Noise in Industry - Fundamentals and Assessment Tools for Occupational Ergonomics - page 629

Applying Equation (31.16) (or OSHA code, Table A-1 19 ):

TWA ¼ 95 : 1 dBA

2. Calculate a rate of dose per minute:

115% dose
375minutes ¼

0 : 3067% dose per minute

D ¼ 660minutes 0 : 3067% dose = minute ¼ 202 : 4%

Applying formula (31.16) (or OSHA code, Table A-1 19 ):

TWA ¼ 95 : 1 dBA

31.5 Industrial Noise Regulation and Abatement

31.5.1 Indicators of the Need for Attention to Noise
The need for management, or perhaps more appropriately, abatement of industrial noise is indicated
when: (1) noise creates sufficient intrusion and operator distraction such that job performance and
even job satisfaction are compromised; (2) noise creates interference with important communications
and signals, such as interoperator communications, machine- or process-related aural cues, or alert-
ing emergency signals; and (3) noise exposures constitute a hazard for NIHL in workers. While this

chapter primarily targets problem 3, which is governed by OSHA federal regulations in general industry 19
and MSHA (Mine and Safety Health Administration) regulations in mining, the principles of noise
measurement, management, and abatement discussed herein may also be applied in mitigating problems
1 and 2.

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31.5.1.1 OSHA Noise Exposure Limits
With regard to combating the hearing loss problem, in OSHA terms if the noise dose exceeds the OSHA
action level of 50%, which corresponds to an 85-dBA TWA, the employer must institute a hearing con-
servation program (HCP) that consists of several facets, to be discussed later. 19 (It is noteworthy that the
OSHA regulation specifically exempts employers in oil and gas well drilling and servicing from the HCP
requirements, although they are subject to the 100% dose criterion.) If the criterion level of 100% dose is
exceeded (which corresponds to the PEL of 90-dBATWA for an 8-h day), the regulations specifically state
that steps must be taken to reduce the employee's exposure to the PEL or below via administrative work
scheduling or the use of engineering controls. It is specifically stated that hearing protection devices
(HPDs) shall be provided if administrative and engineering controls fail to reduce the noise to the
PEL. Therefore, in applying the letter of the law, HPDs are only intended to be relied upon when admin-
istrative and engineering controls are infeasible or ineffective. The final OSHA noise level requirement
pertains to impulsive or impact noise, which is not to exceed a TRUE PEAK SPL limit of 140 dB.

31.5.2 Hearing Conservation Programs and the Systems Approach
31.5.2.1 Shared Responsibility between Management, Workers, and Government
A successful HCP, which includes many facets relating to the measurement, management, and control of
noise, depends upon the shared commitment of management and labor, as well as the quality of services