135. Impact noises at different levels: Where a worker is exposed to impact noises at different levels, the combined effect of these 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 number of impacts at a specific level and N indicates the total
__ __ __ number of impacts permitted according to section 134;
N1 N2 Nm
(2) by computing the equivalent level in dB linear peak value with the following formula:
SEA = Leq + 10 log N
where: SEA = sum of acoustic energies
Leq = equivalent level of impact noises
Ln = impact noise level in dB linear peak value
N = total number of impact noises to which a worker is exposed per day
n = number of impact noises for each sound level of impact noises
Where the method of computation specified in subparagraph 1 of the first paragraph is used, a worker shall not be exposed to an impact sound level such that the sum of the fractions exceeds the unit.
Where the measurements are taken pursuant to subparagraph 2 of the first paragraph, a worker shall not be exposed to impact noises such that the SAE exceeds 160 or such that the peak value in dB linear exceeds 140.
The computations in this evaluation shall not include any exposure of a worker to a sound level of less than 120 dB linear as peak value.