How do dB stack?

If you have 2 30dB fans sitting next to each other, do they run at 60db combined? Is there some formula out there to calculate how loud combinations of fans are?

Sounds are additive, but not in a simple linear way.

* Two 30 dB noise sources make 33 dB
* Four 30 dB noise sources make 36 dB
* Eight 30 dB noise sources make 39 dB
* Sixteen 30 dB noise sources make 42 dB

from http://www.silentpcreview.com/modul...s&file=index&req=viewarticle&artid=121&page=1

Thank you, thats excatly what I wanted to know.

So it is a linear relationship but it is not a straight linear relationship. Do you know how high that formula holds true?

nope, I posted some question here and that was what I got as a response. Thought it be helpful.

arabarabian said:

So it is a linear relationship but it is not a straight linear relationship. Do you know how high that formula holds true?

Click to expand...

10 decibels (one Bel(?)) is 10 times the sound energy. (Subjectively, something 10 dB higher (ten times the sound energy) sounds about "twice as loud".)

Twice the sound energy ends up being (always) ~3 dB louder.

That's because bels = log10(sound energy).

log10(2*SoundEnergy) = log10(2) + log10(SoundEnergy) = ~0.3 bels + Sound = Sound + ~3 decibels.

Ten times the sound energy (ten fans as opposed to one) will be 10 dB more and will sound "twice as loud".

log10(10*SoundEnergy) = log10(10) + log10(SoundEnergy) = 1 bels + Sound = Sound + 10 decibels.

the wesson

Wow, thanks for that formula. Now I can use it for everything I have in my house.