Occupational Noise Exposure and Hearing Conservation

Occupational and Environmental
Noise Risk Identification and
Assessment to Validate Controls
and Hearing Conservation Program
Presented by:
Bernard L Fontaine, Jr., CIH, CSP,
Managing Partner,
The Windsor Consulting Group, Inc.

© 2013 by The Windsor Consulting Group, Inc. All rights reserved. No part of this document may be reproduced or
transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written
permission of The Windsor Consulting Group, Inc.

Occupational Noise Exposure
Course Learning Objectives
Participants will be able to:
 Describe the consequences to health and well being of
excessive noise exposure
 Understand the measurement (including dosimetry) of noise in
relation to current standards
 Conduct surveys in the workplace to assess risks from noise

Copyright © 2013 The Windsor Consulting Group, Inc.

Course Learning Objectives
 Awareness of noise hazards in the workplace, at sporting
events, and during recreational activity
 Direct and indirect effect of noise on people
 Identification and assessment of noise risk
 Understanding of hearing and hearing loss
 Interpret data based on exposure standards
 Select possible noise control measures including hearing
protection


Topics to be Discussed
 Physical properties of sound and human effect
 Risk assessment and noise surveys
 Analysis and interpretation of noise data
 Noise controls – engineering and administrative
 Education and training requirements
 Audiometry and hearing disorders
 Environmental noise sources and effect


WHAT THIS COURSE WILL NOT PROVIDE:
 The course is not intended to provide the skills to become
an acoustics expert
 Select the proper engineering controls based on octave
band analysis

 Specific instruction on how to operate noise measurement
equipment or perform audiometry
 Comprehensive discussion on hearing protectors or
audiometric determination


WHAT THIS COURSE WILL NOT PROVIDE:
 Exposure information on super low, extremely low, and
tremendously low frequency used in submarine and mine
transmission or man-made noise
 Exposure information on high, very high , super high,
extremely high, and tremendously high frequency noise
from radio and television broadcast, microwave or wave
scanners, satellite communications, radio astronomy,
ultrafast molecular dynamics, condensed matter physics
or amateur radio noise


What is Noise?
 Noise is an unpleasant / unwanted sound
 Types of noise
1. Continuous
2. Impulse
3. Impact
 Side effects of noise
1. Loss of hearing
2. Physiological/psychological stress
3. Accidents
4. Behavioural effects
5. Negative impact on health


 Loud noises can cause hearing loss
 Prolonged exposure to a harmless noise can cause
hearing loss
 Damage from hearing loss is irreversible
 Noise induced hearing loss is preventable
 Prevention involves:
1. Noise controls
2. Safe work practices
3. Education


 Occupational hearing loss is the most common workrelated illness in the United States.
 Approximately 22 million U.S. workers exposed to
hazardous noise levels at work, and an additional 9 million
exposed to ototoxic chemicals.
 An estimated $242 million is spent
annually on worker‟s compensation
for hearing loss disability.


Sound Versus Noise
 Sound is a pressure change detectable
by the human ear.

1. Pitch (frequency) ranges between 20 to 20,000 Hz
2. Volume ranges between 0 to 140 dB (decibels)
 Noise is a type of sound.

1. Carries no information
2. Random
3. Generally described as
undesirable or unwanted
sound


Non-Auditory Effects of Noise
 Effects cardiovascular system

 Effects the nervous system
 Interferes with speech and concentration
 Causes annoyance, stress, and fatigue

 Reduces work efficiency
 Lowers morale
 Masks warning sounds


Non-Auditory Effects of Noise
 Psychological – can startle, annoy, and disrupt
concentration, sleep, or relaxation.
 Interference with communication, resulting in interference
with job performance and safety.

 Physiological – noise induced hearing loss, aural pain, or
even nausea.


