In the spring of 2020, the District became aware of a humming sound coming from the Golden Gate Bridge during high winds. The sound is the result of a confluence of sustained high winds coming from the northwest and passing at a specific angle through the recently installed new west sidewalk Bridge railing. This new railing is part of the Bridge Wind Retrofit project.
The Wind Retrofit is necessary to ensure that the structural integrity of the Bridge is not jeopardized during high winds and will allow the Bridge to withstand extreme sustained winds up to 100 miles per hour. The construction of the Wind Retrofit is especially important in the context of increasing severe weather events due to climate change. The project is also essential for the completion of the Suicide Deterrent System, which will include netting along the length of both sides of the Bridge, further increasing wind resistance.
The Wind Retrofit involves the replacement of the existing Bridge railing on the west sidewalk between the two Suspension Bridge Main Towers with new railing that has thin vertical slats designed to allow more air to flow through the railing. The project also includes the installation of a wind fairing just below the sidewalk level on the outside of the Bridge truss.
Progress Update on Measures to Dampen or Eliminate the Sounds
We know this issue is of great importance to our neighbors and we are pleased to provide the following progress update on measures to address the new sounds.
Since July 2020, the Bridge District has engaged the world’s foremost bridge aerodynamics and acoustics experts to better understand the source of the new sounds coming from the Golden Gate Bridge and to develop potential measures to dampen or eliminate them. First, the experts took sound camera measurements from the Bridge sidewalk during high wind events to record the new sound. These measurements confirmed that the sound is generated by sustained high winds passing through the new, more aerodynamic west railing. Beginning in the fall of 2020, the District began conducting wind tunnel testing of a full-scale model of the railing. In the wind tunnel, engineers were able to recreate the noise in a controlled environment, allowing us to further pinpoint the mechanism of railing and wind interaction that creates the sound. We developed a number of measures in partnership with our bridge aerodynamics and acoustics experts, assessed their feasibility for being installed on the Bridge without jeopardizing the aerodynamic quality of the new railing, and conducted further wind tunnel tests of the selected measures that were initially assessed to be effective and practical.
After extensive testing and evaluation of several distinct measures and materials that could be used to fabricate them, we are pleased to report that we have identified a promising solution that could diminish or eliminate the sound. This potential solution requires additional refinement and testing before it is deemed effective, constructible, and suitable for the harsh environment on the Bridge. This additional refinement and review is ongoing and proceeding as quickly as feasible.
We look forward to sharing the final results of our testing and next steps as soon as they become available.
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