Decibel Addition Calculator

Decibels are logarithmic, so you can never just add two dB readings together — two 80 dB sources side by side produce roughly 83 dB, not 160. This calculator does the correct physics: it converts each source back to linear sound intensity with 10^(L/10), sums those linear values (and a third source if enabled), then converts the total back to decibels with 10·log10(sum). That method assumes the sources are incoherent — independent, unrelated noises like two separate speakers or machines — which is the overwhelmingly common real-world case; it would understate the result for two perfectly in-phase copies of the identical signal, which combine differently. The "Increase from Loudest" figure shows how much the quieter source(s) actually add on top of the dominant one — often surprisingly little, since a second source more than 10 dB quieter barely moves the total.

Perceived loudness change applies the rough psychoacoustic rule that every 10 dB increase sounds about twice as loud to human hearing, expressed here as a percentage. Finally, the calculator maps your combined level against OSHA-style hearing-safety exposure limits and gives a familiar real-world reference sound (from "near silence" to "jet engine") so the raw number has context. Use it to plan whether combining a PA system with ambient crowd noise, or a shop full of running tools, crosses into hearing-protection territory — not as an exact acoustic prediction, since real rooms add reflections and distance losses this simple point-source model doesn't capture.