The Physics of Sound


Properties of Sound


Sound Propagation
 Sound is a fluctuation in pressure above and below
the ambient pressure of a medium that has elasticity
and viscosity.
 The medium may be a solid, liquid, or gas.
 Sound is also defined as the auditory sensation
evoked by these oscillations in pressure


Properties of Sound
 Period (T)
is the time it takes to complete one full cycle

 Frequency (f)
is the number of times per second a complete
wave passes a point. The number of cycles per
second is termed Hertz (Hz).
 The period and the frequency are simply related
by the following equation:

T = 1/f (seconds)


Properties of Sound
 Speed (c) of sound in air is governed by air density and
air pressure which in turn relates to the ambient
temperature and elevation at or above sea level
 At sea level, the speed of sound in air is about 343 m/s
 Sound travels about 1 kilometres in 3 seconds (much
slower than the speed of light)


Properties of Sound
 Wavelength (λ)
is the length of one complete cycle, and is
measured in meters (m).
It is related to the frequency (f) and speed of sound (c) by:

Wavelength (λ) = c/f meters


Properties of Sound
Frequency

Wavelength

100 Hz

3 x 107 m

1000 Hz

3 x 106 m

10,000 Hz

3 x 104 m

1 x 106 Hz/1 MHz

300 m

10 MHz

3m

100 MHZ

0.3 m

1,000 MHz

0.3 m

Wavelength in air at standard atmospheric conditions


Properties of Sound
 SLMs have electronic circuits which convert the
microphone signal to an RMS sound pressure level

 The RMS pressure is used because it can be related to
the average intensity of the sound or the loudness of the
sound
 For a pure (simple sine wave) tone it can be shown that
the peak pressure and the RMS pressure are related:

Prsm = Ppeak = 0.707 x Ppeak
√2
For more complex signals, there is no simple relationship
between the two


Properties of Sound
 Peak sound is important to measure

 In particular for loud impulsive or impact noise, such as
gunfire, explosions or punch presses.
 The Crest Factor is the ratio of the peak amplitude of a
waveform to the RMS value.
 Short intense impulses or impacts will have high CF
values.


Properties of Sound
 Sound power is defined as the total sound energy
generated by the source per unit of time.
 Sound power is expressed in units of watts (W) and
sound intensity is vector quantity.
 It is important to keep in mind that for all practical
situations the sound power of a source output is
constant regardless of its location (i.e. inside vs.
outside).
 Conversely, the sound intensity and sound pressure will
change as a function of the environment in which it is
located.


Properties of Sound
 Sound pressure is expressed as force per unit area,
and the unit is the Pascal (Pa).
 Keep in mind sound pressure is the “effect” of a
disturbance. The actual “cause” of the disturbance,
and the resulting reaction effect, is due to sound
power measured in decibels

decibel = 20log (pa /po )


Properties of Sound
Sound Pressure Level:

Lp 10 log

p2
p

2

20 log

ref

p
p ref

dB

 The “L” in each expression stands for “Level,” and the
I, W, and p terms represent intensity, power, and
pressure, respectively for hearing at 1000 Hz.
 Reference intensity (Iref) = 10-12 w/m2
 Reference power (Wref) = 10-12 w
 Reference pressure (pref) = 2 x 10-5 N/m2, or 20 µPa

Properties of Sound
A point sound source will radiate
sound power evenly in all
directions, assuming there are
no reflective surfaces present.
As the power spreads
spherically from its origin, the
surface area in increases and
so the power per unit area
decreases.
The total power remains the
same, but the enclosing area is
increasing, which results in a
decrease in the sound intensity.
This is known as the inversesquare law.

Properties of Sound
 Sound intensity is based on surface area of sphere = 4 r 2
 Therefore at 1 meter from source power will be spread
over a sphere whose surface area is 4 x1
 At 2 meters this will be 4 x 4 (i.e., 4 times as large and
thus the Intensity will be one quarter).
 At 3 meters the surface will be 32 = 9 times bigger, thus as
the distance from source spreads the energy per unit area
diminishes.


Properties of Sound
In air, the expression for each acoustical property is:

Sound Intensity Level:

Li 10 log

Sound Power Level:

LW

I
I ref

dB

W
10 log
dB
Wref


Properties of Sound
The decibel scale and use of reference levels
 Level is used as understood in the term “water level”
i.e. height relative to something else, say the
riverbank.
 The softest sounds heard about 0.000,000,000,001
watts/m2
 Saturn rocket at lift-off is greater than 100,000,000
watts/m2


Common Sound Levels


Common Sound Levels
 1 dB change barely perceptible to person with
excellent hearing

 3 dB difference would be just perceptible to
the average listener
 5 dB change clearly noticeable
 10 dB increase typically perceived as twice as
loud.


