How The iMac Cooling Fan Stays So Silent [Patent]

Apple's new compact fan patent application will be both smaller and quieter than current versions.

Ever wonder how your iMac stays so silent, despite being equipped with three separate fans?

A new patent application, published Thursday, details the innovative computer fan used in present generation Macs and MacBooks.

The patent application describes several different embodiments of the invention that keep the fan from making “vibratory forces” audible to the user — including a method by which the fan’s impeller (the opposite of a propeller, being designed to suck in air rather than expel it) can be stabilized by the thrust bearing to keep the fan from making noise. This results in increased audio performance for the Mac, since there is little to no trace of unwanted fan whirring.

The noise made by cooling fans was a particular sticking point with Steve Jobs who hated including them in his computers, sometimes protesting even to the point of tears. While some of the early Apple computers managed to bypass the need for fans by way of clever engineering solutions involving convection currents, all modern iMacs and MacBooks come with in-built cooling fans. The current generation iMac includes six temperature sensors, three fans, and two massive heat sinks — although you’d never know by listening to it.

The compressed design of the “Compact Fan Assembly With Thrust Bearing” patent also allows the smaller-sized fan to fit neatly into the limited spaces offered by the uber-thin form factor of today’s Macs, while still maintaining maximum efficiency. The patent application additionally describes how the fan motor can be made to turn using nothing more than the power of magnets.

A diagram showing the compact fan as it might appear in a future generation iMac.

A diagram showing the compact fan as it appears in the iMac

A breakdown of the iMac, with the fan highlighted.

A breakdown of the iMac, with the fan highlighted (Credit: iFixit)

The patent application was filed October 23, 2013, and names Apple fan designer Jesse Dybenko, as well as product designers Anthony Aiello, and Brett Degner as inventors.

CORRECTION: Originally I suggested that this application pertained to a future Mac iteration. Fortunately a reader more familiar with the inner workings of Apple’s computers than I am was able to identify the fan featured in the top diagram, and brought it to my attention that this is the one currently being used by Apple.

  • dcj001

    “a method by which the fan’s impeller (the opposite of a propeller, being designed to suck in air rather than expel it)”

    I am pretty sure that, if the fan’s impeller sucks air in, the air must be expelled shortly thereafter.

  • mp73

    “Ever wonder how your iMac stays so silent, despite being equipped with three separate fans?”

    “The current generation iMac includes six temperature sensors, three fans, and two massive heat sinks — although you’d never know by listening to it.”

    I’m pretty sure the current generation iMac has one fan; it’s also indicated in the picture and diagram in your article.

  • Blake Beavers

    My iMac is louder than my gaming PC… In fact, its the loudest thing in my room. Its not really loud at all but its audable and everything else isn’t

About the author

Luke DormehlLuke Dormehl is a UK-based journalist and author, with a background working in documentary film for Channel 4 and the BBC. He is the author of The Formula: How Algorithms Solve All Our Problems, And Create More and The Apple Revolution, both published by Penguin/Random House. His tech writing has also appeared in Wired, Fast Company, Techmeme, and other publications. He'd like you a lot if you followed him on Twitter.

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