Help me understand decibel ratings

Compnewbie01

Senior member
Aug 8, 2005
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What exactly would you say is the highest decibel rating in a fan before the sound bugs you? My current computer is very loud with the 5 fans running all the time, but I can at least bear it and even sleep through it. However for my next computer I will try and keep the noise down. So I need to know if I got an Antec p180 how high can the decibel rating go before it will noticeably cause a loud fan noise?
 

Operandi

Diamond Member
Oct 9, 1999
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dBA ratings can be very misleading since everything changes once the fan is mounted to the case or heatsink. Smoothness and tonal quality (in the form of bearing and motor noise) are also just as important and are not reflected in the dBA rating. Then you also have those such as Thermaltake and SilenX whom more less make up their dBA ratings as they see fit.

I would suggest you head over to SPCR and do some research there since everything has already be covered very, very well.
 

RonAKA

Member
Feb 18, 2007
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Here are a few things to think about:

When the dB levels increase by 10 dB you hear that as twice as loud. A difference of 3 dB is just audibly louder. If you are into sound systems, it takes double the watts to get a 3 dB increase, and 10 times to get a 10 dB. i.e. you can't hear the difference between a 100 watt amplifer and a 150.

A typical quiet house is in the 40 dB range. Case mfg's talk about 25-30 dB but realistically they are not much better than 40 dB, which means a good PC can be built that is barely audible. In a home 50-60 dB is going to be annoying.

The other tidbit is that two 30 dB sources add to give you 33 dB (or +3 dB, when you have two sources at the same dB). So five fans are going to sound about twice as loud as 1 fan, if they are all the same noise level.

The key to keeping the noise down and the cooling up is to use large fans and slow speeds. My suggestion is to consider the Antec Sonta II case, and try to minimize the # of fans -- ideally only the standard 120mm on slow speed, in addition to the two PS fans -- with typically only one running.

Ron
 

RonAKA

Member
Feb 18, 2007
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Originally posted by: Navid
Originally posted by: RonAKA
So five fans are going to sound about twice as loud as 1 fan, if they are all the same noise level.
!

Well more accurately 8. Say 30 dB + 30 dB = 33 dB. Add two more then 33 + 33 = 36. Then add 4 more to get to 39 dB, about twice as loud. Just theory of course.