Decibel Addition
Addition is a simple sum
n

Lp TOTAL

10 log

10

Lp /10
i

i 1

Adding; 89.0dB plus 85.0dB plus 90.0dB
10log [ 1089/10 + 1085/10 + 1090/10] = 93.2 dB


Decibel Addition
Numerical difference
between levels
LP1 and LP2 (dB)

Amount to be
added to the higher
of LP1 or LP2 (dB)*

0

3.0

1

2.5

2

2.1

3

1.8

4

1.5

5

1.2

6

1.0

7

0.8

8

0.6

9

0.5

10

0.4

greater than10

0.0 for all practical
purposes

Decibel Subtraction
This can be done using the equation

Lp 10 log 10

L / 10
1

10

L / 10
2

Subtracting; 85 from 90dB.
10log [ 1090/10 - 1085/10] = 88.3dB
Alternatively the table for addition of dB can be used
in an iterative manner


Average Sound Level Pressure
The equation to determine the average sound
level for a number of measurements of a source
is:

Lp

1
10 log
n

n

10

Lp /10
i

i 1

Averaging; 81, 86, 82 and 84dB.

10log 1/4[ 1081/10 + 1086/10 + 1082/10 + 1084/10] = 83.7dB


Directivity of Sound Propagation


Frequency Characteristics of Sound


Workplace sounds are not simple sine waves



Broad spectrum of frequencies can to be divided into
smaller bandwidths to assist the analysis for risk
assessment, noise control, evaluation of hearing
protection etc.



The sound level meter may contain a filter measure
selected bandwidths of concern or a frequency
analyser can be used. Most common bandwidths are
1. octave bands
2. third octave bands


Overall Sound Level by Frequency
Frequency, (Hz)

63

125

250

500

1000

2000

4000

SPL (dB re 20µPa)

95

72

85

80

86

82

79

Rearranging in
ascending order

72

79

80

82

85

86

95

Difference

7

0.2

1

0.5

2

4.9

Add

0.8

3

2.5

2.5

2.1

1.2

Cum. level dB

79.8

83

85.5

88

90.1

96.2


Octave Frequency Analysis


Weighted Sound Levels
 Microphones and human ears have a different
frequency response.
 Several weighting networks (or frequency filters) were
designed to make the SLM respond to frequency like
our ear.
 The accepted frequency for occupational and
environmental noise is the A weighting.
 Common weightings are A, C, Z and linear


Frequency, Hz

A weighting

C weighting

Z weighting

16

-56.7

-8.5

31.5

-39.4

-3.0

63

-26.2

-0.8

125

-16.1

-0.2

250

- 8.6

-0.0

Flat

500

- 3.2

-0.0

from10Hz

1000

0

0

to 20kHz

2000

+ 1.2

-0.2

4000

+ 1.0

-0.8

8000

- 1.1

-3.0

16000

- 6.6

-8.5


Equal Loudness Contours


Human Audible Range of Hearing
 The normal range in human hearing is 20 Hz to 20,000 Hz.
Sound at higher frequencies is called Ultrasound
whereas lower frequencies is Infrasound
 Human sensitivity to hearing based on configuration of
the ear is greatest from 2,000 to 5,000 Hz
 Minimum audible field in the most sensitive range is
close to 0 dB, which is 20 µPa
 This is the principal reason 20 µPa is designated the
international reference pressure for determining SPL


Time-Varying Noise Sources
 Compressors, fans, electric motors etc. generally
produce sounds that are continuous or steady-state.

 A steady-state sound remains relatively constant in
time, varying by less than +/- 3 dB
 But what if they cycle off and on?

 Sources with levels that fluctuate more than ± 3 dB
are generally classified as variable noise sources like
a brake press
 Which part of the noise should we measure?


 Another type of time varying noise is that produced as
an impact or impulse.
 Impact sound can be generated by the solid collision
between two objects, such as hammering, dropped
objects, a door slamming shut, metal-to-metal impacts,
etc. or by explosions such as gun fire or explosive
tools.
 Impulse sound is defined as an event having an
exponential rise time constant of 35 milliseconds, and
an asymmetric decay time constant of 1.5 seconds.


