Evaluating Hearing Protectors – EPA, ONAC and Your Ears on the Job

By Lee D. Hager - Sonomax Hearing Healthcare, Inc.

September 2005 

Did you know there is a large difference between how well hearing protection can work and how well it actually works?

When selecting hearing protection devices (HPD), most employers and consumers rely upon the noise reduction rating (NRR) printed on the HPD package as a guide to how much noise protection to expect.  The NRR development and labeling process in the US is the responsibility of the Environmental Protection Agency (EPA) under the Noise Control Act – a legacy left over from the 1970’s when EPA maintained an active Office of Noise Abatement and Control (ONAC).  Statutory responsibility for the NRR remains with EPA, even though funding (and staffing and office space) for ONAC was eliminated in the early 1980’s.

This turn of events has, for the most part, orphaned any regulatory updates of HPD evaluation or the NRR.  Under the rules in place today, HPD testing must comply with an outdated ANSI standard (ANSI S3.19-1974) that has been rewritten and superseded twice, most recently in 1996 (ANSI S12.6-1996 R 2002).

This evaluation process entails providing a hearing test to a group of subjects; then providing the same test, only with the HPD put in place by the test administrator or experimenter.  The difference between hearing test results with and without HPD, after some statistical manipulation, was deemed to describe the performance of the HPD, and became the labeled NRR.

Beginning in the 1980’s, it became clear that the protection promised by the labeled NRR values on HPD was not being achieved by users in practice.  Elliott Berger of EAR/AEARO collected and collated a group of field studies, and found that not only were HPD not yielding in the field what was found in the lab, but the differences were not linear – higher NRR did not necessarily mean more protection for end users. 

These differences were so striking that methods for “derating” or discounting the NRR were adopted by the US Occupational Safety and Health Administration (OSHA), which mandated a 50% discount of the NRR (after subtracting 7 dB for spectral uncertainty) when comparing the efficacy of HPD to noise control engineering efforts (search the “directives” section of www.osha.gov for hearing protection, and look for CPL 02-02-035 or 2-2.35A for details).  NIOSH developed their own derating system in the 1998 Criteria Document (http://www.cdc.gov/niosh/98-126.html) based on the type of device - with earmuffs penalized 25% of their NRR value, formable foam earplugs derated 50% like the OSHA system, and premolded earplugs ratings cut by 70%.  The NIOSH derating system is reflected in their on-line hearing protector compendium (http://www.cdc.gov/niosh/topics/noise/hpcomp.html).  Using the “search on a selected noise level” feature results in HPD selections appropriate for the exposure level, reflecting the NIOSH derating criteria.

Some of the differences between lab and field evaluations are accounted for in the latest ANSI standard on this issue.  S12.6-1996 (R2002) contains two methods for testing HPD.  Method A is an updated version of the 1974 ANSI standard, and gives similar results.  Method B takes a different approach, where test subjects are provided the HPD with the written instructions from the manufacturer, are asked to put the devices in place per those instructions, and take the hearing test with no supervisor or experimenter intervention.  This “subject fit” approach yields protection values closer to in-field findings, but still overestimates HPD performance.

In 2003, EPA reopened the book on HPD evaluation and labeling.  A workshop held in March 2003 provided the initial opportunity for input to what promises to be a wholesale revision to EPA’s rule, 40CFR211 Subpart B.  Access to the current EPA rule is available from the Government Printing Office (http://www.gpoaccess.gov/cfr/index.html); search for 40CFR211 and look for Subpart B.  The proceedings of the EPA workshop, background information, and subsequent comments are available for review as well; from www.epa.gov, click “Laws, Regulations and Dockets”, “EPA Dockets”, and “Quick Search”.  Enter the docket number of interest (OAR-2003-0024) in the search field for full access.

Mr. Hager is a Hearing Loss Prevention Consultant with Sonomax Hearing Healthcare Inc.  He can be contacted at 517-647-5882 and at lhager@sonomax.com. 

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