§ 70.502 - Computation of multiple noise exposure.

The standard will be considered to have been violated in the case of multiple noise exposure where such exposure totals exceed one as computed by adding the total time of exposure at each specified level (C1, C2, C3 etc.) divided by the total time of exposure permitted at that level (T1, T2, T3). Thus, [C1/T1]+[C2/T2]+[C3/T3] must not exceed 1.

Example I: Exposure of 2 hours at 92 dBA and 1 hour at 100 dBA during an 8-hour shift.

Total minutes of noise exposure at dBA level/Total minutes of permissible noise exposure at dBA level [120 min./360 min.+60 min./120 min.]=2/6+1/2=2/6+3/6=5/6The sum of the fractions does not exceed one; hence the exposure for the shift would not violate the standard.

Example II: Exposure of 3 hours at 95 dBA and 1 hour at 100 dBA during an 8 hour shift.

3/4+1/2=3/4+2/4=5/4

The sum of the fractions exceeds one; hence the exposure for the shift would violate the standard.

(Secs. 101 and 206, 83 Stat. 745 and 765; 30 U.S.C. 801 and 846)