dB Level Summation (Uncorrelated Signals)
Add two uncorrelated signal levels in dB by summing their powers. Equal levels give +3 dB.
Worked example
Input: Signal A 40 dB(any), Signal B 37 dB(any)
Result: Combined level 41.7643 dB(any), Increase over the larger signal 1.76435 dB
Result: Combined level 41.7643 dB(any), Increase over the larger signal 1.76435 dB
Formula
L = 10·log₁₀(10^(A/10) + 10^(B/10))
Two equal signals → +3.01 dB
How it works
When two independent (uncorrelated) sources are present, the total is not the plain sum of the dB values: you add powers and convert back. Two equal signals give +3 dB, a 6 dB difference raises the larger one by about 1 dB, and a 10 dB difference by only about 0.4 dB.
Practical tipN identical sources add 10·log₁₀(N) dB. This assumes no correlation, though. Phase-coherent signals such as harmonics from one clock add in voltage and can reach +6 dB for two sources.
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Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data. Last updated: 2026-10-10