dB Addition Calculator (Combining Sound Sources)
Quick answer: Enter dB values of multiple sources. Get the combined total and increase from the loudest single source.
Combine SPL (sound pressure level) values from multiple sources logarithmically. Adding two 90 dB sources doesn't give 180 dB — it gives 93 dB. This calculator handles the math correctly for any number of sources.
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Last reviewed: April 2026Report an error
Sound Sources (dB SPL each)
dB SPL
dB SPL
dB SPL
Combined Level
93.65 dB
3 sources combined: 93.65 dB SPL. That's 3.65 dB more than the loudest single source. Two equal sources always add +3 dB; three equal sources add +4.8 dB.
Combined Total
93.65 dB
Increase from Loudest
+3.65 dB
Sources
3
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The Formula
L_total = 10 × log₁₀( Σ 10^(L_i / 10) )
- L_i = Each individual sound level in dB
- L_total = Combined total level in dB
Source: OSHA — Combining Noise Levels ↗
How to Use This dB Addition Calculator
- 1Add each sound source's level in dB SPL.
- 2Add as many as needed (PA stacks, monitors, ambient).
- 3Read combined total dB and how much it increases the loudest source.
Frequently Asked Questions
- dB is logarithmic, not linear. Doubling sound power adds 3 dB. Two equal sources = 2× power = +3 dB. Three equal sources = 3× = +4.8 dB. Ten equal sources = 10× = +10 dB.
- Estimating combined SPL from multiple PA stacks, predicting noise levels from many machines, calculating mix bus levels, evaluating cumulative neighbor noise from venues with multiple stages.
- A source 10 dB lower than the loudest contributes only 0.4 dB to the total. Two sources differing by more than 10 dB: ignore the quieter one for practical purposes (within 1 dB).
- Yes — same math for any decibel measurement (SPL, signal levels in dBu/dBV, noise floor). The logarithmic addition rule is universal.
- This calculator assumes incoherent sources (uncorrelated, e.g. separate noise sources). For coherent sources (same signal from two speakers in phase), addition can be up to +6 dB at the listener — but only at specific frequencies and positions.
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