Decibel level adder
Add incoherent sound levels in dB. Two equal sources are about +3 dB, not double.
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Tool guide
Decibel level adder: how it works
Practical information to understand the result and use this tool correctly.
About Decibel level adder
Decibels are a logarithmic scale. Two identical incoherent sources raise the level by about 3.01 dB, because power doubles.
The combined level is 10 log10 of the sum of 10^(L/10). A much quieter source barely moves the louder one.
This is not an arithmetic average and not L1 + L2. Empty input and values outside -200 to 200 dB are rejected. Nothing is uploaded.
How to use it
- 1Enter one sound level per line, or use an example.
- 2Read the combined level next to the wrong linear sum.
- 3Copy the result. The calculation stays in the browser.
Frequently asked questions
- What is 60 dB plus 60 dB?
- 63.01 dB. Equal incoherent sources add about 3 dB, not 120 dB.
- What is 70 dB plus 60 dB?
- 70.41 dB. The quieter source adds less than half a decibel.
- Can I average the levels instead?
- No. An average understates combined power. Use the logarithmic sum.