Noise Control In Highway Construction Kwangseog Ahn, MS and Susan Moir, MS Department of Work Environment University of Massachusetts Lowell

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 Exposure Evaluation 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 exhaust

Air Compressor exhaust engine

Power Tool Tying Rebars

Short-term Noise Levels

Octave Band Spectra

Noise Control Ideal control hierarchy 1. Engineering 2. Administrative 3. Hearing protectors Practical control hierarchy 1. Hearing protectors 2. Administrative 3. 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) PPETarget Level (dBA) Sound Pressure Level (dBA) Earmuff Formable Earplug Other Earplug

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

Calculating a 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)

Calculating a 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)

Sound Power Level 110 dB Sound Pressure LevelSound Power Level 80 dB74 dB X 2X Single Number IndexDepending on Distance

Calculating a 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)

Calculating a 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)

Engineering Controls Internal combustion engines - acoustical enclosures and barriers Exhausts - mufflers/silencers Vibrating parts, pipes, etc. - isolation/sound absorbing material Good maintenance

Noise Control in Highway Construction Engineering and administrative + hearing protectors Full support of top management –Purchasing policy –Construction plan Hearing conservation program

References - Noise Exposures In Construction Workers Blute N et al, Appl Occup Environ Hyg 14(9): (1998) Legris M and Poulin P, AIHAJ 59: (1998) Neitzel R et al, AIHAJ 60: (1998) Sinclair JDN and Haflidson WO, Appl Occup Environ Hyg 10(5): (1995)