Hearing ConservationTheresa Y. Schulz, PhD.Lt. Col. USAF (ret.)
Topics
Noise And Acoustics
Motivating Workers
Noise Reduction
Reducing Costs for Hearing Loss
Noise + Acoustics
Noise-Induced Hearing LossCauses no pain
Causes no visible traumaLeaves no visible scars
Is unnoticeable in its earliest stagesAccumulates with each overexposure
Takes years to notice a change
Is Permanent + 100% Preventable
Noise + Acoustics
Noise-induced hearing loss is the most common permanent and preventable occupational injury in the world.
World Health Organization
Noise + Acoustics
Worker’s 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)
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)
Noise + Acoustics
Non-Occupational Occupational
Noise + Acoustics
Noise Measurement Devices
SOUND LEVEL METER
Sound is measured immediately in a
specific area
PERSONAL DOSIMETERSound “averaged”
throughout day for sample employee/job
IN-EAR DOSIMETER
Collects personal noise dose – the only real
measure of risk
NOISE AND ACOUSTICS ~ Hierarchy of Controls
ADMINISTRATIVE CONTROLS
• Rotate Workers
• Extended Breaks
•2nd/3rd Shift
ENGINEERING CONTROLS
• Buy Quiet
• Vibration Pads
• Enclosures
• Barriers
• Isolation
PERSONAL PROTECTIVE EQUIPMENT
Noise + Acoustics - Hierarchy of Controls
• Ototoxic by themselves• Synergistic effect with noise• Large differences in sensitivity• Recommend: increased frequency
of audiometric testing
Synergistic Ototoxics• Carbon Monoxide• Hydrogen Cyanide
NOISE
NOISE AND ACOUSTICS ~ Hierarchy of ControlsNoise + Acoustics
Ototoxic ChemicalsConfirmed Ototoxics
Ethyl BenzeneLead and inorganic
compounds (as Pb)StyreneToluene
Trichloroethylene
PossibleCarbon disulfide
n-HexaneXylene
Noise Reduction Rating(NRR)
Hearing Protection Selection
ComfortNoise ReductionSizeCommunicationJob RequirementsHygieneUse with Other PPE
Hearing Protection Selection Factors• The right hearing
protector should feel comfortable
• One protector may not satisfy all workers
• Offer a variety of earplugs or earmuffs to meet varying worker needs and preferences
• Selecting HPDs with suitable attenuation for noise environment
• Avoid overprotection in marginal noise environments
• Consider banded earplugs for intermittent noise or electronic earmuffs for impact noise.
• Every ear canal has its own shape and size
• Ensure proper fit with variety of earplug sizes and shapes
• Sized multiple-use earplugs
• Low-pressure foam earplugs for smaller ear canals
• Keep workers connected to their environment
• Uniform attenuation allows speech/signals to be hear more naturally
• Sound amplification earmuffs for workers with hearing impairment
• Consider job requirements in HPD selection
• Detectable earplugs for process industries
• Hi-visibility earmuffs for dark/high traffic areas
• Dielectric HPDs for electrical environments
• Proper care and maintenance can extend life and performance of HPDs
• Examine and clean all multiple-use earplugs daily
• Clean and replace ear cushions on earmuffs every 4-6 months
• Select HPDs that can work with other PPE without compromise
• Cap-mounted earmuffs for hard hats
• Multiple-position earmuffs for full-brim hard hats
• Ultraslim neckband earmuffs with welding shields
How much noise is reaching the ear of the worker ?
That is completely unknown …
Noise Level = 100 dB
Noise Reduction Rating = 30 dB
(55 – 104 dB)
Noise Reduction Rating
How much protection?
0 dB 0 dB33 dB
EAR #1EAR #2
EAR #3
-10
125
250
500
1000
2000
3150
4000
6300
8000
Frequency in Hz
90
80
70
60
50
40
30
20
10
0
Atte
nuat
ion
in d
B
Max Poor FitNRR = 0dB
Max Good FitNRR = 33dB
Good Fit vs Bad FitFitting Tips
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.
