Download Noise Exposure for Local Governments and Contractors

Noise Exposure for Local
Governments and Contractors
Disclaimer:
This material is designed and intended for general informational purposes only, and is not
intended, nor shall it be construed or relied upon, as specific legal advice.
INTRODUCTION
Loud sounds can damage sensitive structures in the
inner ear and cause hearing loss. Noise-induced
hearing loss can affect persons of any age and can be
caused by a one-time exposure to intense noise or
continued exposure to loud sounds, but it is
preventable. Employee education is crucial for
prevention, including noise exposure awareness,
whether at work or during leisure activities. They need
to understand how noise-induced hearing loss occurs,
the equipment or operations that produce hazardous
noise and the control measures in place to reduce or
eliminate it.
Many employees perform a wide range of tasks over a 12-month period and their noise
exposures vary daily or seasonally. To promote health and safety for local governments and
construction workers, EMC Insurance Companies has compiled noise data from a variety of
noise sources commonly encountered.
This document does not include the requirements of a hearing conservation program (HCP);
however, that information can be found in EMC’s Hearing Conservation LPIM. The information
provided in this document is designed to protect worker hearing by using the recommended
guidelines established by the American Conference of Governmental Industrial Hygienists
(ACGIH) and the National Institute for Occupational Safety and Health (NIOSH). NIOSH and
ACGIH both utilize a 3-dB exchange rate (the rate at which the noise dose doubles) with an 8hour Time-Weighted Average (TWA) exposure threshold of 85 dBA. This approach is more
conservative than the traditional 5-dB exchange rate utilized by OSHA and offers a greater
opportunity to identify high noise exposures and prevent employee hearing loss. EMC’s
Environmental Health Services and many other industrial hygiene organizations1 suggest
implementing a Noise Control Program based on a noise exposure limit for an 8-hour TWA of
85 dBA (a dose of 100 percent) with a 3-dB exchange rate.
Noise intensity (loudness) and duration (time) of exposure are the critical factors in evaluating
the potential for employee hearing loss. Operations that produce “high noise levels” for a short
duration may not be as harmful as a lower noise level task performed for hours daily. On the
other hand, an extremely loud noise (such as gunshots or a jet engine) may only require a short
duration to cause permanent hearing damage. This document addresses the precautions
necessary to protect employees’ hearing when operating equipment typically used by local
governments and construction companies.
EMC has gathered noise level data from various types of equipment over several years from
multiple government and construction jobsites. The actual noise levels on the job site will vary
depending on several factors, including: the equipment age, the presence and condition of any
1
American Industrial Hygiene Association, www.aiha.org, NIOSH, www.cdc.gov/niosh, ACGIH, www.acgih.org
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Noise Exposure for Local
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sound-reducing features (mufflers, etc.), the brand of equipment, the overall maintenance of the
equipment and the operation being performed.
MEASURING NOISE
The two basic instruments used when measuring noise are a sound level meter (SLM) and a
noise dosimeter. Both instruments measure noise, but provide different information about
worker exposure. They are briefly defined below:
A. Sound Level Meter – An SLM is a handheld unit that measures real-time noise levels.
The benefit of this type of monitor is that it can measure the noise generated by a given
piece of equipment (such as operating a concrete saw). The noise levels are expressed
using the “A scale” in decibels (dBA). The dBA scale is used for compliance with OSHA
regulations and guidelines from ACGIH and NIOSH.
B. Noise Dosimeter – A noise dosimeter is generally the preferred method for measuring
employee noise exposures. It is a portable unit worn by the worker throughout the
workday, continually monitoring the employee’s noise exposure levels. The noise levels
are then “averaged” over the work shift by the dosimeter to provide one noise level
number, generally expressed using the “A scale” in decibels (dBA).
The A Scale (dBA) is used when measuring noise in the work environment because it
approximates how our ears respond to sound. Both the SLM and noise dosimeter should be set
to use this scale.
The noise dosimeter is the best way to determine a worker’s exposure on a particular day.
