel and focus the airflow, which allows the NF-F12 to rival the performance of conventional fans running at much faster speeds. The NF-F12’s stator guide vanes are set out in Varying Angular Distance and feature Vortex-Control Notches. Both measures help to spread the noise emission over a broader frequency spectrum and thus make the fan’s sound pattern more agreeable to the human ear. Moving over the stator guide vanes, the fan blades create pressure pulses. This type of rotor-stator interaction significantly contributes to the fan’s overall noise emission. With a uniform distribution of the stator vanes, the relative geometrical constellation of the rotor blades and the stator guide vanes is identical each time the rotor moves over the next stator vane. This means that each time a stator vane is passed by a rotor blade, the same pressure pulses are created. Acoustically, these periodic pulses lead to noises at distinct frequencies and manifest themselves as frequency spikes in the fan’s acoustic spectrum, giving it a more tonal and distinguishable character. To avoid this phenomenon, the NF-F12’s stator guide vanes are set out in Varying Angular Distance (between 31° and 37°). Due to this measure, the geometrical situation between the rotor and the stator parts is slightly different each time the rotor moves over the next stator vane, which results in aerodynamically different pressure pulses and hence spreads the noise emission over a broader frequency range. Producing a less tonal and more broadband acoustic profile, the VAD stator guide vanes make the fan more agreeable to the human ear and let it blend into the background noise more easily. First introduced with the Noctua’s much acclaimed NF-P12 fan, Vortex-Control Notches are an advanced aerodynamic design measure that serves a twofold purpose: Firstly, Vortex-Control Notches make the flows along the suction and the pressure side of the blades or stator guide vanes mix more smoothly at the trailing edge, allowing for less turbulence and velocity loss, which leads to increased efficiency and reduced noise emission. Secondly, Vortex-Control Notches also help to make the fan’s acoustic profile more pleasant to the human ear. Due to the Vortex-Control Notches, trailing edge vortices are split up into several smaller vortices, each having slightly different tonal characteristics. This has a similar effect as the Varying Angular Distance of the stator guide vanes insofar as the noise emission is spread over a wider range of frequencies and frequency spikes are reduced. As a result, the fan’s noise pattern is perceived as much less annoying and more agreeable to the human ear.