Intensity Calculator
Power spread over area, with the sound level in dB.
Spreading thin
I = P / A
A source radiating equally in all directions spreads its power over a sphere, so intensity falls with distance squared: twice as far, a quarter as loud. The dB scale compresses the enormous range of hearing: 0 dB is the 10⁻¹² W/m² threshold, conversation ~60 dB, pain ~120 dB, a full twelve orders of magnitude.