Anatomy of the Human Ear


Healthy Cochlea

The cilia ( sensory hairs)
appear normal


Damaged Cochlea

Loss of cilia from
noise exposure


Threshold Shifts
 Temporary Threshold Shifts (TTS) hearing returns to
normal after noise exposure


Permanent Threshold Shifts (PTS) repeated noise
exposure without a return to normal

 Standard Threshold Shifts (STS) > 10 dB average loss
in 2000, 3000, or 4000 Hz in either ear


Noise and Acoustics
Hazardous noise exposures can occur

On the Job

Off the Job


Noise and Acoustics
 Noise-Induced Hearing Loss
1. Causes no pain

2. Causes no visible trauma
3. Leaves no visible scars
4. Is unnoticeable in its earliest stages
5. Accumulates with each overexposure
6. Takes years to notice a change

Is Permanent + 100% Preventable


Noise and Acoustics
Factors Affecting Hearing Loss
1. Noise Intensity or Sound Pressure
2. Frequency or Pitch
3. Length of Daily Exposure

4. Duration of Exposure in Years
5. Individual Susceptibility
6. Other Factors (disease, genetics, lifestyle, medication,
age, etc.)


Noise and 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 and 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 and Acoustics


Noise Risk Register


Noise Risk Assessment


Noise Risk Register by Job Title



Rank Order
Noise Risks



Chipping Concrete Floor
96 dBA (TWA) at 4.5 hours


Sandblasting - 125 dBA (4 hour sample)
Inside hood - 109 dBA


36" Wall Saw - 100 dBA
(4.5 hour sample)

Noise Risk Management
 What is a “safe” level?
 There is no simple answer as to what constitutes a “safe”
noise exposure limit.
 The answer involves the intricate and diverse variables
associated with an person‟s susceptibility to noise and
characteristics and magnitude of the noise exposure.
 Hearing conservation measures include:
• Noise exposure criteria of 85 dBA for the 8-hour
workday AND
• Peak levels should never exceed 140 dBC.


OSHA Noise Standard
Program Strategy – Noise and Hearing Conservation
Noise Exposure Program – 90 dBA 8 hour TWA
(Equivalent Exposure Concept)
Hearing Conservation Program – 85 dBA 8 hour
TWA

TWA- Time Weighted Average


Table G-16 - Permissible Noise Exposures
Duration per day, hours

Sound level dBA slow response

8

90

6

92

4

95

3

97

2

100

1½

102

1

105

½

110

¼ or less

115

Footnote(1) When the daily noise exposure is composed of two or more periods of noise exposure of different
levels, their combined effect should be considered, rather than the individual effect of each. If the sum of the
following fractions: C(1)/T(1) + C(2)/T(2) C(n)/T(n) exceeds unity, then, the mixed exposure should be
considered to exceed the limit value. Cn indicates the total time of exposure at a specified noise level, and Tn
indicates the total time of exposure permitted at that level. Exposure to impulsive or impact noise should not
exceed 140 dB peak sound pressure level.


Noise Action Level
 Action Level (AL) = 85 dBA for a 8-hour TWA
 Determined without regard to hearing protector attenuation
 Hearing Conservation Program (HCP) required when noise
exposures equal or exceed the action level
 Monitoring program implemented when noise exposures
equal or exceed the action level


Measurement of Noise Loudness
170 dB

Jet airliner

130 dB

Pneumatic chipping and riveting

120 dB

Riveting hammer

110 dB

Shouting loudly or automatic punch press

90 dB

Construction site pneumatic drilling

70 dB

Street sounds

38 dB

Quiet bedroom

This is a logarithmic scale – an increase of 1dB means
about 30% more noise


Exposure Level vs. Duration
140

120

100

80
Decibel
60
- Noise Control Program

40
- Hearing Conservation

20

0

2

4

6

8

Exposure Duration (Hours)


Noise Measuring Equipment


Sound Level Meters (SLM)
Continuous on-mobile sources

 Noise Dosimeters
Mobile various sources

 There are two types or classes of SLMs established
by International Standards

Class 1 - precision meter, and
Class 2 - general purpose instrument with lower
performance specifications than Class 1
 Measurements are undertaken with the appropriate
class of SLM


 There are three types of microphones
1. Random incidence microphones, (omnidirectional)
2. Direct incidence microphones, (free-field)
3. Pressure microphones (pressure-response)
 Most commonly used is the random incidence or omnidirectional microphone


SLM and Octave Band Analyzer



Frequency analysis 1/3 octave-band spectral data for the sound levels
generated by an internal combustion engine.


