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

Hearing ConservationMetrics

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

Topics

Leading vs Lagging Indicators

Motivating Workers

Audiometric Testing

Earplug Fit Testing

Continuous Monitoring

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


Indicators for Hearing Loss:• Standard Threshold Shift

• Temporary Threshold Shift

• Recordable Hearing Loss

• Dosimetry

• In-ear Dosimetry

• Personal Attenuation Level (PAR)

• Hearing Loss Compensation


• Ototoxic by themselves• Synergistic effect with noise• Large differences in sensitivity• Recommend: increased frequency

of audiometric testing

Synergistic Ototoxics

• Carbon Monoxide

• Hydrogen CyanideNOISE

Hazardous Noise

Ototoxic Chemicals

Confirmed Ototoxics

Ethyl Benzene

Lead and inorganic compounds (as Pb)

Styrene

Toluene

Trichloroethylene

PossibleCarbon disulfide

n-Hexane

Xylene


Conduct audiometric testing during the work shift

• TTS vs PTS


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?


Use Early Warning Flags• Identify individuals at risk for significant loss in

future• Identify problem jobs/work areas


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

So…..

Age-Corrected STS

is NOT

an “Early Flag”!


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?


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.


Fit Testing In-Ear Dosimetry


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)

Earplug Fit Testing

How much protection?

0 dB 0 dB>33 dB

EAR #1EAR #2

EAR #3

Earplug Fit Testing

-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

Earplug Fit Testing

Loudness Balance

(Real-Ear Attenuation Above Threshold)

Earplug Fit Testing

Test Sequence

Part 1:Both ears

unoccludedThis sets the baseline level for each ear, and measures any asymmetry.

Part 2:Right ear occluded

Attenuation for the right ear is measured.

Part 3:Both ears occluded

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

OSHA Alliance: Best Practice Bulletin www.hearingconservation.org

Additional Information www.hearforever.org


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

Noise Reduction RatingHearing Conservation Metrics

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


Wor

kers


Distribution of PARs

0

2

4

6

8

10

12


Wor

kers

Personal Factors Gender

Age

Years in Noise

Ear Canal Size

Familiarity

Model of Earplug

Program Factors # Group Trainings

# Personal Trainings


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 / CLAIMSHearing Conservation Metrics

“How well can users predict their attenuation after a short fit-testing

training session?"

Reducing Costs of Hearing LossHearing Conservation Metrics

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%


Personal Attenuation Rating (PAR)

0

10

20

30

40

50

60

70

80

90

0 5 9 14 19 23 28 33 37 42 >42

PAR (in dBA)

# of

Wor

kers

Before After


0

10

20

30

40

50

60

70

<70 70-74 75-79 80-84 84-89 90+

Protected Exposure Level (PrEL)

Nu

mb

er o

f W

ork

ers Initial Final


Protected Exposure Levels (PrEL)

0

1

2

3

4

5

6

7

8

9

< 70 71-75 76-80 81-85 86-90 >90

PrEL Range (in dB)

Nu

mb

er o

f In

div

idu

als

Initial PrEL Final PrEL


"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."


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 of Hearing LossContinuous Monitoring / In-ear-dosimetry

• 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 LossHearing Conservation MetricsContinuous Monitoring / In-ear-dosimetry

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


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

In-ear dosimetry “worst case” scenario …

1 Day


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?”


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?


Personalize Hearing Loss


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/honaaohn


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


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

www.hearforever.org/honaaohn

Documents

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