Background
- When OSHA promulgated its Hearing Conservation Amendment in 1983, it incorporated the Environmental Protection Agency's (EPA) labeling
requirements for hearing protectors (40 CFR 211), requiring manufacturers to identify the noise reduction capability of all hearing
protectors on the hearing protector package. This measure is referred to as the noise reduction rating (NRR). It is a laboratory-derived
numerical estimate of the attenuation that is provided by the protector. The standard also prescribes various methods to estimate the
adequacy of hearing protection attenuation using the NRR. By December 1983, it became evident that the amount of protection users were
receiving in the workplace with the prescribed hearing protectors did not correlate with the attenuation indicated by the NRR. OSHA
acknowledged that in most cases, this number overstated the protection afforded to workers and issued a change in compliance policy in its
compliance instruction CPL 02-02-035, Appendix A,
requiring the application for certain circumstances of a safety factor of 50 percent to the NRR, above and beyond the seven dB subtraction
called for when using A-weighted measurements.
Prompted by the concerns that hearing protection users may not be adequately protected from noise exposure, the National Hearing Conservation
Association (NHCA) created a task force on hearing protector effectiveness. The task force was made up of professional organizations,
government, industry, and accredited standards working groups. Their task was to develop new guidelines for the proper selection, use and
labeling of hearing protectors. In 1997, while the task force was working on their recommended changes, ANSI published a new test method
(subject-fit) for measuring the real ear attenuation of hearing protectors (ANSI S12.6-1997). This method provides more representative
estimates of the real world performance of hearing protectors. It attempts to better approximate the protection attained in real
workplaces by using untrained subjects in the test method (the only instruction they receive is the instruction that comes with the package)
to closely replicate real world users.
Some manufacturers of hearing protectors are testing their products according to the subject-fit method of ANSI S12.6-1997. You may contact
the manufacturer to request such data.
In the future, hearing protector manufacturers who voluntarily test their product according to the subject-fit method may choose to
publish the protector's attenuation data.
Task Force Recommended Changes and Other Relevant Publications
- NHCA task-force recommendations on changes in hearing protector labeling and noise reduction rating methodologies based on ANSI S12.6-1997.
- For further information on the suggested labeling procedures contact the NHCA.
Phone: (303) 224-9022,
Website,
Email
- Publication of NHCA task-force recommendation: Royster LH: Recommendations for the labeling of hearing protectors Sound and Vibration,
29(7), 16-19, 1995.
- In Search of Meaningful Measures of Hearing Protector Effectiveness. Berger, E.H., and Royster, L.H., Spectrum Supplement, 1, 13, p.29.
- Subject-fit versus real-world data. Berger, E.H., Franks, J.R., Behar, A., Casali, J.G., Dixon-Ernst, C., Kieper, R.W.,
Merry, C.J., Mozo, B.T., Nixon, C.W., Ohlin, D., Royster, J.D., and Royster, L.H. (1998). "Development of a new standard laboratory protocol
for estimating the field attenuation of hearing protection devices. Part III. The validity of using subject-fit data," J. Acoust. Soc. Am.
103,665-672.
- Recommendations of the National Institute for Occupational Safety and Health in reference to the subject-fit method and the NRR(SF):
Criteria for a Recommended Standard: Occupational Noise Exposure.
NIOSH Publication No. 98-126, (1998, June).
- For further information on this NIOSH Criteria Document, contact NIOSH.
Phone: 1-800-35-NIOSH,
Website
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