noise and acoustics ~ hierarchy of controls

NOISE AND ACOUSTICS ~ Hierarchy of ControlsNoise + Acoustics

Ototoxic Chemical ExposuresConfirmed Ototoxics

•Ethyl Benzene

•Lead and Inorganic Compounds (Pb)

•Styrene

•Toluene

•Trichloroethylene

Possible

•Carbon disulfide

•n-Hexane

•Xylene

NoiseOtotoxic

Chemicals

Hearing Loss

How We Hear

The Auditory System

Acoustical

Mechanical

Hydraulic

Chem/Elec

Hearing Protection Selection

Hearing Protection Devices (HPDs)

Single-Use / Multiple-Use / Detectable Earplugs Banded Earplugs Passive Earmuffs

Radio & Stereo Earmuffs Intelligent Hearing Protection

Sound Amplification Earmuffs

PRO CON

• More natural sounds• Lower attenuation ideal for

moderate noise environments• Ideal for hearing-impaired workers

• Lower attenuation than most earplugs

• Slightly higher cost

Uniform / Flat Attenuation HPDs

Variation in attenuation is only 5 dB in speech range (250 - 4kHz)

Frequency in Hz

Uniform Attenuation Earplug

Conventional EarplugSpeech will sound more natural with this earplug.

Intelligent Hearing Protection

PRO CON

• Communicate in high, changing noise

• Increased situational awareness• Can integrate active hearing

protection, ANR, fit testing, PSEM• Connect with radios• Compatible with other PPE

• Higher cost than passive HPD• Control unit as additional PPE to

wear• Appropriate for specific applications

or environments (eg. intrinsically safe)

Choosing a protector with an NRR higher than necessary may result in overprotection

Hazards of Overprotection

• Verbal communication may be hindered

• Warning alarms may not be heard

• Machine noises may be too diminished

• HPDs may be removed

Insufficient Protection

Acceptable Protection

Optimal Protection

Possible Overprotection

In the United States, 76% of noise-exposed workers need no more than 10 dB of protection. 90% need no more than 15 dB of protection.

Hearing Protection Selection Factors• The right hearing

protector should feel comfortable

• One protector may not satisfy all workers

• Offer a variety of earplugs or earmuffs to meet varying worker needs and preferences

Comfort

• Selecting HPDs with suitable attenuation for noise environment

• Avoid overprotection in marginal noise environments

• Consider banded earplugs for intermittent noise or electronic earmuffs for impact noise.

Hearing Protection Selection Factors

Noise Reduction

• Every ear canal has its own shape and size

• Ensure proper fit with variety of earplug sizes and shapes

• Sized multiple-use earplugs

• Low-pressure foam earplugs for smaller ear canals

• Keep workers connected to their environment

• Uniform attenuation allows speech/signals to be hear more naturally

• Sound amplification earmuffs for workers with hearing impairment

Communication

• Consider job requirements in HPD selection

• Detectable earplugs for process industries

• Hi-visibility earmuffs for dark/high traffic areas

• Dielectric HPDs for electrical environments

Job Requirements

• Proper care and maintenance can extend life and performance of HPDs

• Examine and clean all multiple-use earplugs daily

• Clean and replace ear cushions on earmuffs every 4-6 months

Hearing Protection Selection Factors• Roll vs. No-Roll

earplugs

• Foam vs. multiple-use earplugs

• Clean and replace ear cushions on earmuffs every 4-6 months

• Clean and examine multi-use earplugs daily

Hygiene

• Cap-mounted earmuffs for hard hats

• Multiple-position earmuffs for full-brim hard hats

• Ultraslim neckband earmuffs with welding shields

• Respirators preventing communication

• Eyewear interfering w/seal of earmuffs, attenuation

Use w/ Other PPE

• Awareness of surroundings• Understand what is

happening around you• Communicate with co-

workers (face-to-face or 2-way radios)

• Increased personal safety, avoid other risks

• Avoid isolation from environment

Connect w/ Environment

How much noise is reaching the ear of the worker ?

Noise Reduction Rating

Noise Level 100 dBA

NRR 25 dB

It’s completely UNKNOWN!

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.

• 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)

Determining the NRR

Attenuation

14 1819

20 22 2423 25

28 30 322627

Determining the NRR

De-Rating Methods (US/CAN)

Class SystemA up to 100

B up to 95

C up to 90

Reduce NRREarmuffs NRR – 25%

Formable Earplugs NRR – 50%

All Other Earplugs NRR – 70%

Fit Test

NRR ÷ 2pending feasibility of engineering controls

Real-World Attenuation ≠ NRR

192 Users of a Flanged Multiple-Use Earplug (NRR 27)

Retraining and refitting resulted in an average +14

Real use

attenuatio

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

Determining New NRR

New NRR (NRsa)

Attenuation

11 14 18

1920 22 24

23 25 2730 33

20% achieved > 26 dB

80% achieved > 20 dB

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%

NRR Change Resources

PDF and other articles available at www.hearforever.org

1.FIT 2. WEAR TIME

A worker who selects an earplug with an PAR of 30

effectively reduced his 8-hour PAR to just …

but then removes that HPD for just …

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.

