Hearing Conservation Theresa Y. Schulz, PhD. Lt. Col. USAF (ret.)

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Hearing ConservationTheresa Y. Schulz, PhD.Lt.
Col. USAF (ret.)
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Topics
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Noise Acoustics

• Noise-Induced Hearing Loss
• Causes no pain
• Causes no visible trauma
• Leaves no visible scars
• Is unnoticeable in its earliest stages
• Accumulates with each overexposure
• Takes years to notice a change

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Noise Acoustics
Noise-induced hearing loss is the most common
permanent and preventable occupational injury in
the world.
World Health Organization
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Noise Acoustics

• Workers Compensation

In many countries, excessive noise is the biggest
compensable occupational hazard. Cost of NIHL to
developed countries ranges from 0.2 to 2 of its
GDP. NIHL is on the rise globally. (Source WHO)
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Noise Acoustics

• United States Statistics

Most common occupational injury in the United
States. 22 million US workers are exposed to
hazardous noise at work on a daily basis. Approx.
8 million Americans suffer from NIHL. (Source
NIOSH, 2009)
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Noise Acoustics
Non-Occupational
Occupational
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Noise Acoustics

• Noise Measurement Devices

SOUND LEVEL METER Sound is measured immediately
in a specific area
PERSONAL DOSIMETER Sound averaged throughout
day for sample employee/job
IN-EAR DOSIMETER Collects
personal noise dose the only real measure of
risk
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NOISE AND ACOUSTICS Hierarchy of Controls
Noise Acoustics - Hierarchy of Controls

• ENGINEERING CONTROLS
• Buy Quiet
• Vibration Pads
• Enclosures
• Barriers
• Isolation

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NOISE AND ACOUSTICS Hierarchy of Controls
Noise Acoustics
Ototoxic Chemicals

• Ototoxic by themselves
• Synergistic effect with noise
• Large differences in sensitivity
• Recommend increased frequency of audiometric
  testing

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How We Hear
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How We Hear

• The Auditory System

Chem/Elec
Acoustical
Hydraulic
Mechanical
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(No Transcript)
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How We Hear

• High Frequency Sounds of Speech

CH
S
TH
P
T
F
SH
K
H
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Noise Reduction Rating(NRR)
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Noise Reduction Rating
Noise Level 100 dB Noise Reduction Rating
30 dB

• How much noise is reaching the ear of the worker ?

That is completely unknown
(55 104 dB)
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Noise Reduction Rating

• Noise Reduction Rating

• A laboratory estimate of the amount of
  attenuation achievable by 98 of users when
  properly fit
• A population-based rating ? some users will get
  more attenuation, some will get less

The NRR is only a population estimate, not a
predictor of individual attenuation.
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Noise Reduction Rating Determining an NRR

• 10 human subjects tested in a reverberant room
• Tested with ears open/occluded at nine
  frequencies
• Each subject tested 3x
• NRR calculated to be population average

A test subject in the Howard Leight Acoustical
Lab, San Diego, CA, accredited by the National
Voluntary Laboratory Accreditation Program (NVLAP)
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NRR
Noise Reduction Rating Determining an NRR
NRR
5
4
Number of test subjects
3
2
1
28
30
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22
24
14
18
20
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25
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Attenuation
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Real-World Attenuation ? NRR
192 users of a flanged reusable earplug 27 NRR
50
NRR 27 Multiple-Use Earplug
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Retraining and refitting resulted in an average
14 dB improvement for this group
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Attenuation in dB
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10
0
-10
From Kevin Michael, PhD and Cindy Bloyer Hearing
Protector Attenuation Measurement on the End-User
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Noise Reduction Rating

• De-Rating Methods

NIOSH Earmuffs NRR 25 Formable Earplugs NRR
50 All Other Earplugs NRR 70
OSHA NRR 2 (feasibility of engineering
controls)
CSA Class A up to 100 B up to 95 C up to 90
Fit Test
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Noise Reduction Rating

• Noise Reduction Rating

• The EPA recently made an announcement about a
  proposed change to the Noise Reduction Rating
  NRR
• This is the first change in hearing protector
  regulation in nearly 30 years

