Work out noise dose percentage instantly with clear inputs, formula shown and shareable results.
Permitted exposure time halves for every exchange rate increase in level: at a five decibel exchange rate, 90 dBA is allowed for eight hours and 95 dBA for four. Dose is actual time divided by permitted time, and the equivalent eight hour average follows from inverting the same relation. Fifty percent dose, equivalent to 85 dBA, is the usual action level.
Permitted time
T = 8 / 2^((L - criterion) / exchange rate)
Dose and TWA
Dose % = 100 x C / T; TWA = criterion + exchange rate x log2(dose / 100)
Preliminary estimate only. Noise exposure assessment must follow the measurement standard and criterion adopted by your regulator and be carried out by a competent person.
T = 8 / 2^((L - criterion) / exchange rate). Permitted exposure time halves for every exchange rate increase in level: at a five decibel exchange rate, 90 dBA is allowed for eight hours and 95 dBA for four.
Three decibels is the equal-energy rule and is used in Europe and by most researchers. Five decibels is a historical US regulatory compromise that allows more exposure at high levels.
This calculator takes 4 inputs: Measured sound level, Exposure duration, Criterion level, Exchange rate. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.