So what do the experts at SPCR think about Apple's claim that the asymmetrical fan design in its new MacBook Pro will make the fan less annoying by spreading out noise across a wider range of frequencies? Is it just a marketing gimmick or could Apple really be on to something here?

Are there any other examples of an asymmetrical fan being used to reduce noise in either laptops or video cards?

Anyone had a chance to try one of these beasts out yet for themselves?

I had a MacBook a few years back and I have to say that the fan noise was by far the worst thing about that notebook. It's good to see Apple at least talking about fan noise, and my hope is that they will push the industry down the path of putting out laptops with quieter cooling.

I think it would help. Here's a large picture:

http://guide-images.ifixit.net/igi/ibt2SIrUkYrNFesU.huge

There are 3 nodes of more densely spaced blades, so this would produce a spectrum of third order resonance which means that they won't reinforce the same resonance.

Engadget's take.

While running Diablo:
"Still, it only took a few minutes of hacking and slashing to get the bottom of this unit warm, and then noticeably hot. That, of course, caused the redesigned fan system to pop on, which draws in air from a pair of vents on the left and right sides of the bottom of the chassis and blows it out through the hinge. It's been optimized to create a less obnoxious sort of whirring noise. Indeed it's a subtle and unobtrusive white kind of sound, but it's definitely not silent. In fact, the fan doesn't sound particularly different than that on the current MacBook Air, though a few decibels less obtrusive. Still, you'll always know when your system is really cranking."

Still, it only took a few minutes of hacking and slashing to get the bottom of this unit warm, and then noticeably hot. That, of course, caused the redesigned fan system to pop on, which draws in air from a pair of vents on the left and right sides of the bottom of the chassis and blows it out through the hinge. It's been optimized to create a less obnoxious sort of whirring noise. Indeed it's a subtle and unobtrusive white kind of sound, but it's definitely not silent. In fact, the fan doesn't sound particularly different than that on the current MacBook Air, though a few decibels less obtrusive. Still, you'll always know when your system is really cranking.

Slashgear:
"Cooling has become something of an obsession among Apple’s engineers, and the new MacBook Pro is evidence of a new strategy for both quiet and effective heat dissipation. Air is sucked in through the hinge section and then funneled through to gills on the sides of the notebook, driven by a newly-designed asymmetric fan with unevenly-spaced impeller blades. That unusual blade design, Apple says, helps to reduce the tonal impact when the fans are spinning.

In practice, it’s a different type of noise to before: not necessarily quieter, but less intrusive. You still hear the fan spool up when doing heavy-duty processing, such as video exports, and the base can become warm – though not hot – to the touch at those times, but it cools again quickly."

Time:
"Some fast laptops tax their processors to such a degree that they heat up like pavement in the summer, forcing the use of noisy fans to bring the temperature down. The famously fan-phobic Apple says that it tuned the ones in the Pro to run at different frequencies so the whirrrrrrrrrrrr is less obvious. Even when I loaded gazillions of browser tabs, streamed videos and ran a virtualized copy of Windows 7 courtesy of Parallels Desktop, the Pro kept its cool and I couldn’t tell if the fans were active without pressing my ear to the case."

Assuming the others' comments can be taken at face value, sounds like he was doing this in a server room; course he doesn't say.

3 nodes....? I'm not sure I get what you mean. It looks to me like the paddles in the blower-style fans are deliberately off-center so the distance between fan paddle and the airflow guide wall is not equidistant all around. Doesn't look like anything more than that. It probably would help "spread" any tonal peaks over a wider range, which could make it sound smoother.

Bottom line: Looks more like clever Apple PR than devastating engineering.

Here is a better image of the fan configuration:
http://guide-images.ifixit.net/igi/YTXU ... G4SY6.huge
(The fan is mounted off center in relation to the air guide, but that's not what is being discussed.)

Look carefully at the fan blade spacing. It's most noticeable at the inner ends of the blades, where they overlap the plastic disc. There is a clear variation in how closely the blades are spaced together, which also creates a variation in blade angle. There are 3 equidistant spots on the fan circumference where the blades are clustered together, and between these spots the fan blades are further apart.

According to Apple, it's this is the design feature that will reduce fan noise.

The spacing of the impeller paddles varies around the circumference of the wheel, that's the innovation. It even looks like it's not quite symmetric on opposing sides.

Having the wall off-center, that might make for a more gradual pressure/velocity/impedance transition at the outlet. I know in superchargers for automotive applications the outlet geometry can really change the perceived noise signature.

The picture 0x17h posted is much better -- the spacing on the blades varies and there are 3 places where they are closer together. I thought they were at even 120 degrees apart, but apparently not. They still have to be dynamically balanced, but the varied spacing would break up the common resonances in the sound. Even ordered harmonics are harsh -- this is why almost no fan has an even number of blades; and why most have 3, or 5, or 7 blades. These are also prime numbers -- a few fans have 11 blades, right? Some do have 9 (I think?) and so these will have some increased harmonics because it has a common multiple; so as each blades passes the support struts, the harmonics of the sound produced will sum up and be louder.

ok, i see it in the big fan pic. i'd be interested in hearing it -- esp against earlier versions of the mac. the handful of hands-on comments suggest it's a subtle improvement at best.

Can't they agree on airflow direction?

I tested the retina MBP 2 days ago, all I can say is that it indeed makes a difference if you are in a total silent room.

The easiest way for me to explain is to compare it to my MBP 13" ( I consider it to be a silent machine on normal use, yes it can be a jet when stressing it REALLY hard, though the fan is a little more "whirrr" then the new rMBP or Air

If I am behind my MBP I can hear a small "hum and little whirr" but with the Retina you almost can't hear anything when your behind it working. Though as soon as you move a little to the "side" of the Mac, lets say you use it in such way connected to an external monitor then it only makes a slight difference. So for me all they with the new fans is reducing the noise when your actually in front of the monitor, that makes sense doesn't it But I use my laptop on an external monitor when I get home.

The retina is still not something I consider quiet, yes the new fans are an improvement like I explained above but it still has 2 fans that are spinning at 2000RPM/2200RPM IDLE. Yes one fan runs at 200RPM higher then the other one when I tested it don't ask me why and no it wasn't the software that was failing. But at night in a silent room you will hear a soft "WOOSH" but don't get me wrong I think I could actually live with it

If you want a silent mac, theres only 1 way and thats the 2012 Macbook Air 13" imo. Also has the Assymetrical fans like the rMBP but a little narrowed down I think it goes from 2.8mm to something 1.9mm? I can't really remember the exact thingy.

Anyway hope this helps for anyone wanting a new 2012 machine.

Greetz