However, workers who perform various jobs on an infrequent schedule would require multiple
monitoring days throughout the year to determine their noise exposure level. Another approach
is to use the SLM to measure the noise exposure of workers while they perform various tasks or
operate various pieces of equipment. If the noise levels are greater than 85 dBA, the workers
need hearing protection.
SOUND LEVEL MEASUREMENTS
The allowable exposure time to a particular noise level can be calculated using Equation 1,
shown below. Table 1 uses Equation 1 to determine the allowable exposure time in hours or
minutes for noise exposure levels between 80 and 110 dBA.
Eq. 1
or
NL is the measured noise level in dBA.
Example: You are purchasing a new portable air compressor to operate a jackhammer. The
manufacturer’s product information estimates that the noise level is 90 dBA at the operator’s
location. Inserting 90 dBA into Equation 1 indicates the operator can be exposed to 90 dBA for
2.5 hours before exceeding the allowable exposure. Exceeding this time limit could result in
noise-induced hearing loss if adequate personal protective equipment was not used.
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Table 1
Noise Levels and Allowable Exposure Time Using ACGIH Calculations
Decibel Reading
from SLM
ACGIH Time Allowable in
Hours
ACGIH Time Allowable
in Minutes
80
25.398
1524
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
20.159
16.000
12.699
10.079
8.000
6.350
5.040
4.000
3.175
2.520
2.000
1.587
1.260
1.000
0.794
0.630
0.500
0.397
0.315
0.250
0.198
0.157
0.125
0.099
0.079
0.063
0.050
0.039
0.031
0.025
1210
960.0
762.0
604.8
480.0
381.0
302.4
240.0
190.5
151.2
120.0
95.2
75.6
60.0
47.6
37.8
30.0
23.8
18.9
15.0
11.9
9.4
7.5
6.0
4.7
3.8
3.0
2.4
1.9
1.5
Tables 2 and 3 list noise level readings for various types of equipment under normal operating
conditions, as measured by EMC’s Environmental Health Services. In some cases, multiples of
the same equipment type are listed to illustrate that similar equipment can generate different
noise levels. The third column lists the maximum exposure time during a workday without
requiring hearing protection, based on ACGIH and NIOSH criteria.
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Table 2
Noise Levels for Equipment Recorded by EMC Environmental Health Services
Noise Level
Allowed Exposure Time
Location or Equipment
dBA
Without Hearing Protection
Power Plant
Generator
105
4.75 minutes
Offices
73
Unlimited
Streets
Jackhammer
98
23.75 minutes
Dump Truck
80
Unlimited
End Loader
93
76 minutes
Road Grader
98
23.75 minutes
Road Grader
91
120 minutes
Tractor
100
15 minutes
Backhoe
98
23.75 minutes
Street Sweeper (new)
88
240 minutes
Street Sweeper (older)
91
120 minutes
Vac Hauler
93
76 minutes
Wastewater
Jet Vac
83
762 minutes
Pump Room
90
151 minutes
Clarifier
89
190 minutes
Control Room/Lab
68
Unlimited
Vac Tron Mini-Vac
93
76 minutes
Large Vac
98
23.8 minutes
Water Plant
Pre-Treat
82
960 minutes
Blower Room
93-101
76 minutes to 12 minutes
Emergency Generator
108
2.37 minutes
Emergency Generator
101
11.9 minutes
Engine Room
99
19 minutes
Applicator
87
302 minutes
Lawn and Snow
Riding Mower
91
120 minutes
Push Mower
92
95 minutes
Push Mower
91
120 minutes
Large Commercial 3-Deck Mower – Open
94
60 minutes
Mower with Cab
81-82
960 minutes to 1210 minutes
Sharpening Mower Blades
97
30 minutes
String Trimmer
95
47.6 minutes
Hedge Trimmer
99
19 minutes
Leaf Blower
96
37.8 minutes
27” Snow blower
94
60 minutes
Data compiled from previous monitoring surveys conducted by EMC Insurance Companies.