 A noise dosimeter is an SLM designed to measure a
worker‟s noise exposure over a period of time.
 The output is available as both noise dose and
noise exposure.
 Noise exposure may be shown as an Leq,8h, LEX,8H, or TWA.
 TWA - Time weighted average - implies an eighthour (8-hour) average.


1/3 Octave Band Analyzer


Case Study: Noise Monitoring
Case Study: Consider a worker who undertakes these
work tasks:
1. Use planer with noise level at the ear of 102 dBA for 0.5
hours
2. Use saw with noise level at the ear of 98 dBA for 4 hours
3. Use of drill with noise level at the ear of 89 dBA for 2.5
hours
4. Hammering with noise level at the ear of 92 dBA for 2
hours


OSHA Maximum Exposure Time
Leq

Time

Leq

Time

Leq

Time

Leq

Time

80

32.0

90

8.0

100

2.0

110

0.50

81

27.9

91

7.0

101

1.7

111

0.44

82

24.3

92

6.1

102

1.5

112

0.38

83

21.1

93

5.3

103

1.3

113

0.33

84

18.4

94

4.6

104

1.1

114

0.29

85

16.0

95

4.0

105

1.0

115

0.25

86

13.9

96

3.5

106

0.87

116

0.22

87

12.1

97

3.0

107

0.76

117

0.19

88

10.6

98

2.6

108

0.66

118

0.16

89

9.2

99

2.3

109

0.57

119

0.14


Noise Exposure Monitoring
Calculate dose using the formula:
Dose = 100 x (C1/T1 + C2/T2 + C3/T3 + ... + Cn/Tn)
where: Cn is the time spent doing each work task
and allowable
Tn =

8
2(L-90)/5

 Calculated noise dose of planer at 102 dB for 0.5
hours, sawing at 98 dBA for 4 hours; drilling at 89
dBA for 2.5 hours; and hammering 92 dBA for 2
hours = 247.1% or 96.5 dBA for 8-hour TWA.


Noise Exposure Monitoring
Source

SPL,dBA

Time Hrs.

OSHA max
PEL 8- Hrs.

OSHA max
PEL 9-Hrs

Planar

102

0.5

1.5

----

Saw

98

4

2.6

----

Drill

89

2.5

9.2

----

Hammer

92

2

6.1

----

9.0

Over maximum
8-hours

Total
LAeq,8h

97 dBA

3.0 Hrs.
(180 mins.)

2.7 hrs.
(160 mins)


No.

Work Process or
Operation

LAeqT

Peak

Risk
Assessment

Complies with OSHA
Requirements

1

Honda Bike

67

-

Very Low

YES

2

Cushman Truck

75

103

Low

YES

3

Cushman Sprayer

76

102

Low

YES

4

Quad Runner

72

101

Low

YES

5

Mower Reelmaster

83

102

Low

YES

6

Mower Ransomes

83

102

Low

YES

7

Mower John Deere

86

105

Moderate

NO, if exposure exceeds
6 hrs. 36 min.

8

Mower John Deere

90

115

High

2 hrs. 32 min.

9

Blower Echo

94

108

Very High

1 hr. 4 min.

10

Whipper Snipper
Kawasaki

98

113

Extremely
High

25 min.


BENCH GRINDER

ENGINEERING SHOP
APPALACHIAN FRUIT RESEARCH STA.

