Hearing
Conservation
Metrics
Theresa Y. Schulz, PhD.
Lt. Col. USAF (ret.)
Topics
Leading vs Lagging Indicators
Audiometric Testing
Earplug Fit Testing
Continuous Monitoring
Motivating Workers
Hearing Conservation Metrics
Indicators for Hearing Loss:
•
•
•
•
•
•
•
Standard Threshold Shift
Temporary Threshold Shift
Recordable Hearing Loss
Dosimetry
In-ear Dosimetry
Personal Attenuation Level (PAR)
Hearing Loss Compensation
Hearing Conservation Metrics
Lagging Indicators vs. Leading Indicators
Hearing Conservation Metrics
Indicators for Hearing Loss:
•
•
•
•
•
•
•
Standard Threshold Shift
Temporary Threshold Shift
Recordable Hearing Loss
Dosimetry
In-ear Dosimetry
Personal Attenuation Level (PAR)
Hearing Loss Compensation
Hazardous
Hearing
Conservation
Noise
Metrics
Ototoxic Chemicals
•
•
•
•
Ototoxic by themselves
Synergistic effect with noise
Large differences in sensitivity
Recommend: increased frequency
of audiometric testing
Confirmed Ototoxics
Ethyl Benzene
Lead and inorganic
compounds (as Pb)
Styrene
Toluene
Trichloroethylene
Synergistic Ototoxics
NOISE
• Carbon Monoxide
Possible
Carbon disulfide
• Hydrogen Cyanide
n-Hexane
Xylene
Hearing Conservation Metrics
Conduct
audiometric
testing during
the work shift
•
TTS vs PTS
Hearing Conservation Metrics
Percentage of exposed workers with STS/year
Affected by: Duration of employment,
Demographics
Recent analysis of large database: 1980-present:
1.5% per year
• In non-noise exposed employees: roughly 1%
• Current corporate policy: 1% rate per year, or
equivalent to internal non-occupationally exposed
population- ?Best Practice?
Hearing Conservation Metrics
Use Early Warning Flags
• Identify individuals at risk for significant loss in
future
• Identify problem jobs/work areas
Hearing Conservation Metrics
Age-Corrected STS Represents Significant
Hearing Loss!
Study of industrial workers:
• 52% of OSHA recordable STS cases
(new definition) had compensable
hearing impairment (AAOHNS
criteria)!
• Median time to develop recordable
STS: approx. 10 years*
* Rabinowitz et al. Impact of OSHA rule: recording hearing loss JOEM 2003
Hearing Conservation Metrics
So…..
Age-Corrected
STS
is NOT
an “Early Flag”!
Hearing Conservation Metrics
Candidate “Early flags” (indicators)
• 10 dB shift from baseline in avg 2,3,4KHz (not
age-corrected)
• 15dB shift from baseline (at least one
frequency 1-6KHz) (Department of Defense)
• 15dB shift from baseline (at least one
frequency 1-6KHz) confirmed on second test
(NIOSH)
• Others:
• 7dB shift 2,3,4KHz?
• 5dB shift 2,3,4KHz?
Hearing Conservation Metrics
Compensable Hearing Impairment:
• How many workers have absolute
loss of >25dB avg 500,1K,2K,3KHz?
• Useful for workers comp liability as well
as need for workplace accommodation,
etc.
Noise Levels- trends over time for
individual departments.
Hearing Conservation Metrics
Fit Testing
In-Ear Dosimetry
Earplug Fit Testing
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)
Earplug Fit Testing
0 dB
0 dB
>33 dB
EAR #1
EAR #2
EAR #3
How much protection?
Earplug Fit Testing
Good Fit vs Bad Fit
90
Attenuation in dB
80
70
60
50
40
30
20
10
0
-10
Max Good Fit
NRR = 33dB
Max Poor Fit
NRR = 0dB
8000
6300
4000
3150
2000
1000
500
250
125
Frequency in Hz
Earplug Fit Testing
Loudness Balance
(Real-Ear Attenuation Above Threshold)
Test Sequence
Part 1:
Part 2:
Part 3:
Both ears
unoccluded
Right ear
occluded
Both ears
occluded
This sets the baseline
level for each ear, and
measures any
asymmetry.
Attenuation for the
right ear is measured.
Attenuation for the
left ear is measured.
