Decibel calculator
Decibel addition calculator
Combine multiple noise sources. Decibels add logarithmically, not arithmetically.
Distance & sound-level calculator
How much a level drops as you move away (inverse-square law, 6 dB per doubling).
How decibel addition works
To combine sources you convert each level back to energy, add the energies, then convert back to decibels: L = 10 × log₁₀(Σ 10^(Lᵢ/10)). Because the scale is logarithmic, two equal sources add just 3 dB, and a source 10 dB quieter than another adds only about 0.4 dB. This is why silencing the quietest machine in a workshop changes almost nothing while dealing with the loudest changes everything.
How distance reduces sound
Outdoors, a point source obeys the inverse-square law: L₂ = L₁ − 20 × log₁₀(d₂/d₁), which works out to about 6 dB lost per doubling of distance. Indoors, reflections slow this down and the level flattens at the room’s reverberant field.
Sound level meters
When a phone app isn’t enough, a dedicated Class 2 meter gives repeatable readings for workplace checks, noisy neighbours or hobby audio.
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