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#### grahamcrackuh

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Decibels are rated on a logarithmic scale. When you add them, they do not add linearly (e.g. 2db source + 2db source != 4db source). I am sure/hope many of you have noticed this.

However, most people seem not to understand the degree to which the decibel as a unit scales. Using 2 30db fans as opposed to one only yields 3 more decibels. Adding on 5 30 db fans once you have that ultra kaze on your TRUE only adds an additional 2 decibels.

So, for those of you concerned about your system being too noisy. Here is a calculator for summing db values. While it will obviously not represent the noise you will here (due to slight interferences and the case itself), it will give you a good idea of whether or not its worth sacrificing 60 cfm for a fan with 20 less DB when it would only add .1 db either way.

Here is a link to a calculator that can sum multiple incoherent (fan noise included) db sources:
http://www.sengpielaudio.com/calculator-spl.htm

And, for the mathematically inclined or curious, a link to the derivation:
http://www.epd.gov.hk/epd/noise_educ...1/intro_5.html

Hope this helps all.

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