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

Angus L. Macdonald Bridge Suspended Spans Deck Replacement Project Sound Study Greg Conley Senior Project Manager/Principal www.rwdi.com

Who is RWDI? Wind Climate & Air Quality Waste & Water Acoustics, Noise & Vibration Sustainable Design 2

Overview of Presentation • Human perception of sound • Purpose of sound study • Ambient sound measurements • Simulated construction sounds 3

Range of Sound Levels Human Perception SPL in dBA Sources of Noise Deafening 125 Sonic Booms 120 Threshold of feeling pain 110 Motorcycle accelerating a few feet away Very Loud 105 Loud auto horn a few feet away 95 Jack hammer at 15 metre distance 90 Indoors in a noisy factory Loud 85 Heavy truck pass-by at 15 metre distance 75 Near edge of major highway 65 Normal human speech at 1 metre distance Moderate 55 Typical urban sound level 50 Typical suburban sound level 45 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 4

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 The above table is applicable to changes in sound level where the noise sources are of the same general character 5

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 6

Ambient Monitoring Locations 7

Ambient Monitoring Site 8

Ambient Monitoring – Example Time History (ALM – Halifax) Maximum Instantaneous Sound Level Average Sound Level Minimum Instantaneous Sound Level Saturday Sunday 9

Ambient Monitoring Results Location Daytime (dBA) Evening (dBA) Night-time (dBA) (7:00-19:00) (19:00-23:00) (23:00-7:00) Halifax 60 58 51 Dartmouth 58 57 51 10

Construction Sound Summary Results Activity/Tool Sound Level Rivet removal Drift pinning on truss Very Loud Drift pinning on trough Air impact wrench on truss Loud Air impact wrench on trough Air torque wrench Moderate Electric torque wrench 11

Construction Noise Simulation – Sound Blankets 12

Construction – Predicted Sound Levels 13

Construction – Predicted Sound Levels 14

Construction – Predicted Sound Levels 15

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 16