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Bay Curious

The Story Behind the Golden Gate Bridge's New Howl

Katrina Schwartz and Rob Speight
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After a wind retrofit the slats along the pedestrian walkway make a howling noise when the wind hits them just right. (Lindsey Moore/KQED)

If you’ve driven across the Golden Gate Bridge in the last couple of months, you may have heard a startlingly loud humming noise coming from the bridge itself. Bay Curious listener Ryan heard it one day while driving his motorcycle across the bridge.

“Once COVID started it was just fun to go on 20-minute rides,” Ryan said. “It was a pretty easy way to get out of the house and not talk to people.”

Ryan normally avoids crossing the bridge on windy days, but had no choice one day after missing his exit. That’s when he heard it.

“It made this really really loud noise, it sounded like, I don’t know, like a howl or a whistle or something like that,” he said. “It kinda sounded like when you blow into a beer bottle.”

Ryan is not the only person wondering what’s going on with the bridge. Residents report hearing it across the bay, at Lands End, and from other points miles away.

KQED’s senior editor for Arts, Gabe Meline, looked into the strange phenomenon back in June. The sound is coming from new sidewalk railing slats installed as part of a wind retrofit meant to make the bridge safer and more resilient.

But Bay Curious’ sound engineer, Rob Speight, wanted to know a lot more. He dug into the issue further, wondering why bridge engineers decided to change the slats in the first place.

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“When bridge engineers were designing the original railings, they wanted to provide pedestrians a sense of safety while allowing drivers to take in views of San Francisco to the east and the Pacific Ocean to the west, while on the roadway,” says Paolo Cosulich-Schwartz, spokesperson for the Golden Gate Bridge, Highway and Transportation District.

The slats used to be fairly big, like two-by-fours, but in the recent retrofit the engineers made them thinner. They noticed that when the wind hit the slats just right, it made a sound. But they were unprepared for how distinctive — and loud — the howling would be. They also may have underestimated how much people would hate it.

Screenshot of a Reddit discussion about the Golden Gate Bridge’s new howl. The whole thread is interesting. (Reddit)

“In order to create the effect, we do need to see winds with a little bit of northwest or southwest [direction to them],” says Cosulich-Schwartz. “We’re only hearing it when there’s a bit of an angle to it.”

Wind speeds have to be fairly high, too, although engineers are still looking into the specifics. So, the bridge definitely isn’t making this sound all the time, one reason why it can be so eerie when it does.

One other cool thing about the howl is its frequency — 440Hz. As any musician will know, A440 is the tuning standard for the musical note A above C. In general, all western instruments use this frequency as the basis of a standard tuning.

“It’s a happy coincidence that the bridge making a new noise is a musical feature,” Cosulich-Schwartz says. “[It’s] certainly not something we designed for, which is why we’re doing testing. And we’ll be evaluating mitigation measures to dampen or eliminate the noise based on feedback we’ve heard from the community.”

That means you have a short window to hear the bridge singing it’s mysterious song across the bay before the district implements a fix. Keep an eye on the forecast for north-westerly or south-westerly winds and then go listen.

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