Hearing Protection 

Devices (HPD’s)

Roberta Hudak

Mining Hearing Loss Prevention 

Workshop

June 21-22, 2005

Pittsburgh Research Laboratory
Outline

 Overview of Hearing Protectors (HPD’s)

 Advantages/Disadvantages of HPD types

 Insertion method

 Noise reduction ratings

 Derating HPD’s

 Dual Protection
Have you heard?

 To reduce noise exposure, remember 3 key points: 

 Less Time

 Further Distance

 Use Shielding--Equipment (barrier)

Ear (HPD)
Hearing Loss Prevention

Approaches

 Remove noise

 Remove worker

then

 Protect the worker...use HPD’s
Problem: Earplugs are 

rarely worn effectively

2 9

2 1 2 3

2 6 2 6

2 2

1 7

1 3

7

2

5

1

8

5

0

5

1 0

1 5

2 0

2 5

3 0 Decibels

Plug A Plug B Plug C Plug D Plug E Plug F Plug G

Likely protection as worn by untrained worker

Amount of protection listed on the box
When to wear hearing protection

 If have to raise voice to speak to a 

person 2-3 feet away

 If your ears “ring” after noise exposure

 If after leaving the noise area, and 

sounds are “dull, flat or muffled”

 If noise is measured at 85dB(A) and 

above
Hearing protection-how does it 

work?

 A device worn to reduce (not eliminate) 

the level of sound entering the ear

 Considered last choice against hazardous 

noise 

 Generally provide greatest protection 

from high frequency noise and less in low 

frequency noise

 To be effective, must fit properly
Hearing Protection Devices

Best protector-REMOVE noise

There is NO single “best” type for all 

individuals or situations. 

 Varies with:

 Individual comfort

 Size of ear canals

 Noise environments

 Work activities

 Environmental conditions 
4 C ’s for Wearing HPD’s

 The “ Best” HPD is one that a worker will 

wear:

– Clean - plugs & hands for insertion

– Consistent - for levels 85 dB(A) and above

– Correct - insertion method

– Comfortable – for user, offer choices

** Wear HPD’s “ every time and all the time” in hazardous noise
How to make HPD’s more 

effective

Even if a worker wears HPD’s, they 

often do not wear it correctly

 Simplify insertion instructions

 Practice correct insertion method

 Train employee-care & use
Hearing Protection Devices

Factors determining worker acceptance of HPD’s:

 Convenience, availability and choices

 Beliefs that the protector

– Can be worn correctly

– Will prevent hearing loss

– Will not impair important sounds

 Comfort

 Adequate noise reduction

 Ease of fit

 Compatible with other personal 

protective equipment
Hearing Protection Devices

Foam Plugs

 1⁄4-1⁄2 inch foam/fiber- rolled, inserted and held 

(30–40 sec.) to expand, to fill ear canal

 Available in standard sizes

 Generally comfortable to wear

 Reusable on a limited basis 

Not washable 

Discard if wet, dirt or wax present
Hearing Protection Devices

Advantages & Disadvantages

Foam Plugs

Advantages:

 Small

 Inexpensive

(10-20 cents/pkg), 

depending on type

 Portable

 Generally more 

comfortable than others

 Worn effectively 

without interference 

from hair or glasses

Disadvantages:

 Can be hard to fit, 

esp. small canals 

 Can introduce dirt into 

canal

 Protection level can 

vary with:

– canal anatomy

– insertion method

– wax/hair in canals
Hearing Protection Devices

Proper Fit

 After the plug is inserted, check the 

fit. The body of the ear plug should 

be within the canal, and not visible 

from front view of person.

 Your own voice should sound 

muffled or hollow (like an echo or 

being in a tunnel).

 If proper fit was not obtained, 

remove plugs and re-insert with 

proper technique. 

