Noise in Industry - Fundamentals and Assessment Tools for Occupational Ergonomics - page 634

protectors alone may not reliably reduce noise levels received by the employee's ear to the levels specified
in Tables G-16 or G-16a of the Standard. Given the present state of the art, hearing protectors which offer
the greatest attenuation may not reliably be used when employees exposure levels border on 100 dBA.”
This guideline alludes to the importance of engineering controls as a primary countermeasure against
high noise levels. The OSHA 31 Technical Manual of the Directorate of Technical Support states:
“OSHA experience and the published scientific literature indicate that laboratory-obtained real-ear
attenuation data for hearing protectors are seldom achieved in the workplace.” Under “Field Attenu-

ation of Hearing Protection”: “When analyzing the attenuation a personal hearing protector may afford a
noise-exposed employee in an actual work environment, the hearing protector shall be evaluated as
follows:

...

2) To adjust for the lack of attainment of the laboratory-based noise reduction calculated
according to Appendix B [laboratory ratings] estimating techniques, apply a safety factor of 50
percent; that is, divide the calculated laboratory-based attenuation by two. 3) For dual protection
(i.e., earplugs and muffs) add 5 dB to the NRR of the higher-rated protector.” For case (2), the derating
factor may appear to be a reasonable strategy; however, these authors and others have argued that a con-
stant derating factor is not appropriate because certain protectors (e.g., earmuffs) are easier to fit prop-
erly than others (e.g., user-formed earplugs), and thus the differences between laboratory and actual in-
workplace performance will not be the same for all devices. In perusing Figure 31.8, this becomes quite
apparent in that the laboratory NRRs for earplugs overestimate the field NRRs by an average of about
75%, while the laboratory NRRs for earmuffs overestimate the field NRRs by an average of only about
40%. These data would argue for the use of derating factors that differ by device type, not a constant
derating such as the 50% OSHA recommendation. But in any case, the use of derating factors or
other modifications of the NRR to adjust it for field applications is tenuous at best and should not be
expected of the end user. The best solution is to establish a testing standard (and attenuation rating there-
from) that accurately predicts workplace protection achieved by HPDs, and this is the ANSI standard
work described in Royster et al. 29

...

31.5.2.2.4 Training Program and Access to Information and Materials
An oft-overlooked, but essential component of an industrial HCP is an annual training program for all
workers included in the HCP. The required training elements to be covered are: (1) the effects of noise on
hearing; (2) purpose, selection, and use of HPDs; and (3) purpose and procedures of audiometric testing.
It is essential to the success of an HCP that workers become acutely aware of the need for hearing con-
servation, understand and believe in the merits of the program, and develop a commitment to and the
motivation for protecting their hearing. Employers must make the OSHA regulations available to
affected employees and, upon request, make all training materials available to OSHA representatives.

31.5.2.2.5 Recordkeeping and Intraprogram Feedback
Accurate records must be kept of all noise exposure measurements, at least from the last 2 yr, and audio-
metric test results for the duration of the worker's employment. It is important, but not required by
OSHA, that noise and audiometric data be used as feedback for improving the program as shown in
the feedback loops of Figure 31.7. Because the primary goal of the HCP is to prevent NIHL for employees,
the program's effectiveness can be evaluated via audiometric database analysis (ADBA) for employees as a
group, as opposed to individuals. By using population statistics from and inferential analysis of the data-
base for exposed employees, problems can be identified early and corrective actions taken before signifi-
cant threshold shifts appear in a number of individuals. 32 ADBA, however, is not a substitute for annual
individual audiogram review and comparison against baseline. As discussed previously, this type of intra-
worker analysis is essential for identifying threshold shifts and implementing preventative measures that
are specific to the individual worker and job environment. Also, discussion of individual audiogram data
with employees can aid in motivating them to exercise care in their daily hearing conservation practices,
and audiometric feedback, sometimes posted anonymously by code number but including each individ-
ual's HPD use information, has been experimentally demonstrated to be an effective means of establish-
ing higher HPD usage rates. 33