SECTION 8: What OSHA Expects From You

By now nearly everyone agrees that hearing loss can be caused by exposures to loud noises. Obviously, the louder the noise the shorter the exposure needed to cause hearing loss: So the Department of Labor, through OSHA, has sought tp provide protection to workers whose jobs involve exposure to high noise levels.

Setting limits on occupational noise exposure, however, has proven a controversial and difficult task, and considerable give-and-take between labor and industry has occurred. As a result, today's rules governing occupational noise exposure have grown more and more complex. What follows is a summary of the rules you should be concerned with as a safety officer.

Department Of Labor Occupational Noise Standards

These rules were adopted in 1971 and still form the core of the federal occupational noise control effort. In essence, they state that if employees are exposed to noise levels that exceed those specified in the following table, a noise control program must be initiated. In essence this means that the employer must work to reduce plant noise exposures by quieting plant machinery or reducing the amount of time workers actually spend in noisy environments. (This is known as an "administrative and engineering controls" program.) On the top of the following page you will find OSHA's limits for occupational noise exposure:

Permissible Noise Exposures



8 90
6 92
4 95
3 97
2 100
1 1/2 102
1 105
1/2 110
1/4 or less 115

When using the preceding table, remember that these are total daily exposures--if employees receive only brief exposures, the exposure times should be added up over the course of the day and compared with the permitted levels. Also remember that exposure to extremely brief, sharp noises (called "impulsive" or "impact" noises") of over 140 dB peak sound pressure levels in intensity is also prohibited.

Hearing Conversation Amendment

This amendment, adopted in 1981 and finalized in 1983, toughened the rule adopted in 1971: In addition to the 1981 rule, it required that if employees are exposed to an 8-hour time weighted average of over 85 dBA, a hearing conservation program must be put into effect. (What a hearing conservation program involves will be explained below.)

However, when computing a time weighted average for the purposes of establishing a hearing conservation program, the law also specified that all noises above 80 dBA must be taken into account. The reasoning behind this was that even though a hearing conservation program is not triggered until a time-weighted average of 85 dBA is reached, noises between 80 and 85 dBA in intensity should also be considered when computing this average because research has shown that long-term exposures at this level can also contribute to hearing loss.

This is a very important aspect of the law, as well as the most confusing, and it bears repeating: An engineering controls program is triggered when employee exposures exceed a time-weighted average of 90 dBA, and only noise above 90 dBA should be taken into account when computing a time-weighted average for this purpose. However, a hearing conservation program is triggered when employee exposures reach a time-weighted average of 85 dBA, but noises as low as 80 dBA should be taken into account for this computation.

The computer program used to calculate time-weighted averages from the data stored by the SNX-85C takes these rules into account so you don't have to worry about them. Your SNX-85 data sheets also take these rules into account on the engineering controls data sheet by multiplying all exposures below 90 dBA by zero so they drop out of the calculation. On the hearing conservation analysis data sheet, on the other hand, all levels between 80 and 90 dBA are included in the calculation.

Hearing Conservation Program

This program is generally required for employees who are exposed to a time-weighted average of over 85dBA, calculated as explained in the preceding section. Here's a brief outline of what such a program includes:

  1. Employees affected shall have their hearing acuity evaluated by an approved professional. The test used to establish hearing acuity is known as an audiogram, and every year after this first or "baseline" audiogram is established, another audiogram should be taken for affected employees to determine whether any hearing loss has taken place in the interim. Employees must be informed of the results of these hearing tests.
  2. A variety of hearing protectors must be available to employees in the hearing conservation program. These employees must wear hearing protection only if they are exposed to a time-weighted average of 90 dBA or more, but they may choose which kind of protector they will wear.
  3. Employees in the hearing conservation program must also be informed of the effects of noise on hearing, the use and protection afforded by hearing protection, and the purpose of the annual hearing tests they are required to take.
  4. Employers must maintain careful records documenting employee noise exposures, hearing testing, and the calibration of instruments used to measure noise and test hearing. Hearing tests shall also be given in rooms where background noise will not interfere with the tests.