A test subject in the Howard Leight Acoustical Lab, San Diego, CA, accredited by the National Voluntary Laboratory Accreditation Program (NVLAP)
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
NRR
Attenuation
Num
ber o
f tes
t sub
ject
s
14 18
1
2
3
4
1920 22 2423 25
28 30 322627
5
Noise Reduction Rating – Determining an NRR
NRR
From Kevin Michael, PhD and Cindy Bloyer “Hearing Protector Attenuation Measurement on the End-User”
192 users of a flanged reusable earplug ~ 27 NRR
Retraining and refitting
resulted in an average
14 dB improvement for this group
Real user
attenuation
<0 to 38 dB
302010
0
-10
Atte
nuat
ion
in d
B
40
50NRR = 27 Multiple-Use Earplug
Real-World Attenuation ≠ NRRNoise Reduction Rating
NIOSH
EarmuffsNRR – 25%
Formable EarplugsNRR – 50%
All Other EarplugsNRR – 70%
OSHA
NRR ÷ 2(feasibility of engineering
controls)
CSA
ClassA up to 100B up to 95C up to 90
Noise Reduction Rating
De-Rating Methods
Fit Test
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
• 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
Noise Reduction Rating
Determining New NRR
New NRR (NRsa)
Attenuation
Num
ber o
f tes
t sub
ject
s
11 14 18
1
2
3
4
1920 22 2423 25 27
30 33
5
20% achieved > 26 dB80% achieved > 20 dB
2826
Current NRR Label Mock-up of New Label
80th %Minimally-
trained
20th %Proficient
Users
Noise Reduction Rating
Noise Reduction Rating
How to Apply the New LabelTwo-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%
1.FIT 2. WEAR TIMEA worker who selects an earplug with an NRR of 30
effectively reduced his 8-hour NRR to just …
but then removes that HPD for just …
30 dB
5 min 10 min 30 min15 min
26 dB 24 dB 22 dB 18 dB
In noise exposures, small intervals of no protection quickly void large intervals of adequate protection.
Noise Reduction Rating
Factors in Achieving the NRR
Noise Reduction Rating
What Can I Do Now?
• 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.
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.
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
Noise Reduction Rating
Earplug Fit TestingProvides 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
Noise Reduction Rating
Earplug Fit TestingAs a problem solver:• Derating Schemes• One-on-One Training• HPD Selection• NRR Change
Noise Reduction Rating
In-Ear DosimetryAs a Problem Solver• Continuously monitors
in noise level at the workers ear
• The only true measure of the hazard!
Reducing Costs of Hearing Loss
Reducing Costs of Hearing Loss
Jurisdiction One Ear(Max)
Both Ears (Max)
Comments
NC $37.2k $80k + aidsSC $38.7
(80 wks)$80k (165 wks)
*NMER
TN $38.6k $77.2k + aidsDOL -LSA 52 wks 200 wks + aids
Sample HL Compensation*
*Source: AIHA Noise Manual
*NMER= No minimum exposure required
Indicators for Hearing Loss:• Standard Threshold Shift• Temporary Threshold Shift• Recordable Hearing Loss• Dosimetry• In-ear Dosimetry• Personal Attenuation Level (PAR)• Hearing Loss Compensation
Reducing Costs of Hearing Loss
Lagging Indicators vs. Leading Indicators
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
Reducing Costs of Hearing Loss
Fit Testing In-Ear Dosimetry
Reducing Costs of Hearing Loss
In-ear dosimetry measures/records worker’s 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
Reducing Costs of Hearing Loss
Research > Alcoa Intalco Works
• Mean Hearing Threshold (2k, 3k, 4kHz): 2000 – 2007 (N = 46)
• Employees using continuous in-ear dosimetry starting in 2005
Mean hearing threshold (2,3, and 4 kHz) Employees using continuous ESP starting in 2005
2000 - 2007 (N=46)
0
5
10
15
20
25
30
35
40
45
50
2000 2001 2002 2003 2004 2005 2006 2007
Year of test
Mea
n HTL
3,4,6kH
z
ESP Introduced trend line
Reducing Costs of Hearing Loss
Preventive Action After NIHLIn 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
0 2 4 6 8 10 12 14 16 Months
• Audiometric test • Retest • Notification
Reducing Costs of Hearing Loss
In-ear dosimetry “worst case” scenario … 1 Day
In-ear dosimetry as a Problem Solver
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
Reducing Costs of Hearing Loss
In-ear monitoring as a Problem Solver
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
Reducing Costs of Hearing Loss
Audiometric FitCheck EARfit VeriPRO
REAT REAT MIRE REAAT
Sound booth Very Quiet Room Quiet Room Anywhere
PAR PAR Derived PAR PAR
Any earplug Any earplugSelected modified earplugs
Any earplug
Special training required
Special training required
Special training required
Anyone can perform
Ear plug fit-testing methods
OSHA Alliance: Best Practice Bulletin
www.hearingconservation.org
Additional Information
www.howardleight.com
Reducing Costs of Hearing Loss
“How well can users predict their attenuation after a short fit-testing
training session?"
