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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

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

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Hearing ConservationTheresa 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

  • Leaves no visible scars

  • Is unnoticeable in its earliest stages

  • Accumulates with each overexposure

  • Takes years to notice a change


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

Noise + Acoustics - Hierarchy of Controls

  • ADMINISTRATIVE CONTROLS

  • Rotate Workers

  • Extended Breaks

  • 2nd/3rd Shift

PERSONAL PROTECTIVE EQUIPMENT

  • ENGINEERING CONTROLS

  • Buy Quiet

  • Vibration Pads

  • Enclosures

  • Barriers

  • Isolation


NOISE AND ACOUSTICS ~ Hierarchy of Controls

Noise + Acoustics

Confirmed Ototoxics

Ethyl Benzene

Lead and inorganic compounds (as Pb)

Styrene

Toluene

Trichloroethylene

PossibleCarbon disulfide

n-Hexane

Xylene

  • Synergistic Ototoxics

    • Carbon Monoxide

    • Hydrogen Cyanide

NOISE

  • Ototoxic Chemicals

  • Ototoxic by themselves

  • Synergistic effect with noise

  • Large differences in sensitivity

  • Recommend: increased frequency of audiometric testing


How We Hear


How We Hear

  • The Auditory System

Chem/Elec

Acoustical

Hydraulic

Mechanical


How We Hear

  • High Frequency Sounds of Speech

CH

S

TH

P

T

F

SH

K

H


Noise Reduction Rating(NRR)


Noise Reduction Rating

  • How much noise is reaching the ear of the worker ?

Noise Level =100 dB

Noise Reduction Rating =30 dB

That is completely unknown …

(55 – 104 dB)


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.


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

A test subject in the Howard Leight Acoustical Lab, San Diego, CA, accredited by the National Voluntary Laboratory Accreditation Program (NVLAP)


NRR

Noise Reduction Rating – Determining an NRR

NRR

5

4

Number of test subjects

3

2

1

26

28

30

32

24

22

14

18

20

19

23

25

27

Attenuation


Real user attenuation <0 to 38 dB

Real-World Attenuation≠ NRR

192 users of a flanged reusable earplug ~ 27 NRR

50

NRR = 27 Multiple-Use Earplug

40

Retraining and refitting resulted in an average

14 dB improvement for this group

30

Attenuation in dB

20

10

0

-10

From Kevin Michael, PhD and Cindy Bloyer “Hearing Protector Attenuation Measurement on the End-User”


Noise Reduction Rating

  • De-Rating Methods

OSHA

NRR ÷ 2

(feasibility of engineering controls)

NIOSH

Earmuffs

NRR – 25%

Formable Earplugs

NRR – 50%

All Other Earplugs

NRR – 70%

CSA

Class

A up to 100

B up to 95

C up to 90

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 Labels


Noise Reduction Rating

  • Determining New NRR

  • 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


New NRR (NRsa)

80% achieved > 20 dB

20% achieved > 26 dB

5

4

Number of test subjects

3

2

1

24

22

11

14

18

20

26

28

30

33

19

23

25

27

Attenuation


Noise Reduction Rating

20th %

Proficient Users

80th %

Minimally-trained

Current NRR Label Mock-up of New Label


Noise Reduction Rating

  • How to Apply the New Label

Two-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

30 min

5 min

10 min

15 min

Factors in Achieving the NRR

1.FIT

2. WEAR TIME

30dB

A worker who selects an earplug with an NRR of 30

but then removes that HPD for just …

effectively reduced his 8-hour NRR to just …

22 dB

18 dB

26 dB

24 dB

In noise exposures, small intervals of no protection quickly void large intervals of adequate protection.


Noise Reduction Rating

  • What Can I Do Now?

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.

  • 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.


