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CAOHC

CAOHC Newsletter: UPDATE

A New ANSI Standard for Measuring Hearing Protection

E. H. Berger, M.S.
CAOHC Representative of the American Industrial Hygiene Association

A new national standard that describes how to measure, in the laboratory, the real-ear attenuation of hearing protection devices (HPDs), was approved last year by the American National Standards Institute (ANSI). This standard, entitled Methods for Measuring the Real-Ear Attenuation of Hearing Protectors (S12.6-1997) was the culmination of nearly a decade of research by Accredited Standards Working Group, S12/WG11, chaired by Elliott H. Berger, Senior Scientist, Auditory Research, E•A•R/Aearo Company. The new standard updates and replaces the 1984 version of the same standard. The most exciting aspect of this new standard is that it includes a procedure, designated Method B, Subject Fit, that provides data intended to approximate the protection that can be attained by groups of informed users in workplaces with representative well-managed and well-supervised occupational hearing conservation programs. The 1997 standard also includes a Method A, Experimenter-Supervised Fit, which retains practices from the 1984 document that are designed to describe the capabilities of HPDs under ideal conditions.

The new standard was developed after years of research and a four-facility interlaboratory study. The results of the research have been recently published in the Journal of the Acoustical Society of America (Royster, et al., 1996; Berger, et al., 1998), with a final publication in preparation at this time. The standard specifies laboratory-based procedures for measuring, analyzing, and reporting the noise-reducing capabilities of conventional HPDs, using tests conducted on human subjects. The standard is not a method of approval of products, nor a quality assurance procedure. It simply provides noise-reduction data. However, the existence of the Method B procedure is quite valuable since leaders in the field have pointed out for over a decade that labeled Noise Reduction Ratings (NRRs) computed from existing data, as specified by the EPA, overestimate work-place protection from 6 to 25 dB, depending upon the hearing protector.

That the new standard exists is the good news. The bad news is that because there is no one home at the Environmental Protection Agency's (EPA) noise office, nothing is being done to revise the existing EPA hearing protector labeling regulation, which not only does not recognize the new standard, but still requires testing by EPA's interpretation of a 24-year old document (ANSI S3.19-1974) that is no longer supported by ANSI. In short, the current hearing protector Noise Reduction Ratings, based upon testing to S3.19 are of even less accuracy and value than the original much-maligned EPA fuel-economy ratings. The fuel-economy ratings were improved; the hearing protector ratings have not been.

The situation is even more egregious since the professional community, lead by a National Hearing Conservation Association (NHCA) Task Force on Hearing Protector Effectiveness developed consensus recommendations in 1995 calling for testing and labeling according to the new Method-B procedure (Royster, 1995), and the recently revised NIOSH Criteria for a Recommended Standard: Occupational Noise Exposure (NIOSH, 1998; also see "Changes Coming," page 3 in this issue) also specifies Method-B testing. Furthermore professional organizations such as CAOHC, and as diverse as the Acoustical Society of America (ASA), the American Speech-Language Hearing Association (ASHA), the American Academy of Otolaryngology / Head and Neck Surgery (AAO/HNS), NHCA, and others, have all written petitioning the EPA to revise the regulation. Yet nothing has happened.

To get an idea of the magnitude of the problem and to be able to implement the newer type data in your programs see EARLog #20 - The Naked Truth About NRRs available from E•A•R Hearing Protection Products. Meanwhile beware that measured as a percentage of the laboratory-rated and labeled attenuation, the field NRRs for earplugs (other than foam earplugs) yield only about 25% of the labeled values, foam provides about 40%, and earmuffs about 60%. Concern for this issue is tempered by the fact that in 90% of noisy industries daily average exposures are less than or equal to 95 dBA and virtually any well fitted, correctly and consistently worn HPD can protect the ear. The problem is that inflated NRRs of 25 to 30 dB or greater make it appear as though any HPD worn in even a slipshod manner will protect virtually any user from any noise exposure. That is simply not the case. Thus the largest part of the problem for the practicing hearing conservationist is training, motivation, supervision, and enforcement - issues germane to all areas of personal protective equipment.

The hearing protector selection process should consist of more than merely scanning manufacturers' specification sheets and price lists. Wear test the products you intend to use, both on yourself and on small groups of employees. By developing your own firsthand knowledge and combining it with employee feedback, you not only improve the likelihood of selecting products your employees will accept, but you also will better motivate your workers by involving them in their own hearing conservation program.


References

Berger, E. H. (1993). "EARLog #20 - The Naked Truth About NRRs," E•A•R Hearing Protection Products, Indianapolis, IN.

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., 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(2), 665-672.

NIOSH (1998). "Criteria for a Recommended Standard: Occupational Noise Exposure," U. S. Dept. of Health and Human Services, NIOSH, Publ. No. 98-126, Cincinnati, OH.

Royster, J. D., Berger, E. H., Merry, C. J., Nixon, C. W., Franks, J. R., Behar, A., Casali, J. G., Dixon-Ernst, C., Kieper, R. W., Mozo, B. T., Ohlin, D., and Royster, L. H. (1996). "Development of a New Standard Laboratory Protocol for Estimating the Field Attenuation of Hearing Protection Devices. Part I. Research of Working Group 11, Accredited Standards Committee S12, Noise," J. Acoust. Soc. Am. 99(3), 1506-1526.

Royster, LH (1995). "In search of a meaningful measure of hearing protector effectiveness: Recommendations of the NHCA's Task Force on Hearing Protector Effectiveness," Spectrum 12(2), p. 1 and 6-13.