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Electronics

RotoSub self-silencing fans promise a quieter way to keep electronic components cool

By Darren Quick
August 09, 2011
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A RotoSub ANC-enabled fan inside an air flow distributor to demonstrate its noise-cancelling capabilities
Traditional noise-cancelling technology and RotoSub's ANC technology
A RotoSub ANC-enabled fan inside an air flow distributor to demonstrate its noise-cancelling capabilities

Silicon chips shuffling all those electrons around inside modern PCs, gaming consoles and home theater systems generate a lot of heat that needs to be dissipated to stop the machines going into meltdown and ruining your day. Fans are the most common form of cooling for modern electronic devices but they can generate a lot of noise that can leave your lounge room or study sounding like an airport runway. Sweden-based company RotoSub has developed an active noise control (ANC) system that is built into the fans themselves that promises to almost eliminate the fan's mechanical noise and leave little more than the sound of the air blowing through the fan.

Noise-cancelling technology like that found in noise-cancelling headphones cancels out ambient noise by generating an "antinoise" signal. This is a sound wave with the same amplitude as the original sound wave, but with inverted phase, so that when the two sound waves combine they effectively cancel each other out. Such systems require a microphone to pickup the original sound wave and a speaker to generate the antinoise signal. Additionally, in the case of a fan where noise is being generated on either side, two speakers would be required to combat both the downstream and upstream noise.

Traditional noise-cancelling technology and RotoSub's ANC technology

To overcome this problem, RotoSub has built the ANC system into the fan itself so that it requires no speakers at all. This is accomplished by slightly bending the fan's blades to alter the angle of attack so that they act as the speakers to generate the antinoise signal. And because the antinoise is aligned in both directions, the noise is reduced both upstream and downstream. The company says fans incorporating its ANC technology have the same form factor and aren't any larger than traditional fans.

RotoSub isn't selling fans using its ANC technology itself, but is instead licensing the technology to other companies. If the video demonstration below is any indication of the system's performance, here's hoping a few companies take them up on their offer.

Via cnet

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ElectronicsCoolingNoise Canceling
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Darren Quick
Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continues as Managing Editor of New Atlas.
8 comments
agulesin
Great but if the noise is cancelled by \"slightly bending the fan\'s blades to alter the angle of attack\", how can they switch off and on the noise cancelling properties as demonstrated in the video?
The design of more expensive fans is more sophisticated and their noise-level significantly lower than el-cheapo (made in PRC?) fans which seem to be everywhere these days.
CeridianMN
I would love to see someone take this idea and try scaling it up to a fan about 4 feet in diameter that rotates at about 2100 rpm. Otherwise known as a propeller on a small airplane. If this really could move the kind of air required by the average 4-seat airplane while signifigantly reducing the noise generated it could potentially change general aviation in a big way - like composites have for instance.
Eletruk
I think that they are using the fan as a speaker, and directly inject the anti-noise signal into the DC power.
In any case, I want these now!
Arf
Good point, agulesin. Unless the blades are bent through some piezo technology, I don\'t see how they are switching that on and off. Makes it seem rather doubtful.
Aurin Ræder
@arf The microphone used for the signal is turned on and off, thus the blades=speakers are only sounding, and thus canceling noise, when the power is turned on
warren52nz
I remember touring the National Research Council facility in Ottawa, Canada in about 1975 and they were working on getting rid of the whistle produced by the blades of jet engines. They did it by cutting out rectangular notches in the blades that created an out-of-phase sound that cancelled the original. The whistle is produced by the blade edges going past a fixed structure. So the concept had been around for quite awhile.
Gary Fisher
Like all great ideas this seems fairly obvious once someone has thought of it. The Rotosub website is instructive, filling in some details Cnet/Gizmag left out. I hope these hit the market soon for electronics, but I\'m also curious how far this can be scaled up for tabletop and larger room air fans and HVAC systems.
johnniesazzler
Great idea! There\'s a significant amount of noise pollution caused by fans in electronic enclusures and other commercial and industrial equipment. The more this can be attenuated at source, the better the conditions for those working nearby.
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