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 Testing

  • Provides 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 Testing

  • As a problem solver:

  • Derating Schemes

  • One-on-One Training

  • HPD Selection

  • NRR Change


Noise Reduction Rating

  • In-Ear Dosimetry

  • As 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

Sample HL Compensation*

*NMER= No minimum exposure required

*Source: AIHA Noise Manual


Reducing Costs of Hearing Loss

Sample HL Compensation*

*NMER= No minimum exposure required

*Source: AIHA Noise Manual


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

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

In-Ear Dosimetry

Fit Testing


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 occupationalhearing loss


Reducing Costs of Hearing Loss


Research > Alcoa Intalco Works

Reducing Costs of Hearing Loss

  • Mean Hearing Threshold (2k, 3k, 4kHz): 2000 – 2007 (N = 46)

  • Employees using continuous in-ear dosimetry starting in 2005


Preventive Action After NIHL

Reducing Costs of Hearing Loss

• Audiometric test •Retest •Notification

0 246810121416

Months

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


In-ear dosimetry as a Problem Solver

Reducing Costs of Hearing Loss

  • 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


Ear plug fit-testing methods


Reducing Costs of Hearing Loss

OSHA Alliance: Best Practice Bulletin

www.hearingconservation.org

Additional Information

www.howardleight.com


Field Verification – Fit-Testing

"Learned A LOT about best earplugs for me"

"I know how to better fit my earplugs now."

"Recently had threshold shift" "Found better earplugs"

"I had no idea I was not using my earplugs correctly."

"Very glad I did the fitting test. Now I know the correct way to fit my ear plugs.”

"I found a more comfortable fit. It was very beneficial."

"I was amazed with the results after being shown the proper way to use earplugs.

"Feel like am protected now!"


Pre and Post-Test

Fit-Testing as a Training Tool

  • “How well can users predict their attenuation after a short fit-testing training session?"


Pre and Post-Test

Fit-Testing as a Training Tool

  • “How much noise do you think your earplugs block?”

  • Self-Efficacy

  • 76% (13 of 17) judged attenuation as HIGHER post-test


Fit-Testing as a Training Tool

  • Data show improved PARs!

  • Results

  • InitialRE=19 LE=22

  • Final RE=29 LE=27

  • Average improvement 7.5 dB


Pre and Post-Test

Fit-Testing as a Training Tool

  • Are you better able to assess the effectiveness of your earplugs after VeriPRO fit-testing?

  • 12345

  • No MaybeNo change Improved Yes

  • Post-Test

64% (11 of 17) rated their abilityHIGHER post-test


Fit-Testing as a Training Tool

Pre and Post-Test

Don't know

how

Expert

Not good

Not good

Expert

I do OK

I do OK

Pretty good

Pretty good

I do OK

Pretty good

Expert Fitter

Post-Test Ability

Initial Ability


Pre and Post-Test

Fit-Testing as a Training Tool

20

18

16

14

12

Number of Ears

(Each subject estimated atten. for each ear)

10

8

6

4

2

0

Within 5 dB

category

+/- 7.5 dB

(one Category off)

+/- 12.5 dB

(2 categories off)

  • Ability to Predict Noise Reduction

56%

32%

12%


Reducing Costs of Hearing Loss

Published NRR


Reducing Costs of Hearing Loss

Personal Factors

Gender

Age

Years in Noise

Ear Canal Size

Familiarity

Model of Earplug

Program Factors

# Group Trainings

# Personal Trainings


REDUCING COSTS / CLAIMS

Reducing Costs of Hearing Loss

Published NRR

Trying a second earplug often improves attenuation


Reducing 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

Tools for HCP Prevention Metrics

  • 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

Off-job+ On-job = STS

Off-job+ On-job = STS


0 dB

0 dB

33 dB

EAR #1

EAR #2

EAR #3

How much protection?


Frequency in Hz

1000

2000

3150

4000

6300

8000

250

500

125

90

Max Good Fit

NRR = 33dB

Max Poor Fit

NRR = 0dB

80

70

60

50

Attenuation in dB

40

30

20

10

0

-10

Good Fit vs Bad Fit


Training + Motivation


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/HearingConservation/Resources/index.html

  • www.cdc.gov/niosh/topics/noise

  • www.dangerousdecibels.org

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


Training + Motivation

  • Hearing Loss Due To

  • Noise Exposure Is …

  • Painless

  • Permanent

  • Progressive

… and veryPreventable!


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