Result ~ Personal Attenuation Rating (PAR)
1. Measures real-world attenuation of any earplug
2. Fulfills requirement to ‘ensure proper fitting’ of
earplugs and evaluate their attenuation
3. On-screen training videos
4. Administered anywhere, quiet room not required
5. Protected exposure level and safe exposure
level calculated
Hearing Conservation Metrics
OSHA Alliance: Best Practice Bulletin
www.hearingconservation.org
Additional Information
www.hearforever.org
Noise Reduction
Hearing
Conservation
Rating
Metrics
Attenuation in dB
Real-World Attenuation
≠ NRR
192 users of a flanged reusable earplug ~ 27 NRR
50
NRR = 27 Multiple-Use Earplug
40
30
20
10
0
-10
From Kevin Michael, PhD and Cindy Bloyer “Hearing Protector Attenuation Measurement on the End-User”
Retraining
and refitting
resulted in an
average
14 dB
improvement
for this group
Hearing Conservation Metrics
Variation from Published NRR
10
Published
NRR
0
-5
-10
-15
-20
Distribution of PARs
-25
12
-30
0
10
20
30
40
50
10 60
Workers
Workers
Difference in dB
5
70
80
90
100
8
6
4
2
0
-30
-25
-20
-15
-10
-5
0
5
10
Variation from Published NRR
15
20
25
30
Hearing Conservation Metrics
Personal Factors
Gender
Age
Distribution of PARs
12
Years in Noise
Workers
10
Ear Canal Size
8
6
Familiarity
4
Model of Earplug
2
0
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
Program Factors
Variation from Published NRR
# Group Trainings
# Personal Trainings
REDUCING
Hearing
Conservation
COSTS / CLAIMS
Metrics
Difference on 2nd / 3rd Test
10
Variation from NRR
5
Published
NRR
0
-5
-10
-15
-20
-25
-30
Subjects
Trying a second earplug often
improves attenuation
ReducingConservation
Hearing
Costs of Hearing
Metrics
Loss
“How well can users predict their
attenuation after a short fit-testing
training session?"
Fitting Tips
Reducing
Hearing
Conservation
Costs of Hearing
Metrics
Loss
Ability to Predict Noise Reduction
100
Accuracy of estimate
(75% were within one category of actual PAR)
47%
90
80
70
60
28%
50
14%
40
30
20
10
0
Same Category
One off
Two off
Three off
Four off
Hearing Conservation Metrics
Personal Attenuation Rating (PAR)
90
Before
80
# of Workers
70
60
50
40
30
20
10
0
0
5
9
14
19
23
28
PAR (in dBA)
33
37
42
>42
After
Hearing Conservation Metrics
70
Number of Workers
60
Initial
50
Final
40
30
20
10
0
<70
70-74
75-79
80-84
Protected Exposure Level (PrEL)
84-89
90+
Hearing Conservation Metrics
Protected Exposure Levels (PrEL)
Initial PrEL
Number of Individuals
9
Final PrEL
8
7
6
5
4
3
2
1
0
< 70
71-75
76-80
81-85
PrEL Range (in dB)
86-90
>90
Reducing
Hearing
Field Verification
Conservation
Costs of–Hearing
Fit-Testing
Metrics
Loss
"I know how to
better fit my
earplugs now."
"I found a more
comfortable fit. It
was very
beneficial."
"Feel like am
protected now!"
"Learned A LOT
about best
earplugs for me"
"I had no idea I was
not using my
earplugs correctly."
"I was amazed
with the results
after being shown
the proper way to
use earplugs.
"Recently had
threshold shift"
"Found better
earplugs"
"Very glad I did
the fitting test.
Now I know the
correct way to fit
my ear plugs.”
Hearing Conservation Metrics
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)
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
Continuous
Monitoring
of Hearing
/ In-ear-dosimetry
Loss
ReducingConservation
Hearing
Continuous
Costs
Monitoring
of Hearing
Metrics
/ In-ear-dosimetry
Loss
Mean hearing
threshold
and 4 kHz)2000 – 2007 (N = 46)
• Mean Hearing Threshold
(2k,
3k, (2,3,
4kHz):
Employees using continuous ESP starting in 2005
• Employees using continuous in-ear dosimetry starting in 2005
2000 - 2007 (N=46)
50
ESP Introduced
Mean HTL 3,4,6kHz
45
trend line
40
35
30
25
20
15
10
5
0
2000
2001
2002
2003
2004
Year of test
2005
2006
2007
In-ear dosimetry
Reducing
Hearing
Conservation
Costs of
asHearing
a Problem
Metrics
Loss
Solver
In-ear monitoring 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
Hearing Conservation Metrics
Preventive Action After NIHL
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
• Retest
• Audiometric test
0
2
4
6
8
10
Months
12
14
• Notification
16
ReducingConservation
Hearing
Costs of Hearing
Metrics
Loss
Tools for HCP Prevention Metrics
PROS
• Estimate
CONS
Measure
• Cost
• NRR obsolete
• Time Investment
• Fulfills OSHA compliance
• Not standardized
• Eliminates need for de-ratings
• Medico-legal cases
• Delineates non-occupational
• Eliminates double protection
• Provides employee feedback
• (HPD Inventory control)
Training +
Motivation
Training + Motivation
Common Objections to Wearing HPDs
“I already lost some of my hearing, “Won’t I get an ear
so why should I wear them?”
infection?”
“Hearing protectors “I don’t need them!
are uncomfortable I am used to the
to wear.”
noise.”
“I can’t hear my
co-workers if I
wear them.”
“Can I hurt my eardrums if I insert an
earplug to deeply.”
“I can always
get fit with a
hearing aid.”
“My machine sounds different.”
Training + Motivation
Personalize Hearing Loss
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
Demonstrate Future Risk
Training Materials
• www.hearforever.org
• www.hearingconservation.org
• atl.grc.nasa.gov/HearingConserv
ation/Resources/index.html
• www.cdc.gov/niosh/topics/noise
• www.dangerousdecibels.org
www.hearforever.org/honaaohn
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 wellstocked 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
www.hearforever.org/honaaohn
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Hearing Conservation Metrics Theresa Y. Schulz, PhD. Lt. Col