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Table 3
Noise Levels for Equipment Recorded by EMC Environmental Health Services
Allowed Exposure Time
Equipment
Noise Level dBA
Without Hearing Protection
Wood Chipper
96
37.8 minutes
Wood Chipper
101
11.9 minutes
Portable Generator
90
151 minutes
Newer Portable Generator
85
480 minutes
Generator
94
60 minutes
Newer Generator
80
Unlimited
Approximately 8 Feet Away
Chain Saw
94
60 minutes
Chain Saw
100
15 minutes
Hammer Drill
97
30 minutes
DitchWitch RT70 Trencher
94
60 minutes
120 minutes
DitchWitch Walk-Behind 1820
91
DitchWitch 350SX Knife Vibrator
99
19 minutes
DitchWitch R40 Trencher
94
60 minutes
New Backhoe in Cab
75-76
Unlimited
New Backhoe Outside
78-83
Unlimited to 762 minutes
Concrete Saw – Hand
102
9.5 minutes
Target Pro 65 II Concrete Saw
96
37.8 minutes
Target Pro 35 II Concrete Saw
98
23.8 minutes
Tanaka Gas Drill
100
15 minutes
Truck Outside Tamp
85
480 minutes
Hydraulic Chain Saw on Bucket Truck
86
381 minutes
Power Washer
86
381 minutes
Jackhammer with Bobcat – Inside
101
11.9 minutes
Jackhammer with Bobcat – Outside
101
11.9 minutes
Tractor with Backhoe
89
190 minutes
Bobcat
99
19 minutes
Mosquito Fogger
101
11.9 minutes
Portable Air Compressor
85
480 minutes
Front-end Loader
86
381 minutes
Air Impact Wrench
98
23.8 minutes
Pneumatic Wrench – 1”
105
4.7 minutes
Pneumatic Wrench – 1/2”
101
11.9 minutes
Chop Saw
96
37.8 minutes
Ground Tamper
94
60 minutes
Drill with Ratchet Clutch
99
19 minutes
Data compiled from previous monitoring surveys conducted by EMC Insurance Companies.
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EVALUATING MULTIPLE NOISE EXPOSURES DURING A WORKDAY – SLM
To evaluate employee noise exposure during a workday, first identify which tasks generate
noise in excess of 85 dBA using a sound level meter (SLM). Position the microphone near and
perpendicular to the worker’s ear while they perform a specific task. Tables 2 and 3 provide
approximate noise exposures, but will not suffice for compliance noise exposure determinations.
After collecting noise measurements for specific tasks or pieces of equipment, determine the
length of employee exposure during a typical day. It may be helpful to use a “worst case”
scenario when determining peak exposures.
If an employee is exposed to the same decibel level for an entire 8-hour shift, the calculation is
relatively easy. The exposure in dBA is simply the noise level of the equipment or task. For
example, if an employee operated a large, commercial 3-deck mower (94 dBA from Table 2) for
8 hours, the TWA would be 94 dBA. However, few tasks on this list are performed for 8 hours or
have an engine at full power for that length of time. To calculate an exposure for multiple tasks,
add the individual exposures using the following formula:
Eq. 2
Where:
% Dose = Percentage of an 85 dBA 8-hour exposure
(any number greater than 100 indicates an exposure over 85 dBA)
C = Actual time spent exposed to a noise level
T = Allowable time at that noise level using Eq. 1 or Table 1
For example: An employee spends 2 hours mowing while exposed to 94 dBA, then spends 10
minutes operating a string trimmer at 95 dBA and 5 hours operating the new backhoe (74-75
dBA exposure). All noise levels below 80 dBA are considered insignificant and not considered in
the calculation. Therefore, the 5 hours spent on the backhoe is treated as zero.
In this case:
Note: The units (minutes or hours) for actual time and allowable time must be the same.
Any number greater than 100 percent indicates a Time Weighted Average (TWA) above 85
dBA. This percentage result can be converted to an estimated decibel level, if necessary. Using
the example above, the noise dose of 221 percent while mowing and trimming is equivalent to a
TWA of 88.4 dBA and requires hearing protection. Contact your EMC Risk Improvement
representative for additional information.