Running (no load)
Running (with load)

76.3 dBA
92.1 dBA

ANGLE GRINDER

ENGINEERING SHOP

Running (no load) 101.4 dBA
Running (with load) 106.2 dBA


SCREW CHILLER

QUARANTINE GREENHOUSE
FOREIGN DISEASE / WEED SCI. RES.
UNIT

102.4 dBA

WELL PUMPS
WATER TREATMENT BUILDING

82.8 dBA


RADIAL ARM SAW

ENGINEERING SHOP
APPALACHIAN FARMING SYSTEMS
RESEARCH CENTER

Running (no load)
Running (with load)

81.5 dBA
90.5 dBA

DRILL PRESS

ENGINEERING SHOP
RESEARCH CENTER

Running (no load)
Running (with load)

88.7 dBA
93.8 dBA


GRINDING HOODS

RESEARCH CENTER

89.3 dBA

AIR HANDLER

QUARANTINE GREENHOUSE
FOREIGN DISEASE / WEED SCI. RES.
UNIT

87.8 dBA



FRUIT GRADER / SORTER
FARM CENTER COMPLEX

91.1 dBA


Statistical Risk Modelling
Predicted Noise Exposure Winter Schedule 1998 + Ballet
All Performances

100

95

85

80

75

Performance

weekly average

29-Oct

19-Oct

09-Oct

29-Sep

19-Sep

09-Sep

30-Aug

20-Aug

10-Aug

31-Jul

21-Jul

11-Jul

01-Jul

21-Jun

11-Jun

01-Jun

23-May

13-May

03-May

23-Apr

13-Apr

03-Apr

24-Mar

14-Mar

05-Mar

23-Feb

13-Feb

03-Feb

24-Jan

14-Jan

04-Jan

70
25-Dec

dB(A)

90

Long term Exposure


Personnel Notification of Results
 The employer shall notify each employee exposed at or above
85 dBA of the noise monitoring results.


Day-Night Environmental Test

WHO guideline for night noise (Lnight, outside) is 40 dB (2002.


Environmental Exposure Model
Comparison of Day/Evening/Night
Exposures

Guidance for Average Background Noise Levels,
LA90,T

Type of Area

WHO interim guideline for night noise
(Lnight, outside) is 55 dB (2002).

Time of Day
Day
(700-1800)

Evening (18002200)

Night (2200700)

Rural (i.e., negligible transportation)

40

35

30

Semi rural and low density
transportation

45

40

35

50

45

40

55

50

45

Borders of industrial areas

60

55

50

Within industrial areas

65

60

55

Near some commerce or industry
Near dense transportation


Environmental Exposure Model


Inversion of Temperature
and Sound
Daytime

Night and
temperature
inversion


Wind Direction and Sound


Noise Engineering Controls







Enclosures
Sound barriers
Complete enclosure
Sound proof cabs
Mufflers
Equipment and exhaust


Sound Contour Mapping
Planograms


Exposure Modelling Risk


Noise and Acoustics
Hierarchy of Controls
ENGINEERING
CONTROLS
 Buy Quiet
 Vibration Pads
 Enclosures
 Barriers
 Isolation

ADMINISTRATIVE
CONTROLS
 Rotate Workers
 Extended Breaks
 2nd/3rd Shift

PERSONAL
PROTECTIVE
EQUIPMENT


Flanking

Absorbed

NOISE

Sound Transmission Loss
Multiple layer panels
combine a sound absorption
material with a high
transmission loss material to
form a composite system.
Can be sound absorbing
material on one side or a
complex „sandwich” panel
with a number of layers


Sound Transmission Loss


Administrative Controls
 If engineering controls are not feasible, administrative controls
should be considered:
 Rotate employees to reduce exposure
 Limit number of at-risk workers
 Modify or upgrade existing machinery

 Specify noise limit on new equipment
 Maintain and repair equipment/machinery
 Post signs for workers to use hearing protection
 Report noisy equipment/machinery to supervisor


Types of Hearing Protection
 There are three types of hearing protection – ear muffs,
earplugs and ear caps.
 Ear muffs and earplugs provide about equal protection, ear
caps somewhat less.

