hearing conservation theresa y. schulz, phd. lt. col. usaf (ret.)
DESCRIPTION
Hearing Conservation Theresa Y. Schulz, PhD. Lt. Col. USAF (ret.). Topics. Noise And Acoustics. Motivating Workers. Noise Reduction. Reducing Costs for Hearing Loss. Noise + Acoustics. Is Permanent + 100% Preventable. Noise-Induced Hearing Loss Causes no pain Causes no visible trauma - PowerPoint PPT PresentationTRANSCRIPT
Hearing Conservation
Theresa 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 trauma
Leaves no visible scars
Is unnoticeable in its earliest stages
Accumulates 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 DOSIMETER
Sound “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 CyanideNOISE
NOISE AND ACOUSTICS ~ Hierarchy of ControlsNoise + Acoustics
Ototoxic Chemicals
Confirmed Ototoxics
Ethyl Benzene
Lead and inorganic compounds (as Pb)
Styrene
Toluene
Trichloroethylene
PossibleCarbon disulfide
n-Hexane
Xylene
How We Hear
How We Hear
The Auditory System
Acoustical
Mechanical
Hydraulic
Chem/Elec
How We Hear
High Frequency Sounds of Speech
STH
SHF
H K
T PCH
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.
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
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
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
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
Real-World Attenuation ≠ 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
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
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
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 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
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 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
Sample HL Compensation*
*Source: AIHA Noise Manual
*NMER= No minimum exposure required
Reducing Costs of Hearing Loss
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
Sample HL Compensation*
*Source: AIHA Noise Manual
*NMER= No minimum exposure required
Indicators for Hearing Loss
Reducing Costs of Hearing Loss
• Standard Threshold Shift• Temporary Threshold Shift• Recordable Hearing Loss• Dosimetry• In-Ear Dosimetry• Personal Attenuation Level (PAR)• Hearing Loss Compensation
Lagging Indicators vs. Leading Indicators
Reducing Costs of Hearing Loss
Indicators for Hearing Loss
Reducing Costs of Hearing Loss
• Standard Threshold Shift• Temporary Threshold Shift• Recordable Hearing Loss• Dosimetry• In-Ear Dosimetry• Personal Attenuation Level (PAR)• Hearing Loss Compensation
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
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.
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
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 boothVery Quiet
RoomQuiet 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
"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."
“How well can users predict their attenuation after a short fit-testing
training session?"
Pre and Post-TestFit-Testing as a Training Tool
“How much noise do you think your earplugs block?”
Pre and Post-TestFit-Testing as a Training Tool
Self-Efficacy
76% (13 of 17) judged attenuation as HIGHER post-test
Fit-Testing as a Training Tool
Data show improved PARs!
Results
Initial RE=19 LE=22Final RE=29 LE=27
Average improvement 7.5 dB
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
Pre and Post-TestFit-Testing as a Training Tool
Post-Test
64% (11 of 17) rated their ability
HIGHER post-test
Initial Ability
Don't knowhow
Not good
I do OK
Pretty good
Expert Fitter
Post-Test Ability
Pretty good
I do OKExpert
I do OK
Pretty good
ExpertN
ot
go
od
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)
Nu
mb
er
of
Ea
rs
(Eac
h s
ub
ject
est
imat
ed a
tten
. fo
r ea
ch e
ar)
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
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
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
Off-job + On-job = STSOff-job + On-job = STS
Reducing Costs of Hearing Loss
How much protection?
0 dB 0 dB33 dB
EAR #1EAR #2
EAR #3
-10
12
5
25
0
50
0
10
00
20
00
31
50
40
00
63
00
80
00
Frequency in Hz
90
80
70
60
50
40
30
20
10
0
Att
enu
atio
n in
dB
Max Poor FitNRR = 0dB
Max Good FitNRR = 33dB
Good Fit vs Bad Fit
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/vpppaivconference2010
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
Hearing Loss Due To Noise Exposure Is …
PainlessPermanentProgressive
… and very Preventable!
Training + Motivation