Noice from Extreme switches

[geffy]

Hi
White paper on Summit X460-G2-48p-10GE4 gives max 64.3-70.8dB(A) in noice depending on F/B or B/F fan. How can I calculate the total noice in a stack of 4 switches ?
Can't find any noice data in tech spec for VSP7400 switches

Any info will be very appreciated

[FredrikB]

Matthew is correct, but IF the dB values are similar you can calculate a pretty good estimate of the resulting sound pressure (or optic signal or anything measured in dB) by taking the average of all values and adding 3 dB for every doubling of the number of signal sources.

2 sources, add 3 dB
3 sources, add 4.8 dB
4 sources, add 6 dB
8 sources, add 9 dB
16 sources, add 12 dB

If one or few values are a lot higher than the others, this method won't work well. If they are all within 2-3 dB of each other with a few values a lot lower, it works pretty good.

Use the correct formula if you need exact results.

/Fredrik

[Matthew_Hum]

For noise, if you have 4 noise sources of equal volume (db level) the total noise volume is +6dB. so f you have 4 sources of 50dB, then the total volume is 56dB.
if you have noise sources of unequal volumes then you need logarithmic addition.
dB=10 * Log10 (10^(N1/10)+10^(N2/10)+...+10^(Nx/10))