Plans have been unveiled to stop San Francisco’s Golden Gate Bridge from emitting strange humming sounds when the wind blows.
Described variously as “screeching”, “trippy” and “otherworldly”, the discordant, multi-tonal arias began to be noticed in June 2020, after the bridge’s western railing was given thinner slats to lessen wind resistance.
Thinner slats were necessitated by the planned addition of suicide-deterrent netting under the bridge’s deck, which would increase wind resistance.
In July 2020, the bridge’s authority, the Golden Gate Bridge Highway and Transportation District, hired what it called “the world’s foremost bridge aerodynamics and acoustics experts” to analyse the cause of the sounds.
In autumn 2020, the authority started testing a full-scale model of the railing in a wind tunnel to further pinpoint the mechanism that made the bridge sing.
The solution it settled on is to stick U-shaped clips, each an eighth of an inch thick and with a thin rubber sleeve inside, down both edges of all 12,000 vertical slats on the railing to dampen wind-induced vibrations. The clips will be painted orange so they fit in with the bridge’s appearance.
This task will cost $450,000, and will be funded from the bridge’s operating budget. It is expected to take until the end of 2022 to complete.
The district said that when it is done, some tones may still be audible during severe wind conditions, but their volume would be reduced by 75%. The district said it would be “barely audible above background noise”.
The installation will not affect the bridge’s structural integrity during high winds.