How are decibel levels calculated?

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saan44

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Dec 13, 2005
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I'm looking into replacing the stock coolermaster case fans on my Praetorian with Nexus 80mm fans. I don't know how the decibel level is calculated though. Since I have four fans, do I add the dBA of each fan together to get the total or is there some formula I should know?

I'm hoping someone out there can tell what kind of difference I can expect and whether it's worth dropping the cash to replace the case fans. I love this case. The looks and functionality are phenomenal, but the whine of the 4x80mm coolermaster fans has been annoying me to no end lately. As near as I can tell, these are the fans in the case (they came stock):

Fan Airflow: 32.11 CFM
Noise Level: 26.0 dBA

I'd be replacing them with the Nexus 80mm version which has these stats:

Fan Airflow: 20.2 CFM
Noise Level: 17.6 dBA

As you can see I'd lose some air movement with the Nexus fans, but I don't do much overclocking at all and my system isn't pushing the limits in terms of specs. I usually run quite cool so I'm not worried about it. I would really like to shed the ~10dBA per fan though and I'm hoping that will make my case sound less like a refrigerator.

Any help is much appreciated.
 
http://www.howstuffworks.com/question124.htm

"On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB."

A wisper is 15dB and convesation is 60dB so at 17dB your fans would be just above a wisper. Personally I just use Speedfan instead of buying new fans.
 
Adding the dB rating of each won't work... I don't think it's going to be simple to predict the summation of sound levels since they are multi frequency and out of phase w/ each other. I'd say it's a safe bet to say that you're computer is going to be considerably quieter though :D
For technical insight, here's a link to a page explaining dB addition.
 
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