Presented by Brad Witt

STOPPING NOISE-INDUCED HEARING LOSS

STOPPING NOISE-INDUCED HEARING LOSS

NIOSH Safe-In-Sound Award Recipient

▪ “Measurable achievements in reducing or eliminating noise-induced hearing loss”

▪ 2011 industrial recipient: Shaw Industries Group Plant WM

▪ Elimination of noise-induced hearing loss

(see www.safeinsound.us)

and off the job.

NOISE AND ACOUSTICS

Hazardous noise exposures are cumulative

on the job ..…

NOISE AND ACOUSTICS

Noise-Induced Hearing Loss

Causes no pain

Causes no visible trauma

Leaves no visible scars

Is unnoticeable in its earliest stages

Accumulates with each over-exposure

Is permanent and 100% preventable

NOISE AND ACOUSTICS

Noise-induced hearing loss

is the most common

permanent and preventable

occupational injury in the world.~ World Health Organization

1997 Report on Occupational Noise

NOISE AND ACOUSTICS

NON-OCCUPATIONAL

► 140 dB

Immediate physical damage

► 120 dB

Pain threshold

► 85 dB

OSHA Action Level

Hearing damage possible

► 60 dB

Comfortable noise level

NOISE AND ACOUSTICS

The decibel scale is a logarithmic scale, not a linear scale

If the noise source is doubled 83 dB

The noise level only goes up 3 dB 86 dB

Small increases in decibel level 89 dB

Represent enormous increases in noise level and risk

92 dB

NOISE AND ACOUSTICS

95 dB

92 dB

89dB

86dB

83dB

NOISE AND ACOUSTICS Sound Level Meter vs. Noise Dosimeter

Sound is measured immediately in a specific area

Sound is ‘averaged’ throughout the day for a sample employee or job

“Area Sampling” “Personal Sampling”

photos courtesy of Quest Technologies

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

EVALUATING NOISE REDUCTION

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)

Which ear is protected?

0 dB 0 dB33 dB

EVALUATING NOISE REDUCTIONThe Noise Reduction Rating (NRR)

A laboratory estimate of the

amount of attenuation achievable

by most 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.

EVALUATING NOISE REDUCTIONDeveloping the NRR

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 LEVEL

NRRSAFE NOISE=_

NOISE LEVEL

? HUMAN FACTOR

? SAFE

NOISE =_

EVALUATING NOISE REDUCTIONReal-World Protection May Not Equal NRR

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

192 users of a flanged multiple-use 27 dB earplug

Retraining and refitting resulted

in an average

14 dB 14 dB improvementimprovement

in attenuation for this group

Real user

attenuatio

n

0 – 38 dB

30

20

10

0

-10

Att

enu

atio

n in

dB 40

50Multiple-Use Earplug Rated for 27 dB

EVALUATING NOISE REDUCTION

The Biggest Factors in Achieving the NRR

1.FIT 2. WEAR TIME

A worker who selects an earmuff 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

19 dB 17 dB 15 dB 12 dB

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

EVALUATING NOISE REDUCTION

100 dB

90 dB

80 dB

70 dB

60 dB

0 1 2 3 4 5 6 7 8

8-Hour Workday

30 dB = 1000x

20 dB = 100x

10 dB = 10x

3 dB = 2x

EVALUATING NOISE REDUCTIONThe Hazards of Overprotection Choosing a protector with an NRR higher than necessary may

result in overprotection Verbal communication may be hindered Warning alarms, telephones, machine noises may not be heard

-85

-80

-75

-70

Worker Exposure at the Ear With Protectors

dB Insufficient Protection

Optimal Protection

Acceptable Protection

Acceptable Protection

Over Protection

EVALUATING NOISE REDUCTIONThe Noise Reduction Rating (NRR)

Current NRR Label Mock-up of New Label

80th %

Minimally-trained

20th %

Proficient Users

REDUCING COSTS & CLAIMSREDUCING COSTS & CLAIMS

REDUCING CLAIMS

Lagging Indicators vs Leading Indicators

Fit Testing

REDUCING CLAIMS

In-Ear Dosimetry

Variation from Published Rating

-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 Rating

Distribution of PARs

0

2

4

6

8

10

12

Variation from Published SNR

Wor

kers

REDUCING CLAIMS

Personal Factors

Gender

Age

Years in Noise

Ear Canal Size

Familiarity

Model of Earplug

Program Factors

# Group Trainings

# Personal Trainings

Distribution of PARs

0

2

4

6

8

10

12

Variation from Published NRR

Wor

kers

REDUCING CLAIMS

What predicts a good fit?

