EPA Proposes Changes to the Noise Reduction Rating for Hearing Protectors
Lee D. Hager, CAOHC Council Representative, AIHA
After 30 years, the Environmental Protection Agency (EPA) is moving ahead with revisions to 40 CFR 211, subpart B; the federal regulation that defines and describes the labels we see on packages of hearing protection devices (HPD). Substantial changes to the attenuation test requirements and the methods for computing and presenting the Noise Reduction Rating (NRR) have been proposed. The labeling requirements in the proposed rule have been extended to a much wider range of electronic and level-dependent hearing protectors for which no rating system had previously been available.
EPA published proposed changes to this regulation on August 5, 2009, and set a deadline of November 4, 2009 for the public to submit written comments to the federal docket. At a hearing in Washington DC on October 7, 2009 representatives from hearing protector manufacturers, occupational health and safety experts, hearing protection users and members of the general public had the opportunity to provide spoken comments.
Why change the NRR?
In the preamble to the proposed rule (EPA, 2009) the EPA recognized that, “Field studies by various researchers over the past three decades, revealed a relatively poor correlation between the labeled NRR of selected protectors, as determined from testing in accordance with the American National Standards Institute (ANSI) S3.19–1974 test procedure, and the attenuation realized by typical users of these protectors when tested without the benefit of the experimenter fitting the device as required in ANSI S3.19.” The authors of the proposed rule went on to say, “...the current required test methodology…can result in unrealistically high sound reductions that are generally not attainable in real world use. The resultant labeled NRR can lead to product selections that may leave users under-protected and subject to potential hearing damage. Further, the procedure lacks suitability for the testing of other than passive devices.”
Highlights of Proposed Rule
With these observations in mind, the proposed rule featured numerous significant changes, including:
- Replacing test methods referred to in the original regulation, which were based on an ANSI standard from 1974, with test methods from the most current version of that standard, published in 2008.
- Expanding the regulation to address new HPD technologies, particularly for electronic and noise-cancelling devices. These technologies did not even exist when the current rule was written.
- New test methods for evaluating HPD for impact and impulse noise environments. These are based largely on a soon-to-be-published ANSI standard (S12.42-200x).
- Replacing the single-number NRR with a dual-number rating.
Figure 1: EPA proposed label
Figure 2: Proposed label for active/electronic HPD
An example of the dual-number NRR proposed by the EPA is shown in Figure 1. It describes a range of performance based on the range of noise reduction obtained in the laboratory with subjects tested using test method A of ANSI S12.6-2008.
The lower NRR value is the attenuation that 80% of the test subjects achieved or exceeded. The higher value reflects the attenuation obtained or exceeded by 20% of the subjects; those who obtained the best fit in the laboratory test.
This protocol allows the person conducting the tests to train and coach the subjects thoroughly, with no time limit for training. Once the experimenter is confident that the test subject has the ability to properly fit the HPD, the experimenter measures the hearing thresholds of the subject while the HPD is not worn and subtracts those values from the hearing thresholds measured while the HPD is worn. This “threshold-shift” procedure is similar to the one used today and is referred to in the standard as Method A.
EPA gave careful consideration to the alternate test methods such as the “untrained-subject” procedure (Method B from S12.6-2008) but ultimately decided that Method A was more reflective of expected use values and was a consistent test of the properties of the HPD.
When the HPD becomes more complex, so does the label. The proposed label shown in Figure 2, for example, shows how an electronic sound restoration HPD might be labeled, with different ranges for the same device when in active and passive modes. Adding in yet different ranges for the effectiveness of the device for impulsive noises further complicates the label.
At the time of this publication, the effective date for the new EPA rule and the dates when hearing protector manufacturers must begin testing and labeling their HPD according to the new procedures have not been finalized.
Implications
There has been much discussion about how this new dual-number rating will be used to manage selection of the proper HPD for a given amount of noise exposure. Since the source of the range is the 80th and 20th percentiles, can hearing conservationists be expected to keep track of which of their noise exposed employees do well with using HPD, or will they simply default to the lower number in the range as a conservative estimate? Will OSHA require derating of either of the NRR values when hearing protectors are used in the workplace? Answers to these and similar questions are certainly not clear at this point.
So what is a hearing conservationist to do? In terms of HPD selection, the best approach, regardless of the noise reduction ratings listed on the package, is to provide in-depth training to noise-exposed workers. New research indicates that face-to-face training interaction is the most effective way to get workers to properly fit and use their HPD. Likewise, many employers are turning to fit testing of hearing protectors to help measure the noise reduction obtained by each employee and identify which employees need additional training in how to fit and wear HPD in the workplace.
Lastly, it’s helpful to keep in mind that 90% of all noise exposures commonly encountered in industry are less than 95 dBA TWA. Nearly any hearing protectors that are fit properly and used consistently will provide the 12 to 15 dB of protection necessary to protect the vast majority of noise exposed workers.