Sunday, August 1

The quest to solve the mysterious ‘spooky’ buzz of the Golden Gate Bridge | San Francisco


SSomewhere in a wind tunnel on the southwestern side of Ontario, a group of the world’s leading bridge acoustics and aerodynamics experts are puzzled over a full-scale model of the Golden Gate Bridge railing.

Experts have been hired to solve the mysterious problem of a strange hum that has been emanating from the famous San Francisco Bridge for the past year, driving some nearby residents into a state of insanity.

The sound, heard only on windy days, has been likened to a “ghostly harmonica”, “monks singing” and a “hissing kazoo”.

The strange moan has quickly become a legendary piece of the San Francisco listening landscape. Amateur detectives have I wandered the hilly city streets tracing the source of the sound and an electronic music producer claimed to have mixed it in a soundtrack of existential dread.

Some fans called it the “relaxing” song of the bridge. Others called it “creepy” or “unbearable.” One woman simply blamed the “aliens”.

“It sounded like a noise that I could imagine jailers using to torture prisoners,” said a disturbed resident on the social media app NextDoor.

But love it or hate it, sometime this summer, according to a bridge spokesperson, engineers will announce their plan to turn off the sound.

Shortly after city residents began complaining about the hum in June 2020, puzzled bridge officials conducted an investigation. They followed the sound and even used instruments to measure the vibrations of the hum, finding that it often emits a frequency of 440 hertz, which matches the musical note A.

As one Nextdoor poster pointed out, you could use it to “tune your oboe.”

Finally, experts determined that the buzzing occurs when ravenous city winds hit a set of newly installed bridge railing slats from a slightly off angle, either slightly north or slightly south of the usual westerly winds.

“After studying this phenomenon extensively, we have determined that the sound is coming from a new, more streamlined railing that we installed on the west sidewalk,” said bridge spokesman Paolo Cosulich-Schwartz. “It was part of a redevelopment of the Golden Gate Bridge designed to protect the bridge for future generations by allowing it to withstand strong sustained winds of up to 100 mph.”

The bridge has been briefly closed three times in its 84-year history by winds of 69 to 75 mph.
The bridge has been briefly closed three times in its 84-year history by winds of 69 to 75 mph. Photograph: Jeff Chiu / AP

He said new, thinner railing cleats were installed to ensure that the bridge did not reach the same end as the ill-fated Tacoma Narrows Bridge in Washington, which began to sway violently in the wind and then collapsed in 1940, shortly after To do it. built. That span, nicknamed “Gallopin ‘Gertie,” has become a classic. engineering school lesson on how not to build a bridge.

“So this was a project we had to do,” Cosulich-Schwartz said of the Golden Gate Bridge, the highway and transit district of last year’s wind resistance modernization, which cost $ 12 million. “With the impacts of climate change leading to more severe weather events, it was even more urgent to complete it as soon as possible.”

A study conducted by the agency in 2013 showed that the maximum sustained wind speed that the bridge was built to withstand was 69.34 mph. It has already been briefly closed three times in its 84-year history by winds of 69 mph to 75 mph in 1951, 1982 and 1983. But there was no damage.

So the bridge engineers thought the new thinner slats would allow the bridge to withstand sustained 100 mph winds, which the study estimated would only occur every 10,000 years. They just didn’t predict that slats would create such a cacophony in normal years.

Sustained 100 mph winds would likely occur only in a tornado, hurricane or tropical storm situation, said Warren Blier, a veteran science officer with the National Weather Service. And none of them have been known or anticipated to reach anywhere near San Francisco.

The sound coming from the bridge, which is only heard on windy days, has been compared to a
The sound coming from the bridge, which is only heard on windy days, has been likened to a “ghostly harmonica”. Photograph: John G Mabanglo / EPA

“It seems highly unlikely to me,” said Blier, who acknowledged that his job is normally to predict the weather seven days in advance, not for the next 10,000 years. “In the history of the state, no hurricane has hit the northern coast of California.”

Meanwhile, bridge engineers are determined to find a solution to the drone.

At the RWDI engineering company, an hour west of Toronto, a full-size model of a 12-foot section of the new railing has been built in a wind tunnel the size of a convention center conference room. Engineers are subjecting it to gusts of various wind speeds and testing modifications to see if they can silence the hum. The same company tested a model of the whole bridge at an earlier stage, but apparently no one realized that hum would be a problem.

“We will share more information on a possible solution this summer,” Cosulich-Schwartz said. “We understand that some of those who live near the bridge tend to find it distressing. We want to be good neighbors. So hopefully we will be soothing our neighbor’s ears with a solution. “

But, in this famous stubborn city, not everyone wants to see the buzz go away. A local blogger even made a Golden Gate Bridge Ambient Sound Playlist to help listeners on those sleepless nights when the sound is missing.

“I like the sound,” said Brianne Howell, a West San Francisco resident who captured a video showing the humming bridge on one of his regular walks along the coast. “It reminds me of the creepy sound in a movie when something creepy is about to happen. I think it’s kind of sad to get rid of him. “




www.theguardian.com

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