Editing Quiet PC (section)

====Fan====
{{Main|Computer fan}}
[[Image:Silent PC-large fan.JPG|thumb|A 120 mm variable speed fan]]

If they use fans at all, quiet PCs typically use larger-than-usual low-speed fans with quiet-running motors and bearings. The 120&nbsp;mm size is common, and 140&nbsp;mm fans are used where cases or heat sinks allow them. Quiet fan manufacturers include Nexus, EBM-Papst,<ref>{{Citation | url = http://www.ebmpapst.com/ | title = EBM Papst}}.</ref> Yate Loon, Scythe,<ref>{{Citation | url = http://www.scythe-eu.com/en | title = Scythe | place = [[EU]]}}</ref> and [[Noctua (cooling)|Noctua]].<ref>{{cite web | newspaper = Digital daily | url= http://www.digital-daily.com/cooling/noctua/index2.htm | title = New coolers Noctua NH-U9 and NH-U12 – quiet and effective cooling | access-date =2008-10-10 | first =Viktor | last = Baranov|date=2006-05-23}}</ref> Extensive comparative surveys have been posted by SPCR<ref>{{cite web| url=http://www.silentpcreview.com/article695-page1.html | publisher =SPCR | title = Fan Round-Up | number = 2 | access-date =2008-10-10 | first = Michael ‘Mike’ | last = Chin| date=2006-11-27}}</ref><ref>{{cite web| url = http://www.silentpcreview.com/article63-page2.html | title = Recommended Fans| first = Michael ‘Mike’ | last = Chin | date=2007-03-04 |publisher=SPCR | access-date=2008-10-10}}</ref> and MadShrimps.<ref>{{cite web| url = http://www.madshrimps.be/?action=getarticle&articID=421 |title=120mm Fan Roundup: 17 Fans Compared |publisher= Madshrimps | place = [[Belgium|BE]] | date=2002-07-16|access-date=2008-10-10}}</ref><ref>{{cite web| url= http://www.madshrimps.be/gotoartik.php?articID=892 |title=120mm Fan Roundup: 35 Fans Compared | date=2008-02-13 | publisher = Mad shrimps | place = BE |access-date= 2009-02-13}}</ref>

Fan noise is often proportional to fan speed, so [[fan control]]lers can be used to slow down fans and to precisely choose fan speed. Fan controllers can produce a fixed fan speed using an inline resistor or diode; or a variable speed using a [[potentiometer]] to supply a lower voltage. Fan speed can also be reduced more crudely by plugging them into the power supply's 5-volt line instead of the 12-volt line (or between the two for a potential difference of 7 volts, although this cripples the fan's speed sensing).<ref name=7vTrick /> Most fans will run at 5 volts once they are spinning, but may not start reliably at less than 7 V. Some simple fan controllers will only vary the fans' supply voltage between 8 V and 12 V to avoid this problem entirely. Some fan controllers start the fan at 12 V, then drop the voltage after a few seconds.

PWM fan control, however, is the easiest and most efficient option for modern motherboards that have PWM fan headers. [[PWM fan]] control rapidly cycles between feeding the fan full voltage and no voltage, to control rotational speed. Typically the motherboard chipset provides temperature data from sensors on the CPU itself to control speed.

Bearing and motor noise is an important consideration. Soft mounting fans (e.g. with rubber or silicone fan isolators) can help reduce transfer of fan vibration to other components.<ref>{{cite web| url= http://www.silentpcreview.com/article262-page1.html| title = AcoustiProducts Vibration Dampers| first = Michael ‘Mike’ | last = Chin|date=2005-08-11 |publisher=SPCR | access-date = 2008-10-10}}</ref>

Piezoelectric fans are often quieter than rotating fans and may consume less power.<ref>{{cite web| url= http://electronics-cooling.com/articles/2007/feb/a1/ | title =Piezo actuators for electronics cooling | first =Ioan | last = Sauciuc |publisher=Electronics Cooling Magazine |date=February 2007 |access-date= 2008-10-10}}</ref><ref>{{cite web|last1=braun|first1=Rob|title=Compact Mac Upgrades|url=https://mac68k.info/wiki/display/mac68k/Compact+Mac+Upgrades|publisher=mac68k.info|access-date=3 April 2016}}</ref> Intel, Murata, and others have recently done development on use of piezoelectric fans in desktop PCs.<ref>{{Cite report |doi=10.21236/ada288571 |title=Ada Compiler Validation Summary Report: Certificate Number 940902S1.11377 UNISYS Corporation. IntegrAda for Windows NT, Version 1.0. Intel Deskside Server with Intel 80486DX266 =&gt; Intel Deskside Server with Intel 80486DX266, |last=Jefferson |first=David K. |last2=Johnson |first2=L. A. |last3=Peifer |first3=Donald J. |date=1994-09-14 |publisher=Defense Technical Information Center |location=Fort Belvoir, VA}}</ref>