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Noise ControlIn Highway Construction
Kwangseog Ahn, MS and Susan Moir, MS
Department of Work EnvironmentUniversity of Massachusetts Lowellwww.uml.edu/Dept/WE/COHP
Big Dig
• Highway construction in Boston• Replacing old elevated highway• Constructing tunnels
Study Objectives
• Evaluate noise• Reduce exposures• Recommend practical controls
Noise In Highway Construction
• Widespread & multiple sources• Exposed at/close to sources• Short-term peak exposures• Vibration & chemical hazards• Safety hazards
Noise ExposureEvaluation Methods
• Personal samples• Octave band samples• Walkthrough observation• Area samples• Conversations with safety officers
and workers
Targeted Sources
• Drilling rig• Portable air compressor• Power tool for tying rebars• Impact/impulsive noise
Drilling Rig
engine
engine
exhaust
exhaust
Air Compressor
exhaust
engine
Power Tool Tying Rebars
Short-term Noise Levels
Source Sound Pressure Level (dBA)
Drilling Rig 95 (79 - 118)
Air Compressor 85 (82 - 85)
Power Tool 96 (70 – 107)
Octave Band Spectra
30
40
50
60
70
80
90
100
110
31.5 63 125 250 500 1000 2000 4000 8000 16000
Octave Band Center Frequency (Hz)
So
un
d P
ress
ure
Lev
el (
dB
)
Drilling Rig
Air Compressor
Power Tool
Noise Control
• Ideal control hierarchy
1. Engineering2. Administrative3. Hearing protectors
• Practical control hierarchy
1. Hearing protectors2. Administrative3. Engineering
Hearing Protectors
• Widely used• Workers often not wearing• Not sufficient protection• Supplemental to engineering and
administrative controls
Noise Reduction Rating (NRR)
• Single-number rating• Tested in laboratory • Derated under real conditions
(NIOSH criteria, 1998)– Earmuffs: subtract 25%– Formable earplugs: subtract 50%– Other earplugs: subtract 75%
Required NRR (dB)
PPE Target Level (dBA)
Sound Pressure Level (dBA)
85 90 95 100 105 110
Earmuff80 16 23 29 36 43 49
85 9 16 23 29 36 43
90 3 9 16 23 29 36
FormableEarplug
80 24 34 44 54 64 74
85 14 24 34 44 54 64
90 4 14 24 34 44 54
OtherEarplug
80 40 57 73 90 107 123
85 23 40 57 73 90 107
90 7 23 40 57 73 90
Assessment of Noise Levels: Existing methods
• Noise dosimetry• Task-based dBA levels• Published reference values
• Takes too much time• Sources/technology not available
Administrative Controls
• Reduce exposure time– Adjust worker schedule
• “Noise perimeter zone”– Keep unnecessary workers out of high
noise zone– Only designated workers within zone
Calculatinga Noise Perimeter Zone
1. Measure sound pressure level at a distance from a noise source
2. Measure distance between the noise source and measurement point
3. Convert sound pressure to estimated sound power (Table #1)
4. Calculate a Noise Perimeter Zone (Table #2)5. Estimate maximum exposure time within a
Noise Perimeter Zone (Table #3)
Calculatinga Noise Perimeter Zone
1. Measure sound pressure level at a distance from a noise source
2. Measure distance between the noise source and measurement point
3. Convert sound pressure to estimated sound power (Table #1)
4. Calculate a Noise Perimeter Zone (Table #2)5. Estimate maximum exposure time within a
Noise Perimeter Zone (Table #3)
Table #1. Converting Sound Pressure Measurement to Sound Power Level (dB)
Measured Sound Pressure Level (dB)
Measured Distance from Source (ft)
5 7 10 15 20 3080 95 98 101 104 107 110
82 97 100 103 106 109 112
84 99 102 105 108 111 114
86 101 104 107 110 113 116
88 103 106 109 112 115 118
90 105 108 111 114 117 120
92 107 110 113 116 119 122
94 109 112 115 118 121 124
96 111 114 117 120 123 126
98 113 116 119 122 125 128
100 115 118 121 124 127 130
Sound Power Level
110 dB
Sound Pressure LevelSound Power Level
80 dB 74 dB
X2X
Single Number Index Depending on Distance
Calculatinga Noise Perimeter Zone
1. Measure sound pressure level at a distance from a noise source
2. Measure distance between the noise source and measurement point
3. Convert sound pressure to estimated sound power (Table #1)
4. Calculate a Noise Perimeter Zone (Table #2)5. Estimate maximum exposure time within a
Noise Perimeter Zone (Table #3)
Table #2. Calculating Noise Perimeter Zone from Sound Power Measurement
Sound Power Level (dB)
Target Control Level (dB)
80 85 9090 3 2 1
95 5 3 2
100 9 5 3
105 16 9 5
110 29 16 9115 52 29 16
120 92 52 29
125 164 92 52
130 292 164 92
Calculatinga Noise Perimeter Zone
1. Measure sound pressure level at a distance from a noise source
2. Measure distance between the noise source and measurement point
3. Convert sound pressure to estimated sound power (Table #1)
4. Calculate a Noise Perimeter Zone (Table #2)5. Estimate maximum exposure time within a
Noise Perimeter Zone (Table #3)
Table #3. Maximum Exposure Time Within a Noise Perimeter Zone
Sound Pressure Level (dBA)
Maximum Exposure Time (Minutes)
NIOSH(85dBA & 3dB)
OSHA(90dBA & 5dB)
85 480 960
90 151 480
95 48 240
100 15 120
105 5 60
110 1 30
Engineering Controls
• Internal combustion engines - acoustical enclosures and barriers
• Exhausts - mufflers/silencers• Vibrating parts, pipes, etc. -
isolation/sound absorbing material• Good maintenance
Noise Controlin Highway Construction
• Engineering and administrative + hearing protectors
• Full support of top management– Purchasing policy– Construction plan
• Hearing conservation program
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