Noctua and RotoSub are working on a CPU cooler that employs active noise cancellation in its pursuit of silence. We saw an early prototype demoed at Computex last year, and an updated version was at this year's show. Noctua has also posted a video of the latest design in action:
The noise-cancellation tech uses a magnetic field to generate minute vibrations in the fan blades. A microphone takes in the noise produced by the fan and then tunes the blade vibration to cancel it out. At least in the video, that approach seems to be effective at masking the fan hum, which admittedly seems a little on the loud side for a modern spinner. You can read more about the design here.
The cooler shown in the video looks a lot more polished than what we saw last year. It sandwiches a single, shrouded, 140-mm fan between a pair of radiator towers fed by six heatpipes. The radiators are shaped to avoid bumping into taller DIMMs, and the microphone is situated on the side of the radiator. Although the design is "almost completed," the finished product isn't expected to hit mass production until the middle of 2014.
Noctua doesn't mention a price, but we were told last year that adding noise cancellation would probably double the cost of the fan. The R-ANC will likely be priced in the same realm as exotic water coolers. Fittingly, perhaps, Noctua is also working on a noise-cancelling fan specifically for liquid cooling radiators. The 120-mm radiator fan is at an "earlier development stage," so I wouldn't expect it to be available anytime soon.
Active noise cancellation is slick, but I can't help but think it's a little wasted on the CPU. Quiet cooling solutions abound, and most of the noise generated by modern rigs seems to come from fans onboard the graphics card. It will be interesting to see if noise cancellation eventually makes its way to GPU cooling.