Tracking Down A Mysterious Hum In San Francisco
In the past year, we’ve had to get used to a lot of things. And if you live within a couple miles of the Golden Gate Bridge, you may notice from time to time there’s an ethereal hum in the background that can make it all feel extra eerie.
In this story, we hear how it started and what's being done about it.
Click the play button above to listen.
It’s a windy summer day, and I’m working from home at my place in The Richmond, when my roommate, Kelsey Alonzo, comes in and asks me, “Do you hear that?”
“Hear what?” I ask her.
She walks me over to a window at the front of the house and points out— and there’s this strange hum floating through the neighborhood. It’s ethereal and ghostly, but also loud, as if it were in the air. My roommate and I figure it must be ringing through the entire neighborhood, The Richmond District, in San Francisco.
“It’s coming from north,” Kelsey says, pointing out the window again. I decide I have to hop on my bike and chase it down.
I head up 22nd Avenue to Lake Street at the top of the neighborhood and stop to listen. The sound is a little fainter now that I’m not on the third story of a house, but still strong, and still coming from the north. I’m trying to guess what it is; it’s summer during corona, so I’m thinking maybe it’s a group of teenagers having some sort of weird meditation bowl party or something?
My part of the neighborhood ends in this gorge, Lobos valley, and the humming is coming from across it, down by Baker Beach. I scoot down to the beach to check it out, but I don’t see any teenagers with meditation bowls. The sound seems to be coming from even further north, around the Golden Gate Bridge.
So I bike through the Presidio and end up at a viewpoint right above the bridge. Sure enough, the sound is louder here— it feels like it’s reverberating through me. Below me there’s an employee parking lot for bridge-workers and a gated fence leading into some buildings. I spot a bunch of guys in overalls and gear going in and out; I’m thinking one of them might know what’s going on.
I head to the lot, and lucky for me I catch them right as they’re switching shifts. A bridge electrician confirms that the noise is coming from the bridge, but he doesn’t know what’s causing it!
“I was wondering just the same thing. It could have to do with those new railings they installed, but that’s just a guess.”
I talk to a few more iron workers, they don’t know either.
“Someone knows though, right?” I ask them.
“Ya, someone knows for sure,” the Iron Worker says. “That s*it’s loud as f*ck!”
After being forwarded to the sheriff’s office by some bridge patrol officers, I end up in the administration building by the south toll booths. It’s there I meet a young man with curly black hair, bright blue eyes, and a blue collared shirt to match. Paolo Costulich-Schwartz, a spokesperson for the Golden Gate Bridge Highway and Transportation District.
"It had been a very localized or low-level harmonic resonance. And then we saw the perfect storm of conditions to create the louder sound that people were tweeting, and recording, and commenting about."
“Almost like a wind chime. It wasn’t loud, but it was absolutely harmonic and musical,” Paolo comments about the first time he heard the bridge hum.
Paolo confirms that the noise is because of new railing they installed on the west-center portion of the bridge, along the walkway. The bridge makes that sound as the wind passes through the railings.
“Largely it had been a very localized or low-level humming or harmonic resonance. And then we saw the perfect storm of conditions to create the louder sound that people were tweeting, and recording, and commenting about online,” Paolo says.
I ask him if the rails are still under construction, and he says they are. So I ask him if it’s going to get louder, because when it gets going I can already hear it from my house on 25th and Geary about 2 miles away, and he says he doesn’t know.
“We did scale model testing, we engaged the world's foremost expert on bridge aerodynamics,” he says. “But you know, it's the limit of the testing and the analysis that we did... that we did not know that the sound would be quite so audible.”
The new rails are part of a larger “wind-retrofit” the bridge has been going through. They’re retrofitting in order to install a suicide-prevention net underneath the bridge. That heavy-duty net— necessary as it is— is going to act like a sail, catching wind as it passes under the structure. If the bridge gets too wind-resistant, it can start wobbling and fall apart. So the new aero-dynamic rails are meant to compensate for the net. They’re meant to keep the bridge structurally sound, and the “acoustic effect,” as Paolo calls it, is actually just a byproduct of the new more aerodynamic design.
“The thing to impress on folks is that what we heard we expect will only happen in very rare and specific circumstances when the wind is approaching the bridge from a very specific direction at very high speeds,” Paolo says.
"This is not something you'll be going to bed hearing, this is not something you'll be waking up to in the morning. It will only really happen on those rare days when the stars align to create this new sound."
Not only that, but it’s possible that as they complete the retrofit the sound could disappear completely. It might just be an ephemeral phenomenon, not a permanent addition. Either way, Paolo emphasizes that we should not expect to hear it often.
“This is not something you'll be going to bed hearing, this is not something you'll be waking up to in the morning. It will only really happen on those rare days when the stars align to create this new sound.”
So for now, if you’re visiting the Golden Gate Bridge, and the wind is blowing hard, and from just the right angle, you might just be lucky enough to hear her sing.
This story first aired on July 16, 2020.