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Noise Reduction Rating

• Three New Labels

LABEL DESCRIPTION
Conventional HPD Perform lab test with subjects who fit the protector after brief training Estimates the range of protection achieved by 20 and 80 of users
Active Noise Reduction ANR Uses a Microphone-in-Real-Ear MIRE method to estimate protection Measured with ANR turned OFF and ON to show the additional attenuation from the ANR
Level Dependent/ Impulse Noise Reduction Testing will occur over a range of impulse noise levels. Multiple tests to determine lower and upper ranges of impulse noise reduction Will include two ranges to identify attenuation for passive and active modes
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Noise Reduction Rating
Determining New NRR

• 20 human subjects tested in a simulated
  industrial room
• Subject trained then fits their own earplugs
• Tested with ears open / occluded at 9 frequencies
• Each subject tested 2x
• NRR calculated to be population average

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New NRR (NRsa)
5
4
Number of test subjects
3
2
1
22
24
11
14
18
20
30
28
26
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23
25
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Attenuation
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Noise Reduction Rating
20th Proficient Users
80th Minimally-trained
Current NRR Label Mock-up of New Label
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Noise Reduction Rating

• Noise Reduction Rating

• Rating methods are based upon idealized
  laboratory testing
• NRR has been criticized for being too generous in
  its prediction of noise reduction attenuation
• Studies indicate that while some workers in
  real-world worksites achieve the NRR on the
  package or even greater protection, many workers
  do not
• This has led to a variety of inappropriate
  de-rating methods for hearing protectors
• Contributed too much confusion in knowing
  how to accurately estimate a HPDs
  attenuation

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Noise Reduction Rating

• The New System A Range

• Represents a range of
  expected protection
• Uses a new ANSI-standard lab testing to generate
  the attenuation ratings
• New NRR will provide an indication of how much
  attenuation minimally-trained users the lower
  number versus highly-motivated trained users
  the higher number can be expected to achieve
• For some hearing protectors, the spread of this
  range may be quite significant

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Noise Reduction Rating

• Current vs. Proposed NRR

Current NRR Proposed NRR
Rating A single-number estimate of protection A high/low range of estimated protection
Description of Rating Estimates the 98th percentile of protection obtained by users when properly fitted Estimates the 80th and 20th percentile of protection obtained by users
Test Protocol ANSI S.3.19-1974 Experimenter Fit 10 subjects for earplugs and earmuffs, HPDs fit by experimenter ANSI S12.6-2008 Method A Supervised Subject-Fit 20 subjects for earplugs or 10 subjects for earmuffs, HPDs fit by subject after brief training
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Noise Reduction Rating

• Current vs. Proposed NRR

Current NRR Proposed NRR
Application Intended for use with dBC noise measurements. Requires a 7 dB correction for use with dBA noise measurements. Can be applied directly to dBA noise measurements
De-Rating Various de-rating schemes promulgated by various organizations including OSHA Designed to be used with no required de-rating
Retesting Currently, no retesting of HPDs required Periodic retesting of HPDs required every 5 years
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Noise Reduction Rating

• NRR Labels

• The proposed EPA regulation addresses for the
  first time the rating of non-standard hearing
  protectors, such as Active Noise Reduction ANR
  or level-dependent or impact noise protectors
• Under the old labeling requirements, these
  specialized protectors were rated with a low NRR,
  simply because they were not tested in the higher
  noise ranges where their noise reduction
  capability is activated
• EPA has included these types of hearing
  protectors in its new labeling regulation so that
  purchasers can make informed choices

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Noise Reduction Rating

• How to Apply the New Label

Two-number range displays the estimated
protection achievable by minimally-trained users
80 versus proficient users 20.
A wider range indicates greater variability in
the fit of that HPD. Smaller ranges indicate more
consistency of fit. For example, earmuffs will
usually have a tighter fitting range than
earplugs, and may have a smaller NRR range.
80
20
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Noise Reduction Rating
Factors in Achieving the NRR
1.FIT
2. WEAR TIME
30 dB
A worker who selects an earplug with an NRR of 30
but then removes that HPD for just
effectively reduced his 8-hour NRR to just
22 dB
18 dB
26 dB
24 dB
In noise exposures, small intervals of no
protection quickly void large intervals of
adequate protection.
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Noise Reduction Rating

• What Can I Do Now?

Although the new labeling regulation takes effect
whenever the final rule is published by the EPA,
there are a number of actions you can take now to
prepare your Hearing Conservation Program for the
change.

• Evaluate Noise Spectra
  to determine if
  spectral balance corrections will be necessary
• Update HC Training Program
  on proper fit of hearing protectors.
  Hold a Toolbox Training and hold a refresher
  fit training session.