Biggest Factors in Achieving PAR

• For extreme noise environments

• To estimate the protected noise level, add about 5 dB to the higher NRR protector

+ DUAL PROTECTION=

EARPLUG EARMUFF

Dual Protection

Earplug PAR 29 dB

Earmuff NRR 29 dB

Maximum Dual Protection

What Can I Do Now?

Evaluate Noise Spectra

• Determine if spectral balance corrections will be necessary

One-on-One Training

• Research studies confirm that one-on-one training is superior to group training

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.

What Can I Do Now?Evaluate HPD Selection• Determine whether they are appropriate

for your noise environment.

• Use the Howard Leight Hearing Protector Selector for recommendations.

Update Training Program• Hold “Toolbox Training” with fit training

refresher

What Can I Do Now?Use Earplug Fit Testing• Train how to properly fit HPDs• Select appropriate HPDs• Document adequate protection

Use In-Ear Dosimetry • Measure, document noise dose

employee is exposed to during work shift

Next Generation

of Hearing Conservation

Technology

Personal Sound Exposure Monitoring (PSEM)

New Measurement Technologies

Earplug Fit Testing

Next Generation of Hearing Conservation Technology

Earplug Fit TestingProvides an accurate, real-world picture of your

employees’ hearing protector effectiveness.ID if your employees are

• Getting the right protection• Need additional training• Need different earplug

Problem Solver:• Eliminate De-Rating Schemes• Improve One-on-One Training• Validate Hearing Protector Selection• Adapt to Impending NRR Change

Fit Testing SystemsReal Ear at Above Threshold (REAAT)

Loudness Balance

Commercial Available System

Personal Measurement SystemsPersonal Sound Exposure Monitoring (PSEM)

Commercial Available Systems

Fit Testing as Best PracticeOSHA / NIOSH / NHCA Alliance

Research studies have suggested that when individuals are involved in the fitting process and receive positive feedback on the proper fit of their earplug, they will be more likely to have a positive attitude about protecting their hearing and will be more apt to use hearing protection correctly and consistently in the workplace. This positive outcome should result in reducing noise-induced hearing loss in the workplace.

Available for download at www.hearingconservation.org

Fit Testing Comments from Workers

"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 a threshold shift. Found better

earplugs."

"Feel like am protected now!"

"I had no idea I was not using my

earplugs correctly."

PROs & CONs of Fit Testing

PRO CON

Estimate / Measure Cost

NRR Obsolete Time Investment

Fulfills OSHA Compliance

Not Standardized

Eliminate De-Ratings

Medico-Legal Cases

Work-Relatedness

No Dual Protection

Employee Feedback

How much protection?

0 dB 0 dB>33 dB

EAR #1EAR #2

EAR #3

Hearing Protector Fitting

Frequency in Hz

Max Poor FitNRR = 0dB

Max Good FitNRR = 33dB

Good Fit vs Bad Fit

Hearing Protector Fitting

Roll-Down Foam Earplugs

2. Pull Back pinna by reaching over head with free hand, gently pull top of ear up and out

1. Roll entire earplug into a crease-free cylinder

3. Insert earplug well into ear canal and hold until it fully expands

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 Materialswww.hearforever.org

www.hearingconservation.org

www.grc.nasa.gov/www/acoustics

www.cdc.gov/niosh/topics/noise

www.dangerousdecibels.org

Demonstrate Future Risk

www.hearforever.org/ AIH

www.hearforever.org

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

Checking Off the OSHA Amendment List

Health effects of noise

Purpose of hearing protection

Advantages/ disadvantages of various

Selection, fit, use and care of HPD

Purpose and procedures of audiometric testing

Professional Organizations

www.hearingconservation.org

Online Resources

www.youtube.com/hlhearforever

Challenges in Industry

Bringing It Together

Hearing Protection Situational Awareness

Hearing Protection Two-Way Communication

Situational Awareness

Two-Way Communication

Too LITTLE Hearing Protection

Worker Isolation, Safety Risk to Self

and Others

Too MUCH Hearing Protection

Noise Exposure, Risk for Occ Hearing Loss

Difficulties in managing two-way communications in extreme noise environments

High Noise Exposure• Most provide attenuation

>25 dB (without de-ratings)• Oil platforms > 110 dBA

• Mining > 105 dBA

Passive Protection• Most designed for constant noise levels• Do not adapt for changing noise levels

or types of noise (intermittent, impact)• Communication without two-way radios

Photo: Øyvind Hagen / Statoil

Difficult Speech Intelligibility•Communication in high noise levels requires concentration by the user•Often raise headset volume to compensate for high ambient noise

