NRRs for Hearing Protectors: A Change is Coming
EPA and most people involved in bringing about the new ratings believe they will reduce hearing loss and improve hearing conservation programs.
- By Brian Myers
- Jun 01, 2008
Perhaps the most common criterion for specifying
hearing protection devices (HPDs),
the NRR or Noise Reduction Rating—that
bold number on every box of ear plugs—is
about to change, hopefully for the better. For years, safety
professionals selecting hearing protection have enjoyed
the seeming simplicity of a single number that
could be used to differentiate products in the purchasing
process, a number which every hearing protector
was required by law to display on the package.
Actual application of that number in noisy workplaces,
though, has proven challenging. OSHA requires
subtracting seven from the number and dividing
it by two for some applications, but not for others.
NIOSH recommends a variable derating based on
HPD type. Transformation of the seemingly simple
NRR to something useful in practice became “rocket
science” as concerns about validity of the labeled values,
derating, population statistics and A-weighted
versus C-weighted sound levels emerged. The Environmental
Protection Agency (EPA) has undertaken a
process to revise hearing protector testing and NRR labeling
using the latest ANSI standards.While the pros
and cons of these NRR changes will have to be determined
in practice in the hearing conservation programs
across the United States, changes in the tests
and NRR labels are a certainty.
What Does This Mean to Me?
In the early months of 2009, safety directors and other
hearing conservationists may start to receive products
labeled with the new NRR from their safety products
distributors. The most noticeable change will be in the
appearance of the label itself.
One number becomes two. The most obvious difference
in the label is that what was once a single NRR
number has now become a two-number range. The
higher number of the new range indicates the amount
of protection which about one-in-five motivated and
highly trained wearers would attain or exceed. The
lower number indicates the protection which four-out of
five individually trained wearers would meet or exceed,
and it is this lower value that should be used to calculate
employee exposures and will probably be used by
OSHA to determine whether protection is adequate.
A range of numbers can provide more information
regarding how consistently the hearing protectors provide
protection within a group. By subtracting the
lower number from the higher one and comparing the
difference to the same calculation for other hearing
protectors, hearing conservationists can get an idea of
the uniformity of protection given by that hearing protector
where smaller differences would indicate more
consistent performance. In the example label, the range
is 13—the difference between the higher number, 34, and the lower number, 21. You should expect that this
protector would give less consistent protection than a
protector that had a range of five or 10 but provide a
more consistent performance than one with a range of
20. As you might guess, ear muffs will generally have
smaller ranges than insertable ear plugs because the
protection they provide tends to be more consistent
across groups of users.
How will the numbers compare to the current single
NRR? The current NRR will likely fall within the
range between the upper and lower values, but it will
vary by product. Until data are reported using the version
of hearing protector test standard that will be required
by the EPA—ANSI S12.6-200X, a document that
will not be finalized and approved until later this year—
the exact numbers are still open to question.
The exit of the single NRR number should bring
about a new appreciation that the protection levels of a
hearing protector in a group of wearers varies—no single
number can adequately describe these changing levels
of protection from one individual to the next. Selecting
and specifying a hearing protector might come
down to issues that today are sometimes considered secondary
but really matter in effective hearing loss prevention
programs: comfort, ease of use, demonstrated
ability of workers to properly use the chosen HPD, and
other, less-quantifiable attributes.
No 7-dB correction required. Many hearing conservationists
have performed their sound level measurements
with A-weighting as required by OSHA.However,
when NRRs have been applied to these A-weighted
sound levels, a correction factor of 7 dB is subtracted
from the old NRR. The new NRR numbers are calculated
to be applied directly to the A-weighted sound level
so that no 7-dB adjustment will be required.
More realistic ratings? Efforts have been made in the
standards development process to get the lab evaluations
to better reflect real performance, to reduce the
likelihood of a need for derating. EPA representatives
have indicated that one of the key reasons to undertake
the time-consuming regulatory process is to do a better
job of making the labeled attenuation values more reliable,
and thus less (or not) subject to after-the-fact derating.
It is not yet clear that the new numbers will produce
values that can be generally expected to reflect
workplace hearing conservation experience.A derating
may still be necessary. This determination may be made
by the professional community or by OSHA as they
begin to plan for application of the new rating method.
Electronic and other specialized hearing protectors
to get an additional label. If you are interested in hearing
protectors that incorporate level-dependent attenuation
or electronics for sound transmission or active
noise reduction, these products will have an additional
graphic (probably a bar as shown in the illustration previous)
within the EPA-specified label to specify the
level-dependent and/or electronic performance. This
additional graphic will be similar to the first, showing a
range of two numbers and bar graph, but in this case,
the attenuation numbers will denote performance of
the device with the electronic or other feature activated.
This will be the first standardized comparison of the
performance for these types of devices available to hearing
conservationists!
More Effective Hearing Loss Prevention
EPA and most of the other individuals involved in
bringing about these changes believe that they will result
in improvements in hearing conservation programs
and reduction of hearing loss. That is the ultimate purpose
for these changes.Whether or not this positive impact
is realized will ultimately depend upon the safety
directors and hearing conservationists who will use this
new system in their product selection processes. The
best way to ensure you get the maximum benefit from
this new NRR for your program is obviously to learn as
much as you can about it, ask questions, and let EPA
know your feelings about the change.
For additional information on this new proposed
NRR, go to www.regulations.gov, click “advanced docket
search” under “More Search Options,” select EPA as
the agency, and then OAR-2003-0024 as the docket
number. To give any opinion or feeling that you may
wish to share with EPA about this proposed label, you
may want to participate directly in a public hearing that
EPA will hold on the matter sometime in 2008.
Individual Fit Validation is
Still the Only Guarantee
No matter what changes are made to the NRR, users
still must recognize it is a population statistic and cannot
be used to accurately predict the amount of protection
an individual actually attains from using that
hearing protector. The only way to gain confidence for
each individual’s protection level is to conduct individual
fit validation—a test of each person wearing his
or her own hearing protector that documents the level
he or she receives from that protector. These fit validation
systems are beginning to make their way into industrial
hearing conservation programs.To learn more
about them, please visit www.e-a-r.com/pdf/hearing
cons/0629.pdf .
This article originally appeared in the June 2008 issue of Occupational Health & Safety.