Difference on 2nd / 3rd Test

-30

-25

-20

-15

-10

-5

0

5

10

Subjects

Va

ria

tio

n f

rom

NR

R Published Rating

Trying a second earplug often improves attenuation

REDUCING CLAIMS

FIT TESTING

Complete Check

● 5 freqs in each ear

● Best for new users, reliability checks

● ↑ accuracy, ↑ test time

Quick Check

● 1 critical freq in each ear

● ↓ accuracy, ↓ test time

● Can use with severe hrg loss

ReportMode

● Individual

● Historical

● Results by freq

Fit Training

● Videos

Fit Testing

REDUCING CLAIMS

In-Ear Dosimetry

In-ear dosimetry measures actual noise dose, with and without protection

Alerts when worker approaches safe limits

Only metric to measure and prevent further progression of occupational hearing loss

IN-EAR DOSIMETRY

Dosimeter records …

• Good fit

• Bad fit

• No fit

Indicator lights give immediate feedback of noise level and dose

IN-EAR DOSIMETRY

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 CLAIMS

In practice, identifying a shift in hearing 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 annual audiometric testing

In-ear dosimetry “worst case” scenario …

1 Day • Audiometric test • Retest • Notification

PROS- Estimate Measure

- NRR obsolete

- Eliminates need for de-ratings

- Medico-legal cases

- Delineates non-occupational

- Eliminates double protection

- Provides employee feedback

CONS - Cost

- Time Investment

- Not standardized

REDUCING CLAIMS

REDUCING CLAIMS

Off-job + On-job = ShiftOff-job + On-job = Shift

CASE STUDIES - CARPET MILL

NIOSH Safe-In-Sound Award Recipient

1. Engineering controlsBrought noise levels down to 100-104 dBA.

2. Annual fit-testing and training Documented successful reduction of noise exposures under the hearing protector below 85 dBA for all employees.

3. End result: reduction of STS to zero in the most recent years of annual audiometric testing.

CASE STUDIES – MILITARY INSTALLATION

U.S. Navy

▪ 60 sailors experienced in earplug use- command-issued standard foam earplug

OR- a second earplug of their choosing

▪ Prior to testing with the “variety” earplug, sailors received brief training (less than one minute in duration) by someone modeling the correct fit of that style of earplug.

▪ Despite no prior experience with the “variety” earplug, 45 of the 60 sailors (75%) achieved higher attenuation with the variety earplug over the command-issued earplug.

Median attenuation for ‘variety’ earplugs = 18 dBMedian attenuation for command-issued earplugs = 9 dB

CASE STUDIES - AEROSPACE

14087

35 12 3

197

110

7563 60

0

50

100

150

200

250

300

350

1st Test 42% pass

2nd Test 44% pass

3rd Test 32% pass

4th Test 16% pass

5th Test 5% pass

Nu

mb

er o

f E

mp

loye

es

Did not meet 15 dB criterion

Met 15 dB criterion

Fit-Testing / 1:1 Training

for 337 noise-exposed workers

Pre-Test

1. Which type of hearing protectors do you normally use on the job?

2. How would you rate your ability to fit your earplugs?

Post-Test

1. After this fit-test, are you better able to fit your earplugs?

2. Did you change your choice of earplugs as a result of the fit-test?

- Yes, 63%No, 37% -

- Yes, 93%Not sure, 1% -

No, 6% -

Poor, 1% -

Okay, 36% -

- Good, 51%Don’t know how, 2% -

Expert, 10% -

- Earplugs, 76%Earmuffs, 8% -

Don’t normally use on-the-job, 16% -

CASE STUDIES - AEROSPACE

Hearing Loss Due To

Noise Exposure Is …

Painless

Permanent

Progressive

… and very Preventable!