Angus L. Macdonald Bridge Suspended Spans Deck Replacement Project - - PowerPoint PPT Presentation

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Angus L. Macdonald Bridge Suspended Spans Deck Replacement Project Sound Study

Greg Conley Senior Project Manager/Principal

Who is RWDI?

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Wind Climate & Air Quality Acoustics, Noise & Vibration Sustainable Design Waste & Water

Overview of Presentation

• Human perception of sound
• Purpose of sound study
• Ambient sound measurements
• Simulated construction sounds

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Range of Sound Levels

Human Perception SPL in dBA Sources of Noise Deafening 125 120 110 Sonic Booms Threshold of feeling pain Motorcycle accelerating a few feet away Very Loud 105 95 90 Loud auto horn a few feet away Jack hammer at 15 metre distance Indoors in a noisy factory Loud 85 75 65 Heavy truck pass-by at 15 metre distance Near edge of major highway Normal human speech at 1 metre distance Moderate 55 50 45 Typical urban sound level Typical suburban sound level Typical noise level in an office due to HVAC Faint 40 Sound in a typical library Very faint 20 Deep inside a forest on a calm day

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Human Response to Changes in Sound Level

Changes in Sound Level (dB) Human Perception of Change 1 - 2 imperceptible change 3 just-perceptible change 4 to 5 clearly noticeable change 6 to 9 substantial change 10 and more half or twice as loud

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The above table is applicable to changes in sound level where the noise sources are of the same general character

Purpose of Study

• 1. Establish existing sound environment

surrounding Macdonald Bridge

• 2. Complete sound measurements of

construction tools and activities

• 3. Compare predicted sound levels from

construction to sound criteria

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Ambient Monitoring Locations

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Ambient Monitoring Site

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Ambient Monitoring – Example Time History (ALM – Halifax)

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Average Sound Level Minimum Instantaneous Sound Level Maximum Instantaneous Sound Level Saturday Sunday

Ambient Monitoring Results

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Location Daytime (dBA) (7:00-19:00) Evening (dBA) (19:00-23:00) Night-time (dBA) (23:00-7:00) Halifax 60 58 51 Dartmouth 58 57 51

Construction Sound Summary Results

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Activity/Tool Sound Level Rivet removal Very Loud Drift pinning on truss Drift pinning on trough Air impact wrench on truss Loud Air impact wrench on trough Air torque wrench Moderate Electric torque wrench

Construction Noise Simulation – Sound Blankets

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Construction – Predicted Sound Levels

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Construction – Predicted Sound Levels

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Construction – Predicted Sound Levels

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Summary and Next Step

• Sound levels above existing background levels are

expected

• Sound blanket was not an effective mitigation option
• Residents can close windows or increase background

sound to help reduce annoyance inside their home

• RWDI will be conducting ongoing sound monitoring

during construction

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