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EVALUATING NOISE EXPOSURES – NOISE DOSIMETRY
When using a noise dosimeter to measure an
employee’s TWA noise exposure, record the various
tasks performed and their duration. Consult with
managers and employees to determine if the noise
exposure during the monitoring period was that of a
typical day. Additional noise monitoring may be
necessary to determine a worker’s true average
exposure.
EMC’s Environmental Health Services recommends
using ACGIH or NIOSH criteria when evaluating
noise dosimeter data. Noise surveys performed by
EMC will provide both ACGIH and OSHA criteria and
recommendations.
HEARING PROTECTION
EMC’s Environmental Health Services recommends hearing protection for all employees
performing tasks that exceed 85 dBA. This approach should protect workers from most
hazardous noise exposures they encounter.
Noise Reduction Rating (NRR) is a unit of measurement used to determine the effectiveness of
hearing protection devices to decrease sound exposure within a given working environment.
The calculation used by OSHA to determine the noise reduction provided by a given hearing
protector is:
Eq. 3
Where:
NRR = Manufacturer-determined noise reduction rating
The selection of hearing protection is determined by subtracting 85 dBA from the highest noise
level exposure. This number represents the minimum sound level reduction in decibels (dBA)
required of the hearing protection in order to achieve a noise level of 85 dBA in the ears.
Example:
The highest exposure experienced by an employee is 96 dBA while using a leaf blower.
The NRR listed on the earplugs package is 31.
96 dBA – 85 dBA = 11 dBA noise reduction required
(31 – 7) ÷ 2 = 12 dBA noise reduction, so the earplugs are adequate
In this case, the earplugs, when properly fitted and worn, will reduce the wearer’s noise
exposure by an estimated 12 dBA, reducing the noise at the ear to 84 dBA.
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OSHA requires employers to provide a variety of hearing protection types (at least two) to
employees at no cost to them. EMC also recommends this practice. Hearing protector types
include:
Rollable/foam plugs – Compressible foam that is rolled and inserted into ear. It expands to fill
the ear canal and seal against the walls.
Preformed/premolded – Reusable PVC or silicone plugs with1-5 flanges on a stem. Available as
one-size-fits-most or in several sizes.
Custom – Vinyl, acrylic or silicone that is molded by filling the ear canal to make a mold; specific
for each ear. NRR depends on quality of the mold.
Canal caps/banded – Generally, a foam cap or tip attached to a headband that caps off the ear
canal entrance. They generally provide less protection than ear muffs or plugs.
Muffs – Plastic cups that fit against the head and enclose the entire external ears and is sealed
off with fluid or foam-filled padding. May be used in conjunction with ear plugs to protect against
extremely loud noises.
When a single type of hearing protection is inadequate, it may be necessary to wear double
hearing protection consisting of earplugs and earmuffs. Earmuffs, when worn in conjunction with
earplugs, will add an estimated 5 dBA to the OSHA-calculated NRR for the earplugs.
Generally, the highest NRR for earplugs is 33, which will provide an estimated OSHA noise
reduction of 13 dBA. Adding 5 dBA for the addition of earmuffs, increases the OSHA-calculated
noise reduction to 18 dBA. This means that an employee wearing both earplugs (NRR 33) and
earmuffs would have a maximum allowable noise exposure of 103 dBA (18 dBA + 85 dBA). As
a general rule, wearing double hearing protection whenever the expected noise level is 100 dBA
or greater is a good occupational health practice and will help protect employees from noiseinduced hearing loss.
EDUCATION & INFORMATION
EMC Environmental Health Services can assist in evaluating the workplace noise levels. To
schedule a noise survey or to request additional information, contact your agent, Risk
Improvement representative or send an email to [email protected].
FOR ADDITIONAL INFORMATION
Occupational Safety & Health Administration: www.osha.gov
•
Occupational Noise Exposure
American Industrial Hygiene Association: www.aiha.org
•
Protect Yourself from Noise-Induced Hearing Loss
National Institute for Occupational Safety & Health: www.cdc.gov/niosh
• Noise and Hearing Loss Prevention
© Copyright Employers Mutual Casualty Company 2014. All rights reserved.
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