30 CFR 62.110 - Noise exposure assessment.
(a) The mine operator must establish a system of monitoring that evaluates each miner's noise exposure sufficiently to determine continuing compliance with this part.
(b) The mine operator must determine a miner's noise dose (D, in percent) by using a noise dosimeter or by computing the formula: D = 100(C1/T1 C2/T2 . . . . Cn/Tn), where Cn is the total time the miner is exposed at a specified sound level, and Tn is the reference duration of exposure at that sound level shown in Table 62-1.
(1) The mine operator must use Table 62-2 when converting from dose readings to equivalent TWA8 readings.
(2) A miner's noise dose determination must:
(i) Be made without adjustment for the use of any hearing protector;
(ii) Integrate all sound levels over the appropriate range;
(iii) Reflect the miner's full work shift;
(iv) Use a 90-dB criterion level and a 5-dB exchange rate; and
(v) Use the A-weighting and slow response instrument settings.
(c) Observation of monitoring. The mine operator must provide affected miners and their representatives with an opportunity to observe noise exposure monitoring required by this section and must give prior notice of the date and time of intended exposure monitoring to affected miners and their representatives.
(d) Miner notification. The mine operator must notify a miner of his or her exposure when the miner's exposure is determined to equal or exceed the action level, exceed the permissible exposure level, or exceed the dual hearing protection level, provided the mine operator has not notified the miner of an exposure at such level within the prior 12 months. The mine operator must base the notification on an exposure evaluation conducted either by the mine operator or by an authorized representative of the Secretary of Labor. The mine operator must notify the miner in writing within 15 calendar days of:
(1) The exposure determination; and (2) the corrective action being taken.
(e) The mine operator must maintain a copy of any such miner notification, or a list on which the relevant information about that miner's notice is recorded, for the duration of the affected miner's exposure at or above the action level and for at least 6 months thereafter.