Reducingthe Risk of Noise-Induced Hearing LossThrough Best Practices
Theresa Y. Schulz, PhD, LtCol, USAF (ret.)
Topics
Noise And Acoustics
Motivating Workers
Noise Reduction
Reducing Costs for Hearing Loss
Noise + Acoustics
Noise + Acoustics
Non-Occupational Occupational
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 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
OSHA Update: Feasibility• Oct 2010 – Intent to change
interpretation of “feasibility”• Must use engineering controls that are capable
of being done
• First extended comment period then withdrew that interpretation• Proposing public hearings and asking NIOSH
and professionals for input
Noise + Acoustics - OSHA Update
Noise Reduction Rating(NRR)
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
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.
• 10 human subjects tested in
a simulated industrial 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)
Noise Reduction Rating – Determining an NRR
NRR
Attenuation
Num
ber
of t
est
subj
ects
14 18
1
2
3
4
1920 22 24
23 2528 30 3226
27
5
Noise Reduction Rating – Determining an NRR
NRR
NIOSH
EarmuffsNRR – 25%
Formable EarplugsNRR – 50%
All Other EarplugsNRR – 70%
OSHA
NRR ÷ 2
(feasibility of engineering
controls)
CSA
Class
A up to 100
B up to 95
C up to 90
Noise Reduction Rating
De-Rating Methods
Fit Test
From Kevin Michael, PhD and Cindy Bloyer “Hearing Protector Attenuation Measurement on the End-User”
Noise Reduction Rating –
Real-World Attenuation ≠ NRR
192 users of a flanged reusable earplug ~ 27 NRR
Retraining and refitting
resulted in an average
14 dB improvement for this group
Real user
attenuatio
n
<0 to 38 dB
30
20
10
0
-10
Att
enu
atio
n i
n d
B
40
50NRR = 27 Multiple-Use Earplug
1.FIT 2. WEAR TIME
A 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
Biggest Factors in Achieving NRR
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
Noise Reduction Rating
Current NRR Label Mock-up of New Label
80th %
Minimally-trained
20th %
Proficient Users
Noise Reduction Rating
Three New LabelsLABEL 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
• 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
of t
est
subj
ects
11 14 18
1
2
3
4
1920 22 24
23 25 2730 33
5
20% achieved > 26 dB80% achieved > 20 dB
2826
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%
Noise Reduction Rating
What Can I Do Now?
• Evaluate Noise Spectra to determine if spectral balance corrections will be necessary
• Upgrade to One-on-one Training research studies confirm that one-on-one training is superior to group training
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.
NRSG table B = L C - L A -1 2 6 13
x = 20% 36.7 34.4 33.5 31.9x = 80% 29.8 25.5 24.1 22.9
ProtectionPerformance
0
5
10
15
20
25
30
35
40
45
50
-2 0 2 4 6 8 10 12 14 16
Noise Spectral Balance, B = L C - L A (dB)
Es
tim
ate
d N
ois
e L
ev
el R
ed
uc
tio
n, d
B
possible for a few motivated proficientusers to achieve or exceedpossible for most individually trainedusers to achieve or exceed
NRSG
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.
• Update Hearing Conservation Training Program on proper fit of hearing protectors. Hold a “Toolbox Training” and hold a refresher fit training session.
Noise Reduction Rating
What Can I Do Now?Use VeriPRO® fit testing
• Train how to properly fit HPDs• Select appropriate HPDs• Document adequate protection
Use QuietDose™
• In-ear dosimetry measures and documents the noise dose employee is exposed to during their work shift
Reducing Costs of Hearing Loss
Reducing Costs of Hearing Loss
2000-2010 12.4
0.3
10.5
26
17.9
0.30.4
10.2
22
0.1 Dermititis
Radiation
Occ Disease-Injury
Loss of Hearing
Contagious Disease
Cancer
AIDS
Mental Stress
Cumulative Injury
Other
Source: Texas Department of Insurance
Workers Compensation Claims Data
Reducing Costs of Hearing Loss
2010 18.7
11.6
28.8
15.3
13.1
11.80.6
Dermititis
Occ Disease-Injury
Loss of Hearing
Contagious Disease
Mental Stress
Cumulative Injury
Other
Source: Texas Department of Insurance
Workers Compensation Claims Data
Fit Testing In-Ear Dosimetry
Reducing Costs of Hearing Loss
Noise Reduction Rating
Earplug Fit TestingProvides an accurate, real-world picture of your employees’ hearing protector effectiveness.
ID if your employees are:
• Getting the right protection• Need additional training• Need different earplug
Field Verification – Fit-Testing
As a problem solver:• Derating Schemes• One-on-One
Training• HPD Selection• NRR Change
Real-Ear
Attenuation at Threshold
(R.E.A.T.)
Field Verification – Fit-Testing
Loudness Balance
(Real-Ear Attenuation Above
Threshold)
Field Verification – Fit-Testing
Microphone in Real-Ear
(M.I.R.E.)
Field Verification – Fit-Testing
In-Ear Dosimetry
Field Verification – Fit-Testing
Microphone in Real-Ear
(M.I.R.E.)
Audiometric, IntregaFit,* 1,2
MultiFit
FitCheck*HPDWellFit
QuickFit 1
EARfit*SafetyMeter*
VeriPRO*
REAT, 1One freq REAT, 1One freq MIRE Loudness Balance
Sound booth Quiet Room Anywhere Anywhere
PAR PAR Derived PAR PAR
Any earplug Any earplug Modified or custom earplugs
Any earplug
COHC2Training included
COHC Training provided Training included
Field Verification – Fit-Testing
* Commercially available
OSHA Alliance: Best Practice Bulletin www.hearingconservation.org
Additional Information www.hearforever.org
Reducing Costs of Hearing Loss
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
Dif
fere
nce
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
Va
ria
tio
n f
rom
NR
R Published NRR
Trying a second earplug often improves attenuation
REDUCING COSTS / CLAIMSReducing Costs of Hearing Loss
“How well can users predict their attenuation after a short fit-testing
training session?"
Reducing Costs of Hearing Loss
Fitting Tips
Ability to Predict Noise Reduction
Accuracy of estimate
(75% were within one category of actual PAR)
0
10
20
30
40
50
60
70
80
90
100
Same Category One off Two off Three off Four off
28%
47%
14%
Reducing Costs of Hearing Loss
"I know how to better fit my
earplugs now."
"I was amazed with the results
after being shown the proper way to
use earplugs.
"Learned A LOT about best
earplugs for me"
"I found a more comfortable fit. It
was very beneficial."
"Very glad I did the fitting test.
Now I know the correct way to fit my ear plugs.”
"Recently had threshold shift" "Found better
earplugs"
Field Verification – Fit-Testing
"Feel like am protected now!"
"I had no idea I was not using my
earplugs correctly."
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 2005Mean 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
Mean
HTL
3,4,6
kHz
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.
0 2 4 6 8 10 12 14 16
Months
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 • Audiometric test • Retest • Notification
Reducing Costs of Hearing Loss
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• http://adl.grc.nasa.gov • www.cdc.gov/niosh/topics/noise• www.dangerousdecibels.org
www.hearforever.org/TXA&M
Demonstrate Future Risk
Training + Motivation
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
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
Make Hearing Conservation Part of Your
Everyday Life
Download today’s presentation at
www.hearforever.org/TXAM
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