If I have 1 fan that is rated at 14db, it obvoiusly has a noise level of 14db. But if I have 2 fans that run together at 14 db each does this mean that they have a combined noise level of 28db?
In theory two fans running together would generate more noise than just one on its own, however I don't think it would consititue 28db being the total volume of both fans.
I don't think you would notice the difference personally, unless you were to have 10x the number.
I'm sure there is some science behind this.. however it does not warrant such an investigation at this point!
The Decibel Scale (as an indication of sound pressure levels) is logarithmic therefore you cannot add the values of two sound sources to calculate the resultant intensity.
In simple terms, every 3dB increase should see a doubling of sound intensity, therefore in your example 14dB + 14dB = 17dB.