Earmuffs

Earplugs

Ear caps

Hearing Protection
Selection and Use
 Ensure it is suitable for the job
 Make sure it hearing device does
not interfere with other safety
equipment
 Discard disposal ear plugs

 Regular maintain ear muffs and
ear channel caps
 Home-made protectors don‟t work
(e.g., cotton, wool)
 Use hearing protection with
communication devices


Noise and Acoustics
 Overprotection/Underprotection

20-25% workers exposed between 80-90
dB will still get NIHL. While HPD use is
mandatory at 90 dB, you should protect to
at least 85 dB.

Avoid overprotection – protected levels
below 65-70 dB can create additional
safety risk.


Sports and Recreational Activities
Protect your hearing off the job too……
 Loud music
 Personal stereos
 Car entertainment
 Electronic devices
 Lawn mowers
 Chain saws
 Fire arms and fireworks
 Sporting events
 Racing
 Highway driving with vehicle windows open

Hearing Protector Attenuation
 For overexposed employees
and those at-risk of being over
exposed
 At a minimum attenuate
< 90 dBA 8-hr TWA
 For workers with an STS
attenuate < 85 dBA 8-hr TWA
 Whenever noise exposures increase risk to more workers
exposed, change in operation, process or machinery

 Reevaluated to determine adequacy of the selected devices


Noise Reduction Rating (NRR)
 Defined as the maximum number of decibels (dB) that the
hearing protector will reduce the sound level when worn.
 NRR must be on the hearing protector
package.
 NRR example for A-weighted data
Estimated exposure (dBA) = TWA (dBA) - (NRR - 7)
Example (plugs or muffs):
TWA = 109 dBA, NRR= 29
109 - (29-7) = 109 dBA - 22dB = 87 dBA


Noise Reduction Rating
80th %
Minimallytrained

Current NRR Label

20th %
Proficient
Users

Mock-up of New Label

Proper Use of Hearing Protection
 It takes just a few minutes of
unprotected exposure at noise
above 115 decibels to risk hearing
damage.
 Earplugs not well inserted into the
ear canal will not provide complete
protection.
 Likewise, earmuffs not snug against
the head will “leak” noise into the
ear.


Audiometric Testing Program
 Baseline audiometric test taken when noise exposures equal
or exceed the action level.
 A qualified person performs the hearing test, usually an
audiologist.
 Results interpreted by qualified person
 Audiometer checked before each use and calibrated
acoustically annually

 Records of calibrations required


Audiometric Testing
 Provided at no cost to the employee
 Baseline audiogram within 6 months of first noise exposure at
or above action level
 For mobile test van, < 12 months
 Provided initially and annually
 Allowance for aging
 STS notification


Example of Audiogram

Baseline

Annual


STS Notification
 Recall standard threshold shift (STS) definition:
 > 10 dB avg. loss 2kHz – 4 kHz
 Employer may retest within 30 days to verify the STS.
 Audiologist shall determine need for further evaluation.
 Employer shall notify the affected employee of the STS
in writing within 21 days.


Audiogram with Hearing Loss

2KHz

3KHz

4KHz


Personnel Training
 Training is required for employees who are exposed to
noise at or above 8 hr. TWA of 85 dB.
 Topics must include:
1. Effects of noise on hearing
2. Purpose of hearing protectors
3. Advantages and disadvantages
of hearing protectors
4. Attenuation of hearing protectors
5. Instructions on selection, fitting,
use, and care of hearing protectors
6. Purpose of audiometric testing


Post the Standard
 Make available to affected employees or their representatives
copies of the standard.
 Post a copy of the standard in the workplace


Recordkeeping
 Permanent hearing loss is a OSHA recordable illness
 Provide access to employee exposure monitoring and
audiometric data
 If business terminates. transfer records to successor or
forward documents to NIOSH
 Otherwise, keep noise measurements: > 2 years
 Audiometric tests > employment duration:
1. Name, job classification and dBA-TWA
2. Date, examiner‟s name and calibration date
3. Background measurements of audiometric test room


Don‟t Take Noise for Granted!

 Hearing damage creeps
up on you
 Hearing loss is easily
preventable

 Once it has happened,
there may be no cure


Contact:
Bernard L Fontaine, Jr., CIH, CSP
The Windsor Consulting Group, Inc.
Email: windsgroup@aol.com
Tel: 1+ 732.221.5687

Occupational Noise Exposure and Hearing Conservation

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