WAC 296-817-30015   Use these equations when estimating full-day noise exposure from sound level measurements.  

     You 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




[Statutory Authority: RCW 49.17.010, 49.17.040, 49.17.050, and 49.17.060. 03-11-060, § 296-817-30015, filed 5/19/03, effective 8/1/03.]