Example
Input: 80dB + 80dB
Result: 83.01 dB
Step-by-Step Guide
- Identify Sources: Measure the dB level of each sound source independently.
- Input Values: Enter levels (e.g., 80, 85).
- Calculate Sum: Perform logarithmic addition.
- Result: View total combined SPL.
What is Decibel Summation Calculator?
Decibels (dB) are logarithmic units, meaning you cannot simply add them together linearly (e.g., 80dB + 80dB ≠ 160dB). This calculator performs logarithmic addition to determine the combined sound level of multiple sources.
How it Works
The formula converts dB levels back to linear intensity, sums them, and then converts back to log scale: Total dB = 10 * log10( Σ( 10^(L/10) ) ). For two equal uncorrelated sources, the increase is exactly +3 dB.
FAQ
What happens if I add two 100dB sounds?
The total will be approx 103 dB. Doubling power adds 3 dB.
What if sources are coherent?
If waves are perfectly in phase (coherent), they add to +6 dB. This calculator assumes incoherent (random phase) sources like typical noise.
How much louder is +10dB?
A 10dB increase is perceived by the human ear as roughly doubling the loudness.
Can I subtract decibels?
Yes, logarithmic subtraction is used to remove background noise from a measurement.
Is 0 dB silence?
0 dB SPL is the threshold of human hearing, not the absence of sound.
Conclusion
Understanding logarithmic addition is critical for acoustics, noise pollution control, and audio mixing. It explains why doubling the power of an amplifier only yields a modest increase in perceived volume.