Proper

Fit

Incorrect

Fit
Hearing Protection Devices

Molded/Pre-molded

 Soft, flexible devices (silicone/plastic/rubber) 

that fit into ear canal

 Variety of styles, some sized 

 FLANGES provide seal against canal wall

 Re-useable ...retain size and flexibility, if kept 

clean daily with soap and water
Hearing Protection Devices 

Advantages & Disadvantages

Molded (flanged) plugs

Advantages:

 Stem for clean 

insertion

 Variety of sizes

 Carrying caseconvenient 

 Washable, 

re-useable

Disadvantages:

 May need different 

size for each ear and 

individual fit.

Critical Tip:

 Insert and remove 

with rotation/twisting 

motion

 Do not pull straight 

out upon removal
Hearing Protection Devices

Earmuffs

 Ear cushions that seal against head and 

directly over outer ear

 Made of smooth, plastic envelope filled with 

foam or fluid material

 Require periodic replacement (cushions 

become stiff or brittle)- Inspect daily for 

defects

 Easily seen for use/compliance at distances

 One size fits most

 Generally provide greater protection

 Can be uncomfortable in hot work areas, or 

vigorous work activity
Hearing Protection Devices

Earmuffs

After inspection, reasons for replacement
Hearing Protection Devices

Advantages & Disadvantages

Earmuffs

Advantages:

 Easy to fit properly

 Designed to fit “most” 

people

 Less time & effort 

applying and fitting

 Easily visible/monitored

 Not misplaced/lost as 

easily

Disadvantages:

 Uncomfortable in hot 

environments

 May be cumbersome 

& restrict head motion

 Hair, beards, sideburns 

and glasses can alter 

protection

 Protection less in low 

frequency noise 

environment
Interventions and outreach with 

the Hearing Loss Prevention Unit

• Traveled to 42 sites nationwide

• Performed 5,414 

series of tests on...

– 3,609 workers

– 1,914 miners

Updated: 6/16/2005
Roll-Pull-Hold earplug 

technique

You’ve heard of: Stop, Drop, Roll

Now there’s Roll, Pull, Hold

Roll

Pull

Hold
Simplify the instructions:
Correct Completion of RollPull-Hold steps

96

54 49

0

10

20

30

40

50

60

70

80

90

100 Performed Step Correctly (%)

Roll Pull Hold
Increased earplug attenuation 

from completing Roll-Pull-Hold 

steps

14.87

16.14

21.43

23.51

0

5

10

15

20

25 Attenuation at 500Hz (dB)

None Roll Roll+Pull Roll+Pull+Hold

Using plug rated at 35.8 dB attenuation at 500Hz
Hearing Protection Devices

Noise Reduction Ratings

 NRR required on all HPD labels

 A measure of hearing protector attenuation

(noise reduction)

 Determined in a lab with open and 

occluded (protected) ears on trained 

subjects

 Based on decibel difference between the 

open and occluded hearing thresholds
Noise Reduction Ratings 

(NRR)

NRR=20 NRR=29

NRR=27
Hearing Protection Devices

Noise Reduction Ratings

 Some people select HPD’s by the highest 

NRR

 But NRR tends to overestimate realworld protection

 The NIOSH Noise Criteria document 

(1998) suggests derating:

– Earmuffs - 25%

– Foam plugs - 50%

– Molded (flanged) plugs - 70%

 Derating is still only a rough guide –

actual protection can vary
Derating Examples

Muffs:

NRR=20

Derated by 25% to 15

Foam plugs:

NRR=29

Derated by 50% to 14.5

Molded plugs:

NRR=27

Derated by 70% to 8
Dual Protection +

Using a combination of ear plugs and muffs.

Recommended for exposures of 8 hours above 

100-105dB(A) (time weighted avg.)

 Examples: Roof bolter, underground auxiliary 

fans, continuous miner, miner/bolter, coal 

processing equipment

 To compute NRR from dual protection:

Add 5dB to the HPD with most protection/highest 

derated NRR of two selected
For more information

Roberta Hudak

Phone: 412-386-4599 Fax: 412-386-4865

rph4@cdc.gov

www.cdc.gov/niosh/mining

Pittsburgh Research Laboratory
Value the “gift” of hearing--Sounds good to me !!