PDFWAC 296-307-63415
Use these equations when estimating full-day noise exposure from sound level measurements.
The employer must compute employee's full-day noise exposure by using the appropriate equations from Table 3 "Noise Dose Computation" when using a sound level meter to estimate noise dose.
Table 3
Noise Dose Computation
Description | Equation |
Compute the noise dose based on several time periods of constant noise during the shift | The total noise dose over the work day, as a percentage, is given by the following equation where Cn indicates the total time of exposure at a specific noise level, and Tn indicates the reference duration for that level. D = 100*((C1/T1) + (C2/T2) + (C3/T3) + ... + (Cn/Tn)) |
The reference duration is equal to the time of exposure to continuous noise at a specific sound level that will result in a one hundred percent dose | The reference duration, T, for sound level, L, is given in hours by the equation: T = 8/(2^((L - 90)/5)) |
Given a noise dose as a percentage, compute the equivalent eight-hour time weighted average noise level | The equivalent eight-hour time weighted average, TWA8, is computed from the dose, D, by the equation: TWA8 = 16.61* Log10(D/100) + 90 |