220.127.116.11. Continuous noises at different levels: When a worker is exposed to continuous noises at different levels, the combined effect of these levels shall be estimated:
(a) by adding the following fractions:
C1 C2 Cm,
—— + —— + ....——, where C indicates
T1 T2 Tm
the total exposure hours at a given level and T indicates the total time of exposure hours permitted by section 18.104.22.168; or
(b) by calculating the equivalent sound level in dBA with a sound level meter, an audio-dosimeter or any other measuring device corresponding to the following formula:
Leq = 16.61 Log10
where: Leq = equivalent sound level in dBA
L = instantaneous sound level in dBA
T = total exposure time of the worker, expressed in hours
and by using the level so obtained to apply the table in section 22.214.171.124.
In the case where the evaluation method mentioned in subparagraph a of the first paragraph is used, a worker shall not be exposed to a sound level such that the sum of the fractions is higher than unity.
Any exposure of the worker to a sound level lower than 85 dBA shall be excluded from the calculations mentioned in this section.