Pre and Post-TestFit-Testing as a Training Tool
Pre and Post-TestFit-Testing as a Training Tool
Ability to Predict Noise Reduction
0
2
4
6
8
10
12
14
16
18
20
Within 5 dB category
+/- 7.5 dB(one Category off)
+/- 12.5 dB (2 categories off)
Num
ber o
f Ear
s (E
ach
subj
ect e
stim
ated
atte
n. fo
r eac
h ea
r)
56%
32%
12%
Variation from Published NRR
-30
-25
-20
-15
-10
-5
0
5
10
0 10 20 30 40 50 60 70 80 90 100
Workers
Diffe
renc
e in
dB Published
NRR
Distribution of PARs
0
2
4
6
8
10
12
Variation from Published NRR
Wor
kers
Reducing Costs of Hearing Loss
Distribution of PARs
0
2
4
6
8
10
12
Variation from Published NRR
Wor
kers
Personal Factors Gender Age Years in Noise Ear Canal Size Familiarity Model of Earplug
Program Factors # Group Trainings # Personal Trainings
Reducing Costs of Hearing Loss
Difference on 2nd / 3rd Test
-30
-25
-20
-15
-10
-5
0
5
10
Subjects
Varia
tion
from
NR
R Published NRR
Trying a second earplug often improves attenuation
REDUCING COSTS / CLAIMSReducing Costs of Hearing Loss
Earplug fit-testing as a Problem Solver
• 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 worker’s specific noise level• Selection of appropriate HPDs for new hires
• Benefits per Best Practices Bulletin (OSHA Alliance)
Reducing Costs of Hearing Loss
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
Reducing Costs of Hearing Loss
Tools for HCP Prevention Metrics
Training + Motivation
Common Objections to Wearing HPDs
“Hearing protectors are uncomfortable to wear.”
“I don’t need them! I am used to the noise.”
“I already lost some of my hearing, so why should I wear them?”
“I can’t hear my co-workers if I wear them.”
“I can always get fit with a hearing aid.”
“Can I hurt my eardrums if I insert an earplug to deeply.”
“My machine sounds different.”
“Won’t I get an ear infection?”
Training + Motivation
Show, Don’t 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 couldn’t hear?• What sounds connect you to people
and your environment?
Training + Motivation
Personalize Hearing Loss
Training + Motivation
Training Materials• www.hearforever.org• www.hearingconservation.org• atl.grc.nasa.gov/
HearingConservation/Resources/index.html
• www.cdc.gov/niosh/topics/noise• www.dangerousdecibels.org
Demonstrate Future Risk
www.hearforever.org/ILCA2010
Training + Motivation
Send Clear Message On + Off JobHC Part of Everyday Life• Include recreational hearing
conservation in annual training• Provide extra HPDs for home
use• Promote Hearing Conservation
at company/family events
Training + Motivation
Remove Barriers to HPD UseMake 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
Listen Up!Hear Forever
Make Hearing Conservation a Part of
Your Everyday Life
HearForever.org