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Noise Reduction Rating

• What Can I Do Now?

• Evaluate Current HPD Selection to determine
  whether they are appropriate for your noise
  environment. Use the Howard Leight Hearing
  Protector Selector for recommendations.
• Upgrade to One-on-One Training research studies
  confirm that one-on-one training is superior to
  group training

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Noise Reduction Rating

• Earplug Fit Testing

Provides an accurate, real-world picture of your
employees hearing protector effectiveness.

• Identify if your employees are
• Receiving optimal protection
• Require additional training
• Need to try a different earplug style

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Noise Reduction Rating

• Earplug Fit Testing

• As a problem solver
• Derating Schemes
• One-on-One Training
• HPD Selection
• NRR Change

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Noise Reduction Rating

• In-Ear Dosimetry

• As a Problem Solver
• Continuously monitors in noise level at the
  workers ear
• The only true measure of the hazard!

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Reducing Costs of Hearing Loss
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Reducing Costs of Hearing Loss
Sample HL Compensation
Jurisdiction OneEar (Max) Both Ears (Max) Comments
AL 11.7k (53 wks) 35.9 (163 wks) aids, NMER
FL 9k 52k aids, NMER
GA None 150 wks
MS 11.2k 42k aids, NMER
NMER No minimum exposure required
Source AIHA Noise Manual
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Reducing Costs of Hearing Loss
Sample HL Compensation
Jurisdiction One Ear (Max) Both Ears (Max) Comments
NC 37.2k 80k aids
SC 38.7 (80 wks) 80k (165 wks) NMER
TN 38.6k 77.2k aids
DOL -LSA 52 wks 200 wks aids
NMER No minimum exposure required
Source AIHA Noise Manual
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Reducing Costs of Hearing Loss

• Indicators for Hearing Loss

• Standard Threshold Shift
• Temporary Threshold Shift
• Recordable Hearing Loss
• Dosimetry
• In-Ear Dosimetry
• Personal Attenuation Level (PAR)
• Hearing Loss Compensation

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Reducing Costs of Hearing Loss
Lagging Indicators vs. Leading Indicators
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Reducing Costs of Hearing Loss

• Indicators for Hearing Loss

• Standard Threshold Shift
• Temporary Threshold Shift
• Recordable Hearing Loss
• Dosimetry
• In-Ear Dosimetry
• Personal Attenuation Level (PAR)
• Hearing Loss Compensation

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Reducing Costs of Hearing Loss
Fit Testing
In-Ear Dosimetry
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• In-ear dosimetry measures/records workers actual
  noise dose, with and without protection
• Provides real-time monitoring and alerts when
  worker approaches/exceeds safe limits
• Only metric with direct potential to measure and
  prevent further progression of occupational
  hearing loss

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Reducing Costs of Hearing Loss
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Research gt Alcoa Intalco Works
Reducing Costs of Hearing Loss

• Mean Hearing Threshold (2k, 3k, 4kHz) 2000
  2007 (N 46)
• Employees using continuous in-ear dosimetry
  starting in 2005

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Preventive Action After NIHL
Reducing Costs of Hearing Loss
In practice, an OSHA-recordable STS is not a
preventive action It is documentation of a
hearing loss after the fact. How soon will an
employee suffering NIHL be re-fit / re-trained ?
Best case scenario per Hearing
Conservation Amendment
In-ear dosimetry worst case scenario
1 Day
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In-ear dosimetry as a Problem Solver
Reducing Costs of Hearing Loss

• Employees with Documented Noise-Induced Hearing
  Loss or Standard Threshold Shift STS
• Employees At-Risk for NIHL
• Employee Training Sampling
• Dual-Protection/Extreme Noise Exposure
• Engineering Controls

