Bridges are supposed to be quiet, steady things. You drive across, maybe admire the view, and move on. But some bridges have a voice. One of the most famous landmarks in America started singing in 2020, and people for miles around could hear it.
Here's what happened. In June 2020, residents across San Francisco and Marin County began noticing a humming, whistling sound on windy days. The Golden Gate Bridge's managers traced it to new railing slats, installed starting in 2019 to help the bridge handle stronger winds. When the wind blows hard through those slats, they hum like the reed of a giant instrument.
A Safety Upgrade With a Soundtrack
Wind has always been a concern for the Golden Gate. The bridge was designed to safely handle winds up to 68 miles per hour. In 1951, a windstorm showed the deck could sway and roll, and the bridge was later reinforced with extra bracing. To keep watch, wind instruments called anemometers sit midway between the two towers on the west side and on one of the towers.
The newer slats on the west side were chosen to raise the bridge's wind tolerance to 100 miles per hour. They're more flexible than the old ones. The sound had actually been predicted in wind tunnel tests, but it wasn't mentioned in the project's environmental report, so the public was caught off guard.
Two Different Notes
Engineers found the bridge actually makes two sounds. When wind passing through the slats reaches about 22 miles per hour, it produces a low tone between 280 and 700 hertz. When the wind hits the slats at an angle at around 27 miles per hour, they produce a higher-pitched sound, around 1,100 hertz.
Not everyone loved the new music. People described it as eerie and as a shrill screeching sound. In December 2021, the bridge district approved a fix: 12,000 U-shaped clips with rubber dampers placed between the slats, at a cost of $450,000. Testing suggested it would cut the noise by about 75 percent, though some of the high-pitched sound was expected to remain.
Kentucky's Original Singing Bridge
The Golden Gate isn't the first bridge known for singing. In Frankfort, Kentucky, the St. Clair Street bridge is so well known for its sound that it's simply called the Singing Bridge.
There, the music comes from traffic instead of wind. In 1937, the bridge's solid floor was replaced with an open steel grate. Ever since, vehicles crossing it have made a distinct humming noise.
The bridge itself dates back to 1893, built over the Kentucky River and stretching more than 400 feet. As of 2019, it carried over 5,000 vehicles a day between downtown Frankfort and South Frankfort. But after more than 125 years, the steel had grown too deteriorated to repair. The bridge was closed in 2024, and plans call for it to be torn down and replaced.
When Engineering Makes Music
Bridges sing for different reasons. Air flowing past thin slats can set them vibrating. Tires rolling over a metal grate can create a steady hum. Either way, the structure becomes, for a moment, an instrument.
So if you ever find yourself near a big bridge on a blustery evening, pause and listen. You might hear the wind playing a song that the engineers never quite meant to write.
