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Behold the fan that muffles itself

How to make your noisy PC less obnoxious: Have its fans generate their own anti-noise.

I like working at home. It's quieter than the office. It'd be near silent if were not for this noisy computer under my desk; the fans make a racket. But a new line of fans using technology from the Swedish company RotoSub could cut down on the noise a lot, and for not much additional money.

All fans make noise, and there are many solutions to damping that down. There are low-noise fan blades, there are muffled enclosures, and there's active noise cancellation, in which a sound signal that's the exact opposite of the offensive noise is generated to cancel out the sound waves. Noise cancellation could, theoretically, be the most effective sound-killing technology, except if you don't put the reverse-wave sound generator at the exact location of where the sound is created, you don't have perfect cancellation everywhere, and you hear noise as you move in relation to the fan.

Rotosub has a noise-canceling technology that solves the noise problem at the source. It makes the rotating fan blades themselves into the anti-noise speakers. RotoSub CEO Lars Stromback told me by modulating the angle of attack of the blades very slightly, the RotoSub generates sound with "the same phase structure as the noise, the same position, and radiation pattern." The power draw is minimal: the RotoSub electronics take very little juice, nor does quickly bending the blades in the fan motor.

I'd like to see RotoSub fans in my desktop computers. Or at the office in the ventilation system. Strombac says the technology could even scale up to turbofans, and an aircraft engine manufacturer is interested in it. RotoSub is a pure technology play, and plans to make money by licensing its intellectual property.

See also: Fanless heat sink design promises cooler, quieter CPUs.