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Reducing Costs of Hearing Loss
Real-Ear Attenuation at Threshold (R.E.A.T.)
Loudness Balance (Real-Ear Attenuation Above
Threshold)
Microphone in Real-Ear (M.I.R.E.)
In-Ear Dosimetry
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Ear plug fit-testing methods
Audiometric FitCheck EARfit VeriPRO
REAT REAT MIRE REAAT
Sound booth Very Quiet Room Quiet Room Anywhere
PAR PAR Derived PAR PAR
Any earplug Any earplug Selected modified earplugs Any earplug
Special training required Special training required Special training required Anyone can perform
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Reducing Costs of Hearing Loss
OSHA Alliance Best Practice Bulletin www.hearing
conservation.org
Additional Information www.howardleight.com
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Field Verification Fit-Testing
"Learned A LOT about best earplugs for me"
"I know how to better fit my earplugs now."
"Recently had threshold shift" "Found better
earplugs"
"I had no idea I was not using my earplugs
correctly."
"Very glad I did the fitting test. Now I know the
correct way to fit my ear plugs.
"I found a more comfortable fit. It was very
beneficial."
"I was amazed with the results after being shown
the proper way to use earplugs.
"Feel like am protected now!"
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Pre and Post-Test
Fit-Testing as a Training Tool

• How well can users predict their attenuation
  after a short fit-testing training session?"

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Pre and Post-Test
Fit-Testing as a Training Tool
Self-Efficacy

• How much noise do you think your earplugs block?

76 (13 of 17) judged
attenuation as HIGHER post-test
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Fit-Testing as a Training Tool
Results

• Data show improved PARs!

Initial RE19 LE22 Final RE29
LE27 Average improvement 7.5 dB
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Pre and Post-Test
Fit-Testing as a Training Tool
Post-Test

• Are you better able to assess the effectiveness
  of your earplugs after VeriPRO fit-testing?
• 1 2 3 4 5
• No Maybe No change Improved Yes

64 (11 of 17) rated
their ability HIGHER post-test
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Pre and Post-Test
Fit-Testing as a Training Tool
Post-Test Ability
Initial Ability
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Pre and Post-Test
Fit-Testing as a Training Tool

• Ability to Predict Noise Reduction

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Reducing Costs of Hearing Loss
Published NRR
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Reducing Costs of Hearing Loss
Personal Factors Gender Age Years
in Noise Ear Canal Size Familiarity
Model of Earplug Program Factors Group
Trainings Personal Trainings
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REDUCING COSTS / CLAIMS
Reducing Costs of Hearing Loss
Published NRR
Trying a second earplug often improves attenuation
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Earplug fit-testing as a Problem Solver
Reducing Costs of Hearing Loss

• Training tool for noise-exposed workers
• Train-the-trainer tool
• Follow-up on significant threshold shifts in
  hearing
• Documentation of HPD adequacy
• Assessment of overall HCP effectiveness
• Match HPD to workers specific noise level
• Selection of appropriate HPDs for new hires
• Benefits per Best Practices Bulletin (OSHA
  Alliance)

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Reducing Costs of Hearing Loss
Tools for HCP Prevention Metrics

• PROS
• Estimate Measure
• NRR obsolete
• Fulfills OSHA compliance
• Eliminates need for de-ratings
• Medico-legal cases
• Delineates non-occupational
• Eliminates double protection
• Provides employee feedback
• (HPD Inventory control)

• CONS
• Cost
• Time Investment
• Not standardized

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Reducing Costs of Hearing Loss
Off-job On-job STS
Off-job On-job STS
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0 dB
0 dB
33 dB
EAR 1
EAR 2
EAR 3
How much protection?
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Good Fit vs Bad Fit
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Training Motivation
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Training Motivation
Personalize Hearing Loss

• Show, Dont Tell
• Provide copy of annual audiogram to worker
• Use personal examples to demonstrate consequences
  of hearing loss
• Ask questions
• What is your favorite sound?
• What sound would you miss
  the most if you couldnt hear?
• What sounds connect you to
  people and your environment?

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Training Motivation
Demonstrate Future Risk

• Training Materials
• www.hearforever.org
• www.hearingconservation.org
• atl.grc.nasa.gov/HearingConservation/Resources/ind
  ex.html
• www.cdc.gov/niosh/topics/noise
• www.dangerousdecibels.org

www.hearforever.org/vpppaivconference2010
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Training Motivation

• Send Clear Message On Off Job

• HC Part of Everyday Life
• Include recreational hearing conservation in
  annual training
• Provide extra HPDs for home use
• Promote Hearing Conservation at company/family
  events

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Training Motivation
Remove Barriers to HPD Use

• Make HPDs Available
• Highlight where to find HPDs in annual training
• Make sure HPDs are well-stocked and accessible
• Include group of workers in selection process for
  increased acceptance
• Offer wide variety to match comfort, job
  requirements

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Training Motivation

• Hearing Loss Due To
• Noise Exposure Is
• Painless
• Permanent
• Progressive

and very Preventable!