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