• Additional risk for NIHL•Boom microphones may pick up ambient sound when transmitting speech•Position critical for boom mics

• Outgoing communications may be compromised

Wear with Other PPE•Hearing protectors with headsets or boom mics not always compatible with other PPE

Dual Protection Requirements•Requirements for earplugs and earmuffs in noise levels >100-105 dBA•Properly fit earplug inhibits worker’s ability to hear through a headset•Workers do not like to wear both

Improper Use = Unknown Attenuation?•Workers wearing one cup on, one cup off to hear surroundings•At risk for binaural NIHL

Extreme Climates / Weather•Earmuffs very uncomfortable to wear in very hot and humid conditions•Earmuffs preferred in colder climates

• Wear with hats and balaclavas may compromise optimal attenuation

Low Frequency Sounds•Noise felt as vibration•More intense in closed or confined spaces

•Continued exposure can lead to worker fatigue, annoyance

Mobile Workers•Exposed to changing noise throughout work day•May require different hearing protectors for each environment or task

•Intelligent protection solutions

Photo: Helge Hansen / Statoil

Noise Levels

105-112 dBA

HPD Requirements

Dual Protection

Key Challenges

•Reducing noise levels, especially in high noise areas, via engineering controls

•Ensuring workers wearing hearing protection properly, especially in extreme heat/humidity

•Validate amount of attenuation each worker achieves

Case Study #1: Shaw Industries

Tactic #1: Engineering Controls

Location Pre-Enclosure dBA Post-Enclosure dBA Hood Insulation dBA Total Reduction dB

F/16 #2 111.4 104.9 103.9 7.5

F/16 #6 110.8 102.7 101.8 9.0

F/16 #11 107.3 100.2 99.7 7.6

Packout Table 106.4 98.6 96.8 9.6

Tactic #2: Earplug Fit Testing

Site Procedure•All workers showing a shift (decrease) in hearing now receive a fit-test as part of “retraining.”•All new (or re-hire) employees receive a fit-test prior to beginning work to •Departments prioritized and tested per protocol•Find the appropriate earplug •Ensure they know how to fit it properly.

The Results

The Data•17% achieved adequate Personal Attenuation Rating (PAR) on their first test

•78% were able to achieve adequate protection at their first training session to bring their noise exposure to 82 dB or below

•67% of workers changed from their initial ear plug selection, mostly due to comfort of proper fit

The Results: Distribution of PAR Shifted

Goal of > 25 dB of protection achieved by most workers

The Results: Reduction in Recordables

Year Confirmed STS

Comment

2006 5 Prior to noise control2007 02008 02009 1 Non-production associate2010 0

Best practices at this plant have been adopted at other Shaw locations

The Results: Hearing Conservation Program Changes

HC Program Improvements•Expanded HPD offerings from 3 to 6 choices

•Workers are “certified” to a particular earplug

•Mandated job rotation in departments

•Emphasis on equipment maintenance

www.hearforever.org/shaw

The Results: Award Winner

Recognized for the demonstrated results in noise control and its use of fit testing to better train and protect workers

www.safeinsound.us

Noise Levels

87-90 dBA TWA

HPD Requirements

100% wear when on plant floor (even walking through)

Key Challenges

•Intermittent noise exposures•Moderately low TWAs•Possible overprotection

Case Study #2: Gulfstream Aerospace

Tactic #1: Engineering Controls

Quieter Equipment•Purchase new equipment that does not exceed 82 dB during normal operation

•Implement engineering controls around test generator

www.buyquietroadmap.com

Tactic #2: Earplug Fit Testing

Photo courtesy of Gulfstream Aerospace

Earplug Fit Testing: Value-Added Time Investment

118 32 9

Test 155%

Test 252%

Test 345%

Test 431%

Test 5+36%

Did not meet 15 dB criterion

Met 15 dB criterion

Identified workers with poor fit and spent value-added time

Earplug Fit Testing: Goal

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46

Mean Personal Attenuation in dB

Personal Attenuationn = 688

Goal of > 15 dB protection now achieved by most workers

Light Blue – Initial Fitting

Dark Blue = Final Fitting

The Results: OSHA Recordable Drop

Dramatic Drop in Recordable Hearing Loss Cases

The Results: Hearing Conservation Program Changes

HC Program Improvements•Workers are “certified” to a specific earplug

•High worker engagement in safety solution

•Continued earplug fit testing in other business units

•Possible development of earplug fit testing stations throughout facility

•Expanded hearing protector offering

noise and acoustics ~ hierarchy of controls

active hearing protection

attenuation achievable

noise reduction ratingits

nrr higher

lessthe nrr

fita populationbased

frequencieseach subject

howard leight acoustical

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