How to Add Decibels: Combining Noise Sources
Because decibels are logarithmic, you cannot simply add them. Two equally loud sources add only about 3 dB, not double the number.
➕ Add Two Sound Levels
Key points
- Two equal sources (e.g. 80 dB + 80 dB) combine to about 83 dB — just +3 dB.
- Doubling the number of identical sources always adds about 3 dB.
- If one source is much louder, the quieter one barely changes the total.
- Use the formula: total = 10 × log10(10^(L1/10) + 10^(L2/10)).
- The calculator above does this for you — enter two levels to combine them.
FAQ
Do two 60 dB speakers make 120 dB?
No. They combine to about 63 dB. Adding an equal source raises the level by only about 3 dB because decibels are logarithmic.
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