132. Continuous noises at different levels: Where a worker is exposed to continuous noises at different levels, the combined effect of those levels shall be computed by using one of the following methods: (1) by adding the following fractions:
C1 + C2 + ...Cm , where C indicates the total time in hours
__ __ __
T1 T2 Tm
of exposure at a specific level and where T indicates the total duration in hours of exposure permitted in accordance with section 131;
(2) by computing the equivalent sound level in dBA equivalent with the following formula:
Leq = 16.61 log10 1 o∫T 10 L(t)/16,61 dt,
where: Leq = equivalent sound level
L = instantaneous sound level in dBA
T = total duration of worker’s exposure, expressed in hours and by using the sound level thus obtained to apply the table in section 131.
Where the method of computation specified in subparagraph 1 of the first paragraph is used, a worker shall not be exposed to a sound level such that the sum of the fractions exceeds the unit.
The computations specified in this evaluation shall not include any exposure of a worker to a sound level of less than 85 dBA.