Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
On Fri, 10 Jun 2005 11:24:01 -0400, nospam@needed.com (Paul) wrote:
>In article <vnafvs79siwu$.ocy1vu0xpr7r$.dlg@40tude.net>,
>signmeuptoo@earthlink.net wrote:
>
>> Could some of you recommend some 92mm fans for CPU heatsink that are quiet
>> but move are anyways. Links would be helpful. Thanks a lot for anyone
>> with input. I don't want to just go by Db ratings because they can be
>> deceptive.
>
>In terms of design concept, this fan has the potential to be
>a quieter solution:
>
>http://www.verax.de/verax.php?SID=2274042a9a0a02187a&template=cms_entry_technik&groupid=1&entryid=7
>
>The fin shape provides smoother acceleration for the air. The fans
>they make are super-expensive, and also are not available in all
>popular sizes.
>
>One contributors to fan noise is bearing type (sleeve is 3dB quieter
>than ball bearing, but sleeve has potentially shorter life, unless
>perhaps it is something like the Panaflo hydrowave design). The fan
>body can make a difference, in terms of placement of struts and whether
>the fan body is perforated or not.
>
>The material the fan is constructed of, could also make a difference.
>A fan with a metal body might offer better rigidity, and avoid
>resonances better.
>
>One brand of fans has a magnetic bearing in the hub, but I've never
>read any user reports of how effective that is at reducing noise.
>
>I don't know if fan motor design makes much of a difference.
>The only innovation I know of, was the "tip magnetic" motor, which
>puts the magnets on the periphery of the fan, rather than in the hub.
>I think that ended up being more noisy than the traditional design.
>I'm not aware of much in the way of attempts to smooth the pulsations
>of the brushless DC motor, at least for use in cheap fans.
Actually, the tradeoff of capacity vs noise was very good in the
Vantec Aerocool with the tip-magnetic fan, at least with that
particular heatsink (it might have been good heatsink design rather
than the tip-magnetic fan that made the Aerocool quiet). At its
introduction a couple of years ago, it was the by far the quietest
HS/F combo when compared to products with similar cooling capacities.
The theoretical advantage of the TMF was that there was no central
motor to impede flow, so it could move a greater volume than a
conventional fan at the same speed and therefore run more quietly. It
must have had other problems, however, because Vantec discontinued
this fan and returned to using a conventional one on the current
Aerocool. Mine is still running perfectly, though.
>
>Another source of noise, is the nature of the power source. If
>you use PWM (a.k.a Q-fan), the switching frequency of the PWM
>power source can beat against the rotational frequency, and
>"cogging noise" is generated by the fan motor. What that means is,
>as the fan speed is reduced by Q-fan, the fan begins to produce
>a whine due to cogging noise. A simple rheobus or a Zalman fanmate
>is a cleaner source of power for the fan, and can avoid cogging noise.
>Not all Q-fan implementations use PWM - some use linear control and
>don't suffer from that problem. You can tell which type your CPU
>header uses, by downloading the datasheet for the SuperI/O chip that
>controls the fan.
>
>In terms of noise, there are fans that have wideband noise (the
>"rush of air"), versus the ones that tend to make a dominant tone.
>When a fan with a dominant tone is measured by a weighted sound
>measuring instrument, it tends to have good looking spec numbers.
>But would be damn annoying to the user. I worked on a minicomputer
>once, that had four fans on it with dominant tone type noise.
>If I closed the door on the room I was working in, then walked
>100 ft down the hallway, I could still clearly hear the fans. That
>is the kind of fan you want to avoid.
>
>Most of the "quiet fans" being offered for sale, simply trade off
>reduced air flow for reduced noise. I picked up a fan like that
>locally, and was unimpressed by how much air it moved. A simple
>comparison of CFM for the various products, will show you which
>fans are kinda worthless to own.
>
>Some of the "quiet PC" sites have articles on fans. Here is a
>sample:
>
>http://www.silentpcreview.com/article25-page1.html
>
>The data collected by the author of that article is here:
>
>http://www.silentpcreview.com/files/fanspecs/fanspecs.pdf
>http://www.silentpcreview.com/files/fanspecs/fanspecs.xls
>
>If you scatterplot the data in the XLS file, and then
>select a fan along the top diagonal edge of the plot,
>those should be good fans. You may need to edit the file
>a bit (for example, just put 92mm fans in the table etc).
>Or, if you sort the data in the columns by dB instead of
>by CFM, you may be able to find a winner that way (because
>with the columns of data, you can see the fan size at the
>same time as the other stats).
>
>HTH,
> Paul
Ron
idqe.21912$ld3.12175@trnddc04...
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